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Could anyone suggest, why lifetime of Pb batteries is so short in UPSes?

3 years till 0 mAh - I've seen that several times, and some UPSes were not low-end (~250$)...

Are there any ways to make it last longer when designing new device?

Same for LiIon - if we rarely charge/discharge them, how long they could last? (I've heard things like '2 years of shelf-life and they are garbage')....

BarsMonster
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  • Pb is not a notation I am used to, it may be very common and I have not seen it, I am much more used to Lead acid, but Pb is shorter, which people seem to prefer the shortest name. – Kortuk Mar 11 '11 at 12:07
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    Just to clarify this, pb is the symbol for lead in the list of chemical elements. its not a preferred short name, its actually a defined symbol and not something people use because of preference. – 1amtoo1337 Mar 11 '11 at 13:07
  • no prob. :) if you own a car, i think youve been using your Pb "battery" kinda frequently. eventhough its not the battery it are the electrodes/cathodes which are out of Pb. – 1amtoo1337 Mar 11 '11 at 15:05
  • @shitake83, I am just used to lead acid, even Pb acid would have done the job, just clearing it up, the question was answered. – Kortuk Mar 16 '11 at 11:53
  • @kortuk: sorry to be a smart ass again, but Pb = lead. And there is no lead (or pb) acid, since the battery is a Pb+acid battery. Not Pb acid battery. – 1amtoo1337 Mar 16 '11 at 12:09
  • @shitake83, are you used to hearing them called Lead batteries? I have only every heard or read lead acid. I am not implying it is an acid solution of lead, I do not pretend to be a good chemist, I am saying that if I just see Pb I assume that I may not know this batter technology. – Kortuk Mar 16 '11 at 12:18
  • Yes in germany we call them "Autobatterie" "Bleiakkumulator" or "Blei-Säure" Batterie which means Lead/Acid-Battery. If you write "lead acid" it comes off as one word and someone with minor knowledge might just put that in his head as something that is existent ;). Did i mention its 13:37 over here xD. And just to show you that other people are aware of the fact. http://electronics.stackexchange.com/questions/78/charging-lead-acid-batteries – 1amtoo1337 Mar 16 '11 at 12:34
  • @Shitake83, it is a name of the technology to most whom use it I believe. Honestly, for an electronics guy, does it hurt anything if he thinks it is an acid based on lead? This seems to be more nit picking then important to me. Most people call it lead acid and identifying it in a standard way seems more important. – Kortuk Mar 18 '11 at 07:18

2 Answers2

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This is due primarily to internal corrosion of the lead frames and the electrodes, short circuits cause the sulfation of the lead. This causes sulfation, that makes the PbSO4 crystals merge into ever larger networks. This reduces the electrochemical active surface of the PbSO4. Due to the now smaller surface, the PbS04 cannot be "come off" that good , as it could before. So it takes very long until a sufficiently high concentration of Pb2+ is present. In addition, the electrical conductivity of the sulfate is lower than that of lead. The resulting increased Internal resistance of the load cell leads to increased voltage drop. Give that process enough time and your at the point where you wont have any cell voltage at all.

I hope this helped you.

P.S.: i didnt know a good word for "ablösen" in english, since unsolder is not the one i was looking for and peel of is not the right term. but i think youll still get it.

1amtoo1337
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UPSes destroys batteries due to over voltage. In a UPS the manufacturer prefers to have fast battery recharging over battery life, thus reducing the battery life.

What you could do to increase battery life in an UPS is to disconnect the charging circuit and instead use a normal battery charger for the type and size of battery/ies that the UPS uses.

Gunnish
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