An alternator is not a battery charger and a battery resting that low is being undercharged which will result in a battery that won't recharge or become more difficult to recharge. A low battery by itself is hard on an alternator add in posible sulfation it makes it double tough on the alternator.Sorry guys. I'm just lost when it comes to this. I don't have a battery charger. And i've ran the same electrical for 2 years now and all of a sudden, the batteries won't hold a charge. Since I don't have a charger, would it be a good test to put my old alt back in there and see if it could charge the batteries?