My car battery is oversized for the car. The battery is a bit old
>but usually works fine. The battery is flat (I left the lights
>on).
>
>My fancy new modern charger senses a poor battery and only puts in
>very little charge.
>
>I used to use a really old charger to charge this battery
>successfully. I opened up the old charger and saw it was only a
>transformer and a big rectifier. That's it. No soothing.
>
>Is this ok for a car battery or is it way too crude?
Electrons are electrons to the battery. If they are at high enough potential to cause a charge condition on the battery, they will.