Dead SLA lead acid - Page 1
Forum section: electronics / beginners

author: paulca
author_rank: Super Contributor
timestamp: November 27, 2017, 01:03:47 pm
content: I have a 7Ah lead acid SLA battery which the last time I used it about two years ago worked fine. It was fully charged, used for a small amount of time, not enough to come close to flatten it and then stored.I brought it out to check and charge it and it's completely dead.Putting a DMM across it's terminals reads about 4V, but connecting it to a charger gives "Connection Error". Putting my bench supply on it's terminals give me 14V 0.000amps.Is it completely dead or is there anyway to force it back to life?

author: sstepane
author_rank: Regular Contributor
timestamp: November 27, 2017, 01:07:22 pm
content: Hi there,You could try to fill it with distilled water, wait a bit and try to charge it. If You don't see filling holes - it might be hidden under some plastic cover and glued or welded (ultrasonic welding).

author: paulca
author_rank: Super Contributor
timestamp: November 27, 2017, 01:16:07 pm
content: Thanks. I found this:https://www.instructables.com/id/How-to-revive-old-lead-acid-batteries/It seems that sealed and maintenance free batteries can in deed dry out.I might have a go at recovering it. I also have another 10Ah motorcycle battery that I might try first as it's "maintenance free", but not sealed, it has caps that can be pryed off.

author: Monkeh
author_rank: Super Contributor
timestamp: November 27, 2017, 01:27:10 pm
content: It's dead, and you really can't just sit a lead-acid on a shelf untouched for two years. They don't like it.

author: paulca
author_rank: Super Contributor
timestamp: November 27, 2017, 01:44:04 pm
content: Quote from: Monkeh on November 27, 2017, 01:27:10 pmThe general blurb on SLAs is:* Among the lowest self-discharge of rechargeable battery types.* 10 year life.* Cannot be stored in discharged state.Battery University suggests they can be stored for up to 2 years from a 70% charged state. It does say to check them once in a while though. I'm wondering if it managed to discharge somehow. It was connected to a device (an RC buggy starter box) which has a big old ignorant mechanical contact switch with a good 8mm gap so no change of arc'ing. Big heavy spring too so unlikely to have been accidentally switched on.Mine was stored for 2 years. However the dozen or so LiPos stored at roughly the same time had lost about 1 tenths of a volt from their storage voltage and all but one were absolutely fine. (the one that wasn't fine was a tiny 280mAh single cell that was puffed up and I discharged it with some parallel LEDs and binned it once flat). The rest I restored back to storage voltage and put them away again.

author: Monkeh
author_rank: Super Contributor
timestamp: November 27, 2017, 01:45:16 pm
content: 2 years is pushing your luck with self discharge on an SLA, IME. And all it takes is one weak cell.

author: sstepane
author_rank: Regular Contributor
timestamp: November 27, 2017, 01:49:09 pm
content: It takes longer to discuss than to try it. Distilled water costs a penny, if it is dead - so dispose of it properly, if it is of any use - think of it as of saving a little bit for greener planet =)

author: Mechatrommer
author_rank: Super Contributor
timestamp: November 27, 2017, 02:51:53 pm
content: dont dispose it. its a good paperweight or to hold something in place. i keep several dead car SLAs, recently to raise some wood panel/mdf for sawing and painting. a very handy bricks with handle built in... in the mean time i'll wait until a magical method to be discovered to ressurect them...

author: tautech
author_rank: Super Contributor
timestamp: November 27, 2017, 03:23:58 pm
content: Quote from: Mechatrommer on November 27, 2017, 02:51:53 pmWon't happen.Once they're sick it's all downhill until plate sulphation is so bad the plates force against each other and swell the cell/battery.Like any LA battery it must be charged periodically and you will get 10 years IF you keep them fully charged.I've used 7AH SLA's for spotlight hunting of vermin for decades and I refresh batteries NO more than every 2 months, used or not. After use, charge ASAP to minimise plate sulphation growth.Desulfation battery zappers do help prolong plate life but are an unnecessary substitute for poor battery maintenance.

author: CJay
author_rank: Super Contributor
timestamp: November 27, 2017, 03:30:21 pm
content: Go low and slow.I've just recovered 2 1.2AH Yuasa batteries out of an industrial DIN rail UPS, they were brand new but had been allowed to discharge to 4V and 0V, the 4V one came back in a couple of days, the 0V one took just over a week and initially showed as close to zero current as made no odds but it slowly climbed and hit the current limit I'd set (half the recommended max charge current).Both of them sit at ~12.5-12.6V after being disconnected from the bench supply for a few days and both easily power a 20W 12V halogen bulb with no noticeable dimming after five minutes and recover to 12.5V within five minutes which suggests to me they're in fairly good condition despite the abuse they've been subjected to.I've got my eye on a bank of 24 cells in a phone backup system, think they're 540AH each, now

author: rsjsouza
author_rank: Super Contributor
timestamp: November 27, 2017, 03:42:48 pm
content: Quote from: tautech on November 27, 2017, 03:23:58 pmExactly. As others have said, Lead-Acid batteries tend to die if left untouched for prolonged periods. Depending on the construction you can get a very low self-discharging, but even with that I haven't seenpreviously usedbatteries last two years intact.The condition worsens if it was extensively used in the past, as excessive sulfation can cause the plates to crack, which is an unrecoverable problem.

author: macboy
author_rank: Super Contributor
timestamp: November 27, 2017, 04:00:55 pm
content: Quote from: CJay on November 27, 2017, 03:30:21 pmWhat did you do?

author: paulca
author_rank: Super Contributor
timestamp: November 27, 2017, 04:15:43 pm
content: I'm told the lack of charge current <1mA can be normal for a battery needing recovered. The idea is to bump the voltage up to 10% over the max boost charge voltage (15.5V) and leave it for a good while (with a LOW current limit set). Apparently the voltage can break down the sulfate crystals and convert them back to active material. If it doesn't take a normal 0.1C-0.3C charge current within 24 hours it's unlikely to be recoverable. I should probably check it's not dry though, if the cells are completely glued closed.Obviously if the battery does recover it will probably have lost 30-50% of it's capacity. If any of the cells are completely dead or short they could pop their caps (or vent) if I attempt to charge it to full 14.4V again.To be honest I just wanted a crack at it and I have on real need for an SLA currently, as a 5Ah 3S LiPo is more reliable, lighter, smaller and can deliver at least as much current. Just needs as much or more respect for fire safety of course.

author: tautech
author_rank: Super Contributor
timestamp: November 27, 2017, 04:21:06 pm
content: Quote from: paulca on November 27, 2017, 04:15:43 pmA gassing charge would not be advisable for SLA's but they're fine for old LA's where you can top up the electrolyte though.

author: paulca
author_rank: Super Contributor
timestamp: November 27, 2017, 04:30:39 pm
content: Quote from: tautech on November 27, 2017, 04:21:06 pmDoes it matter that there is no current flowing into the battery? My idea was to give it at an hour or two on 15.5V to see if it starts to take any current at all. If it starts to take current I'll set the current limiter to like 10mA and let the voltage come down to 13.5V on CC (float voltage on the SLA in question), then set the current limit up to 0.5A and ease it up slowly. I'm not going to leave it over night and I need the PSU tonight for electronics stuff, so I just want to see if I can get it to respond within an hour or so.Any sign of heat, venting, swelling or fizzling noises and I'll call it quits.

author: CJay
author_rank: Super Contributor
timestamp: November 27, 2017, 04:36:06 pm
content: Quote from: macboy on November 27, 2017, 04:00:55 pmJust connected them to a bench PSU that was current limited to roughly half their maximum charge current and 13.6V then waited, I've been getting useful batteries this way for decades, I used to get a lot of abused UPS battery packs and it seems to work often enough that it's worth a try.The 0V one took a few hours to begin to take enough current to register on the PSU ammeter, once it started it was about two days before it hit the current limit and then after a few more hours it seemed to stabilise at a couple of hundred milliamps, didn't get warm to the touch (if it had got too warm I'd have thrown it away).Wouldn't rely on them for anything important but as a handy battery to run, for instance, the Pixie transceiver I've been playing with, they're ideal.

author: tautech
author_rank: Super Contributor
timestamp: November 27, 2017, 04:51:45 pm
content: Quote from: paulca on November 27, 2017, 04:30:39 pmIf you get into the electrolyte gassing zone/voltage it's unlikely you'll observe anything.Sulphation is the primary cause of inactive LA and SLA battery failure. There are a few types (long time since I played with all this) but the soft bonded sulfates are just part of the charge/discharge cycle were when the sulfates are released into the electrolyte when charging to regain the specific gravity of electrolyte.The hard bonded sulfates are the problem, they form a blind over the plates to limit its capacity and are very difficult to remove/recycle.Good luck with it, I've spent many hours years ago on this wild goose chase that educated me to take better care of all LA batteries I own. I now spend much less time fiddling and more on charging to keep them in good order.You occasionally win one but many are lost.

author: paulca
author_rank: Super Contributor
timestamp: November 27, 2017, 09:58:13 pm
content: Well, it's been on at 15.5V for an hour and the PSU isn't registering any current yet. However about 5 minutes ago I connected the DMM and it's risen from 700uA to 1.8mA and continues to rise slowly. It fluctuates a few hundred uA from time to time but that could just be environmental noise.Rather annoyingly my PSU still reads 0.000A. Yet if I dial in 0.001mA current limit the CC limiter kicks in. Seems the current display is slightly off.2.5mA by the time I wrote this post. However I'm going to bed and I'm not leaving this running overnight.Woo hoo! She's going!3.1mA and the PSU suddenly started registering 2mA.I'll play more tomorrow.

author: CJay
author_rank: Super Contributor
timestamp: November 28, 2017, 06:53:21 am
content: Now it's starting to take charge I'd wind the voltage down to something more like a recommended charge voltage or you'll find it heats up the battery rapidly (it's why I decided on 13.6V)You'll also find the charge current will take off and bang up against the current limit so be sure it's set at a decent level, as above, I tend to use half maximum float charge limit.I'm sure someone will tell me it's a terrible idea and can't possibly work but I found giving the battery a good thump flat down on a wooden worktop also seemed to helpThe two 1.2AH batteries I 'recovered'?The one that was 0V, after approx two weeks sat untouched, terminal voltage is 12.35V, the one that was 4V, again untouched for ~2 weeks is 11.81V so I'll put them both on low current charge this evening (work has to happen first).

author: floobydust
author_rank: Super Contributor
timestamp: November 28, 2017, 07:05:32 am
content: It's dead Jim.Sulfated SLA plates never recover, I've tried charging them for eons and the terminal voltage comes up but high internal resistance (no decent output current).There are some pulse de-sulfator projects but the ones I've tried did not work. Lead sulfate crystals are just impossible to get rid of in a gel cell it seems.Once the rotten egg stench shows up, then you'll know...In flooded lead-acid batteries, all I've seen work is pumping very high charge current through them; basically a bubbling acid, hydrogen-generating festival to dislodge or dissolve the sulfate crystals.

author: tautech
author_rank: Super Contributor
timestamp: November 28, 2017, 07:13:36 am
content: 13.6V is too low.Standby (float) is typically 13.8 but that's for continuous connection to a voltage source.Cyclic usage is more typical of portable battery use and charge voltage is higher at 14.4-15V depending on brand.With a bench PSU that you can monitor current (voltage set in correct range) watch for the current to fall away as full charge nears.If you get the chance with these old batteries give them some mild exercise with a couple of discharge cycles before trusting them as anything like worthy.Quote from: floobydust on November 28, 2017, 07:05:32 amYep, it's called a gassing charge or sometimes equalisation charge, already mentioned above.

author: paulca
author_rank: Super Contributor
timestamp: November 28, 2017, 07:38:36 am
content: Quote from: tautech on November 28, 2017, 07:13:36 amBoth are right, this battery actually has it's charge parameters printed on it, which is rare.Cycle use: 14.4-15.0V(20*C)Standby use: 13.5-13.8V(20*C)Initial Current: 2.1A MaxI don't really have an application for this battery, so I don't think I need to trust it. I'm trying to recover it purely for fun.

author: Circlotron
author_rank: Super Contributor
timestamp: November 28, 2017, 08:03:18 am
content: Back in 1990 I worked at a place that sold UPSs. Some had been in storage for several years and the batteries would be replaced before sale. The old batteries would be typically at 1 or 2 volts. I experimented a whole heap with the old batteries and eventually had great success with the following formula: Apply a REVERSE charge with current limit set to 2% of Ah rating for 48-72 hours. The battery may not draw any current initially but just leave it alone. After this time, set the charge to normal polarity and charge for 3-4 days, still with the 2% current limit. During this time, do NOT be tempted to wind up the current limit - one cell will start to get hot and then it is junk. Fixed many new but neglected batteries this way. One 12v 24Ah SLA Yuasa started off at 2 volts and had been sitting for about 3 years, got it going and used it in my Diahatsu Charade for 2 years until I sold it.

author: tautech
author_rank: Super Contributor
timestamp: November 28, 2017, 08:21:58 am
content: Quote from: Circlotron on November 28, 2017, 08:03:18 amWhich is bloody good considering their max charge current.I've got a pair of 45AH SLA's that I'mto use for automotive use as they're only rated to 15A max charge current.Datasheets on SLA's can be very revealing.

author: CJay
author_rank: Super Contributor
timestamp: November 28, 2017, 09:05:32 am
content: Quote from: floobydust on November 28, 2017, 07:05:32 amI've definitely seen this and thrown a few away for it too, hence the reason I load them up with a halogen bulb and monitor terminal voltage, if it stays in what I consider a reasonable range and recovers in a reasonable period of time after the load is removed then I consider the battery good enough for my needs though I'd never put it into anything important like a UPS or emergency lights.

author: CJay
author_rank: Super Contributor
timestamp: November 28, 2017, 09:21:44 am
content: Quote from: tautech on November 28, 2017, 07:13:36 amDepends on the battery, for float charging the 1.2AH batteries I have used as an example here Yuasa quote 2.275V per cell +/- .005V, which works out to somewhere between 13.62V and 13.68V.I figure 20mV below the lower recommended voltage isn't that big a deal and adjusting my 10A bench supply that accurately isn't that easy so it's a 'nominal' 13.6V.13.8V would also work just fine I think, again, 120mV over the upper recommended limit isn't a big deal in this situation either so 13.6 or 13.8, it's not going to make a huge difference, it'll just take a marginally more or less time to reach full charge.For Cyclical use they quote a higher voltage, I think it's 14.5V as you say but my prime aim when trying to recover a battery is to keep it from heating up if at all possible so low and slow seems to work better in that respect, I can charge at higher rates once I've worked out if the battery is likely to work in a useful fashion and it's been through a couple of charge/discharge cycles.

author: IanMacdonald
author_rank: Frequent Contributor
timestamp: November 28, 2017, 11:59:38 am
content: Frankly if it's this far gone it isn't worth bothering with. If they are left discharged for a long time the plates pick up a thick layer of lead sulphate, which is an insulator.

author: floobydust
author_rank: Super Contributor
timestamp: November 29, 2017, 01:54:17 am
content: Quote from: tautech on November 28, 2017, 07:13:36 amThey hit a (flooded) car battery with >25A charging current, regardless of cell voltage, to blast off the sulfate out of the plate's pores.I saw it a battery recycling company. I guess nothing else worked for them.I've never seen eons of trickle charging do anything to help a sulfated battery.