Reaction is reversible
Since you have a 12V battery, I'm guessing it is a lead-acid type like you find in cars. Lead acid are fairly forgiving in how they can be charged, unlike other chemistries, especially certain types of lithium. Basically charge a lead acid with power that is both current and voltage limited. When you recharge a battery, you change the direction of the flow of electrons using another power source, such as solar panels. The electrochemical processes happen in reverse, and the anode and cathode are restored to their original state and can again provide full power. The maximum current depends on the size of the battery. A ordinary car battery can take several amps easily. For example, a power supply that is limited to 5 A and 13.6 V will work just fine to charge ordinary car batteries, although that's not pushing the maximum allowed current. Increasing the charge voltage to 14.4-volts will reduce battery recharge time for a 125-AH battery to 3-4 hours. Once a battery reaches 90% of full charge, the voltage must be reduced from 14.4-volts to 13.6-volts to reduce gassing and water loss. Find out how to charge a car battery the right way. You can recharge a car battery when your car refuses to start. On average, most batteries do not require a recharge for at least five years. That's if you're taking good care of your car. Non-rechargeable batteries, or primary cells, and rechargeable batteries, or secondary cells, produce current exactly the same way: through an electrochemical reaction involving an anode, cathode and electrolyte. In a rechargeable battery, however, the reaction is reversible. A rechargeable battery is a battery that can be recharged and used many times. It is also known as a 'storage battery' as it has the ability to accumulate and store energy. A rechargeable battery is also known as a 'secondary cell' . Gone are the days when we had to buy new batteries every time it stopped working. We give you an inside look at how alkaline batteries work. You can think of a battery as a small power plant that converts a chemical reaction into electrical energy. Various dry cell (or alkaline) batteries can differ in several ways, but they all have the same basic components. A jump start isn't the only way to recharge a car battery, and it's not necessarily the best way. You can recharge a car battery when your car refuses to start. On average, most batteries do not require a recharge for at least five years. How to charge a battery. An average car battery has a capacity of around 48 amp hours which means that, fully charged, it delivers 1 amp for 48 hours, 2 amps for 24 hours, 8 amps for 6 hours and so on.
http://electronics.stackexchange.com/questions/30537/how-does-a-battery-recharge http://www.qrg.northwestern.edu/projects/vss/docs/Power/2-how-do-batteries-work.html http://electronics.stackexchange.com/questions/30537/how-does-a-battery-recharge http://www.progressivedyn.com/battery_basics.html http://www.carsdirect.com/car-maintenance/4-tips-for-recharging-a-car-battery http://electronics.howstuffworks.com/everyday-tech/battery5.htm http://humantouchofchemistry.com/how-do-rechargeable-batteries-work.htm http://www.energizer.com/about-batteries/how-do-batteries-work http://www.carsdirect.com/car-maintenance/4-tips-for-recharging-a-car-battery http://www.howacarworks.com/electrical-systems/using-a-car-battery-charger
how does recharging a battery work