OffGridInTheCity
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- Joined
- Dec 15, 2018
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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.
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.