watts to volts

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watts to volts

Postby clan Macleod » Thu Apr 07, 2005 8:16 am

im trying to figure out how big a solar panel i need for my rv. a 15 watt panel will chage my 12volt battery how fast? how do i figure out how long the 12 volts will last for different apliances? e-mail me at macleod1518@hotmail.com
clan Macleod

Postby Guest » Thu Apr 07, 2005 6:14 pm

Power = voltage x amperage, or P = V*I

A 12 V battery is hardly ever 12 v. It typically charges at about 14.4 V and discharges (into a light load) about 13.2 V, less when starting vehicle or driving other heavy loads. A typical vehicle battery may have a capacity of 72 Ah, it could drive at 7.2 A load for 10 h. (battery capacity is normally rated in terms of a 10 h discharge rate).

So your 15 W charger, at 14.4 V can put out 1.04 A, and charge a totally dead battery in 69 h, obviously less if it was only partially discharged. In general, it is bad for battery life to discharge below 50% capacity

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