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Overkill BMS trips with 2 inverters

So why is the BMS going over voltage. It should just shut down charging while allowing discharge otherwise there is no point to a seperate port for charge and discharge.
The BMS goes into overvoltage shut down daily on sunny days. Not sure why it shuts down both. I contacted Overkill and they were asking if the batteries were top balanced and other questions that had nothing to do with the issue.
 
The BMS goes into overvoltage shut down daily on sunny days. Not sure why it shuts down both. I contacted Overkill and they were asking if the batteries were top balanced and other questions that had nothing to do with the issue.
Top balance is quite relevant to the issue.
 
@Flip do you have a resistor or incandescant bulb suitable to prime the caps?
We are assuming that this is the problem but in order to proceed we need to confirm this.
 
Top balance is quite relevant to the issue.
@Flip do you have a resistor or incandescant bulb suitable to prime the caps?
We are assuming that this is the problem but in order to proceed we need to confirm this.
The cells were brand new, all bought together, all measured the same voltage and then left in parallel for a couple weeks before I got around to installing them. But technically I did not top balance them.
I haven't primed caps before so I'll have to look up the process, but I imagine I have something that would work.
 
The cells were brand new, all bought together, all measured the same voltage and then left in parallel for a couple weeks before I got around to installing them. But technically I did not top balance them.
Cells need to be top balanced.
Rookie mistake.
 
Lack of top balancing will usually result in cell overvoltage disconnect if you are charging above 3.45Vpc. You need to top balance. This can be done with 50W 1 ohm resistors to pull down the high cells, or a power supply connected to the low cells one at a time.
 
Cells need to be top balanced.
Rookie mistake.
I understand top balancing will eliminate cutting out too early on both ends of the cycle and such, but what does it have to do with the BMS shorting out when I connect 2 inverters or cutting off the batteries entirely in an under or over voltage situation?
 
I understand top balancing will eliminate cutting out too early on both ends of the cycle and such, but what does it have to do with the BMS shorting out when I connect 2 inverters or cutting off the batteries entirely in an under or over voltage situation?
It is relevant to the high voltage disconnect.
 
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I guess I should explain.
The cells that we purchase are effectively bottom balanced.
My rough guess is that decent unmatched and unbatched cells will "usually" vary in capacity by ~<3%.
For example you could have one 97ah cell and 3 100ah cells.
If you configure these in serial and then charge them the 97ah cell will trip the high cell cutoff while the others cells are still well within the safe envelope.
If you are using a BMS you almost certainly want to top balance.
Unless you are an expert please take our word for it.
 
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The BMS is disconnecting because its seeing an under/over voltage condition. balancing the cells will remedy some of this. You should be able to reach a full charge without disconnect.

Disconnecting at low voltage just means you need to adjust your equipment accordingly.

The BMS doesn't do any magic regulation. All it does it protect the cells/pack from over/under voltage or over/under temperature. You need to configure your charge and discharge sources to avoid disconnects under normal operation.
 
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