Electronics > Power/Renewable Energy/EV's

10 year old rechargeable acid battery

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james_s:
I've taken a few old SLA batteries apart and they were more than sulfated, all of the negative (I think) plates had crumbled into bits.

floobydust:
It's a metal in an acid, who thinks that is going to last? Corrosion disintegrates the plates and interconnects. Or they dry out, or sulphate gets them.
After reading research papers with SEM photos of sulphate crystal forming in a plate's pores, and that the crystals are an insulator (effectively reducing plate surface area) and there's no proven way to clear them... I no longer waste a lot of time hoping to rejuvenate lead-acid batteries.

vinlove:
Yeah, they wouldn't be able to jump start cars at that state for sure.  But for powering up Shortwave radios running at 12V DC, they seem to doing the job for powering them for a night per a few hours recharge for now.
If they stopped even doing that, then sure they will be dropped off at the local supermarket, where they collect the used batteries.

Rick Law:

--- Quote from: floobydust on March 20, 2023, 08:04:28 pm ---It's a metal in an acid, who thinks that is going to last? Corrosion disintegrates the plates and interconnects. Or they dry out, or sulphate gets them.
After reading research papers with SEM photos of sulphate crystal forming in a plate's pores, and that the crystals are an insulator (effectively reducing plate surface area) and there's no proven way to clear them... I no longer waste a lot of time hoping to rejuvenate lead-acid batteries.

--- End quote ---

I also went through a lot of research paper as well.  Some claim very successful results.  Hence I got a de-sulfator to try for myself knowing that unlike the research ones with high-power and sophistication, the de-sulfator I have is low power low feature so it is not likely to do much.  Then there is the recent-dead or already fossilized dead.  There is a point beyond hope. 

So my current approach is the following two steps, and if that doesn't work, that it.

1.  Slow charge and then soak for a day or two then test.  Working is defined as normal charging and getting it to store a useful charge.  So far, from a new sample of two (not the original 6 really dead ones), I have only needed step 1.

2.  Since I already have the de-sulfator...  With prior experience (results written in the prior thread, link in prior reply), I know it works a little.  So I will use the de-sulfator again for a few days duration then do step 1.  Repeat de-sulfation untill it stops improving significantly -- prior experience would make me guess it would be 3 to 5 runs.  When improvement stopped and charge capacity is still far from useful, it is considered dead.  So far, my "new sample of two" have not needed step 2 yet, so step 2 is merely an untried but intended plan.

My "really dead" original sample of 6, the best was the 22AH battery with capacity "improved to around 1.5AH".  In thar prior thread, I said improvement was "measurable but not meaningful."  While i can use it for emergency lighting.  A 200mA LED during power outage is indeed welcome even if just for an hour or two.  But it is not a "worthy amount" to be meaningful.  Since SLA needs to regularly maintain the charge or keep it float charging.  While maintenance float or drip charging a good battery is proven to be rather safe, I am nervous leaving a bad battery with little life left to "safely degrade" under power continuously.  That is risk (and lots of hassle monitoring it) with very little gain.

vinlove:

--- Quote from: Rick Law on March 22, 2023, 05:32:11 pm --- While maintenance float or drip charging a good battery is proven to be rather safe, I am nervous leaving a bad battery with little life left to "safely degrade" under power continuously.  That is risk (and lots of hassle monitoring it) with very little gain.

--- End quote ---

Risk?  SLA battery voltage always drops as it is used - it never rises.  The device it powers will simply stop working when the voltage drops to below 10V (for 12V devices). What / how could it damage or harm?

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