Battery Life

[Paul Komski]

Battery life can be (a) the time a battery will operate a device for or (b) the time before it begins to fail and won't hold a recharge effectively.

I have found lots of Googling advice on how to optimise the former but the latter is more problematic; and I am only talking about rechargeable batteries here (and about which I have been given conflicting advice in the past). I'm also not including the lead car batteries, for which different rules apply (as far as I know).

In general:-
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Does letting a battery almost totally discharge itself before recharging it have beneficial or detrimental effects or does it matter?
Does leaving the battery's charger-unit attached (when the battery is already fully-charged) have any detrimental effects?
If a battery is first fully-charged and then removed from a device and is then not used for a period of time; will this non-use degrade the battery?
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Perhaps it depends exactly on the battery's exact chemistry but some useful rule-of-thumbs would be most useful.


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Take nice care of yourselves - Paul
"Those who say they don't let little things annoy them have never tried to sleep in a room with a buzzing mosquito."

[penta_chris]

For Ni-Cd batteries, answer "beneficial" to 1, "yes" to 2, and "to a small degree in cool dry conditions, to a much greater degree in hot conditions" to 3. A quick fix for Ni-Cd batteries for the results of 1 and 2 is to use a "conditioning charger" which first totally discharges the battery, then generates a special reverse current to electrically clean the battery's internals, so it can be recharged more often and run longer on each recharge. Even with this special charger, it's not going to last forever - about 1000 charges in most PC Ni-Cd batteries.

For Ni-MH batteries, answer "detrimental, but not quite to the degree that it is beneficial to Ni-Cd batteries" to 1, "yes, but to a much less degree than Ni-Cd batteries" to 2, and "about the same as for Ni-Cd, with the same heat-related issues" to 3. Again, all the care in the world won't result in the battery lasting forever. Ni-MH batteries can be used to replace Ni-Cd batteries.

For Li-Ion batteries, answer "doesn't matter" to 1, "no" to 2 (an overcharged Li-Ion battery will explode - they all come with special circuitry to prevent this), and "no or negligibly so" to 3. Again, it still won't last forever - they can't take as many charges as the other two, but you get more life out of each charge. Li-Ion batteries can only be used in devices made for them.

Paraphrased from Mike Meyers A+ Passport.

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I fight authority,
Authority always wins

[This message has been edited by penta_chris (edited 06-21-2002).]

[Paul Komski]

Wow. Comprehensive and Quick. What a man!

To summarise (hoping I got it right) and in simple fashion then:

Running down NiCd is good (and a conditioner can help)
Avoid total rundown of NiMH if possible.
Dont overcharge NiCd or NiMH.
LiIon more stable than NiMH which more resilient than NiCd
Don't let stored batteries get warm.



[This message has been edited by Paul Komski (edited 06-21-2002).]

[penta_chris]

That's a good summary. You could change the last point to "Don't let rechargeable batteries get warm." The heat won't be any less detrimental to batteries that are in the device and aren't being "stored" per se.

Looking back at the book to double check myself, Ni-MH batteries can be conditioned as well. Other points: the condensation that will occur when batteries are put in a freezer or refrigerator makes doing so a bad idea (they don't need to stay that cool); keep battery contacts clean with a little denatured alcohol or a dry cloth; never handle broken or ruptured batteries, as they contain toxic and dangerous chemicals; always recycle old batteries because of these chemicals.

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I fight authority,
Authority always wins