Cummins/Onan — Recovering Deeply Discharged Batteries
Repair & overhaul · Battery bank
From a Cummins/Onan owner's manual covering: 1.5HJBAA, 2.0HJBAA, 2.5HJBAA, 3.0HJBAA. Check it applies to your exact model before use.
Browse Cummins/Onan generators & specs →
Before you start
- Batteries can cause severe personal injury due to sparks, explosion and acid. Always connect or disconnect a battery in accordance with CONNECTING / DISCONNECTING BATTERIES.
Procedure
- Disable Inverting and Charging, disconnect all DC loads and AC power, and measure voltage across the battery bank and the Inverter-Charger DC terminals.
- Repair connections: replace a blown DC fuse, close any open DC switch, clean and tighten DC connections and replace or repair DC cables as necessary.
- If less than 3 volts, let the batteries rest several hours or until voltage increases to 3 volts.
- Reconnect AC power to the Inverter-Charger and enable Charging.
- If the CHARGING light blinks, let the batteries charge 30 minutes or until Fault 71 occurs; check for equal voltage at battery and Inverter-Charger terminals.
- If the voltage increases to 3 volts or more, go to recovery from less than 10 volts; otherwise re-enable Charging for another 30 minutes.
- Replace the batteries if they do not recover to 3 volts or more during the second 30-minute charging period.
- For less than 10 volts, enable Charging; when fully charged, continue Low (Float) Charging for 24 hours without DC loads and then, if appropriate, Equalize Charge.
Tools required
- voltmeter Amazon
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- Inverter-Charger limits DC output to 25 amps when it senses less than 2 VDC at its terminals
Source: Cummins/Onan owner's manual. Steps and values are as documented; always cross-check against the official manual and any later revisions for your exact serial number before servicing.