How to charge a spare car battery at home and in the car?

Situation: I want to add another car battery to power my electronics in my car.



Question:

1. How do I charge it to full capacity at home?

2. How should I wire the battery so the car will charge my battery when the car is on?

3. Can I use a voltmeter to measure the capacity of the battery?
How to charge a spare car battery at home and in the car?
Would suggest you try to stop by or call your nearest Batteries Plus store ( http://www.batteriesplus.com ).



They always were able to help me when I've add odd battery questions