Sealed lead acid battery maintenance?
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From: keithw86 on 28 May 2010 08:37 On May 28, 12:51 am, John Doe <j...(a)usenetlove.invalid> wrote: > I would like to learn something about proper care of sealed lead > acid (SLA) batteries. Is there any good authoritative science on > how SLA batteries should be cared for? I am searching... I suppose > battery makers/distributors would be one of the best sources of > information about that? > > Specifically... I wonder why instructions that come with SLA > batteries so strongly emphasize charging the battery immediately > after use, without specifying how much use. Are they concerned > that the battery might eventually self discharge too deeply? Or > does it degrade an SLA battery to rest it in any state but fully > charged? > > Thanks. http://www.amazon.com/Rechargeable-Batteries-Applications-Handbook-Engineers/dp/0750670061/ref=sr_1_12?ie=UTF8&s=books&qid=1275050161&sr=1-12 Everything you ever wanted to know about SLACs.
From: John Doe on 28 May 2010 14:37 Robert Roland <fake ddress.no> wrote: > John Doe <jdoe(a)usenetlove.invalid> wrote: >> does it degrade an SLA battery to rest it in any state but >> fully charged? > > All lead-acid batteries degrade with time. The degradation rate > goes up with increasing temperature and/or decreasing charge > state. Is the degradation versus charge state rate linear? I guess not. > In other words: Keep them cool and fully charged. Does the act of charging an SLA battery also degrade it? I have always thought that charging a battery degrades it, but maybe that is a misinterpretation of the maximum number of charge cycles. Anyway... Keeping it fully charged is impossible here since it has to be used. But of course degradation takes place over time, so I guess that is why they emphasize recharging the thing immediately after using it. And the deeper the discharge, the more important that is. Thanks. -- > Note that proper charge voltage is dependent on temperature, so > if you keep the battery in the freezer, your charger must be > able to adjust the voltage accordingly.
From: Sjouke Burry on 28 May 2010 18:45 John Doe wrote: > Robert Roland <fake ddress.no> wrote: > >> John Doe <jdoe(a)usenetlove.invalid> wrote: > >>> does it degrade an SLA battery to rest it in any state but >>> fully charged? >> All lead-acid batteries degrade with time. The degradation rate >> goes up with increasing temperature and/or decreasing charge >> state. > > Is the degradation versus charge state rate linear? I guess not. > >> In other words: Keep them cool and fully charged. > > Does the act of charging an SLA battery also degrade it? I have > always thought that charging a battery degrades it, but maybe that > is a misinterpretation of the maximum number of charge cycles. > > Anyway... Keeping it fully charged is impossible here since it has > to be used. But of course degradation takes place over time, so I > guess that is why they emphasize recharging the thing immediately > after using it. And the deeper the discharge, the more important > that is. > > Thanks. Very long trickle charge will kill one. That sulfates the plates, and is difficult to recover from. Also leaving a small consumer on for the winter period is a great killer. Often someting like a radio, a voltmeter, a computer chip, etc. Best to remove one cable from the battery, to make sure.
From: John Tserkezis on 28 May 2010 19:44 John Doe wrote: > I would like to learn something about proper care of sealed lead > acid (SLA) batteries. Is there any good authoritative science on > how SLA batteries should be cared for? I am searching... I suppose > battery makers/distributors would be one of the best sources of > information about that? The long and short of it: Don't discharge the battery. Don't overcharge the battery. That kinda impedes on your actual use of the battery, so, a more useful compromise would be: Don't discharge the battery any deeper than you can help it, and charge as soon as possible afterwards. While charging, don't exceed the maximum charge rate for your battery. Use a float charger, and ensure the maximum float voltage is not higher than the maximum spec. This varies with temperature, so may be an issue if the environment changes widely. As an example, we used 100A/hr or so SLAs in an application where they were deep discharged (over a week or so) as a matter of course. Perhaps left for a couple of days in that state, then charged afterwards. We'd get end of life after about two years of constant abuse like this - about 80% or less service capacity left before it was no longer acceptable in our application. Which is not bad, considering two years is considered the service life of SLAs in more critical applications like UPSs and such, in an environment SLAs must love. > Specifically... I wonder why instructions that come with SLA > batteries so strongly emphasize charging the battery immediately > after use, without specifying how much use. Are they concerned > that the battery might eventually self discharge too deeply? Or > does it degrade an SLA battery to rest it in any state but fully > charged? Not quite, at deep discharge states, the plates under go irreversible chemical reactions that prevent an ideal charge from taking place afterwards. There's more that can go wrong too. Which is why I said "don't discharge the battery" not entirely tongue in cheek. :-)
From: Robert Baer on 29 May 2010 06:04
John Tserkezis wrote: > John Doe wrote: >> I would like to learn something about proper care of sealed lead >> acid (SLA) batteries. Is there any good authoritative science on >> how SLA batteries should be cared for? I am searching... I suppose >> battery makers/distributors would be one of the best sources of >> information about that? > > The long and short of it: > > Don't discharge the battery. > Don't overcharge the battery. > > > That kinda impedes on your actual use of the battery, so, a more useful > compromise would be: > > Don't discharge the battery any deeper than you can help it, and charge > as soon as possible afterwards. > > While charging, don't exceed the maximum charge rate for your battery. > > Use a float charger, and ensure the maximum float voltage is not higher > than the maximum spec. This varies with temperature, so may be an issue > if the environment changes widely. > > > > > As an example, we used 100A/hr or so SLAs in an application where they > were deep discharged (over a week or so) as a matter of course. Perhaps > left for a couple of days in that state, then charged afterwards. > > We'd get end of life after about two years of constant abuse like this > - about 80% or less service capacity left before it was no longer > acceptable in our application. > > Which is not bad, considering two years is considered the service life > of SLAs in more critical applications like UPSs and such, in an > environment SLAs must love. > >> Specifically... I wonder why instructions that come with SLA >> batteries so strongly emphasize charging the battery immediately >> after use, without specifying how much use. Are they concerned >> that the battery might eventually self discharge too deeply? Or >> does it degrade an SLA battery to rest it in any state but fully >> charged? > > Not quite, at deep discharge states, the plates under go irreversible > chemical reactions that prevent an ideal charge from taking place > afterwards. > > There's more that can go wrong too. Which is why I said "don't > discharge the battery" not entirely tongue in cheek. :-) > As a "point" of reference, i have an old UPS by APC and replaced the batery only once so far in the appx 15 years of "use". Most of the time it just sits there - maybe on trickle charge, who knows. But on rare occasion when the power goes out and i am online, it keeps all running for a careful save and shutdown. |