My trickle charger, 750 mA, has a light on it that turns from red, while charging, to to green when the battery is charged. And I use it on a regular basis to charge the battery from my truck. It will charge a low battery over night, and I have used it on a car battery that would not take a charge from my regular battery charger. And it took a charge. Now it won't do it every time but if you are lucky will work, I think it depends on how degraded the battery acid is.