I have a 24v battery connected to solar panels. I have two BMS's connected to the two 8S banks. I can't get the BMS's to connect to bluetooth yet to set the maximum charge. Until I can figure that out what is the maximum charge I can let the battery reach?
Maximum charge for (16) 3.2v 280A LiFePO4 cell battery
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DIYrich
Solar Wizard
Without a BMS, 28.0v should be safe. That is 3.50v per cell. If you get close to 29.2v, that is 3.65v per cell ON AVERAGE. that means some are over 3.65v, which is bad. Maybe charge to 27.0v, and check each cell. Then go to up by 0.5 volt, and check again. Repeat until the top cell gets close to 3.60v.
I've disconnected the solar panels and turned the inverter off. I could leave the inverter on which would draw the battery down to 27.0v or 28.0v but the Samlex EVO 2224 needs around 20v to even start up. So, the charge is at 29.0v at this time. Thanks for the help.
I've got the BMS's connected. They are two 8S 100A 24v Overkill BMS's connected to two banks of (8) EVE 3.2v 280Ah LiFePO4 cells wired in 24v. The MT-50 and my shunt are reading in the 27v-29v range; the BMS's each read in the same range. Shouldn't the voltage for both banks be twice as high on the MT-50, say 54v-58v? Screenshots are attached for one bank. I have not adjusted the BMS's yet.
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LakeHouse
Solar Enthusiast
If the two batteries are wired in parallel, as it seems they are, then they’ll have the same voltage. Voltage would only be additive if they were wired in series.
LakeHouse
Solar Enthusiast
I have no idea what units those temperatures are in.
The cell and pack voltage numbers all look reasonable. You just need to update the cell capacity value to match your 280Ah cells.
I see what you mean. I believe Centigrade is enabled by default but the numbers in the file are a mystery.
LakeHouse
Solar Enthusiast
It’s a very odd choice, but I think the temperatures might be 1/10ths of a Kelvin. 274.1K is about 1C, which would be a reasonable charge cutoff temperature. All the rest look like they basically make sense as well.
mikefitz
Solar Wizard
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The default protection values in the Overkill BMS are suitable, and apart from capacity do not normally need changing. The Overkill pdf file seems suspect. Keep to the default values shown in the screen shots.
As sugested the BMS is last resort protection, charge current and voltage should be selected by the user and programmed Into the charger.
For a 24 volt system set up your Epever solar charger for the following charge perameters. ( only these values determine charging, the others relate to load output and warnings)
Temperature compensation , set to zero
Equilisation volts, set to 28.4
Boost volts, set to 28.4
Float volts, settings 27.0
Boost reconnect volts, set to 26.4
Boost duration, set to 30 minutes
Equilisation duration set to zero ( some versions of controller will not accept zero, set to 10 minutes)
Mike
As sugested the BMS is last resort protection, charge current and voltage should be selected by the user and programmed Into the charger.
For a 24 volt system set up your Epever solar charger for the following charge perameters. ( only these values determine charging, the others relate to load output and warnings)
Temperature compensation , set to zero
Equilisation volts, set to 28.4
Boost volts, set to 28.4
Float volts, settings 27.0
Boost reconnect volts, set to 26.4
Boost duration, set to 30 minutes
Equilisation duration set to zero ( some versions of controller will not accept zero, set to 10 minutes)
Mike
