Cummins/Onan — Checking Specific Gravity
Maintenance · Starting batteries
From a Cummins/Onan operator's manual — check it applies to your exact model before use.
Applies to: Cummins/Onan DFE, Cummins/Onan DFEJ, Cummins/Onan DFEK, Cummins/Onan QSX15 engine
Procedure
- Use a battery hydrometer to check the specific gravity of the electrolyte in each battery cell.
- Hold the hydrometer vertical and take the reading.
- Correct the reading by adding four gravity points (0.004) for every ten degrees the electrolyte temperature is above 80 F (27 C).
- A fully charged battery will have a corrected specific gravity of 1.260.
- Charge the battery if the reading is 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
- Fully charged corrected specific gravity: 1.260
- Charge if below: 1.215
Full service-parts list: Cummins/Onan DFE →, Cummins/Onan DFEJ →, Cummins/Onan DFEK →
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.