What causes lead acid battery cells to short out? - Page 1
Forum section: electronics / general

author: Red Squirrel
author_rank: Super Contributor
timestamp: May 14, 2019, 03:34:06 am
content: Not exactly renewable energy (UPS) but figured it might fit here.I noticed one of my 12v batteries was getting warm in my UPS. I've had this happen before, twice actually, and it's usually a shorted cell. What ends up happening is because 1 cell is shorted out it essentially turns into a 10 volt battery as it's 5 active cells instead of 6. Downside is the battery is basically a write off at this point. I could try to carefully open it and try to see if I can find and clear the short, but it would be a messy job.So my question is, what causes that in first place and anything I can do to prevent it? I figure it's material shedding and then bridging between two plates. Is this just because they are cheap batteries, would I be better off going with more expensive ones like 6v golf cart batteries? The ones I'm using now are RV/marine so think because they are also meant for starting the plates are not as robust as a full deep cycle, is that right?Still not sure if that is what is happening with this particular battery, I'm letting it sit unconnected to see how low the voltage gets but when I first disconnected it, it was 13.2v when the other one also connected in paralell was 13.3. So not a good sign that it dropped that fast. I don't have control over the float voltage as the UPS does that, but they usually float at 13.5 which is reasonable.Just wondering what is best course of action here, should I just look at getting better batteries, or is there anything I can do to prevent this? I do add water every now and then to top them up. I'm almost wondering if I'm somehow triggering the short when I do that, could that be?Edit: tested the cells with the hydrometer, and yep one of them is completely dead. Another one bites the dust... really need to figure out what's causing this, this is the 3rd one I lose now. Will I have better luck going with golf cart batteries instead of the RV/Marine ones I'm using now?

author: bsdphk
author_rank: Regular Contributor
timestamp: May 14, 2019, 06:17:01 am
content: Lead-Acid batteries are quite picky when it comes to charging conditions and raised temperatures.Both too high and too low float-charge voltage will shorten the lifetime, through different chemical mechanisms, and the ideal charging voltage depends on the temperature (3mv/cell/°C) and the exact alloy of lead used in the electrodes.In general UPS's use the batteries in a very aggressive way, getting better as the UPS gets (much) more expensive.The best and simplest way to get longer lifetime out of your batteries is to not mount them inside the UPS where the temperature is usually 30-40°C, but freestanding and preferable no warmer than 25°C. The cabling and fusing is important, and as a rule you will need more copper in the cabling than were used inside the UPS, because the cable is longer.There is a conference called "BattCon" every year, there are a lot of good papers presented there about just how troublesome lead-acid batteries are and what to do about it.

author: Red Squirrel
author_rank: Super Contributor
timestamp: May 14, 2019, 09:36:30 pm
content: In my case I don't think temp is the issue, as they tend to run fairly cool. They are also in a battery cabinet with room to breathe. Though I had to disable the fans since they were cheap fans and the ballbearings started to go.Also any way to recover from a shorted cell or is it pretty much over? Even if I was to remove the short the cell would be at 0% discharge, so is that even recoverable?I always just get a new battery and recycle the bad one but it feels so wasteful.For the time being I won't replace this one though, I'll keep the 3 I got going and wait till I upgrade my system. Want to build a separate battery box as this cabinet makes them harder to maintain. I may also upgrade to a 48 volt system at some point. Harder to find the equipment for that though. The big name brands like Cordex or Eltek don't really sell to individuals.I kinda want to incorporate solar into the system too but we get so much snow it's a lot of maintenance to keep the panels clear every day.

author: NorthGuy
author_rank: Super Contributor
timestamp: May 15, 2019, 04:22:42 am
content: A short cell will have less water, and very low specific gravity, and zero voltage. Is this what you're observing?

author: Red Squirrel
author_rank: Super Contributor
timestamp: May 15, 2019, 04:51:03 am
content: I don't have a way to test voltage as it's too awkward getting a multi meter in there, but what basically happens is the specific gravity of all the cells is super high (overcharged) but the one cell is super low (basically pegged as low as it can). The voltage also reads 10.6ish volts if I recall when it's sat for a bit. If I charge it, it will actually go high enough but quickly drop back to 10.So it may not be shorted, but it's clearly bad in a way or the other, but also not open, otherwise I would just get no voltage.As a side note, I was just looking at battery prices on a solar site and noticed that the bigger you go, the more expensive they are per amp hour, does that seem right? Is there still an advantage of going with bigger batteries vs just having more small ones? I'm thinking more small ones means it's not as expensive if one does die, but I'm hoping that by going with higher end solar rated batteries they will simply last. It's one thing to lose charge over time as they age, but these are dying completely on me.

author: mvas
author_rank: Contributor
timestamp: May 15, 2019, 06:46:11 pm
content: RV / Marine Batteries arenottrue Deep Cycle Batteries.It is a hybrid "Engine Starting & Trolling Motor" type battery.Who is the Mfr and what is the Model # of the battery?What are the voltage & amperage details of your 3-Stage Charger?When was the last time that you Equalized this battery?What is the WARRANTY period?That will tell you how long the mfr expects the battery to last.Is the battery, now older than the warranty period?Golf Cart batteries are typically good / inexpensive Deep Cycle batteries.Typically, a shorted cell is death ...

author: Red Squirrel
author_rank: Super Contributor
timestamp: May 15, 2019, 07:30:09 pm
content: Yeah I kinda figured too, when I originally picked this battery I had not noticed they were a hybrid and not full deep cycle but they are indeed not true deep cycle. Then I just kept buying them so I can match them up. But after 3 deaths I think it's time to stop replacing them and move on to another model. These cheaper retail store batteries don't really tend to have any specific specs or a data sheet but this is the one:https://www.canadiantire.ca/en/pdp/motomaster-nautilus-group-27-starting-deep-cycle-battery-0102799p.html#srpThe warranty is like a year if I recall, it's not much. Used to be more but they actually dropped it a few years ago. This particular one is from 2013. I would expect to lose some charge but not just outright die this early.They also have a full deep cycle version of that battery, which would probably be better, but think I will look into the golf cart ones instead. Am I right to think that by going 6v because the cells are bigger there's also less chance of failure? Ex: thicker plates, or do they just use more thin plates?The inverter-charger floats at 13.5 pretty much constantly, which is good but it does have a bulk/equalize phase as well after a power outage. It will go up to 14-15 volts for a bit. Don't think I've ever seen it go past that. Every now and then I'll turn the breaker off to the UPS as a routine capacity test, which also forces the inverter charger to charge at a higher voltage to somewhat give it an equalize once power is returned. (it's bulk/absorption charge really but guess it still kinda equalizes it). This is it here:https://www.tripplite.com/750w-powerverter-aps-12vdc-120v-inverter-charger-auto-transfer-switching-2-outlets~APS750Though you got me thinking... could lack of proper equalize be an issue causing sulfation of plates and more material to eventually shed? I don't have any real control over telling it to do an equalize, but I could maybe just make sure to cut power to it more often to force it into it's bulk/absorb modes at least.I do eventually want to look at a dual conversion setup with rectifiers/inverters and I'll probably end up making my own rectifiers as they are actually very hard to find. They are used in telecom but not something that's really sold to individuals. If done properly they can have different options such as weekly equalize. A crude way would also be to use a solar charge controller, I think you can just feed a DC source straight to the input of one right? As long as it can support that voltage.

author: NorthGuy
author_rank: Super Contributor
timestamp: May 31, 2019, 04:51:55 am
content: Quote from: Red Squirrel on May 15, 2019, 04:51:03 amBigger deep cycle batteries can discharge deeper (say 80% compared to 50% with smaller batteries such as Golf Cart). They also give you more charge/discharge cycles and therefore will last much longer. So, bigger batteries are actually cheaper in a long run.

author: floobydust
author_rank: Super Contributor
timestamp: May 31, 2019, 06:20:08 am
content: I don't see you doing anything that would give such short battery life due to plate-corrosion failures.Is it the same cell, closest to the (-) terminal, that shorts on the Motormaster Nautilus? It seems they are low quality now and people finding this happens repeatedly on their battery banks.I would make sure hydrogen cannot build up in the battery box, it should have some air vents. Fans are a bit overkill. I can dig for a CSA battery standard that talks CFM air exchange for the number and size of batteries.

author: SparkyFX
author_rank: Frequent Contributor
timestamp: June 08, 2019, 02:10:40 pm
content: If a cell actually shorted, then it probably is conductive sludge at the bottom or a plate corroded and tipped over. If its internal resistance got too high it might have a sulfated surface area and can be resurrected by cycling or it might be too low on electrolyte (fill up if it is user maintainable).There are models for photovoltaic buffering, not built like the automotive type to withstand much vibration or high cold crank amps (grid shape), but for amount of cycles it can withstand. A high weight per amphours should be a good indication about the thickness of the lead plates.

author: Red Squirrel
author_rank: Super Contributor
timestamp: June 09, 2019, 03:26:31 am
content: Quote from: NorthGuy on May 31, 2019, 04:51:55 amAhh I see makes sense then! I was kind of thinking if the smaller ones are cheaper then it makes sense to just do more strings, but if the bigger ones last longer then it makes sense to go with those.I don't recall which cell shorted, but the last one was the cell closest to the positive. I do recall one where it was not an end cell but one of the more middle ones. I'm starting to think this may just be a quality control issue, is that to be expected from cheaper batteries, and is it something not likely to happen on higher end ones? I'm willing to pay more if it means they last longer.As a side note how good are AGMs? I'm a bit worried that they still vent a little bit such as if I do an equalize, but don't think you can add water to those.

author: mvas
author_rank: Contributor
timestamp: June 15, 2019, 02:35:14 am
content: Quote from: Red Squirrel on May 15, 2019, 07:30:09 pmThat battery has A 1 YEAR WARRANTY.Every day after 1 year, is a bonus.If this battery was born in 2013, then I would expect it be dead in 2019.Yes, the plates have shed and shorted one cell.Yes, one day it goes from 12.8 Volts, then down to 10.6 volts = shorted cell .How often do you "Deep Discharge" this battery?How many Deep Cycles has this battery provided in 6 years?Is your avg Depth of Discharge = 50% ?How many Ah's consumed per deep dischargeIt is only a 80Ah battery, so 50% DOD = 40Ah which is only 4 hours at 10 amps.Batteries die from use and non-use ( aging )Even if you do not use a Lead Acid battery ( Float Charge ) it will not last forever.3 - 5 years is typical for a Marine-Hybrid type batteryThe Plate thickness is not based on volts nor amp-hoursPlate Thickness ...0.040" = Automotive SLI battery ( sponge lead )0.070" = Marine-Hybrid Battery0.110" = GC2 Golf Cart0.265" = Deep Cycle Rolls-Surrette Battery ( paste lead )Many thinner sponge lead plates is for starting cars.Fewer thicker paste lead plates is for deep cyclingThere is no hard line between what is a "car" battery and what is "deep cycle" battery.There is a huge range of plate thickness, ratings and naming conventions, in the middleTypically, any plate thicker than 0.100" ( GC2 Golf Cart ) is considered a "Deep Cycle" battery.The thicker the plates, the better for Deep Cycle applications.

author: NiHaoMike
author_rank: Super Contributor
timestamp: June 15, 2019, 02:52:38 am
content: Quote from: Red Squirrel on June 09, 2019, 03:26:31 amGo with lithium. Keep them at 4V/cell for standard lithium and 3.45V/cell for LiFePO4.

author: mvas
author_rank: Contributor
timestamp: June 15, 2019, 02:53:05 am
content: Quote from: Red Squirrel on June 09, 2019, 03:26:31 amStrings?You have strings of batteries?What exactly are the connection details ?Parallel and / or series ?

author: mvas
author_rank: Contributor
timestamp: June 15, 2019, 03:15:31 am
content: Quote from: NiHaoMike on June 15, 2019, 02:52:38 amAt 4 times the price for the same "usable" amp-hours, Lithium is still too expensive.Lithium does not last 4 times longer.

author: Red Squirrel
author_rank: Super Contributor
timestamp: June 15, 2019, 03:25:23 am
content: Quote from: NiHaoMike on June 15, 2019, 02:52:38 amToo hard to find and still very expensive, and I don't like the idea of messing with that, too dangerous if you mess up the circuitry/logic etc. Lead acid is more forgiving and everything is designed for it. That and you have to balance charge lithium ion which makes the system WAY more complicated than I want to. At some point I do want to look into them, hopefully when they become easier to find. Yeah you can buy old laptop batteries and stuff but just too much trouble having to test them all etc.Quote from: mvas on June 15, 2019, 02:53:05 amWell right now my strings arn't exactly traditional strings, just a bunch of 12v in parallel on separate switch/fuses. I do eventually want to do a 48v system though so I would use 2 or more strings of 4x 12v or 8x 6v cells in series. Always want to do at least 2 strings for redundancy.I was kinda wanting to do solar, and then it would just be one big system, but I only have room for around 3kw worth due to physical space on the roof, shadows etc so it's not really worth it. Especially after I saw all the work involved with the small system on my shed this winter. I tried to keep it going but ended up having to just shut off everything. Too much work to keep up with the snow. Though I might come up with an automated mechanism at some point then I can look at putting in a bigger system.Quote from: mvas on June 15, 2019, 02:35:14 amAre you saying they are literally designed to fail after warranty? For their cost (especially bigger ones) I would hope they can last a good 10-20 years at least! They have been deep cycled a few times, but that's about it. I usually start shutting stuff down when they hit 11.3ish volts. If it's a planned power outage and it's going to end soon I sometimes stretch a little longer. Ideally I don't like to go lower than like 11.8ish though, and it's rare they get that low as we don't really get that many power outages here that last long.

author: NiHaoMike
author_rank: Super Contributor
timestamp: June 15, 2019, 03:04:25 pm
content: Quote from: mvas on June 15, 2019, 03:15:31 amSurplus EV battery packs are actually getting quite competitive with lead acid on a per kWh basis and are already cheaper than sealed lead acid. BMS modules with built in balancing are very common nowadays.Something to consider is implementing hardware/software to switch all devices to their lowest runtime power levels when operating on battery power. Probably just a matter of adding some simple scripts to the UPS monitoring software to force the lowest supported CPU frequency and/or offline all cores but one.

author: Red Squirrel
author_rank: Super Contributor
timestamp: June 15, 2019, 03:19:45 pm
content: Quote from: NiHaoMike on June 15, 2019, 03:04:25 pmIs that actually something doable? Like without proprietary software that would only work in Windows? Would not be a bad idea to get more run time.There's hardly any EVs here so I don't imagine battery packs would be easy to come by. Shipping that from the states would probably be super expensive too. Still a lot involved in disassembling it as well to get all the cells. If it got taken out of a car there's probably a reason for it, such as it having a bad cell or other defect so have to find it.I'm hoping at some point they will make lithium ion batteries that are basically lead acid replacements, where you can float them and everything, and they just take care of everything internally. The biggest attraction to lead acid is that you can float them at a single voltage with all the cells in series and they're happy. You may add a mid point voltage check just to monitor for any issues and that's it. They are very simple to setup in solar/backup situations.

author: NiHaoMike
author_rank: Super Contributor
timestamp: June 15, 2019, 04:01:36 pm
content: Quote from: Red Squirrel on June 15, 2019, 03:19:45 pmOpen source UPS software like apcupsd and NUT support custom scripts.http://www.apcupsd.org/manual/manual.html#customizing-event-handlinghttps://networkupstools.org/docs/user-manual.chunked/ar01s07.html#_the_advanced_approach_using_upssched

author: Bratster
author_rank: Frequent Contributor
timestamp: June 15, 2019, 05:29:30 pm
content: Quote from: Red Squirrel on June 15, 2019, 03:19:45 pmThose already exist. Look up battleborn batteries.That's just one of two or three manufacturers.They're very expensive up front, but if you take into account the life of the lithium battery and compare that against the cost of the equivalent lead acid battery and the replacement cost of the lead acid to keep the same effective life and capacity they are cheaper in the long run.Also keep in mind that when comparing those 100ah lithium batteries you don't compare to a 100ah lead acid, you would compare to a 200ah. Since you don't want to take the lead acid below 50% discharge to extend the life.Sent from my Pixel 2 XL using Tapatalk

author: Red Squirrel
author_rank: Super Contributor
timestamp: June 15, 2019, 06:41:00 pm
content: Quote from: NiHaoMike on June 15, 2019, 04:01:36 pmOh that I know, I was talking more about throttling the CPU and such. My UPS is somewhat custom using an inverter-charger and I have a completely separate arduino to detect power outages and read voltage, so I need to add scripting capability to it but it's planned. It's more than just a UPS app, it's a whole monitoring app. Right now it has basic stuff like sending emails or showing an alert on a "noc view" screen. I'm even monitoring mouse traps with it. Once I add scripting capability I could technically script anything I want triggered by any event.

author: Red Squirrel
author_rank: Super Contributor
timestamp: June 15, 2019, 06:42:46 pm
content: Quote from: Bratster on June 15, 2019, 05:29:30 pmGood to know, maybe eventually they'll make their way in stores like Canadian Tire. That's the issue with lot of this stuff it's not easy to get if it's not actually available for direct sale in Canada. As long as they can be used as a drop in replacement for a lead acid, including be put in series, then they would probably be a very viable battery for UPS / renewable.

author: NiHaoMike
author_rank: Super Contributor
timestamp: June 15, 2019, 07:05:17 pm
content: Quote from: Red Squirrel on June 15, 2019, 06:41:00 pmhttps://wiki.archlinux.org/index.php/CPU_frequency_scaling#cpupower

author: G7PSK
author_rank: Super Contributor
timestamp: June 27, 2019, 07:53:32 am
content: Leads acid batteries do develop internal shorts, the plates disintegrate and the material builds up in the bottom of the cells until it reaches the bottom of the plates and shorts them out. With the old fashioned wet type you can flush them out, something I have done many times over the years. With gel and glass absorbed mat type cells the usual thing is warping of the plates which crushes the separators nothing you can do about that except to try and avoid overheating. I prefer wet type batteries unsealed for this reason.

author: NorthGuy
author_rank: Super Contributor
timestamp: June 27, 2019, 01:36:56 pm
content: Quote from: Bratster on June 15, 2019, 05:29:30 pmBased on the information I could gather (and my own experience with Laptops, phones and alike) Lithium batteries do not have very long life, certainly not dramatically longer than good LA.Quote from: Bratster on June 15, 2019, 05:29:30 pmBig deep-discharge LA batteries can be discharged to 80% DoD without problem. With Lithium batteries, you probably will want to cycle them between 20% and 80% DoD (60% usable) to make their life longer.

author: Bratster
author_rank: Frequent Contributor
timestamp: June 27, 2019, 06:02:57 pm
content: Quote from: NorthGuy on June 27, 2019, 01:36:56 pmI will go double-check my information when I get home from work.I'm talking about lithium ion phosphate (LiFePO4) batteries not standard lithium ion.This is the company I was looking at:https://battlebornbatteries.com/(I'm not affiliated with them in any way shape or form, they are just the ones that I was looking at when I eventually put some solar panels on my truck.)Sent from my Pixel 2 XL using Tapatalk

author: NorthGuy
author_rank: Super Contributor
timestamp: June 27, 2019, 09:52:08 pm
content: Quote from: Bratster on June 27, 2019, 06:02:57 pmI found this comparison on their Web site:https://battlebornbatteries.com/breaking-better-battery/I cannot tell what are the LA batteries they're comparing, I can only tell you about mine. I bought them 7 years ago. They're about the same price (slightly over $1k/battery when I bought them). They have 673 AH capacity, but they're 6V, while "Battle Born" are 12V. Counting 200 AH per day, it's roughly 500,000 AH over 7 years. Re-scaling the cost to 12V, it's $2k/500,000 = $0.4 cents/AH. I cannot tell how long my batteries will last, but even if we only count up-to-date benefits, it's still roughly 25% of what they say the LA battery would cost and about equal to what they claim the "Battle Born" batteries can do. Of course, we don't really know how true their claims are - very likely to be exaggerated. Thus, I would conclude LA batteries win.

author: Bratster
author_rank: Frequent Contributor
timestamp: June 28, 2019, 08:09:35 am
content: Quote from: NorthGuy on June 27, 2019, 09:52:08 pmLooks like they don't stack up as best as I thought they did if you can take into account going with a gigantic battery bank.Although if you're comparing their 100ah LiFePO4 to a 200 amp hour LA they may fair better, which is probably more in line with what their test was.perhaps their intended application is only one or two of these, then they're better than LA maybe, but if you actually have the space and weight capacity for some really high-end LA that route will be more cost-effective.I'm curious what LA batteries you have? They sound like they must be pretty massive, size and weight wise.Just thinking like for my truck solar power setup, I was going to do one or two of their 100 amp hour model.So that would be either a 200-400 amp hour lead acid battery bank in my opinion for comparison.I don't have the available space or weight capacity, so if I went lead acid it would be probably a couple 6 volt golf cart type batteries in series or two 12 volts in parallel.I'm tired, been staying up too late too many days in a row. Please excuse grammar mistakes etc.Also nothing I said was ever intended to come off as defensive / offensive whatever. I am more than happy to be talked out of spending a couple $1,000 on batteries that aren't as good as I first thought they were.G'nightSent from my Pixel 2 XL using Tapatalk

author: NorthGuy
author_rank: Super Contributor
timestamp: June 28, 2019, 03:11:31 pm
content: Quote from: Bratster on June 28, 2019, 08:09:35 amhttps://www.trojanbattery.com/products/deep-cycle-flooded/industrial-line-flooded/About 300 lb per battery. The charging methods they recommend don't work and their support is absolutely unhelpful, but batteries themselves are well built and working OK so far.Quote from: Bratster on June 28, 2019, 08:09:35 amFor the truck you definitely need something lightweight - take into account all the extra gas you'd have to buy to haul the batteries around.

author: floobydust
author_rank: Super Contributor
timestamp: June 28, 2019, 07:04:00 pm
content: LiFePO4, they are 3X the price and 3X the life of SLA, so I didn't see any real advantage.

author: NiHaoMike
author_rank: Super Contributor
timestamp: June 28, 2019, 09:48:27 pm
content: Quote from: floobydust on June 28, 2019, 07:04:00 pmLess weight and better endurance.

author: Red Squirrel
author_rank: Super Contributor
timestamp: July 01, 2019, 02:18:22 am
content: Harder to find though. Found a few on Amazon but I don't like to trust that. And you don't know in a year from now if that seller or product will even still be around if you want to expand.I really do hope they start becoming a more commodity item though. I do like the bigger cells, easier to work with than trying to tack weld a bunch of 18650's together. But even 18650's are hard to find in bulk. The genuine ones are about 10 bucks a pop on Amazon. The cheaper ones are probably fakes.Most of the sites that sell them outside of Amazon are American so not really an option either.Found a site that sells the big flooded acid batteries for solar here in Canada though, so chances are when I upgrade I might go with something like that. Never took the weight into account though... no idea how I would move a 300+ lbs battery.I guess I would need to design some kind of lift mechanism that can lower/lift it one stair at a time. I wonder if a moving company could help with something like that, they might have special tools for that.

author: Red Squirrel
author_rank: Super Contributor
timestamp: July 05, 2019, 01:47:42 am
content: Well I just discovered something interesting. So my server UPS charger is always charging at 13.5. Perhaps that's too much. Unfortunately I have no control.Today I just realized that I had one of these batteries in my shed powering my solar setup and it's been through all sorts of conditions from -50 to +30 along with being constantly discharged/charged. We are in a heat wave right now and it's at least +35 inside the shed. So it sees pretty harsh conditions. Decided to go check the cells to top them up with water. Believe it or not, after a bit over a year of operation they were completely full. Being in a solar application, it does see 13.5 when sun is out, but it's not constant, since at night it discharges a little then it gets charged back up. I wonder if having a constant cycling like this is actually better for the battery than being on float constantly with no discharge time.I eventually want to learn more about power electronics and build my own rectifiers and do a telecom setup that way I'll have more control (and rectifiers are very hard to find), so it will be something to keep in mind. I can maybe have a scheduled discharge just to cycle them a little. Suppose an equalize is also good too.I can sorta simulate that with my current setup by shutting the breaker off for an hour once in a while. I have a feeling I would really need to be doing this every day to have an effect though. Of course the fact that the solar charge controller is temperature compensated and this charger isin't might also play a role. Though that just leads to a higher charge rate since the batteries are cold more often than they are hot, so not sure if it's that. Today is kind of an exception with the heat wave. I imagine these +30's are probably hard on the battery that's in the shed. But given how full the cells are it seems to be doing good.

author: NorthGuy
author_rank: Super Contributor
timestamp: July 05, 2019, 02:44:43 pm
content: Quote from: Red Squirrel on July 05, 2019, 01:47:42 amIMHO, any discharge shortens the battery life. If you never discharge it, lt'll live the longest.If you discharge it, then, while in discharged state, it'll sulphate (that is sulphate on the plates will harden). To combat this, you need to overcharge the battery from time to time. The overcharge causes corrosion end depletion of water in the electrolyte. Therefore you need to add water periodically. Corrosion decreases capacity and increases the danger of a short. Therefore, the battery will eventually die - either of sulphation or of corrosion.You can measure specific gravity of the electrolyte. Low specific gravity in a fully charged battery will indicate sulphation.

author: schmitt trigger
author_rank: Super Contributor
timestamp: July 05, 2019, 05:01:52 pm
content: About 35 years ago, I serviced large UPSs (50 to 100 KVA) for corporate main frames.The battery bank would be either 300 or 500 volts nominal, made up of many individual 2 volts wet lead acid cells.Each cell was about 60 cm tall, and had a transparent vase, completely flooded in acid. There was about 10 cm separation between the bottom of vase and the bottom of the plates. One could see lead sulfates, which had flaked off the plates, collecting at the bottom as the battery aged.Once that the sulfates were getting close to the plates, the cell was flagged for replacement.Of course, one would also observe the pitting and thinning on the plates.And this is when it interesting; if the thinning started at the top, eventually the plate structure would not be able to support the heavy weight of the remaining plate, would fall off and short that cell. With the amount of available energy, the acid would boil and next morning one could not enter the room without a respirator. It was like a fork pitched up your nose.I don’t want to make this post excessively long, but there were many maintenance procedures, as described above, to lengthen the bank’s life.

author: Red Squirrel
author_rank: Super Contributor
timestamp: July 05, 2019, 07:05:09 pm
content: Quote from: NorthGuy on July 05, 2019, 02:44:43 pmThat's what I kinda figured too, even our telecom ones are floated at 54v (same as a 12v at 13.5) but I just find it interesting the the battery that is in the more harsh usage scenario lost no electrolyte at all. I guess that means nothing about the actual state of the plates though. Ideally you don't want any material to shed, as no matter how deep the bottom is, it will eventually go bad. The big telecom ones we have at work have really thick plates and some kind of foam material between each one so there's no material that can fall. I imagine the more expensive batteries will be like this too hopefully. Less chance of complete failures that way.

author: floobydust
author_rank: Super Contributor
timestamp: July 05, 2019, 07:13:26 pm
content: Some research says that always-on float charging, the battery is being constantly overcharged and leads to more corrosion I think the positive plate, compared to sulphate on the other plate if not being charged.The researchers tried switching to constant current just above the self-discharge rate. So maybe 50-100uA/Ah, enough to overcome self-discharge rate and then some. It seemed to have better life.This might explain why some batteries last longer when they are not always being charged.

author: tautech
author_rank: Super Contributor
timestamp: July 15, 2019, 08:33:01 am
content: Seems a few of you here have worked with big 2V LA cells and since I've scored a set of 6 old ones maybe you can help with some advice.Not that I have a real plan for these babies other than to attempt to get them back into some sort of usable capacity.When I got them a couple of weeks back they were mostly ~1V OC and had been neglected/abandoned for some years.They have a significant capacity of some 1000 AHrs/cell.Initially I put some charge into each cell just to see that each would take some and as I could see each slowly taking more I figured they might be worth some effort although not much is involved with just clipping on a charger and checking them a couple of times/day.However I've played with LA cells for decades and used desulphators to improve and lengthen battery life but first I'd like to improve the odds of a successful outcome.Hunting out how others maintain and service these monstrous 2V cells I came across this Instructable(yes I know) that seemed very interesting in that Phosphoric acid can be used to renovate and/or prolong life of LA cells:https://www.instructables.com/id/Lead-Acid-Battery-Care-and-How-to-Restore-Them/Particularly Step 4 is worth a read.Comments ?Their current state (please excuse pun) after ~2 weeks charging.One is damaged with a broken positive connection to the plates. (possible repair later)The 5 other cells are seriesed up and taking a light charge (unrestricted A) that is growing some 20mA/day.2 cells appear in reasonable condition in that they are ~2.1V while on charge which suggests they are taking what the series string can supply them. The remaining cells are 2.5, 2.7 and 3.3V in the series string charging @ ~13V. (CV)The string is only drawing ~2A and up to 8A is available for charging duties when they might be able to withstand it.All electrolyte levels were low but still above the plates and 2L water added to each to get them into the mid level range. Each cell is specified to hold 20L of electrolyte.PlansGet each cell to where it's properly starting to take some charge and below a nominal 2.2V like the 2 better cells.Buy some Phosphoric acid for cell treatment as described in the article above.Electronic desulphation of some kind....tests to confirm my 12V homemade 70V 6A 1 KHz pulser will perform on just 5 cells.Attempt to fix the 6th cell with the broken terminal link. The cell lid can be removed and the electrolyte tipped into a 20L bucket and the plates removed as a package for washing and then repair.If successful, attempt to recover this cell too.Lost cause ? Why ?Possible ? Tips and guidance please.Thanks for reading.

author: GeorgeOfTheJungle
author_rank: Super Contributor
timestamp: July 15, 2019, 08:51:08 am
content: That's more than 13 kWh @C120. I'm green with envy. BP makes PV batteries? What do the tesla fanbois have to say?

author: tautech
author_rank: Super Contributor
timestamp: July 15, 2019, 09:07:53 am
content: Quote from: GeorgeOfTheJungle on July 15, 2019, 08:51:08 amHaha, nuthing like 13 kWh in their current state.BP PV batteries are now Li and it’s hard to find these big 2V LA’s now.The cells above are ‘96 vintage so already 20+ yrs old.

author: NorthGuy
author_rank: Super Contributor
timestamp: July 15, 2019, 12:17:43 pm
content: Quote from: tautech on July 15, 2019, 08:33:01 am8A is nothing. You'll need charge currents 100A or so. Normal bulk charging currents are between 0.10*capacity to 0.15*capacity.

author: Red Squirrel
author_rank: Super Contributor
timestamp: July 16, 2019, 01:34:12 am
content: At 1v open circuit I'd say these are probably completely pooched unfortunately. I suppose it won't hurt to try to get them to 2.25v to see how long they stay that way though but I don't think there is a good chance.That's a nice score though... I would love to get my hands on big cells like that but they arn't cheap and is typically not something you can just buy around here. There's lot of regulations about what companies can do with old batteries and usually they have to go to a recycler. Otherwise I would try to get my hands on some of our work ones when they swap out battery banks. For my own use they would have tons of life left in them even when they arn't good enough for telecom use.

author: john61ct
author_rank: Regular Contributor
timestamp: July 19, 2019, 04:23:14 pm
content: The best deep-cycling battery value in NA by far is Duracell (actually Deka/East Penn) FLA golf cart batteries, 2x6V, around $200 per 200+AH @12V pair from BatteriesPlus or Sam's Club. Deka labeled same batts also sold at Lowes.UPS standby mode is actually a specialist application, different from true deep cycling applications, but still for long-term value these can't be beat.Ideally you use CC load testing for loss of Ah capacity, compared to a benchmark run after breaking the bank in.Standard for EoL is 80% SoH, but consumer non-critical use cases, can push to 65-70% without much risk.The other way to go is just buy cheap and proactively replace on a schedule say every two years.Or go to "exotic" chemistries like LFP or LTO.Obviously whatever you do, the charge profile must match the battery specs.