# How to charge and discharge a battery?

I need to know how a battery could be charged and discharged in time.

If I have a 12V battery with 200 amp, then how long does it take to download with a consumption of 3 kWh? And what voltage and current do I need to recharge the battery?

If they have steps and formulas to implement would be of great help to me.

• You probably shouldn't be charging a 12V battery at 200A. Few batteries are rated for that. – Hearth May 5 '17 at 1:01
• AGM deep cycle batteries, yes, but how? – Bastian Stuardo May 5 '17 at 1:07
• I would strongly discourage you from attempting to put 200 amps into one of those. The recommended charging current, as a rule of thumb, should be no more than around C/5. So unless you have a 1000 Ah battery, I advise against trying to charge at 200A. – Hearth May 5 '17 at 3:09

If I have a 12V battery with 200amp, How long does it take to download with a consumption of 3kwh? And what voltage and current do I need to recharge the battery?

In order to calculate that you need to know the capacity of the battery. Batteries are usually rated in Amp-hours (Ah) which specifies how much current the battery can supply for 1 hour. For example a 1Ah battery could supply 1A for an hour, or 0.5A for two hours.

$$Discharge Time(Hours) = Capacity (Ah)/Discharge Current (A)$$

If you multiply that Ah capacity by the voltage you get the total amount of energy the battery holds in Watt hours (Wh), and when divided by a total load power you get how long the battery will supply that power output.

$$Energy_{Battery}(Wh) = Capacity_{Battery}(Ah)*V_{Battery}$$

$$Discharge Time(Hours) = Energy_{Battery}(Wh)/Load (W)$$

That's the math involved. Once you know what your battery voltage and capacity are you can go from there.

With regard to charging, the recommended charge currents and voltages are usually specified by the manufacturer. You can also look up specs on similar batteries for a ballpark figure.