How do you calculate the tides?

Is there a way to calculate how long it will take for a battery to recharge?

• Is there a way to calculate how long it will take for a battery to recharge? Is there a way to calculate how long it will take for a battery to recharge, based in watt and volts, and how long the charge will last based on how many watts and volts are used? I need to know how to calculate how long it will take for the solar panels to recharge the batteries, and how long they will last. Since I will be adding more panels, batteries, and lights/outlets later, I need to know how to do the calculations myself instead of just asking in here.

• Answer:

  Yes. The battery capacity in amp-hours is the product of amps * hours. If you have a battery of 7.2 Ah, for instance, that means it will take 7.2 hours to charge up from totally flat at 1 amp, or 24 hours to charge at 300mA. (Actually, it will probably take a little bit longer than that to charge due to inefficiency -- but on the other hand, it probably won't be totally flat before you start either.) That works both ways around; such a battery could supply a load of 1 amp for 7h12m, or 7 amps for just over an hour. All you need to know then is the charging or discharging current. A centre-zero ammeter (or a digital one) will show you how much current is flowing into or out of the battery with no need to swap over the connections.