

All About Batteries - MichaelAO
https://learn.adafruit.com/all-about-batteries/overview

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jacquesm
All about batteries:
[http://batteryuniversity.com/](http://batteryuniversity.com/)

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K2h
I have found wikipedia useful on the basics, especially around form factor,
chemistry, and protection circuitry (or not) in lithium. for example, 18650
lithium cell now popular in flashlights, computers and cars that can be very
confusing when it is referenced with protection circuitry and 18650 does not
have protection officially.

[http://en.m.wikipedia.org/wiki/List_of_battery_sizes](http://en.m.wikipedia.org/wiki/List_of_battery_sizes)

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zwieback
I saw this 220um thin battery in an ST update recently, thought that was
pretty cool for ultra-low power apps:

[http://www.st.com/st-web-
ui/static/active/en/resource/techni...](http://www.st.com/st-web-
ui/static/active/en/resource/technical/document/datasheet/CD00270103.pdf)

~~~
Wingman4l7
There is also the THINERGY thin-film lithium rechargeable battery, which was
used in a prototype super-slim eInk watch on Kickstarter.

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lam
The article is not accurate in some places. E.g., some coin cells are
rechargeable such as the LIR2032.

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userbinator
Also funny to see "and lithiums are 3V" (not mentioning li-ion at all) next
to... the 3.7V lions they're selling on the same page.

Fortunately the actual page on li-ion gives 3.6V

Personally I think the safety risks of using li-ion cells like 18650s are a
bit overexaggerated -- the torch/"vape" community has been using them in large
quantities (in China they are becoming nearly as common as AAs), and there
have only been a few notable cases of significant damage. Yes they are not as
safe as something like an alkaline but even lead-acid and NiMH/NiCd can source
significant amounts of current too.

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gdrulia
These days lMR(IMR) batteries (so called safe chemistry) are probably most
commonly used by "vape" community.

The benefit is that they do not explode and proven to be safe choice when you
need high drain batteries. Granted, you need a good charger for them, to make
sure you're not overcharging them, but this should be on your safety list
anyway.

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minikites
Some lead-acid batteries can also be completely drained, unlike many other
rechargables:
[https://www.youtube.com/watch?v=rhIRD5YVNbs](https://www.youtube.com/watch?v=rhIRD5YVNbs)

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TeMPOraL
Hah, how nice it's here today. I just started a small hardware project
(hopefully a Show HN in a month or two) and I got hit by the fact that I don't
understand jack squat about batteries, especially Li-Ions and Li-Polys.

This (and jacquesm's) link is godsend.

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IgorPartola
Important thing I learned today: 9 Volt batteries are crap. I was just about
to re-build my charcoal grill air blower which used two 9V's. Now I will go
with some AA's or even a lantern battery.

~~~
joshvm
9V's aren't crap, they're useful because you can linearly regulate them down
to the majority of the common bus voltages used in electronics. Mainly they're
by far the simplest way to get 5V in a portable system (9V + LM7805). LiPOs
will do fine for anything below 3.7V so most modern systems with 3.3/2.7/1.8
will be OK. But if you need a 5V system with anything aside from a dedicated
supply or a 9V battery you need to include a step-up converter which adds
complexity (though some ICs only need a few capacitors) and cost.

The main downside [for a 9V battery] is that linear regulation is inherently
wasteful and you lose (4V x your current) to heat. They also have a comparably
low capacity compared to AA's so they're not the best choice for a long life
application. In that case you're better off using a 95%+ efficient switch mode
supply, but then if your system requires low noise you have other
considerations.

It's not cut and dry!

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mindslight
9v+7805 is fine if you're playing around, but if you're making something to
use and especially if it's to be powered continuously, you'd be better off
with 4 AAAs and a low-quiescent low-dropout regulator. 9v batteries can't
supply much current (a guideline of 20mA is mentioned in the article). The
first 7805 datasheet I came across specifies it's bias current at 4.3mA
typ/8mA max. So just by powering the regulator, you're drawing a significant
load from the battery even if the rest of the circuit is doing nothing.

Funnily enough, I've never seen a stacked 9v as pictured in the article. The
few that I've opened up have had elongated cells laid out like a six pack of
beer.

~~~
joshvm
Well quite, 4xAAA is a better choice in lots of cases. Just a point that it's
still a very common design pattern, particularly in cheap devices. When you
look at the capacities, 9V batteries are awful.

Bear in mind that 9V batteries also have far easier interfaces than AAA packs,
requiring a single plastic/metal tab rather than an injection moulded
retainer. In some cases, the price difference for both manufacture and battery
cost makes it worthwhile.

As for current, plenty of devices run under 20mA happily. A microcontroller in
active mode will probably use under 15. Most 9V devices aren't used
continuously, my IR temp gun uses a single 9V for instance. However I've also
seen smoke alarms and other home sensors that use them.

I'm not disagreeing with any of the criticism here, I would never use a 9V
batt in a project, but there is good reason to consider it and people should
understand why so many products still use them.

Stacked 9V batteries are typically the old Alkaline sort or rechargable.

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chillingeffect
In the name of strengthening the case for 9V batteries:

Not many people know this, but it's now possible to get lithium, secondary
(aka "rechargeable") batteries. They really put out about 8.0V, but sub swell
in many apps.

And have ~70mA constant discharge rate.

I've been enjoying using them in many applications, esp with a buck-switching
regulator.

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nraynaud
just when I thinking about ditching batteries in favor of capacitors for some
projects.

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IgorPartola
From what I've read, super capacitors still have about 1/10th of the energy
density of good rechargeables.

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rasz_pl
all about rechargeables? :

[http://www.lygte-
info.dk/info/indexBatteriesAndChargers%20UK...](http://www.lygte-
info.dk/info/indexBatteriesAndChargers%20UK.html)

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pkolaczk
"All" in the title is a heavy exaggeration. The site covers very basics only.

