# Where to Get (DRM-free) Ebooks

This post grew out of a comment I made on Reddit in response to someone who was frustrated with the Kindle walled garden and wanted more generally-usable books.

## Context

I like to read. I have no idea how many books I’ve read in my lifetime, but I own hundreds and hundreds of physical books, at least half of which I’ve read; my digital library has around nine hundred books, most of which I have yet to read; and I’ve read many more books besides the ones I own. (When I was a teenager I’d walk out of the public library with a literal armful of books, read them, then return two weeks later to do the same thing all over again.) These days I prefer to read ebooks. It’s easier to manage my ebook library and I can carry a lot more books around with me in ebook form as compared to physical form. (No more armfuls of physical books.) It really helps that I have a tablet that doubles as an excellent ebook reader.

But I also prefer to actually own the things I’ve nominally purchased. Many ebooks, including everything in Amazon’s Kindle ecosystem, come with digital rights management, or DRM. DRM gives a book’s publisher control over how you use your copies of their books. It’s theoretically intended to impede piracy, but (a) it’s not too hard to bypass if you’re actually intent on pirating the material, and (b) it effectively means that you don’t fully own things you’ve purchased unless you go out of your way to bypass it. It has enabled things like Amazon removing a copy of Nineteen Eighty-Four from a high school student’s Kindle library.

As a matter of principle, I will not pay for DRM-encumbered digital media. If I buy something, I want to feel I actually own it, which means that I don’t have to rely on someone else mediating my use of the media. So here’s where I get my DRM-free ebooks.

## The List

When I want to buy a particular book, my first stop is eBooks.com. They have a good selection of books, and they clearly indicate whether a given book has DRM or not.

Many book publishers or imprints have their own book stores, and some of those offer DRM-free copies of their books. Some of the ones I know of are:

• InformIT for several of Pearson’s imprints, including Addison-Wesley. InformIT ebooks are DRM-free, but are digitally watermarked to connect them to your account.
• No Starch Press - programming, computers, and other “geek entertainment”. They’ve got a very good line of books for getting kids into programming.
• Baen’s eBook Store - primarily science fiction/fantasy books.
• Verso Books - Indepentent publisher primarily focused on politically left-oriented content. Books are DRM-free but watermarked.

I don’t have a problem with digital watermarking like InformIT does. It doesn’t prevent any personal use of the watermarked ebook; all it does is allow the publisher to take a copy shared online and track it back to the person who originally bought it. For the most part, digital watermarking doesn’t restrict use of the book any more than copyright law restricts use of a physical book.

In addition to their eBook store linked above, Baen also has the Baen Free Library, which has a periodically-rotating selection of their books completely for free (and also without DRM).

Tor Books, another science fiction/fantasy publisher, doesn’t have its own storefront (it sells through eBooks.com, among others, and appears to generally do DRM-free books), but it does have the eBook of the Month Club. Basically, you sign up for their newsletter and every month you get a link to download a free, DRM-free book from their catalog.

A good resource for out-of-copyright books is Standard Ebooks. It’s a volunteer-run organization dedicated to turning existing books into high-quality ebooks. Because of the nature of their operation, they mostly focus on books that are no longer restricted by copyrights. Their books are all well-typeset, with a uniform appearance and consistent, well-curated metadata. (If you’re so inclined, you can also contribute your own time and talents to their efforts.)

Standard Ebooks largely stands as as an alternative to Project Gutenberg. Project Gutenberg also has ebook versions of many out-of-copyright books, but Project Gutenberg focuses more on quantity than quality. (Also, they’ve been around a lot longer; Project Gutenberg will celebrate its 50th anniversary later this year.) In general, if a book is available from both Standard Ebooks and Project Gutenberg, get it from Standard Ebooks. But if Standard Ebooks doesn’t have it and Project Gutenberg does, Project Gutenberg’s copy will be serviceable, even if it’s not necessarily formatted prettily and has occasional typos from the automated optical character recognition.

I also follow Humble Bundle. They periodically offer ebook bundles which are typically DRM-free and available in EPUB, PDF, and MOBI formats. (Their quality has been gradually declining over time, unfortunately; for example, some recent book bundles have not had all of the formats for every book.) Not all of Humble’s partners have good books (looking at you, Packt), and I’m not always interested in the style, genre, or even just the particular selection of books in a bundle. But I have gotten some good books out of the bundles over the years, so I keep following them.

The FreeEBOOKS subreddit is more focused on ebooks that don’t cost anything, as opposed to ebooks without DRM, and they don’t restrict themselves by ereader compatibility. Nevertheless, many of the free books they link to are available as DRM-free EPUBs.

## Dishonorable Mention

O’Reilly, a publisher of high-quality computer-related and technical books, used to sell DRM-free copies of their books. If you’d previously bought any of those, you can still access them through members.oreilly.com, but you can’t buy new copies, as far as I can tell. O’Reilly seems to be moving instead to subscription-based access to their ebooks, while still selling the physical versions. They still have O’Reilly Open Books, which links to all of the books they’ve published under open licenses of various sorts, but very few of them are available in EPUBs. Most of the open book links go to webpage versions of the books, which aren’t as easy to get into an ebook reader as a premade EPUB is.

# RampingIOS V3 Manual

The Emisar D4S flashlights use a firmware named RampingIOS V3. (The Emisar D4, D1, and D1S all use RampingIOS V2.) There’s not really a manual; the only thing we get is the diagram on the right. It’s reasonably comprehensive, but there’s a fair amount of detail it merely summarizes, so I thought a textual manual would be nice.

The Emisar D4S only works when the head and tailcap are tightened fully. You can physically lock it out—prevent it from turning on accidentally—by simply loosening the tailcap a small amount. A quarter turn will do it.

Emisar lights are known for their ramping interfaces. Rather than have a small number of distinct brightness levels, they can vary their brightness anywhere between their lowest and highest levels, like a light on a dimmer. The D4S is in ramping mode by default, but it also has a stepped mode that can be configured to be closer to how non-ramping lights work.

Each mode—ramping and stepped—can have differently-configured brightness floors and ceilings.

The driver for the D4S has two different chipsets. At low brightness levels, a fairly-efficient but low-power chipset (called a 7135) is used. These lowest brightness levels are called the “regulated levels”. Each regulated level will always be the same brightness regardless of how much charge the battery has. Above a particular brightness level, the light switches over to a less-efficient but high-power chipset (called a FET). These levels are called “direct-drive”. The brightness of the direct-drive levels is directly related to the battery’s charge level; the more charged the battery, the brighter the levels. The light is at its most efficient, in terms of power used for every lumen generated, at the brightest regulated level. When the light is first powered by tightening the tailcap, it will default to this level.

At higher brightness levels, the light’s LEDs generate a lot of heat. If the light exceeds its configured maximum temperature, it will begin dimming itself automatically until the temperature drops below the allowed maximum.

The D4S has a set of cyan-colored auxiliary LEDs that can be on when the main LEDs are off. You can configure the behavior of the aux LEDs.

## Basic Usage

The default mode for the light is ramping mode. Triple-pressing the button (3 clicks) while the light is on will toggle between ramping and stepped mode.

While the light is off, press and release the button (1 click) to turn it on. It will turn on at the last-used brightness level. (This is called “mode memory”.) Immediately after loosening and tightening the tailcap (or after changing the battery), the memorized level will be the light’s max regulated level.

When the light is on, 1 click will turn it off. The current brightness level will be memorized for future use. There’s a fraction of a second delay between pressing the button and the light actually turning off. That’s because of the way the light processes input; it’s waiting to make sure you’re only going to press the button once (since multiple presses will trigger other actions).

When the light is on, holding the button down will brighten the light. In ramping mode, the brightness will increase gradually ("ramping up"). In stepped mode, the light will jump through increasing brightness levels. If you press, release, and then hold the button, it will begin dimming. In ramping mode, the brightness will decrease gradually ("ramping down"). In stepped mode, the light will jump through decreasing brightness levels. While the light is changing, if you release the button and immediately hold it again, the direction (dimming or brightening) will switch.

In ramping mode, while the light is ramping, it’ll briefly blink off and on again at two different brightness levels: the maximum regulated level and the brightness ceiling.

While the light is off, double-pressing the button (2 clicks) will immediately jump to the brightness ceiling.

While the light is on, 2 clicks will jump to the maximum brightness level, regardless of the configured brightness ceiling. Another two clicks will go back to the previous brightness level.

While the light is off, if you hold the button the light will turn on at its lowest level. If you continue holding the button, the light will begin brightening from there.

The light has several different configuration modes. Each of those modes works more or less the same way. The mode will have a series of menu items that it will go through. For each menu item, the light will first blink a number of times corresponding to the item number (first, second, etc.) After that, the light will begin fluttering on and off fairly quickly. While the light is fluttering, you can click the button a number of times; the light will count the number of button presses and use that number as its new configuration for that menu item. After a short period of time, the fluttering will stop and the light will move on to the next menu item. After the light has gone through all of the menu items, it will return to whatever mode it was in before entering the configuration mode.

If you don’t press the button during a particular menu item’s fluttering, that item will remain unchanged.

### Configuring the Basic Modes

While the light is on, 4 clicks will enter ramping or stepped configuration mode, depending on which mode the light was in before the 4 clicks.

For ramping mode, there are two menu options:

1. Brightness floor (default 1/150)
2. Brightness ceiling (default 150/150)

During the floor configuration, press the button equal to the number of ramping levels (out of 150) at which the floor should be. To set the lowest possible floor, click the button once.

The ceiling is configured similarly, but you press the button equal to the number of steps away from maximum brightness. To set the highest possible ceiling (at max brightness), click the button once.

For stepped mode, there are three menu options:

1. Brightness floor (default 20/150)
2. Brightness ceiling (default 120/150)
3. Number of steps (default 7)

## Other Modes

The other modes largely involve multiple clicks from off. Most of them are not generally needed for everyday use, but they supplement the light’s basic operations.

### BattCheck/TempCheck Modes

From off, 3 clicks will enter “BattCheck” mode, which blinks out the current battery voltage. First it blinks the number of volts, then it pauses, then it blinks out the tenths of volts. Thus, if the battery were at 3.5 volts, the light would blink three times, pause, then five times. For zeroes, it gives a very short blink.

A fully-charged lithium-ion battery is 4.2 volts. The light considers 2.8 volts to be an empty battery and won’t turn on if the battery is at or below 2.8 volts.

The voltage sequence will continue blinking until you turn off the light with a single click.

While the light is in BattCheck mode, 2 clicks will enter TempCheck mode. Instead of blinking out the battery voltage, the light will start blinking out its current temperature in degrees Celsius, first the tens digit then the units digit. Like BattCheck mode, the light will continue blinking out the temperature until you turn it off with a single click.

While the light is in TempCheck mode, 4 clicks will enter thermal configuration mode. See the thermal configuration mode documentation below for how that works.

### Tactical Mode

From off, 4 clicks will enter “tactical” or “momentary” mode. The light will flash once to show that it’s entered the mode. The auxiliary LEDs will turn off (if they were on). In tactical mode, the light will turn on at its memorized brightness for as long as the button is being held down. It will turn off as soon as the button is released.

There’s no button press combination that will exit tactical mode. To exit it, you will have to partially unscrew and retighten the tailcap.

### Lockout Mode

From off, 6 clicks will enter lockout mode. The light will flash twice to show that it’s entered the mode. There’s a separate aux LED mode for lockout mode, so you can tell whether the light is in lockout or not.

In lockout mode, pressing the button will turn on the light at its lowest brightness ("moonlight mode") for as long as the button is held down.

Another 6 clicks will exit lockout mode. The light will flash twice to show that it’s left the mode.

While in lockout mode, 3 clicks will cycle through the various settings for the aux LEDs in lockout mode. The four modes are, in order: low, high, blink (on high), and off. The default mode is blink.

Remember that loosening the tailcap a quarter turn will also lock out the light. Using the 6 clicks is called “electronic lockout”, while turning the tailcap is “physical lockout”.

### Aux LED Configuration

From off, 7 clicks will cycle to the next aux LED mode. The four modes are, in order: low, high, blink (on high), and off. The default mode is low.

### Beacon Mode

From off, 8 clicks will enter beacon mode. In beacon mode, the light will blink on and off every few seconds.

By default, the light will blink every two seconds. To change the timing, use 4 clicks while in beacon mode. The light will enter a one-item menu. During the flickering for input, press the button a number of times equal to the number of seconds between blinks.

1 click will exit beacon mode.

### Thermal Configuration Mode

From off, 10 clicks will enter thermal configuration mode.

1. Current temperature (every click is one degree Celsius)
2. Temperature ceiling (every click is one degree above 30°C)

The “current temperature” item can be used to adjust the calibration of the light’s temperature sensor. To use it, make sure the light has been off long enough that all of its components have cooled (or warmed) to the ambient temperature. Check the ambient temperature using a thermometer you trust. Go to thermal configuration mode, and enter the current temperature by clicking the button a number of times equal to the temperature in degrees Celsius. (If it’s 22°C, click the button 22 times.)

You can check the default calibration by entering TempCheck mode from a room-temperature light. The D4Ss are supposed to go through a temperature calibration at the factory, so hopefully most of them won’t need manual thermal calibration.

The temperature ceiling is simply the highest temperature the light should be allowed to reach. Once it hits its temperature ceiling, it will progressively dim itself until the temperature stabilizes below the ceiling. Note that the number of clicks in that menu option is added to 30 to reach the actual ceiling. (Thus, you can’t set a ceiling below 31°C.) The maximum allowed ceiling is 70°C.

The default temperature ceiling is 45°C.

# RampingIOS V2 Manual

The Emisar D4, D1, and D1S flashlights all use a firmware named RampingIOS V2. (The earliest D4s were released with V1, but there aren’t many of those around. The Emisar D4S uses RampingIOS V3.) There’s not really a manual; the only thing we get is the diagram on the right. It’s pretty comprehensive, but I thought a textual manual would be nice, so I decided to write one.

The Emisar lights only work when the head and tailcap are tightened fully. You can physically lock out the lights—prevent them from turning on accidentally—by simply loosening the tailcap a small amount. A quarter turn will do it.

The lights use a ramping interface. Rather than have a small number of distinct brightness levels, they can vary their brightness anywhere between their lowest and highest levels, like a light on a dimmer.

The drivers for the lights have two different chipsets. At low brightness levels, a fairly-efficient but low-power chipset (called a 7135) is used. These lowest brightness levels are called the “regulated levels”. Each regulated level will always be the same brightness regardless of how much charge the battery has. Above a particular brightness level, the light switches over to a less-efficient but high-power chipset (called a FET). These levels are called “direct-drive”. The brightness of the direct-drive levels is directly related to the battery’s charge level; the more charged the battery, the brighter the levels. The lights are at their most efficient, in terms of power used for every lumen generated, at the brightest regulated level. When the light is first powered by tightening the tailcap, it will default to this level.

At higher brightness levels, the lights' LEDs generate a lot of heat. If a light exceeds its configured maximum temperature, it will begin dimming itself automatically until the temperature drops below the allowed maximum.

## Basic Usage

While the light is off, press and release the button (1 click) to turn it on. It will turn on at the last-used brightness level. (This is called “mode memory”.) Immediately after loosening and tightening the tailcap (or after changing the battery), the default level will be the light’s max regulated level.

When the light is on, 1 click will turn it off. The current brightness level will be memorized for future use.

When the light is on, holding the button down with gradually brighten the light ("ramping up"). If you release the button and immediately hold it again, the ramping direction will switch, so if it had been ramping up it’ll be dimming ("ramping down") afterward.

While the light is ramping, it’ll briefly blink off and on again at three different brightness levels: the minimum brightness, the maximum brightness, and the maximum regulated level.

While the light is either on or off, double-pressing the button (2 clicks) will immediately jump to the maximum brightness level. Another two clicks will go back to the previous brightness level. If the light was off before the the initial two clicks, the second two clicks will go to the memorized brightness level.

While the light is off, if you hold the button the light will turn on at its lowest level. If you continue holding the button, the light will begin ramping up.

## Other Modes

The other modes largely involve multiple clicks from off. They’re not generally needed for everyday use, but they supplement the light’s basic operations.

### BattCheck/TempCheck Modes

From off, 3 clicks will enter “BattCheck” mode, which gives the battery level. It blinks out the current battery voltage. First it blinks the number of volts, then it pauses, then it blinks out the tenths of volts. Thus, if the battery were at 3.5 volts, the light would blink three times, pause, then five times. For zeroes, it gives a very short blink.

A fully-charged lithium-ion battery is 4.2 volts. The light considers 2.8 volts to be an empty battery and won’t turn on if the battery is at or below 2.8 volts.

The voltage sequence will continue blinking until you turn off the light with a single click.

While the light is in BattCheck mode, 2 clicks will enter TempCheck mode. Instead of blinking out the battery voltage, the light will start blinking out its current temperature in degrees Celsius, first the tens digit then the units digit. Like BattCheck mode, the light will continue blinking out the temperature until you turn it off with a single click.

### Tactical Mode

From off, 4 clicks will enter “tactical” or “momentary” mode. The light will flash four times to show that it’s entered the mode. In tactical mode, the light will turn on at maximum brightness for as long as the button is being held down. It will turn off as soon as the button is released.

Another 4 clicks will exit tactical mode. The light will flash twice to show that it’s left the mode.

### Lockout Mode

From off, 6 clicks will enter lockout mode. The light will flash four times to show that it’s entered the mode. In lockout mode, the light will not turn on, no matter how the button is pressed.

Another 6 clicks will exit lockout mode. The light will flash twice to show that it’s left the mode.

Remember that loosening the tailcap a quarter turn will also lock out the light. Using the 6 clicks is called “electronic lockout”, while turning the tailcap is “physical lockout”.

### Beacon Mode

From off, 8 clicks will enter beacon mode. In beacon mode, the light will blink on and off every two and a half seconds.

1 click will exit beacon mode.

### Thermal Configuration Mode

From off, 10 or more clicks followed by holding down the button will enter thermal configuration mode.

In thermal config mode, the light will first blink out the current maximum temperature. As with TempCheck mode, it blinks the tens digit followed by the units digit. If you release the button at this point, the light will turn off and no changes to the configuration will be made.

If you continue to hold the button, the light will then flicker for a second or so. After that, it will turn on at its maximum brightness. It won’t turn off until you release the button, which you should do when you feel like the light has gotten too hot. The temperature at that point will be the new maximum temperature. The light will blink out that new maximum temperature and then turn off.

The default temperature threshold is 45°C.

# Podcasts

I listen to a lot of podcasts, usually while I’m in the car, but also when I’m doing yardwork and similar solitary tasks. These are the podcasts I listen to.

I break my podcasts into several categories and generally listen to the categories in order. (I listen to all of the news podcasts before starting on the politics podcasts, and so on.) My currently-preferred podcast client, BeyondPod, lets me set up a “smart playlist” that puts everything in the appropriate order automatically every time I update my feeds.

BeyondPod also lets me speed up podcasts. I listen to most of my podcasts at 1.5x playback speed. I can still process the information comfortably, but it gets through them faster. Exempted are more highly-produced podcasts and ones that are really short anyway.

## News

First, I listen to my “News” podcasts. These are short and, well, about news. I listen to these in reverse chronological order, so I get the newest news first.

### NPR News Now

The NPR News Now podcast is updated every hour and contains a recording of the five-minute news summary they make available to their member stations at the start of every hour. I have BeyondPod update its feeds within an hour of my normal times for leaving home and work, so I always start off my listening with an up-to-date news summary.

• Schedule: Every hour, but you (obviously) only ever need the most recent episode.
• Playback: 1x because it’s short.

### Up First

Up First is NPR’s podcast version of a morning show. It’s hosted by the same people who host Morning Edition, and it’s available every weekday morning. It spends about ten minutes discussing two to four news topics in more depth than the hourly news summary can cover them.

• Schedule: Every weekday, posted by 6am Eastern time.
• Playback: 1x because it’s relatively short.

### WAMU Local News

WAMU Local News is just what it sounds like; short news items from WAMU in DC. (WYPR is closer to me, but the reasons I instead listen and donate to WAMU are a whole other post.)

• Schedule: Somewhat ad-hoc; it depends on what reporting WAMU has done on a given day. In general, there are three to five short episodes every weekday.
• Playback: 1.5x.

## Politics / Topical

The podcasts in this section are ones that cover topical issues, with a focus on politics. I try to stay up to date on all of their episodes. Sometimes I skip individual episodes in the interest of keeping up with all of them.

### 1A

I’m a bit on the fence about 1A, hosted by Joshua Johnson. I want a podcast that covers a wide range of relevant topics, particularly politics and cultural issues, and I want to come away from discussions with a sense of understanding the perspectives on all sides of an issue, regardless of whether I agree with them. The Diane Rehm Show used to be very good at that; Diane assembeled good panels for discussion, and she was extremely talented at guiding the discussion for the edification of her listeners. 1A took over Diane Rehm’s time slot and covers the same sorts of topics, to a first approximation, so I’ve been listening to it since its inception.

1A is different in a few ways, of course. The focus of the cultural topics is a bit different, but I generally like the topics covered by the show. I don’t think Joshua Johnson is as good a host, though. Diane was good, in my opinion, at guiding her guests to present useful information and perspectives to her listeners. Joshua has often come off as condescending or offputting to his guests, in ways that I don’t think have contributed to genuine, useful conversations. (In more than one show he’s asked a guest a question that basically came off as him saying, “Do you even understand why people think you’re wrong?") I’m a little on the fence about what they’ve done with the podcast format, too. The radio show is two hours long, with a different topic each hour. For the podcast, they pick one of the two topics and edit that show down to a half hour. If you want to listen to the other show, you have to go to the website; it’s not available in a podcast.

I still feel like I’m getting useful information and perspectives from the show, but not to the same degree as I got from the show that previously filled my “topical panel discussion” need. If anyone has suggestions for better podcasts, I’m open to them.

• Schedule: One 30-minute episode every weekday, distilled from the two shows that aired that day. There’s often a bonus episode on the weekend taken from one of the week’s episodes that didn’t get put into its day’s podcast.
• Playback: 1.5x, on general time principles, but Joshua also speaks a little slowly and speeding him up helps.

### Diane Rehm: On My Mind

On My Mind is the podcast that Diane Rehm has been doing since she retired from hosting the on-air Diane Rehm Show. Every week she records and collects conversations with people where she discusses political or cultural topics. Her new format doesn’t really cover the sort of broad, multifaceted discussions that I really liked about her old show, but she’s still informative and insightful, so I’m still listening.

• Schedule: Weekly. One hour-long episode every Friday.
• Playback: 1.5x. Diane Rehm was the reason I started speeding up podcasts in the first place. She’s an excellent host, but she talks extremely slowly. (There are health reasons for some of that, but it still makes it difficult to listen to her show sometimes.) Speeding her up makes it a lot easier to get past the way she sounds and get into the communication of ideas, where she excels.

The Economist has multiple podcasts; I listen to all of them through their “all audio” feed, available at the top of that page. I do skip their “Tasting Menu” episodes; I find the format they use for them jarring. (It consists of one person reading excerpts from an article they’ve written for the magazine intercut with the host’s commentary on the article. It feels like a conversation format where the two people aren’t actually talking to each other and I don’t like it.)

The Economist has the nice additional benefit of giving coverage of the US from an outside perspective. I appreciate that because pretty much all of the other podcasts I listen to are based on the US.

• Schedule: There are currently five podcasts; each one is published weekly on a different day of the week, so the all audio feed gets a new episode every weekday.
• Playback: 1.5x

### FiveThirtyEight Politics

The FiveThirtyEight Politics Podcast doesn’t have its own page, but you can find it on the FiveThirtyEight Podcasts page. This weekly podcast features concrete, numbers-based discussions about political developments. I really like their approach to trying to understand the population’s political opinions by asking them (generally through polls) and trying to fairly listen to the answers.

• Schedule: Weekly. Episodes are recorded around noon on Mondays and posted that afternoon. Sometimes they do “emergency podcasts” on other days to discuss particularly interesting political news developments.
• Playback: 1.5x

### On the Media

On the Media is a weekly show that discusses how the US—and sometimes global—media is covering (or miscovering or failing to cover) the news, particularly political news. They also tend to discuss free speech and various other things that fall within a similar penumbra

• Schedule: Weekly plus. The hour-long radio show airs on Fridays, so they post new shows to the podcast feed on Fridays, too. The podcast also gets “podcast extras” every Wednesday.
• Playback: 1x. Although it might not sound like it at first, the show is very highly produced and edited. Each episode packs a lot more content into each time period than most of the other podcasts I listen to, so I leave this one at 1x playback.

## Education

These podcasts are excellent places to learn new things. They’re not necessarily as time-sensitive as the ones in my “Politics / Topical” section, so I get to these only when I’ve caught up on all the topical stuff. I am currently about five months behind on this section.

### 99% Invisible

99% Invisible discusses the design of things made by humans, with a focus on architecture. I’ve learned a lot about all sorts of things that people have made from this show.

• Schedule: Weekly. One half-hour episode every Tuesday.
• Playback: 1x. This show has high production values and it’s worth listening at regular playback speed.

Radiolab tells stories about science. I’ve learned a lot from this podcast about new developments in science, obscure but interesting scientific discoveries, and science history. They also do a lot to try to express concepts and atmosphere through audio cues. At least one person I know finds their “bleeps and bloops” offputting and can’t listen to them.

• Schedule: They don’t seem to have a hard and fast schedule these days. They usually put out two to three episodes a month.
• Playback: 1x. A lot of work goes into the show’s production, and it doesn’t sound the same when sped up.

### Ted Talks (audio)

The TED Talks audio feed is just that: an audio-only podcast of TED talks. I’m a little on the fence about this one. I’ve listened to some really great talks through this feed, but a lot are just okay or worse. The ratio is not really in the feed’s favor. I haven’t fully given up on it yet, though.

• Schedule: Every weekday. Most talks are 18 minutes or less.
• Playback: 1x. A lot of the talks could probably be sped up without issue, but the good ones usually have a rhythm and performace aspect to them that is better appreciated at 1x, so that’s where I leave the entire feed.

### What’s the Point

What’s the Point was a podcast from FiveThirtyEight that discussed uses of data in various aspects of our world. One of the early episodes I distinctly remember was a discussion of analyzing traffic data in New York City to optimize traffic flows in Manhattan (including closing a street to improve the traffic). The podcast has ended, but I haven’t yet listened to all of the episodes in the feed.

• Schedule: Ended. When it was active, it was weekly, with a new episode every Friday.
• Playback: 1.5x.

## Catching Up

If I ever get caught up on my “Education” category, I have the “Catching Up” category to work on. When I find a podcast that I like and want to listen to every episode of it, I put it in this category. Once I’m caught up on the podcast, it gets moved into an appropriate other category (usually “Education”). 99% Invisible, TED Talks, and Radiolab all started out here.

### Intelligence Squared US

Intelligence Squared US holds one or two debates every month on interesting topics, often political ones. Each debate begins with a motion, e.g. “Video games make us smarter.” There are two teams in the debate; one argues for the motion and the other argues against. Each team has two members. The debate has three phases: opening statements, answering questions from the moderator and audience, and closing statements. The audience is polled about their opinion on the statement before and after the debate; the side that had the greatest increase in supporters is said to have won the debate. I don’t care so much about who wins or loses, but the debates are generally good platforms for understanding opposing perspectives on contentious topics.

• Schedule: One to two hour-long episodes every month.
• Playback: 1x. I think the performace aspects of the debate are better expressed at normal playback speed.

# How to Buy Batteries for Flashlights

Questions about buying batteries come up periodically on the /r/flashlight subreddit. This is the guide I wish had existed when I had those questions. The primary focus of this guide is on batteries that go into flashlights, though some of what’s here can certainly be applied to other battery-powered devices.

If you just want to know how to get 18650 batteries, skip down to the Lithium-Ion section. Be careful when buying lithium-ion batteries from marketplaces like Amazon; unsafe batteries abound. See the section for advice on making safe purchases.

## Types of Batteries

Batteries can be separated into different types that largely have to do with their voltage. A battery’s voltage is determined by the chemical reactions it uses to generate electricity (and occasionally with additional circuitry added to the battery). The usual way we refer to batteries (AA, AAA, C, etc.) specifically references their size, not voltage. Fortunately, for the most part, particular sizes only come in particular voltages. I’ll note a few places you might have to take care.

Flashlight batteries generally fall into one of three categories (links go to the sections on each type of battery):

• 1.5V - These include the most common battery types in use, including AAA, AA, C, and D.
• 3V - The most common 3V flashlight battery is the CR123A. Many button cells (watch batteries) are also 3V, like the common CR2032.
• Lithium-Ion - This is a whole class of batteries that have higher outputs and last longer than many other flashlight batteries, but they require more care in handling. Lithium-ion flashlight batteries usually have five-digit designations, like 18650 and 10440.

I’m omitting stuff like 9V batteries and 6V “lantern batteries”, since they’re not used in flashlights to the same degree that the above categories are.

## 1.5V Batteries (AA, C, etc.)

Flashlights that use AAA, AA, C, and D cells are very common. They’re useful because those cells are also very common.

People sometimes refer to these batteries as either “primaries” or, less often, “secondaries”. “Primaries” are synonymous with non-rechargeable; you use them and then throw them away. “Secondaries” are synonymous with rechargeable, though people will more often just call them “rechargeable”.

The main consideration when choosing 1.5V batteries is the chemistry used inside. There are three common chemistries:

• Alkaline - The cheapest and most common. Not recommended unless they’re your only option. They’re not rechargeable, so you have to replace them every time you use them up. They lose their charge over time, so if you leave them alone for a while, they might not even be useful when you do pick them up. They tend to leak, which becomes more likely the more they discharge (and remember, they lose charge even if you’re not using them). When they leak, they can destroy whatever device they’re in.

• Nickel-metal Hydride (NiMH) - Rechargeable. People will often refer to “Eneloops”, a specific, well-regarded brand of NiMH batteries. Good for frequently-used flashlights because you can reuse them rather than buying new ones all the time. They also don’t leak, so you don’t run the risk of damaging your devices. Standard NiMH batteries lose charge much faster than alkaline batteries, but you can get “low self discharge” NiMH batteries that only lose their charge slightly faster than alkalines do. (Rough comparison: after a year without use or charging, an alkaline battery will have 80-90% of its original charge, an LSD NiMH will have 70-80%, and a regular NiMH will have 15-20%.) Although alkalines usually claim more energy storage than NiMH on paper, NiMH batteries tend to give longer runtimes in flashlights in practice because of the way modern flashlights use electricity.

• Lithium - Expensive, but long-lasting. Not rechargeable. These typically cost three times or more what alkalines do. (So do NiMH batteries, but those are rechargeable, so the cost is amortized over many reuses.) They lose their charge more slowly than alkalines, they can store more energy than alkalines or NiMH, and they don’t leak. Good for devices you want to leave alone for months or years at a time and still work as soon as you pick them up again.

There are rechargeable alkaline and rechargeable lithium batteries, but rechargeable NiMH are the most common at the moment. Nickel-cadmium (NiCd) used to be the most common rechargeable chemistry, but it’s been replaced by the NiMH, which is better than NiCd in practically every way.

In most cases, you should get NiMH rechargeable batteries for flashlights that get used frequently. For flashlights that sit and wait to be used (emergency flashlights, bug out bags, etc.), use lithium primaries.

Lithium batteries handle temperature extremes better than NiMH and alkaline batteries, so lithium is also the best choice for things like flashlights that live in cars.

The Wirecutter has recommendations for NiMH AA and AAA batteries and NiMH AA and AAA chargers.

## 3V Batteries (CR123A, etc.)

3V batteries are common in a number of more niche devices, like cameras. There are a lot of flashlights that use 3V CR123A batteries. Pretty much every 3V battery uses lithium, so everything about lithium in the 1.5V section applies to 3V batteries, too.

The higher voltage lets some CR123A flashlights put out more light than similarly-sized AA flashlights. Aside from that, there’s not much to consider about buying CR123A batteries.

The Parametrek battery database lists several CR123A batteries ranging from $1.50 to$5 apiece. On Amazon, Amazon Basics, Streamlight, and Energizer CR123A batteries range from $1.50 to$2 apiece.

Some places sell “RCR123A” batteries, which are basically CR123A-sized lithium-ion batteries. (Specifically, they’re 16340 cells; lithium-ion naming conventions are covered below.) Some RCR123A batteries have integrated voltage-regulating circuitry to deliver a constant 3V so they behave just like a regular CR123A. Others do not; like other lithium-ion batteries, they’ll be 4.2V when fully charged. If you’re going to buy RCR123A batteries, either make sure your device can handle voltage up to 4.2V or check the specs on the RCR123A to see whether it has a 3V output. (Lithium-ion batteries will often be listed as having a 3.6V output or so.)

All of the usage considerations in the lithium-ion section apply to RCR123A batteries, too.

## Lithium-Ion Batteries

Lithium-ion batteries brought a revolution in compact energy storage. They can hold more energy and discharge it faster than any of the common handheld battery technologies that came before them. Lithium-ion batteries are used, in some form, in devices ranging from smartphones to laptops to electric cars.

Lithium-ion batteries supply 4.2V when fully charged. As their energy is drained, their voltage drops. When they reach 2.5V or so, they’re considered empty. Lithium-ion batteries are usually referenced by the average voltage across their entire discharge range, which is usually 3.6V or 3.7V.

Although a lithium-ion battery can continue to supply power below 2.5V, doing so runs ths risk of permanently damaging the battery’s chemistry. That might reduce the energy the battery can hold when full, render the battery useless, or cause an internal short circuit that could lead to a fire.

Lithium-ion batteries are also potentially more dangerous than the other batteries described above. If they get too hot, they can catch fire or explode. Charging and discharging lithium-ion batteries both generate heat, so doing either one too fast can cause a fire or explosion. A short circuit—connecting the positive and negative ends without enough resistance in between—will almost certainly discharge the battery too rapidly. (For people who remember the Samsung Galaxy Note 7 fires, those were caused by unsafe lithium-ion batteries.)

The above doesn’t need to put you completely off lithium-ion batteries. They’re incredibly useful; you just need to take a little more care with them than other common batteries. Some lithium-ion batteries are more safe than others; that’ll be covered below.

You do need to be careful about where you buy your lithium-ion batteries. Many large marketplaces, like Amazon and AliExpress, have unsafe or mislabeled lithium-ion batteries for sale. Because of the dangers of unsafe usage of such batteries, you need to make sure you’re getting them from a reputable seller. That will be covered in the buying lithium-ion batteries section.

Some flashlights have built-in charging circuits. If yours doesn’t, you’ll also need a charger, covered in the chargers section.

### Lithium-Ion Names and Shapes

The Lithium-ion batteries that flashlights use—at least, flashlights with removable batteries—are generally cylindrical and are described by a five-digit identifier, like “18650”. The first two digits give the diameter of the cylinder in millimeters (mm). The last three digits give the length of the cylinder in tenths of a millimeter. Thus, an 18650 cell is nominally 18mm by 65mm. There’s some variation in those values, particularly in the length, but they give a rough approximation.

Some common sizes are:

• 18650 - The most ubiquitous size for lithium-ion flashlights, as well as for a lot of other things (laptop batteries, smartphone power banks, and so on). Because this is currently one of the most popular sizes in industrial use, it’s gotten the most research into making it efficient. As of January 2018, no other shape matches the energy density of the 18650. (e.g. a 26650 has twice the volume of a 18650, but the best 26650 only has 1.5 times the energy of the best 18650.)
• 26650 - The 18650’s larger sibling. Used by some flashlights to give more runtime per battery.
• 21700 - A relatively newer size that some companies are starting to use. It seems possible that 21700 might someday replace 18650 as the most popular (and, thus, best-engineered) battery size. For now, there are a few flashlights that make use of the larger capacities and discharge currents that 21700 cells have in comparison to 18650 cells.
• 18350 - Almost half the size of an 18650. A number of flashlights have options for swappable longer and shorter battery compartments, so you can decide on a daily basis whether to have a shorter light that uses 18350s or a longer light (with longer runtimes) that uses 18650s.
• 16340 - More or less the same size as a CR123A. There are used in “RCR123A” batteries as described in the 3V section above.
• 14500 - More or less the same size as a AA battery. Some flashlights can use either AA or 14500 cells. Don’t use a 14500 battery in a AA light unless the flashlight manual says you can. If the flashlight only expects 1.5V batteries, using a 4.2V 14500 can destroy the light and possibly start a fire.
• 10440 - More or less the same size as a AAA battery. Some flashlights can use either AAA or 10440 cells. Don’t use a 10440 battery in a AAA light unless the flashlight manual says you can. If the flashlight only expects 1.5V batteries, using a 4.2V 10440 can destroy the light and possibly start a fire.

A number of flashlights allow you to use either an 18650 battery or two CR123A batteries. As with 14500/AA and 10440/AAA, don’t do this unless the flashlight manual says you can, since two CR123A batteries in series will give the flashlight 6V.

When speaking, most people break up the five digits of a lithium-ion battery into three groups: xx-y-zz. Thus, “18650” is pronounced “eighteen-six-fifty”. (“14500” is usually pronounced “fourteen-five-hundred”.)

### What You Need to Know About Lithium-Ion Options

With 1.5V batteries, you have just one thing to decide about: the battery chemistry. With lithium-ion batteries, there are four options you need to consider: protection, top shape, capacity, and discharge rate.

If in doubt, you’ll probably be okay with protected, button-top batteries of the highest capacity you can afford (ignoring discharge rate).

#### Protection

As noted above, lithium-ion batteries should not be discharged below 2.5V or so and should not be discharged too quickly. Many manufacturers take plain lithium-ion cells and add small protection circuits to them. These circuits stop providing power if the battery voltage drops too low or if the current draw gets too high, protecting the cell from things that could damage it. This makes the protected batteries a bit safer, since it’s more difficult to accidentally push them too hard.

A protection circuit makes the battery a little longer, and sometimes a little wider. There are flashlights that have so little extra space inside that they must be used with unprotected batteries. Usually such flashlights will have their own low-voltage protection (LVP) and will stop trying to use the battery if the voltage gets too low. If you use an unprotected battery in a flashlight without LVP, you’ll have to be careful not to drain the battery too far or you risk permanently damaging the battery.

Protected batteries usually cost a little bit more than their unprotected counterparts, typically in the realm of an extra \$1.50 or so.

Some high-powered flashlights need to draw so much current that they can’t use protected batteries because they’d trip the protection with their power usage. For those flashlights, make sure you get unprotected batteries with a high enough discharge rate (covered later).

Flashlights that need unprotected batteries should say so on their website and in their manual. If there’s nothing about protection, you should be able to use protected batteries (and you ought to do so).

#### Top Shape

Lithium-ion batteries, like all other batteries, have a positive end and a negative end. Putting a lithium-ion battery in backwards can damage the flashlight, the battery, or both. In some cases, it can start a fire.

On a plain cylindrical lithium-ion cell, the disk on the positive end is a little smaller than the disk on the negative end. Some manufacturers take bare cells and put buttons on top of them, like the buttons on top of 1.5V batteries. This makes the battery a little longer, but not as much as a protection circuit does. Most unprotected-batteries-only flashlights will still work with button top batteries.

Button top batteries usually cost slightly more than flat top batteries. The extra cost is generally somewhere around ten to twenty cents.

Many flashlights will work with either button top or flat top batteries. Some are shaped so that only a correctly-inserted button top battery will work. This serves as mechanical enforcement of correct battery polarity. If your flashlight takes more than one battery in series, you’ll need to use button-top batteries.

Protected batteries pretty much always come with button tops.

In general, any flashlight that works with flat tops will also work with button tops, except for rare cases where the battery compartment spacing is incredibly tight. Consequently, I’d recommend getting button top batteries unless you specifically know you need flat tops.

#### Capacity

A battery’s capacity, most commonly measured in milliamp-hours (mAh), governs how long it can continue providing power. More mAh generally equals more flashlight runtime. Even if you don’t expect to run a battery all the way down, keep in mind that as a lithium-ion battery discharges its voltage drops. In many flashlights, that means that a partially-discharged battery can’t support the brightest modes on the light. A higher-capacity battery will continue to provide higher voltages for longer periods of time.

If all else is equal, you should get the highest-capacity battery you want to spend money on.

Many disreputable battery vendors claim impossibly high capacities for their batteries. As of January 2018, here are the highest manufacturered capacities for some common lithium-ion sizes; if a battery claims significantly higher numbers, it’s probably lying (and if it’s lying about capacity, it’s a lot more likely to be lying about other things, like safety):

• 16340 - 700mAh (see the note below about Efest)
• 18350 - 1200mAh
• 18650 - 3600mAh (but see the note below)
• 26650 - 5500mAh

(Note: Efest, a reasonably reputable brand, sells “850mAh” 16340s, but testing indicates that they’re more than a little optimistic about that claimed capacity. In practice, 700mAh is the most you’ll get out of a 16340.)

(Note: Only one 18650 cell claims a 3600mAh capacity, and it’s arguably cheating a little to get that number. For most practical purposes, you can regard 3500mAh as the highest available 18650 capacity, and consider any “3600mAh” battery to really be 3500mAh.)

#### Discharge Rate

Depending on their particular chemistry, lithium-ion batteries can have a maximum discharge rate anywhere from 3 amps (A) to 40A. Most flashlights stay under 3A-4A, so pretty much any battery will be fine for them. Some of the higher-output flashlights need or can benefit from 10A, 15A, or even 20A batteries.

There’s a tradeoff between battery capacity and discharge. The chemistries that do very well on one metric are not as good on the other. As of January 2018, the best high-capacity batteries store 3500mAh with a maximum discharge of 10A, while the highest-discharge batteries can sustain 40A but only store 2000mAh.

The most-demanding flashlights I’ve seen top out at about 20A, so you probably don’t need to go out looking for batteries with higher discharge rates than that. (Unless you’re also using the batteries in your vape or something.) Many people with high-drain flashlights like to use Sony VTC6 or Samsung 30Q batteries; both are 3000mAh/15A.

Some people refer to high-discharge batteries as “IMR” batteries, after a commonly-used chemistry for such batteries.

In general, you should see if your flashlight has a maximum current drain listed. If it doesn’t, ignore discharge rate and get the highest capacity batteries you want. Otherwise, get the highest-capacity batteries with a high enough maximum discharge rate.

#### Other Considerations

There are all sorts of other characteristics that people care about with their batteries, but those are less relevant than the above four things, especially if all you care about is getting your flashlight to work.

There’s actually a really complex relationship between batteries' capacity, voltage, and current. Batteries are a little less efficient at higher amperages, so a flashlight that’s constantly used on its turbo setting will generally drain its battery even faster than the numerical difference between the light’s brightness levels would indicate. Similarly, batteries providing higher amperages will have their voltage drop a bit relative to the same battery with the same charge but at a lower current draw. Different batteries will have different balances among those relationships (e.g. Samsung 30Qs exhibit slightly more voltage sag than Sony VTC6s, even though their top-line ratings are the same).

These sorts of things only tend to matter to people who want to squeeze every last lumen out of their lights, and those are just a small subset of the people who use lithium-ion flashlights on a regular basis. If you’re interested in this level of detail, though, you will want to look at HKJ’s battery and charger reviews. The website is a little confusing in its layout, but there’s a wealth of information about all of the batteries HKJ has tested, and HKJ has tested a lot of batteries.

### Where to Buy Lithium-Ion Flashlight Batteries

Don’t just go to Amazon, search for “18650”, and buy the first search result. There are a lot of cheaply-made and more-unsafe-than-necessary batteries in large marketplaces like Amazon. You should buy from a vendor who will only sell properly-labeled stock from trusted manufacturers.

One of the easiest ways to do that, as well as to search for batteries that match all of the options you need, is to use the Parametrek Battery Database. The person who maintains the database has links to purchase batteries from reputable sellers. For a search example, here’s all of the protected 18650 batteries, with the highest-capacity ones first:

Note that to search for capacity, the mAh numbers I’ve talked about are on the “mAh” category. The “capacity” section sorts by watt-hours (Wh) instead. (The basic difference is that milliamp-hours are only directly comparable for batteries at the same voltage, while watt-hours give meaningful comparisons even between batteries with differing voltages. Lithium-ion batteries are generally marketed with their mAh rating—since the voltage is known—so that’s what this guide uses, too.)

If you have questions about a particular battery seller, you can always come ask about it on the /r/flashlight subreddit.

#### Notes on Particular Lithium-Ion Battery Brands

Unprotected batteries are pretty much all made by LG, Panasonic, Samsung, Sanyo, or Sony.

Some of the more popular brands for protected batteries include AW, EVVA, and Keeppower. (As mentioned previously, these companies buy unprotected batteries from the above vendors, add their own protection circuits, and sell the resulting batteries.)

Many flashlight manufacturers have their own branded batteries. Those are generally of good quality, but they’re often more expensive than equally-good batteries from other reputable sellers. Some people prefer to pay the extra amount just to avoid trying to figure out whether a particular other seller is reputable or not.

Batteries from Olight are a little unusual. They’re a reputable manufacturer (and seller, if you buy directly from them), but they do some extra things to their batteries. The tops of their batteries have a positive button, like any button top battery, but also a negative ring around the button. This is required for the batteries to work in their proprietary flashlight charging cradles, but it increases the chances of short-circuiting the batteries. (The protection circuit should prevent a short-circuit from starting a fire, but it’s still not something you want to do to a battery.) Unless you’re using an Olight flashlight with an Olight charger, you probably don’t want an Olight battery.

Ultrafire batteries should be avoided. They’re known to cut corners on their batteries in order to make them cheaper. If you buy one of their batteries, you might get something that works, but you also might get a battery with a defective protection circuit, or a battery that contains a smaller, cheaper battery, and a lot of sand to fill the extra space. Given the care that needs to be taken with lithium-ion batteries, the risk isn’t worth the lower prices.

## Chargers

If you go with rechargable batteries, you’ll need a charger. (Some lithium-ion flashlights have built-in charging, but even with those an external charger can be useful sometimes.)

The best option is to look at the list of chargers reviewed by HJK, pick one with the features you need (number of bays, NiMH, lithium-ion, etc.) and a good rating (two or more smiling faces), and buy it from one of the reputable battery vendors discussed above.