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?