How Do I Know My Car Battery Is Fully Charged. The first thing you are going to need to do is fully charge the battery with either a charger or solar panels. Defective Battery Charger.
At that point we knew charging the battery any further was futile and the battery needed to be replaced so we closed the hood and went back inside to warm up. And the same with a solar charge controller if you are using solar panels. Then fully charge the battery leave it for 12 hours and test it.
Just let your car sit with the lights on for about 2 minutes.
To avoid this situation the battery should be replaced before its capacity drops to a critical level. The small red triangle shows the amps flowing on the 2 amp setting. And the same with a solar charge controller if you are using solar panels. The ideal car battery voltage with the engine running is between 137 and 147V.
