Saving SLA batteries

[alibro]

I got a load of old 90amp per hour lead acid batteries from a computer UPS It was for a big room full of computers. When I got them they all showed around 12.7V and I used them for a while on my battery bank. Unfortunately I let them get very low (below 8V) and was going to dump them. Do you think they could be saved? It sure would save me a ton of money as I am rebuilding my wind turbine.

Cheers

AliBro

PS while on the subject can I harm lead acid batteries by charging with a normal car battery charger

[AbyssUnderground]

If youve let them fall below 11.5v and left them there, you can pretty much guarantee they will sulphated to hell and back by now.

I don't know about using a "normal battery charger" since you didnt state what a "normal battery charger" is. Im assuming you mean a car battery charger or similar charger. The answer is no you cant use one, since they charge a battery differently to an SLA battery charger.

[JW]

Hi Alibro,

 I have 2 of the reactor type automotive batterys. I have been playing around with them for years. Mine are technically VRLA batterys, valve regulated Lead Acid, which I feel are the same thing as a Sealed lead acid battery as long as there not bulging or anything. These glass mat batteries are weird. I worked with flooded lead acid before messing around with these and they are indeed strange. I have found that, depending on state of charge, that can only be checked with a DVOM, they can float all week at 13+ volts(on the charger) and not take any power. After a good discharge I bring mine up with a regulated power supply set to 13.25v. This takes about 5 days or so. Conversly, any flooded lead acid type battery will come up with a regular charger in about 24hrs. What really stumps me on these glass mat battery types, is that a 14v float voltage(while charging) apparently will damage them. When mine are down as low, as I will let them get, at 11.10v. I find that I can stick them on a regular charger that will float to 15v, and they will stay below 13v for at least 6hrs(or less). But,,, if I dont watch them very closely they will run away to 15v within 15 minuites, once they hit a voltage over 13v. its weird I know, but thats gennerally what they will do. the first time i encountered this with my 2amp AC charger, i could not imagine how bad wind charging could effect them.

 I use mine with a very stable charging voltage matched to the load, they hold surges of power pretty good, but for the most part, every thing is even in relation to discharge rate and 10amps peak charge rate during load.(while they are in use, not being charged without a load)

 if your batts are just down to a low voltage, i would try bringing them back up slowly, with a regulated power supply @ -12v 1.5amps/ and +12v 4.0amps to 6.0amps peak, connected to the terminals. This setting works well for me with these batt's, when they just wont take a charge. Generally I can get the battery to float disconnected at, 12.56v for 2day's or more once charged this way. I only equalize when driving a load and use no more than 10amps to maintain operating voltage per battery, (I want to say) but would feel more comfortable with 15a for two. The load is always calibrated to this charge setting(for me atleast). Compared to flooded lead acid batterys, you seem to have to jump thru hoops with these.

I use low charging amps, to charge, compared to a regular battery charger that will pump 8 or more amps when there dead, then back of. Wheras the charging scheme ive been using will regulate at 4.5 amps no matter how dead the battery is, then back of from there, after a couple of days.

 Like I said, it takes a week or two bring mine back up with the regulated power supply, being charged individually(floating disconected at 11v before charge). If they come up before ten days with a disconnected float voltage of 8v, well they are probably shot. But you never know, its hard to get these to take a good charge period. I know cycling mine with whatever charge they will take, greatly improves discharge capacity, as long as I charge them slowly inbetween cycles.

JW      

[nothing to lose]

Try it. If your going to toss them otherwise you have nothing to lose right.

Just don't blow them or yourself up.

90amp  hour lead acid batteries should be ok with normal car battery charger.

If they are just normal sealed lead acid batteries they should be just like any other deepcycle lead acid battery basically.

Don't charge too fast, being sealed you can't put back in any water you boil out. I would not equalize them for same reason, although if your going to toss one that is not working well then might as well try it anyway before tossing.

At 90amps/20hrs =4.5amps for a C20 rate.

I would wire 2 for 180amps and charge at 10amps, or better 3 for 270amps and still charge at 10 or 12amps. Slower charging gives sulphates more time to disolve and helps alot sometimes, I would pulse charge them if you can to disolve sulphates also. Pulse charging is not the same as equalizing and should not boil out water.

Depending on the charge rates available to you, alot of chargers seem to vary, I would try for about 30hr charge period to bring them back up. 2amp is probably too slow, 45HRs per battery, 6amp is too fast at only 15hrs per battery.

Unfortunately today there is no such thing really as "a normal car battery charger" if you go to the store and buy a new one. There are the older kinds (if you can find them), Truely Smart Chargers, Brain dead chargers reffered to as Smart Chargers etc...

The old style, connect it, turn it on, it works. It tries to work even on a junk battery. No specail features normally, just straight amps like 2/6/12 or such.

"Brain dead" Smart Charger like the Vector 40 amp I had, good for alot of things, but if a battery was good but DEAD it would give an error and not turn on untill I charged the battery some other way a bit first. Then it would work. It had a pulse feature to desulphate.

 This type probably will not work for you since it probably would not turn on for your dead batteries. Even if the batteries are still good the charger may show they are junk just because they are dead!

Black & Decker "truely" smart charger (made by vector) will turn on even on the worst batteries. Will flash an error message but tries to charge even the deadest of dead batteries. I used this on several cars that sat many months-year and the battery had NOTHING and this charger started at like .2amps and slowly worked it's way up as the battery would take more charge till it got to the 10amps I had it set for. It was flashing an F02 or such error at times on the charging amps display, but it worked!

 Has modes for Normal Lead acid, Gells, and AGM types. Has desulphate mode, equalize mode, and other nice features.

 If you need to buy a charger I would recomemend this type. I paid $45US for my 2/10/15amp charger. The only smart charger I have had that will at least TRY to work on ANY battery so far.

If you try a "Smart" battery charger and it will not try to charge your batteries or it shows an error code saying the battery is junk, try a different charger!

 Also sometimes you can "trick" the braindead stuff to work by connecting a charged battery for a few minutes to the dead one then take the charged one back off once the charger is working a few minutes and then it will stay on.

If you have a bunch of those batteries you should be able to save at least some of them I would think, maybe most of them. It may take a bit of time and playing around, but if they are not physically damaged like shorted you may be ok.

[alibro]

Thanks for all your help guys,

I have a charger with an over night trickle charge feature and will try it on one tonight. I didn't realise they could take up to a week to recover. These batteries were a few years old when I got them. They were replaced in the UPS during a routine service so I thought they would not last much longer anyway. I used them as my battery bank, charging them with a wind turbine but when the turbine went up in smoke the batteries got drained and I never got round to recharging them. That was around two years ago so they have gone down even more since then.

Alibro

[nothing to lose]

Sat dead about 2 years? WOW.

 That is a long time to be dead. Try them all and any that don't seem to be comming back around try other things before tossing.

Alot of times it's just geussing if something really works or not. I mean you can look at a stick and see it is broken, you can look at a battery and GEUSS why it's not working.

 A GEUSS that might work is to take batteries not working well and use an always on type charger. One of those that will turn on and run a 12V fan without connecting a battery to make it work. Connect a turn signal type flasher inline with the battery and charger. That should make a crude pulse charger sortof. The flasher should work like normal, kicking on and off, thus sending shots of charge to the batteries.

Like I say, it's a geuss type thing. I geuss it worked on batteries for me, but do I really know?? My weak batteries did work better after, but maybe 2 more days of 2amp charging would have done the same thing??

It was an idea I got from somethng I read here long ago to try a flasher.

[asheets]

Do a search here for a drawing called watgas.gif.  I've had pretty good results with that thing as a battery buzzer.

[DingBat]

Courtesy of wooferhound, just linked to the one from his post.

--DingBat

[alibro]

Do you think it would work on 240V ac?

[DingBat]

It should, however you'll need higher ratings on the caps an bridge diodes.

I wouldn't go less than 660V for either. If you left this hooked up indefinitely it'd try to get your batteries voltage up to 240VDC.

I'd use a 240V to 120V transformer as a plus you'll get some isolation from the line.

It'd likely be cheaper/safer to go the transformer route. I'd get a 120V to 15V instead of the direct hook-up to the line if this is planned to be used more than experimentally.

--DingBat

[alibro]

I guess going straight from 240Vac to 15Vac or so would do the same thing. I might be able to get a high powered transformer from a big old UPS which is lying around work. I just need to check out the voltages and give it a try.

Thanks again

AliBro

[DingBat]

Even if you use a 120V to 12V transformer, on 240V input that's 24V.

Seems a bit safer than 240V or even 120V through a 12V battery in case something goes wrong. I'd rather have twice the battery voltage max, rather than 10 or 20 times the battery voltage. I've had too many SLA's crack open on me in float service to trust running too much more than rated voltage through them, even if recovering.

-- DingBat

(Elec-Trak owner, FYI http://www.elec-trak.com/)

[nothing to lose]

I had forgot what Watgasgif was by name, yes I like that one also.

Be AWARE the battery voltage will try to climb to whatever the line voltage is and you have to watch it close. I think that's kinda been mentioned maybe now.

 I should be using that more often myself, but for most things I been needing to just connect a charger and forget it for awhile and that is not a good system to just forget, so I been using a comercail charger alot more myself.

It's a pretty easy simple charger that works well if you watch it and careful. Good for about any voltage bank and any amps as limited by the caps used.

Battery holds the volts down as it charges and the amps are held back by the caps.

Once the battery starts reaching full charge though the volts rise unlimited till it fries a battery if not watched or controlled in some way.

Be sure to heat sink the bridge rectifier well also.

I had found a Variac at a scrap yard, it worked, I used it on 120V to adjust line volts to 14V, the caps to hold back the amps, and rectifiers to convert the AC to DC.

 An adjustable transformer like that was good for any volts, mine was 15amps I think, and using caps to cut back to 2 or 3 amps I could charge about anything.

Dial in 7V for 6V batteries, 54V for 48V bank, it was nice. My Variac got broke though, busted a wire and I have not tried to solder it or such yet, just put it away for now.