APC UPS 3000 overcharging my battery

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OffGridInTheCity

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I have a couple of APC 3000 UPSs that are key to my off-grid infrastructure.

These units operate on 2individual 24v batteries - each one plugs in to the unitby itself to provide 48v. I use 2 x7s7p 18650 batteries that I made.

One of the units, which has a pretty constant load of 1000w (all the computers/tvs) has been in operation for over 2 years now and the 7s7p batteries max out at about 3.9v/cell - 27.3v overall. No problems!

The other one, which has very light load during the winter - e.g. K-Cup - decided to start overcharging one of the batteries. I found one battery was normal but the other starting floating at4.27v/cell - YIKES.

I read that these APC max float resisters can 'get off' - so I bought another unit on eBay - but its the same problem. One battery was at 3.0v/cell and the other was at 4.0v/cell and after a couple of hours - it was 3.5v/cell and 4.22v/cell. Again YIKES!!

Does anyone know why these APCs are overcharing one of the batteries? Is it because it's 2 batteries in series and it doesn't care about the individual batteries so its like a multi-battery balance issue?

Any insight into this would be appreciated.

Meanwhile, I'm going to balance the 2 batteries and then see if it continues to overcharge the one.
 

daromer

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They are made for LEAD acid and not lithium. They have bulk and float settings and Will Charge a normal la Up to 14.5 or even more depending on series. On 24v thats 29v.

Theres a reason why you shouldnt use a standard Ups in lithium with charging enabled.

With that Said There are rumours you can change the settings somewhat.

And No. It doesnt Care much about each cell. It charged att total voltage. Since la can take it.
 

Crimp Daddy

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The APC is unaware of your battery arrangement, nor does it care. Even with lead acid its just one big 48v battery as far as the unit is concerned and only looks at the total voltage. Any imbalance in resistance in cells or connections may be contributing to this.

As far as lithium use in APC, my plan was to use it as an inverter and not even have it plugged into the wall.

I don't know for sure, but some units have the ability to be adjusted or calibrate either thorough the management interface or CLI, not sure if you need the optional add on card wich allows you to control it over IP. I had plans to do this on one of mine until I learned the inverter inside the unit is actually dead.

I would just use it as an inverter if I were you, but they are also a bit power hungry when it comes to standby/efficiency power as well.
 

OffGridInTheCity

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CrimpDaddy said:
I would just use it as an inverter if I were you, but they are also a bit power hungry when it comes to standby/efficiency power as well.
Mine is off-grid with ATS. I use these as 'whole house' UPSs to smooth the daily ATS switchovers.

daromer said:
They are made for LEAD acid and not lithium. They have bulk and float settings and Will Charge a normal la Up to 14.5 or even more depending on series. On 24v thats 29v.
Yes - I understand. The regularcharge/discharge range of APC is OK for 18650. It tops out at 54.5v.


I'm starting tothinkthat the APC 3000 (where there are2 x independent 24v batteries in series) treats this as 148v battery. It's set to maintaina 54.5v 'top charge'. In theory this is fine as that's 27.25v per battery - and that's what I've been observing (the last 2 years) till recently.

I had assumed the APC would control the voltage of each individual battery - but maybe that's not the case. So if 1 is 30.1v(4.3v/7s-cell)the other can be 24.4v(3.5v/7s-cell) and the APC is happy.

This would explain what I'm seeing. I must have out of balance7s7p batteries - that over time drifted apart. Maybe 1 is a little bit self discharging.

Sigh.... is there any such thing as something to keep 2 x 24v batteries in balance - sort of a 2s @ 24v BMS? Something that does 14s but doesn't care its 2 x 24v in series - like Batrium.. but of Batrium is way to expensive for this.
 

Crimp Daddy

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I would consider just getting one of those Bluetooth BMS boards I am testing out and wiring it up.

You can have two 7s packs, but I would build each one without a BMS. After you connect them in series, you can then connect the BMS to manage both packs as a single unit.
 

OffGridInTheCity

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CrimpDaddy said:
I would consider just getting one of those Bluetooth BMS boards I am testing out and wiring it up.

You can have two 7s packs, but I would build each one without a BMS. After you connect them in series, you can then connect the BMS to manage both packs as a single unit.
Yes sir. I just took my 'extra one' apart - and sure enough, it may have 2 x anderson plugs for 2 x 24v batteries - but its just simple wiring to put these 2 in series.
In fact, there's plenty of room to fit in a 14s BMS and wire up the 48v cut-off.

Not sure why I thought it was managing each individual battery... I guess I just expected more. The OEM batteries are actually 2 x 12v connected as a 24v - so its 4 x 12v in series to get 48v. So this is why AGM(s) die as well - in fact I've had a case where an AGM swelled / burned-a-bit - probably due to 1 battery failing which in turn let the other one overcharge!
 

Crimp Daddy

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Most all APC products use the same 12v battery arranged in series to make up the voltage. This is pretty typical across a bunch of different battery sizes depending on the UPS.


image_vfonfe.jpg


image_pyvuzh.jpg
 

not2bme

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I stopped buying APC for this reason. I must say some of the newer models are somewhat better, but older models used to suck my SLA dry in 3 years guaranteed. I use Eatons now. They don't float like APCs do, instead they drain slightly down to 80% and also it means they are constantly tested. My eatons now last 5 years between changes, and that's because I do it to ensure optimum uptime. I used to remember older APCs (circa 90s) where they would perform a test and if the battery fails, it would cut the power instead of just going back to line mode. Caused more server headaches than it was worth. That was back when dual redundant power supplies were quite expensive.
 

daromer

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You are aware that the UPS will Bulk charge before it goes into float? Bulk charge will raise voltage to (Depending on version) 14.1-14.6V.
Float on that (depending on version and temperature) is between 13.8 and 14.1

Thats a span of 55.2V to 58.4. With 14s is thouls be fine.

But im not sure but it looks like you used 2 packs and if so 2 BMS systems? Or no bms at all since you could overcharge? Your first thing to do is to sort a proper 14s bms and hook up. Then you dont get into a situation where the UPS will kill your cells.



The reason why batteries dies in UPS systems as above is 2 factors or you coud say 3
1. To hot
2. The UPS overcharges the batteries running on Bulk/Float to high.

After we at work went from UPS systems with the batteries in the UPS to have dettached batteries we went from 3 years to 8+ years with same cells :) Though they are only ment to sit there for 5.
 

Korishan

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OffGridInTheCity said:
The other one, which has very light load during the winter - e.g. K-Cup - decided to start overcharging one of the batteries. I found one battery was normal but the other starting floating at4.27v/cell - YIKES.

I read that these APC max float resisters can 'get off' - so I bought another unit on eBay - but its the same problem. One battery was at 3.0v/cell and the other was at 4.0v/cell and after a couple of hours - it was 3.5v/cell and 4.22v/cell. Again YIKES!!

Do you have a bms on these?? If not, why not? Even a cheaper unit would be better to help keep the voltages in check.
 

OffGridInTheCity

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Korishan said:
OffGridInTheCity said:
The other one, which has very light load during the winter - e.g. K-Cup - decided to start overcharging one of the batteries. I found one battery was normal but the other starting floating at4.27v/cell - YIKES.

I read that these APC max float resisters can 'get off' - so I bought another unit on eBay - but its the same problem. One battery was at 3.0v/cell and the other was at 4.0v/cell and after a couple of hours - it was 3.5v/cell and 4.22v/cell. Again YIKES!!

Do you have a bms on these?? If not, why not? Even a cheaper unit would be better to help keep the voltages in check.
I use BattGo(s) as my BMSbecause they show the voltage and will beep with trouble - e.g.undervoltage. However, I've discovered that they don't do anything on overvoltage (I expected them to beep).

>why not?
I'm not OK putting a BMS on that I can't see what its doing - I want to see the voltages. I don't have androidfor the cheap BMS interfaceand I don't want to fool around with some GitHub iPhone hack - don't want a phone interface at all.

I'm looking for a solution. Chargery 16 is a bit expensive for what you get... Looking for cheaper BMS with screen of voltages- maybe something like this:
https://www.ebay.com/itm/10S-24S-Sm...hash=item48e11d8e4d:m:mBFgf3Ju4IoPbGgqh8SgrAg
 

Korishan

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I suggest using diyBMS by Stuart Pittaway. There's plenty of work that's been done on it and it's quite versatile because each parallel section has it's own monitoring system that all report back to a central system.
 

Overmind

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Using Li-ion in server APCs was something I always wanted to test and I will when I get my hands of a good APC UPS.
 

daromer

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You are not ok with a bms that doesnt show voltage but you are ok running without protection? You do unde stand how thta sounds like? :)

Any bms is better than No bms.
You can Always add a voltage display on the Side. You can even run The simplest Arduino or esp with multiplexer and added adc to report thta data with those dumber bms systems
 

OffGridInTheCity

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daromer said:
You are not ok with a bms that doesnt show voltage but you are ok running without protection? You do unde stand how thta sounds like? :)
I have no confidence in cheap BMS that I can't monitor doing anything at all. The BattGo's visible voltage (for monitor) andaudible alarm makes them a cheapBMS. I just didn't realize they didn't sound alarm at overvoltage. However, due to visible voltage they did they're job and alerted me to a bad condition.

I also didn't realize that the individual batteries in APC 3000are not charge voltage limited - they're just 'dumb' serialized.

So I agree in that I'm moving ahead and will try Chargery 16 and a 'cheap BMS with voltage panel' - both seem similar cost and I'll see how they work out :)

I'm nearing 3 years in now... and since I'm in the 24/7 power production business (rather than now and then ebike riding) one thing thats gotten clearer is you have to take the long view - as things may be fine today or next year but what about 3 years from now when you've stopped looking. You need reliable equipment / systems for the inevitable battery degradation/failure. So yea, BMS is needed - but I want it to be something I can monitor and not just close my eyes and hope its working.
 

daromer

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This is how you always should look for a bms

1. Protection, Over and under voltage is key including temp. Most Cheap ones have this and it actually do work. Its easily tested.
2. Reporting. reporting is very nice but do you really sit at the battery 24/7? If you dont its just useless more than for casual checking.
3. balancing and management. This is the last step and its there for longeivity.

You can always monitor a cheap BMS. Just add a voltage display or 14 or whatever you have. As you all know, stuff doesnt fail when you stand watching but when you turn your back around.

And cheap stuff or not. I do hope everyone do test the equipment? For instance i have tested both over and undervoltage and know that the breaker will be triggered and shut down. (As an example)

Thats also why you have a test button on for instance fault protection :)
 

OffGridInTheCity

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I ordered a Chargery 16TPro to remedy my APC 3000 battery problem. While I was waiting for it to arrive, I manually tweeked the 2 independent 24v batteries to try to keep them in range... but I forgot to check for a few days and on Friday I found that one was up to 4.4xxx volts/cell. YIKES!!! OK I'm convinced - BMS from now on. Its a journey (of foolishness) to learn these things at the gut level. 4.4v on very gentle charging - but still - yikes yikes yikes.

Looks like the Chargery is perfect for me as it has the visual panel/voltage display on BMS so I can see what's going on! Here's my new - BMS'ed - APC 3000 solution :)
The battery is 14s12p Sony G5/G7(s) that I had left over because they average 200mOhm IR - no good for my powerwall but OK for this purpose. The relay is a Gigivac 12v-coil 200a contactor.

image_wbtfoz.jpg


For my remaining APCs, I think I'm going with the cheaper Chargery - no shunt and display built into the BMS as its only $109. Thanks to a forum member for finding it.
 
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