Cummins/Onan B43 / B48 — Battery Specific Gravity Check
Maintenance
For the Cummins/Onan B43 / B48, from the Cummins/Onan owner's manual.
Applies to: Cummins/Onan B48, Cummins/Onan B43M engine, Cummins/Onan B48M engine
Before you start
- Ignition of explosive battery gases can result in severe personal injury; do not smoke or allow any ignition source near the battery.
Procedure
- Use a battery hydrometer to check the specific gravity of the electrolyte in each cell.
- Hold the hydrometer vertical and take the reading.
- Correct the reading by adding four gravity points (0.004) for every five degrees the electrolyte is above 80 F (27 C), or subtracting for below.
- A fully charged battery will have a corrected specific gravity of 1.260; charge if below 1.215.
Tools required
- Battery hydrometer Amazon
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- Corrected specific gravity 1.260 fully charged
- Recharge if below 1.215
Full service-parts list: Cummins/Onan B48 →
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.