
There's truth to 'dead battery bounce' after all (2015) - dcminter
https://theconversation.com/it-turns-out-theres-truth-to-dead-battery-bounce-after-all-38680
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bxparks
I have switched to using NiMH rechargeables almost exclusively now, even for
low power devices (e.g. remote controls, clocks). The problem I have
encountered with alkaline batteries is that they leak chemicals which can
destroy the electrical contacts and sometimes the entire device. I've never
had a NiMH rechargeable battery leak in the roughly 15-20 years that I've used
them. But I have seen so many alkaline batteries leak that I don't trust them
anymore. Maybe it's my imagination but alkaline batteries seem to leak far
more often today than 10-20 years ago. Is it just me, or are Duracell brand
batteries worse than others in terms of leaking?

The traditional argument for not using rechargeables on low-power devices is
that the self-discharge rate for the rechargeable battery is higher than the
power consumption of the device itself. However, some NiMH batteries (e.g
Eneloop, [https://eneloop101.com/](https://eneloop101.com/)) seem to use a
special chemistry that results in only a 30% discharge after 10 years. I use
the Eneloop brand pretty much exclusively. I think the extra cost of the
rechargeable batteries have more than paid for themselves by avoid the damage
caused by leaking alkaline batteries. The cost of NiMH batteries are now low
enough that they may be far cheaper than alkaline batteries for almost all
applications.

~~~
leggomylibro
The difficulty that I have with NiMh batteries is that it is very difficult to
tell when they are done charging, and they are less tolerant of overcharging
and "trickle charging" than the NiCad chemistries which preceded them.

Most chargers will just assume that you've discharged them fully between uses,
and perform a "full" charge cycle when one is plugged in, maybe with a
temperature sensor to stop if they get too hot. You can't really use resting
voltage as a gauge, and it's tricky to find a good charger which can reliably
detect the small and brief "dip" in voltage which occurs around the time that
the batteries are fully charged.

They're great batteries, and I also prefer them for applications where the
batteries get fully drained before being plugged in, but they can still be
iffy for applications where you only discharge them briefly and want to keep
them "topped up".

For those applications, these days you can buy 1.5V lithium cells in AA/AAA
form factors with built-in microUSB charging ports. But those are lithium-
based, so you have to be careful about thermal runaway.

Life is a balancing act full of compromises...

~~~
bxparks
The NiMH chargers that I've seen have a negative delta-V detection and a timer
shutoff. I've had problems charging the Eneloops when used on devices that
drain the battery too much. When they are inserted into the charger, the
voltage seems to rise too quickly and and somehow confuses the charger so that
it stops charging early. In those situations, I've resorted to charging those
batteries twice. First time, charge for 5-10 minutes to raise their voltage.
Then remove and reinsert the batteries to charge a second time using a more
normal voltage curve. Maybe it's a quirk of my charger.

I didn't know about lithium AA/AAA rechargeable batteries. Interesting. I see
that most are rated at 1200-1500mAh (AA) and 400-500mAh (AAA). These are only
a little over 1/2 the capacity of the NiMH that I normally use. I guess the
charging circuitry takes up room in the battery.

~~~
leggomylibro
Got any charger recommendations? :)

And yeah, the lithium AA/AAAs were news to me too. I learned about them when I
got a headlamp that could either take 3 AAA batteries or a same-sized lithium
battery with +/\- contacts in the right places. I think the single-cell ones
include a buck converter along with the charging circuit, which probably cuts
down on the space they can devote to the battery itself.

~~~
bxparks
Yup, it's old but I use this Titanium Smart Fast 8 Bay AA/AAA charger
([https://www.amazon.com/gp/product/B0035HCTLS](https://www.amazon.com/gp/product/B0035HCTLS)).
The manual states that it has negative delta-V and timer shutoff. One of the
Amazon reviewers mentions a problem with deeply discharged batteries, similar
to what I've seen where I need to charge the battery twice.

By the way, this situation happens mostly on my motion-activated staircase LED
lights which take 4 x AA. That thing is amazing because it works until 3 x AA
are essentially dead and only 1 x AA is giving out power. For most of my other
devices, the device stops working before the battery voltage becomes that low.

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sergj
Wow! I was asked by a friend if dead/flat batteries were weighing less, since
I was working a little bit with batteries. Back then I dismissed it as utter
nonsense. But I still googled the question because you never know right? and I
stumbled upon either this article or a similar one: [https://www.quora.com/Is-
a-charged-battery-heavier-than-a-de...](https://www.quora.com/Is-a-charged-
battery-heavier-than-a-depleted-one)

After finding and reading an answer that agreed with my initial assessment I
never continued to investigate why my friend would make such a claim, but now
I guess it was related to this phenomenon. Guess I owe somebody an apology.
Crazy how somethings seem so outlandish that I did not even ask myself if this
was possible or what fundamental differences there are between batteries of
different states of charge. Also it would have been quite easy to test this in
retrospective... Note to myself: I should be more careful and curious in the
future!

~~~
lightedman
Energy equals mass times the speed of light squared.

That alone tells me a dead battery of one composition will weigh some fraction
less than a fully-charged one of the same composition, assuming all other
things are truly equal (number of atoms in the containing can, etc.) The
fractional difference might be very, very small (billionths of a gram
difference?) but should still be present.

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skunkworker
The linked video is something else.

[https://youtu.be/ZywsCbWEun8](https://youtu.be/ZywsCbWEun8)

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test6554
Now they just need to study the drop's impact on battery lifetime.

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6nf
I've been using this trick to tell dead from fresh alkalines for years! I
thought the science was well understood

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nathancahill
Blast from the past, I remember doing that when I was little. Forgot all about
it. Thank god for rechargeables.

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ggm
Ignobel material

