That lead/acid battery is like a giant sponge or buffer to keep the pulsating DC being put out by your alternator from destroying the electronics in your car....including your ECU......DANGER DANGER Will Robinson.
The battery acts like a big filter capacitor and only smooth even DC is supplied to car after the battery.
PS on charging...I dunno about now (I suppose the laws of physics have not changed) but you charger lead acid batteries by voltage....you can put one on 13 V forever and never hurt it. How do you know you are charging at 10A ? Did you put an ammeter inline and measure the current ??
Don't put too much stock in the labels on Battery Chargers. Nicads you charge by current. If you are using a variable power supply to charge at 10A what is your voltage.....one must increase voltage to get higher current.
It is all right here
