Cummins/Onan — Battery Testing - Check Specific Gravity
Testing & diagnosis · Batteries
From a Cummins/Onan owner's manual covering: 6CTA8.3, CFP83-F10, CFP83-F20, CFP83-F30, CFP83-F40. Check it applies to your exact model before use.
Applies to: Cummins/Onan 6CTA8.3, Cummins/Onan CFP83-F10, Cummins/Onan CFP83-F20, Cummins/Onan CFP83-F30, Cummins/Onan CFP83-F40, Cummins/Onan 6CTA8.3G2 engine, Cummins/Onan 6CTAA8.3G3 engine
Before you start
- Batteries can emit explosive gases. Always ventilate the compartment before servicing the batteries.
- Acid is extremely dangerous.
Procedure
- Use a hydrometer to measure the specific gravity of each cell.
- Check the battery fluid column in the refractometer to determine the state of charge of each battery cell.
- If charge is low, charge the batteries.
- Replace the battery if it will not charge to the manufacturer's specifications.
Tools required
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- 100% charged: 1.265 non-tropical / 1.225 tropical
- 0% charged: 1.120 non-tropical / 1.080 tropical
- Measured at 26.7 oC [80 oF]
Full service-parts list: Cummins/Onan CFP83-F10 →, Cummins/Onan CFP83-F20 →, Cummins/Onan CFP83-F30 →, Cummins/Onan CFP83-F40 →
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.