Overkill Solar 120A 4s 12V BMS, Instruction Manual

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Appendix B: Calibration
Your BMS should come calibrated. In certain use-cases, the voltages and currents might be off. In most cases,
calibration can fix this. We do not recommend doing this unless your readings are ​way​ off. It’s possible to
damage your BMS or your battery bank if this process is not followed to the letter.
B.1 Voltage Calibration
You will need an accurate voltmeter to perform voltage calibration. Make sure that you trust the readings that
it gives. It needs to be accurate to at least 1 millivolt. If you use a cheap or badly-calibrated voltmeter, you will
only make your calibration worse. Also, if your meter came with CATIII / CATIV test lead shields, install them.
These are typically used when working around high voltage. However they’re also handy when working
around low-voltage, high-current. There will be less chance of short-circuiting adjacent bus bars, which could
damage the battery cells or the BMS.
Note: At the time of writing, calibration can only be done via the iPhone app, or the JBDTools USB Windows
application. These instructions cover the iPhone app.
Open the app. Click on ​
Config​ . Then ​ Voltage Cal​ . A warning message will appear. Heed its advice and only
continue if you know what you’re doing.
A list of each cell’s voltage will appear. Starting with Cell #1 (most negative), measure the cell voltage with
the multimeter. Convert the voltage measurement into millivolts (multiply by 1000). Type this number into
the app for Cell #1 (see image below). Click the ​
Write​ button. Repeat for the remaining cells.