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Electronics => Power & Renewable Energy => Topic started by: Dave92F1 on February 13, 2019, 02:24:44 am

Title: Swollen AGM batteries in APC brand UPS?
Post by: Dave92F1 on February 13, 2019, 02:24:44 am
I have a number of APC-brand UPSes that I use to backup computers and stuff (non-professional environment). Different models, in the range of 400 VA to 1500 VA.

I buy new AGM batteries and leave them in there until the UPS starts beeping (complaining about the battery) - that usually takes about 4 years.

Over the last dozen years, with 4 or 5 different UPS units, I find that whenever I replace the batteries, they're almost always puffy and swollen (sometimes a little, sometimes a lot).

I read that this is caused by overcharging. But I thought APC (https://www.apc.com (https://www.apc.com)) was one of the most reputable manufacturers of small UPSes, so I'm surprised.

Why does APC "overcharge" the batteries? Is it perhaps intentional, to get a little more run time during an outage?

Is this because I buy the cheap Chinese batteries from eBay? (They do work OK for 4 years or so.)

Or is it just bad design? Or is it inevitable?

Title: Re: Swollen AGM batteries in APC brand UPS?
Post by: edpalmer42 on February 13, 2019, 03:48:00 am
I've seen the same thing.  It's not just APC, it happens with many brands.  I've also heard that it tends to be caused by overcharging.  The only reason that I can think of to set the charge voltage too high is to decrease the recharge time so that the UPS will be ready for another outage quicker.

Some brands of UPS go out of their way to be nice to the batteries.  Depending on the brand, they might use a couple of different charge voltages to speed up the recharge without damaging the batteries.  One brand even turns off the charger after a while and only turns it back on when needed.

Ed
Title: Re: Swollen AGM batteries in APC brand UPS?
Post by: george80 on February 13, 2019, 04:31:18 am

I also have several APC UPS's I use for my play off grid setup.  I use a solar charger I can punch the actual charge voltage I want in rather than charge them from the UPS. They tend to push the batteries to 15V or above which is far too high for my liking. As I am mainly using the the UPS as inverters with nice power input, I tend to fire them up only when I am using them.

I am sure that if you can get into the control program at least on the larger units, you can set the charge voltage or at least set the battery type.  There may be some ajustment on the board as well but I would tend to think it will be software controlled.
Because I use the UPS units with car batteries, It's easy for me to measure the float voltage.  It may be possible to take the little 7 Ah batteries out enough while they are connected to see what they are being floated at to verify if the charge rate is too high. The batteries always have the recommended float and cyclic use float voltages stamped on them.  The float voltage is the one that would apply for UPS usage.

I would suspect this over volting is deliberate so as to get the max run time possible out of the batteries when they are needed, or, the manufacturers may just want to ensure the ridiculous over inflated price they charge for these standard batteries makes them pleny of back end $$ in replacements. Their main customers would be businesses whom need reliable back up so aren't going to question their prices. They probably have replacement programs in place anyway so every 3 years just come and replace them wether they need it or not.


See if you can get into the settings of the UPS ( need a cable) and ajust to what the batteries themselves say.
Title: Re: Swollen AGM batteries in APC brand UPS?
Post by: BradC on February 13, 2019, 04:37:46 am
Why does APC "overcharge" the batteries? Is it perhaps intentional, to get a little more run time during an outage?

Yes. They run the batteries at the ragged edge of the manufacturers recommended float voltage. The newer (SUA->) units are a little better in that they attempt to measure the battery temperature and apply compensation, but they still tend towards overcharge.

Couple this with any small drift in the voltage divider component values and it doesn't take many years for the float voltage to drift high. Over a 4 years battery life it doesn't take much extra voltage to cause what you are seeing.

As edpalnmer42 says, its not unique to APC, but they tend to sell a *lot* of UPS, so you hear about it.

The first thing I do when I get a new (to me, mine are all 10+ years old) one is recalibrate that. I still get ~4-5 years out of the 5 year design-life batteries, but they don't swell up.
Title: Re: Swollen AGM batteries in APC brand UPS?
Post by: tsman on February 13, 2019, 04:44:55 am
It is due to the internal resistance of the battery rising because of age. This change in internal resistance will cause overcharging in the regular charge cycles and continuous trickle charging. The UPS manufacturers will tell you to replace the batteries after some specific number of years to reduce the chance of swelling and to ensure you get the rated runtime. Follow those recommendations and you shouldn't normally see any massively swollen batteries.
Title: Re: Swollen AGM batteries in APC brand UPS?
Post by: digsys on February 13, 2019, 05:32:28 am
I've worked on / designed many UPS systems over the years, and have not really come across many blatant over-charging scenarios.
The main issues I come across - 1/ battery balancing ie NOT properly balanced, thus one or more go lower and screw up the levels for all.
I find this to be the #1 killer, by far. Yeah, some chargers are set a bit high (on trickle), but good batteries should have a reasonable margin.
2/ Sedimentation. Unless you select a specific type of lead-acid that doesn't require some vibration to keep the plates clean, it shortens their life.
We buy specific made types from www.snaptec.com.au/industrial-batteries.html (http://www.snaptec.com.au/industrial-batteries.html)  and are getting 10yrs (or longer), sitting in camera towers, out in the
hot sun. Funnily enough, UPSs that have noticeable vibration (from the DC-AC converter) actually help battery life.
The problem has become so common lately, I have started making up a balancer (using the LTC3305)
Now, this may not be your case, but stuff to keep in mind. Either way, if you use properly rated batteries, you can eliminate possibilities.
Title: Re: Swollen AGM batteries in APC brand UPS?
Post by: floobydust on February 13, 2019, 05:44:17 am
It's poor charge management software.

What happens is one cell shorts and the charger then goes full tilt roasting the other cells. Think of a 12V battery becoming a 10V battery.
I see it happen a lot with gel cells and simple chargers cook 24/7 until another cell dries out and open circuits due to being overcharged. You will see bulged batteries with electrolyte leakage.

Decent charger firmware can test and predict a shorted cell, but it's very rare to find programmers or state-machines that cover this scenario.
Title: Re: Swollen AGM batteries in APC brand UPS?
Post by: george80 on February 13, 2019, 09:58:10 am

What happens is one cell shorts and the charger then goes full tilt roasting the other cells.

My nephew has been working on a program to bring community solar, battery charging and lighting to villages in places like cambodia and Viet nam.
A lot of households have car batteries they use to power radios and lighting. The torture they put the batteries though is unreal and they must be getting about a 50th of capacity if that.

They run the things down to flat, dead flat, like 6V no load flat.  They then strap them to the back of a bike and often the kids take them into town to be recharged. That is accomplished by getting a load of batteries from everyone which are all different sizes, types and conditions and then either charging them in series off a clapped out diesel 240V generator rectified ( somewhat) or in parallel off a couple of  truck alternators which may or may not be actually regulated.

Full charge is determined by the batteries literally boiling with off gassing. I have seen my Nephews vids, it's scary. You are waiting for a spark and the things to blow up which apparently happens with regularity.  The guy doing the charging and often others waiting, sit round the batterys with the fumes from the batteries ( and the smoking diesel)  all around and breathing them in.  How that does not burn their skin I don't know but I'll bet the guy doing the charging lost his olfactory senses a long time ago and probably his eyesight isn't too good either. with the diesel thumping all day and sitting on top of that, I'll bet the only thing he could hear would be point blank gunshots.

The batterys are taken home again and run till they will barely make a tail light globe glow and then taken back to town for another boil up.
They use the battery for years like this as they are expensive for these people whom earn the equivalent of $2 a week to replace.  One can only wonder how the things hold any charge at all.
Title: Re: Swollen AGM batteries in APC brand UPS?
Post by: tautech on February 13, 2019, 10:08:54 am

What happens is one cell shorts and the charger then goes full tilt roasting the other cells.

My nephew has been working on a program to bring community solar, battery charging and lighting to villages in places like cambodia and Viet nam.
A lot of households have car batteries they use to power radios and lighting. The torture they put the batteries though is unreal and they must be getting about a 50th of capacity if that.

They run the things down to flat, dead flat, like 6V no load flat.  They then strap them to the back of a bike and often the kids take them into town to be recharged. That is accomplished by getting a load of batteries from everyone which are all different sizes, types and conditions and then either charging them in series off a clapped out diesel 240V generator rectified ( somewhat) or in parallel off a couple of  truck alternators which may or may not be actually regulated.

Full charge is determined by the batteries literally boiling with off gassing. I have seen my Nephews vids, it's scary. You are waiting for a spark and the things to blow up which apparently happens with regularity.  The guy doing the charging and often others waiting, sit round the batterys with the fumes from the batteries ( and the smoking diesel)  all around and breathing them in.  How that does not burn their skin I don't know but I'll bet the guy doing the charging lost his olfactory senses a long time ago and probably his eyesight isn't too good either. with the diesel thumping all day and sitting on top of that, I'll bet the only thing he could hear would be point blank gunshots.

The batterys are taken home again and run till they will barely make a tail light globe glow and then taken back to town for another boil up.
They use the battery for years like this as they are expensive for these people whom earn the equivalent of $2 a week to replace.  One can only wonder how the things hold any charge at all.
Because a gassing charge is good for LA batteries......but with the risk of a spark then causing an explosion.
If electrolyte levels are maintained the occasional gassing charge helps desulphate the plates.....something you can't do with SLA.
Title: Re: Swollen AGM batteries in APC brand UPS?
Post by: tautech on February 13, 2019, 10:25:17 am
OP
There's lots of threads on UPS's and their battery issues along with numerous mentions of the APC brand....have a search.  ;)

From another thread and might be of use:
http://www.jjoseph.org/notes/apc_smartups_battery_float_voltage (http://www.jjoseph.org/notes/apc_smartups_battery_float_voltage)
Title: Re: Swollen AGM batteries in APC brand UPS?
Post by: BradC on February 13, 2019, 11:32:36 am
One can only wonder how the things hold any charge at all.

Oh that one is easy. Lead acid chemistry is fairly simple and incredibly robust. In the old days you'd get a hot knife to sever the bitumen that held the top on, wash the sediment out of the case, give the plates a bit of a tweak, seal it back up and pour in the acid. Good for another couple of years.

It's like anything. It has become tweaked to within an inch of its life trying to squeeze out the maximum performance, and you trade the performance for robustness. A simpler and more forgiving construction (such as those found in batteries made in lesser developed countries) will "keep on keeping on" well past the point our fragile snowflake "elite athlete" batteries are being read their last rites.
Title: Re: Swollen AGM batteries in APC brand UPS?
Post by: Red Squirrel on February 14, 2019, 02:50:54 pm
I like flooded cells as they vent hydrogen, but won't swell.  As long as you keep adding distilled water they are good for a long time. Well still need to charge them right, avoid too deep of discharges etc but in general they are quite robust.

Got 4 of them for my inverter-charger (basically UPS) at home, gives me about 4 hours of run time for my servers.   I eventually want to switch to a 48v dual conversion setup though.
Title: Re: Swollen AGM batteries in APC brand UPS?
Post by: IanMacdonald on February 23, 2019, 09:08:01 pm
It's about time they started using lead-calcium technology in SLAs. The car batteries that use this tech last for years without trouble. They will also tolerate a somewhat higher charge voltage, up to about 14.8 for non-float applications, without significant gassing.
Title: Re: Swollen AGM batteries in APC brand UPS?
Post by: larrybl on February 25, 2019, 07:16:32 pm
I had a bad case of bloated batteries.
Title: Re: Swollen AGM batteries in APC brand UPS?
Post by: Red Squirrel on February 25, 2019, 11:43:46 pm
Ouch batteries that size arn't cheap either.