[DAVID GAGNARD]

blykins;

Depends on the condition of the battery and what the alternator has to put out to keep up with the demand... Anywhere from 1 to 3 hp I'd say.... Have proof,way back 20 years ago,a buddy and I had a hunting camp way back in the woods,no electricity.... We used a car battery and 12v bulbs for lighting,then we got a "bulldozer battery",weighed about 125 or more pounds,would last all weekend for lights.... BTW,I forgot to mention this camp was only accessable by water,so everything had to be brought in and out by boat,big pain....Got tired of lugging the hernia maker in and out to recharge it,so I got the bright idea of taking a GM alternator,mounting it on a stand,connected to a lawn mower engine to the alternator with a fan belt to recharge the battery at the camp and leave the battery and homemade charger there....First time used a 3hp Briggs and Stratton,worked real good on car batterys,but when the "big" battery was almost dead and we started up the charger and hooked it up it would "kill" the 3 hp B & S motor in about 2 secounds..... Put a 5 hp B & S motor and it worked great,used it for years....

On a regular auto battery the 3hp motor would pull it and charge it up with no problems even when it was stone dead,so I'd imagine a good battery would pull less than 2 hp from an alternator.....

David