You can charge a 12-volt battery in several ways. As long as the battery is in good working order and does not have a bad battery that prevents it from holding a charge, you can use the following ways to charge it.
Use a battery charger
Hook the dead battery up to a 12 volt battery charger. On the control panel in front of the charger, it is clearly described between 1 and 3 ways that allow you to “slow and steady charge” (2 amps) your battery, fast charge (50 amps) or medium charge (10 amps). The best option for a long lasting charge is slow and continuous. Most 12-volt chargers have a front panel connector that allows you to charge both low-maintenance 12-volt batteries and deep-cycle marine batteries.
Use your car as a charger. Charge your 12 volt battery by starting the car with a good battery and then manually remove the good battery while leaving the engine running. Hook the dead battery in place to charge it while the engine is running. A 15-minute charge should give the battery enough current to jump start it again.
If you’re on the road, look for power cables in case your battery doesn’t work. A cable from another car will help you get the car to the garage or auto parts store to get it fixed. Just attach the positive (red) alligator clip to the positive terminal of the rescue car battery while the driver starts the car. Hook the negative (black) to the negative terminal. Keep the two alligator clips on the opposite end of the connecting cables separate to avoid sparks, place the positive (red) on your positive (red) terminal and the negative (black) to the negative terminal or socket.
Solar Power
Use the sun’s free energy to charge your 12-volt battery. A 13 watt amorphous fold out solar panel can save your day if you use it to charge your 12 volt battery with the power your boat, car or RV needs without any problems. Just hook the positive and negative alligator clips of the solar panel to the corresponding battery terminals and place the panel in the sun.
Hook up a solar powered battery to keep it charged with power from the sun. A solar panel fits on your dashboard and hooks directly to the battery, keeping it fully charged.
Attach the panel to the roof of the car and connect it directly to the car battery for a constant charge.
Tips
Always carry charging cables in your trunk for emergency use.
Warnings
Always hook up the terminals correctly, as you can damage the alternator if you do it wrong.