Thread Rating:
  • 0 Vote(s) - 0 Average
  • 1
  • 2
  • 3
  • 4
  • 5
APC UPS 3000 overcharging my battery
#1
I have a couple of APC 3000 UPSs that are key to my off-grid infrastructure.   

 These units operate on 2 individual 24v batteries - each one plugs in to the unit by itself to provide 48v.    I use 2 x 7s7p 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 at 4.27v/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.
Reply
#2
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.
NOTE! My links supplied in this message may be affiliated with Ebay and by clicking on them you agree on the terms.
YouTube / Forum system setup / My webpage  Diy Tech & Repairs

Current: 10kW Mpp Hybrid | 4kW PIP4048 | 2x PCM60x | 100kWh LiFePo4 | 20kWh 14s 18650 |  66*260W Poly | ABB S3 and S5 Trip breakers
Upcoming: 14S 18650~30kWh
Reply
#3
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.
Reply
#4
(04-30-2020, 05:38 PM)Crimp Daddy Wrote: 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.

(04-30-2020, 05:17 PM)daromer Wrote: 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 regular charge/discharge range of APC is OK for 18650.   It tops out at 54.5v.


I'm starting to think that the APC 3000 (where there are 2 x independent 24v batteries in series) treats this as 1 48v battery.   It's set to maintain a 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 balance 7s7p 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.
Reply
#5
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.
Reply
#6
(04-30-2020, 08:24 PM)Crimp Daddy Wrote: 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!
Reply
#7
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.


Reply
#8
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.
Reply
#9
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 Smile Though they are only ment to sit there for 5.
NOTE! My links supplied in this message may be affiliated with Ebay and by clicking on them you agree on the terms.
YouTube / Forum system setup / My webpage  Diy Tech & Repairs

Current: 10kW Mpp Hybrid | 4kW PIP4048 | 2x PCM60x | 100kWh LiFePo4 | 20kWh 14s 18650 |  66*260W Poly | ABB S3 and S5 Trip breakers
Upcoming: 14S 18650~30kWh
Reply
#10
(04-30-2020, 03:03 PM)OffGridInTheCity Wrote: 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 at 4.27v/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.
Proceed with caution. Knowledge is Power! Literally! Cool 
Knowledge is Power; Absolute Knowledge is Absolutely Shocking!
Certified 18650 Cell Reclamation Technician

Please come join in general chit-chat and randomness at Discord Chat (channels: general, 3d-printing, linux&coding, 18650, humor, ...)
(this chat is not directly affiliated with SecondLifeStorage; VALID email req'd)
Reply


Forum Jump:


Users browsing this thread: 1 Guest(s)