Author Topic: What causes lead acid battery cells to short out?  (Read 2261 times)

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Offline Red Squirrel

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What causes lead acid battery cells to short out?
« on: May 14, 2019, 03:34:06 am »
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?
« Last Edit: May 14, 2019, 06:07:39 am by Red Squirrel »
 

Offline bsdphk

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Re: What causes lead acid battery cells to short out?
« Reply #1 on: May 14, 2019, 06:17:01 am »
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.
 

Offline Red Squirrel

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Re: What causes lead acid battery cells to short out?
« Reply #2 on: May 14, 2019, 09:36:30 pm »
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.
 

Offline NorthGuy

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Re: What causes lead acid battery cells to short out?
« Reply #3 on: May 15, 2019, 04:22:42 am »
A short cell will have less water, and very low specific gravity, and zero voltage. Is this what you're observing?
 

Offline Red Squirrel

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Re: What causes lead acid battery cells to short out?
« Reply #4 on: May 15, 2019, 04:51:03 am »
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.
« Last Edit: May 15, 2019, 04:52:40 am by Red Squirrel »
 

Offline mvas

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Re: What causes lead acid battery cells to short out?
« Reply #5 on: May 15, 2019, 06:46:11 pm »
RV / Marine Batteries are not true 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 ...
 

Offline Red Squirrel

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Re: What causes lead acid battery cells to short out?
« Reply #6 on: May 15, 2019, 07:30:09 pm »
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#srp

The 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~APS750

Though 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. 
« Last Edit: May 15, 2019, 07:31:54 pm by Red Squirrel »
 

Offline NorthGuy

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Re: What causes lead acid battery cells to short out?
« Reply #7 on: May 31, 2019, 04:51:55 am »
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?

Bigger 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.
 

Offline floobydust

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Re: What causes lead acid battery cells to short out?
« Reply #8 on: May 31, 2019, 06:20:08 am »
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.
 

Offline SparkyFX

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Re: What causes lead acid battery cells to short out?
« Reply #9 on: June 08, 2019, 02:10:40 pm »
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.

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Offline Red Squirrel

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Re: What causes lead acid battery cells to short out?
« Reply #10 on: June 09, 2019, 03:26:31 am »
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?

Bigger 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.

Ahh 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.
 

Offline mvas

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Re: What causes lead acid battery cells to short out?
« Reply #11 on: June 15, 2019, 02:35:14 am »
The 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. 

That 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 discharge

It 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 battery

The Plate thickness is not based on volts nor amp-hours

Plate Thickness ...
0.040" = Automotive SLI battery ( sponge lead )
0.070" = Marine-Hybrid Battery
0.110" = GC2 Golf Cart
0.265" = Deep Cycle Rolls-Surrette Battery ( paste lead )

Many thinner sponge lead plates is for starting cars.
Fewer thicker paste lead plates is for deep cycling

There 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 middle
Typically, 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.

« Last Edit: June 15, 2019, 02:50:12 am by mvas »
 

Offline NiHaoMike

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Re: What causes lead acid battery cells to short out?
« Reply #12 on: June 15, 2019, 02:52:38 am »
I'm willing to pay more if it means they last longer. 
Go with lithium. Keep them at 4V/cell for standard lithium and 3.45V/cell for LiFePO4.
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Offline mvas

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Re: What causes lead acid battery cells to short out?
« Reply #13 on: June 15, 2019, 02:53:05 am »
Ahh 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.
Strings?
You have strings of batteries?
What exactly are the connection details ?
Parallel and / or series ?
 

Offline mvas

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Re: What causes lead acid battery cells to short out?
« Reply #14 on: June 15, 2019, 03:15:31 am »
I'm willing to pay more if it means they last longer. 
Go with lithium. Keep them at 4V/cell for standard lithium and 3.45V/cell for LiFePO4.
At 4 times the price for the same "usable" amp-hours, Lithium is still too expensive.
Lithium does not last 4 times longer.
 

Offline Red Squirrel

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Re: What causes lead acid battery cells to short out?
« Reply #15 on: June 15, 2019, 03:25:23 am »
I'm willing to pay more if it means they last longer. 
Go with lithium. Keep them at 4V/cell for standard lithium and 3.45V/cell for LiFePO4.

Too 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.

Ahh 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.
Strings?
You have strings of batteries?
What exactly are the connection details ?
Parallel and / or series ?

Well 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.


The 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. 

That battery has A 1 YEAR WARRANTY.
Every day after 1 year, is a bonus.

Are 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.
« Last Edit: June 15, 2019, 03:39:52 am by Red Squirrel »
 

Offline NiHaoMike

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Re: What causes lead acid battery cells to short out?
« Reply #16 on: June 15, 2019, 03:04:25 pm »
At 4 times the price for the same "usable" amp-hours, Lithium is still too expensive.
Lithium does not last 4 times longer.
Surplus 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.
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Offline Red Squirrel

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Re: What causes lead acid battery cells to short out?
« Reply #17 on: June 15, 2019, 03:19:45 pm »
At 4 times the price for the same "usable" amp-hours, Lithium is still too expensive.
Lithium does not last 4 times longer.
Surplus 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.

Is 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.
 

Offline NiHaoMike

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Re: What causes lead acid battery cells to short out?
« Reply #18 on: June 15, 2019, 04:01:36 pm »
Is 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.   
Open source UPS software like apcupsd and NUT support custom scripts.
http://www.apcupsd.org/manual/manual.html#customizing-event-handling
https://networkupstools.org/docs/user-manual.chunked/ar01s07.html#_the_advanced_approach_using_upssched
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Offline Bratster

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Re: What causes lead acid battery cells to short out?
« Reply #19 on: June 15, 2019, 05:29:30 pm »
At 4 times the price for the same "usable" amp-hours, Lithium is still too expensive.
Lithium does not last 4 times longer.
Surplus 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.

Is 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.
Those 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.

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Offline Red Squirrel

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Re: What causes lead acid battery cells to short out?
« Reply #20 on: June 15, 2019, 06:41:00 pm »
Is 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.   
Open source UPS software like apcupsd and NUT support custom scripts.
http://www.apcupsd.org/manual/manual.html#customizing-event-handling
https://networkupstools.org/docs/user-manual.chunked/ar01s07.html#_the_advanced_approach_using_upssched

Oh 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.   
 

Offline Red Squirrel

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Re: What causes lead acid battery cells to short out?
« Reply #21 on: June 15, 2019, 06:42:46 pm »
At 4 times the price for the same "usable" amp-hours, Lithium is still too expensive.
Lithium does not last 4 times longer.
Surplus 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.

Is 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.
Those 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.

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Good 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.
 

Offline NiHaoMike

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Re: What causes lead acid battery cells to short out?
« Reply #22 on: June 15, 2019, 07:05:17 pm »
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Offline G7PSK

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Re: What causes lead acid battery cells to short out?
« Reply #23 on: June 27, 2019, 07:53:32 am »
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.
 

Offline NorthGuy

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Re: What causes lead acid battery cells to short out?
« Reply #24 on: June 27, 2019, 01:36:56 pm »
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.

Based 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.

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.

Big 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.
« Last Edit: June 27, 2019, 02:15:35 pm by NorthGuy »
 


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