Sometimes even though the voltage at charging is good the battery or alternator could be low on charge or charging low for your vehicles specs.
It normally means the alternator is not putting out enough voltage to keep the battery charged and is defective. Can be a loose alternator belt also.
The battery warning light illuminates when the battery isn't being charged , get it checked out to find the problem and then repair.
because the battery needs charged or need a whole new battery
Your battery is not fully charged. Can mean the battery is going bad or the alternator is failing.
The battery warning light is normally an indication that the battery is not being charged. In most cases, it means that the alternator is not generating electrical power. Driving a car in this condition does not cause any danger but all electrical power is being supplied by the battery rather than the engine. When the battery discharges, the car will simply stop running. Although it is safe to continue for a short time, it's important to get the car looked at and repaired.
It is important to pay attention to the warning lights on the dashboard. The Battery warning light turns on when there the battery of a car is having a problem.
The check power light on a vehicle is a warning indicator. A common cause of this is a improperly charged battery.
That is the charging system warning light. If it stays on or flickers it means the alternator is not outputting enough voltage to keep the battery charged. With a digital volt meter you should read from 13.5 to 15.5 volts at the battery with the engine running. If not the alternator or the voltage regulator is defective. The voltage regulator is more than likely built into the alternator.
you change the battery
Battery Idiot LightIf by battery light you mean the instrument panel charging system warning light, then that means that more electricity is flowing out of the battery than is being put into it.The charging system is not putting out as much electricity as the electrical system is using. In other words, the battery is being "drained" rather than being charged.
When it is no longer able to keep the system charged. Starting with 2001 model, when the car is started, if you see either the battery warning or the battery along with the brakes warnings on, or intermittently flashing on, you need to have your alternator checked. Otherwise, its fine.
From your description it sounds as if the warning light is operating correctly. When the engine is running the battery is being charged and the electrical needs of the vehicle are being fully met by the alternator's output and the battery is not expending stored power. When you turn the engine off the alternator stops running and anything in the vehicle that requires electircal power is suddenly dependent upon the battery to supply it. Thus, the battery begins discharging power, which triggers the warning light indicating that the battery is being discharged.