Generac — Testing a Battery (Removable Vent Cap Batteries Only)
Testing & diagnosis
From a Generac service manual covering: GN-190, GN-191, GN-320, GN-360. Check it applies to your exact model before use.
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Before you start
- Adding of sulfuric acid is NOT recommended.
Procedure
- Visually inspect the battery case for cracks and other defects; if damaged, replace the battery.
- Check the electrolyte level in all battery cells; if distilled water is added, recharge before taking a specific gravity reading.
- Charge the battery until it is gassing freely, then take the specific gravity reading.
- Check each cell using an automotive type battery hydrometer and record readings.
- Add the required points if the fluid temperature is above 80 F and subtract if below 80 F.
- Subtract the lowest reading from the highest; more than 30 points difference means the battery is probably defective and should be replaced.
Tools required
- Automotive type battery hydrometer Amazon
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- More than 30 points difference: replace battery
- Reference temperature 80 F
Source: Generac service 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.