Volts.
12.6 volts = Full Charge
12.4 volts = 75% Charge
12.2 volts = 50% Charge
12.2 volts = 25% Charge
Actually A "12" volt battery produces 12 to 14 volts at almost any charge %, even though your guage showes the charge in volts, Its actually amperes that get reduced in batterys.,,,,,,,, 80% should be sufficient charge to start A vehicle that is in good condition.
12 Volts x .83 Amps = ROUGHLY 10 WATTS. (automotive batterys are actually 12.6 volts and are charged at 13.5-13.8 volts). Any wattage will charge it, the question of how fast is determined by the total wattage you're supplying. It will damage the battery if you're overcharging it, and it will not work if you are using the battery while you're charging it. Using it on and off intermittenly will keep the battery charge and will work I:E: using it for a 12 volt cigarette lighter and you smoke a pack a day. ;)
You will have 24 volts DC.
With the engine off check the voltage at the battery. A fully charged battery will read 12.6 volts. At 75% charge it will read 12.4 volts, 12.2 at 50% charge, and 12.0 volts at 25% charge. Now start the engine and check the voltage at the battery. It should read 13.5 to 15.5 volts if the alternator is working properly.
Sure you can and you will end up with 36 volts. Connect them in Parallel and you will have 12 volts.
A fully charged 12 volt battery with engine not running, ignition off will read 12.6 volts at 100% charge. 12.4 volts at 75% charge. 12.2 volts at 50% charge. 12.0 volts at 25% charge.
Connect them in series and you will have 24 volts but you will have the same A/H as one of the batteries. Volts double but A/H stay the same.
12.6 volts = 100% Charge 12.4 volts = 75% 12.2 volts = 50% 12.0 volts = 00%
100% charge = 12.6 volts 75% charge = 12.4 volts 50% charge = 12.2 volts 25% charge = 12.0 volts
You will need a digital voltmeter. Set the voltmeter to 20 volts DC. Check it with the probes. 1. 12.68 Volts = 100% Charge 2. 12.45 Volts = 75% 3. 12.24 Volts = 50% 4. 12.06 Volts = 25% 5. 11.89 Volts = 0%
First, make sure the battery is good. Check the water level, then check the voltage. Must have more than 12 volts on the meter. If not, charge and check again. This will ensure that the battery does hold a charge. If all is good, then, with the engine running, check the voltage at idle, should have around 13 + volts, and at 2000 rpm, should have around 14 volts. If not, 2 things, the voltage reg. or the stator will have to be replaced.
Your question needs clarification. Car battery, Cell phone battery, camera battery, etc. Question was posted in car batteries category. You can check it with a digital volt meter car not running. Set the meter to 20 volts DC. Here is what you will see. 12.6 volts = 100% charge 12.4 volts = 75% charge 12.2 volts = 50% charge 12.0 volts = 25% charge