Parasitic drain on battery.

[Timco]

Originally Posted by Joe B

If you just recharged the battery that went dead and are still using it, it may no longer be capable of holding a charge. I'd take it to an auto parts store that can do a load test on it. You may have to replace it. I find that my battery doesn't like to be left without being charged for more than about 2 weeks, or it drops to around 12 or fewer volts.

My charger said 25% when hooked up and said full charge in about 20-30 min at 10A fast charge. Seems odd, like it only has the top end.

Just check voltage with car running and batt unhooked to get alt voltage?

[woodsman]

Sounds like some of the cells are dead or disconnected. Charging at 10A is a good way to warp the plates....

[Joe B]

Originally Posted by woodsman

Charging at 10A is a good way to warp the plates....

On their website, Interstate Batteries recommends charging at a 10-amp rate.


"Step 3: Charge the battery at a 10-amp rate. 42 amp-hours needed by the battery divided by 10 amp charge = it will take around 4-1/2 hours to recharge the battery. (The best charger to use in order to charge a car battery is a 3-stage automatic 12 volt /10amp charger.) "

[Pdwight]

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

[Joe B]

Originally Posted by Timco

Just check voltage with car running and batt unhooked to get alt voltage?

No, no, no! As Steve said, never disconnect the battery with the engine running. Excess juice fries diodes in the alternator. Just put the meter on the + and - terminals while the engine's running. This will tell what the alternator's putting out, but nothing about the condition of the battery. Load test it.