Addressing Battery Unbalancing for Onyx 41Ah HD and EK Batteries

Unbalancing in the Onyx 41Ah HD and EK batteries over time can often result from charging habits. The battery might not spend enough time past its “start voltage” to balance effectively. Adjusting settings to lower the “start voltage” and disabling “bal. only when charging” allows the battery to balance continuously, even without being plugged in. This helps correct imbalances and maintains long-term battery health.

Here’s a detailed guide to balancing your Onyx 41Ah battery using the Overkill Solar BMS app:

Step-by-Step Instructions

Initial Setup

  • Download and install the Overkill Solar BMS app:
  • Open the app within 5 feet of your battery.
  • Connect to your Onyx 41Ah battery by selecting the Bluetooth name that starts with HD or EK on the devices page.

Adjusting BMS Settings

  • Tap Settings at the bottom of the app.
  • Tap BMS Read in the top left corner.
  • Update the settings as follows:
  • Start Voltage: Change to 3700.
  • Bal. Only When Charging: Toggle OFF (grey, not yellow).
  • Tap BMS Write to save the changes.

Charge the Battery

  • Charge the battery to between 80V and 83V.
  • If the Balance Delta is:
  • 0.300V – 0.500V: Let the battery rest for 3 days without use to allow balancing.
  • Above 0.500V: Make a post in ONYX AF for assistance.

Monitor Progress

  • After 3 days, check the Balance Delta:
  • If it reduces to 0.030V, revert the settings to stock:
  • Start Voltage: 3900
  • Bal. Only When Charging: ON (green).
  • If the delta is still above 0.030V, continue to monitor daily. Ensure it’s decreasing.
  • If the delta increases, stop and post in ONYX AF.

Monitor Temperature

  • Ensure the battery temperature stays below 35°C (95°F).
  • If it exceeds this threshold, stop immediately and post in ONYX AF.

Simplified Checklist for Balancing

Step 1: Initial Setup

  • Connect to the battery using the Overkill Solar BMS app.
  • Select the Bluetooth device name starting with HD or EK.

Step 2: Change BMS Settings

  • Start Voltage: Set to 3700.
  • Bal. Only When Charging: Turn OFF (grey).
  • Save the changes with BMS Write.

Step 3: Charge and Monitor Balance Delta

  • Charge to 80V–83V.
  • Monitor the balance delta:
  • 0.300V–0.500V: Rest the battery for 3 days.
  • Above 0.500V: Seek help in ONYX AF.

Step 4: Check After 3 Days

  • If the delta reduces to 0.030V, revert settings to:
  • Start Voltage: 3900.
  • Bal. Only When Charging: ON (green).
  • If still unbalanced, monitor daily.

Step 5: Watch Temperature

  • Ensure temperatures stay below 35°C (95°F).
  • If higher, stop and post in ONYX AF.

Important Notes

  • Changes are temporary and may take 3 days to 2 weeks to complete balancing.
  • Always monitor both balance delta and temperature to ensure safe operation.
  • This process addresses common unbalancing issues due to charging habits and helps prevent premature cutoffs, ensuring optimal battery life.