Cummins/Onan B43 / B48 — Battery Cleaning, Specific Gravity and Electrolyte Level
Maintenance
For the Cummins/Onan B43 / B48, from the Cummins/Onan operator's manual.
Applies to: Cummins/Onan B48
Before you start
- Do not smoke or allow any ignition source near the battery.
- Do not add water to battery in freezing weather unless the engine is run two or three hours.
Procedure
- Keep the battery clean by wiping it with a damp cloth whenever dirt appears excessive.
- If corrosion is present, remove cables and wash terminals with an ammonia solution or a solution of 1/4 pound baking soda in 1 quart of water.
- Ensure vent plugs are tight; flush the outside of the battery and compartment with clear water.
- Keep terminals clean and tight; coat with a light application of petroleum jelly or non-conductive grease.
- Use a battery hydrometer to check specific gravity of electrolyte in each cell.
- Correct reading by adding 0.004 for every 5°F the electrolyte is above 80°F (27°C) or subtracting 0.004 for every 5°F below.
- A fully charged battery will have a corrected specific gravity of 1.260; charge if below 1.215.
- Fill the battery cells to the bottom of the filler neck; add distilled water and recharge if low.
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
- Charge if reading below 1.215
Full service-parts list: Cummins/Onan B48 →
Source: Cummins/Onan operator'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.