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

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take five hours per cell. Do not leave the cells unattended during the balancing process. Plan your day
accordingly.
1. Obtain a lab CC/CV (constant-current, constant-voltage) regulated power supply capable of providing
at least 10 amps.
2. If you already jumped ahead and wired your battery pack up, disconnect everything now (remove the
BMS, the bus bars, temp sensor, double-sided tape, everything.
3. Wire all cells in parallel, using the bus bars (all positives wired together, and all negatives wired
together). If you do not have enough bus bars, you may use 10-12 AWG cable with crimped ring
terminals. Be extremely careful to ensure that all cells are connected together with the proper polarity.
4. Configure the power supply for 3.65V, and set the current to around 1/10 C rate (e.g: For a 100A
battery, set the current to 10 amps). Lower currents will work, but will take longer. Higher currents
may work, but could affect accuracy, as the discharge curves vary depending on the current draw.
5. If the power supply does not have a voltage readout, then connect a digital multimeter to the positive
and negative bus bars. This will need to be monitored throughout the test.
6. If the power supply does not have a current readout (in amps), then connect a digital current meter in
series with the circuit, or use a clamp-style meter clamped onto the lead between the supply and the
battery (clamp to either positive or negative lead is fine, but not both).
7. Shut the power supply off.
8. Connect the battery positive lead to the power supply positive terminal.
9. Connect the battery negative lead to the power supply negative terminal.
10. Now, turn on the power supply.
11. Wait until the current readout goes to zero. This may take many hours. If the voltage ever exceeds
3.65, stop immediately.
12. At this point, your cells have been top-balanced. Disconnect the power supply leads, and disconnect
the bus bars.
WARNING: If the lab power supply polarity is reversed by accident, a tug-of-war between the batteries and
the power supply will ensue. The batteries will win, and the power supply will likely be permanently
damaged. Use caution.
Figure 2.3.1:​ Top-balancing cells in parallel (power supply connection not shown)