Originally Posted by millinnium
Hi there, try a free pc app called FORscan and see if it read the battery charge. I am quite sure it should work
I gave up using the % charge equation. Using the battery current equation you can see how much the alternator is charging the battery. When the battery is nearly full (probably above 80%) it appears to charge around 1-2 Amps (Trickle charge?). Just after starting it will charge the battery 10-20 A depending on how well the battery was charged beforehand. Anything around the 1-2 A when turning off the car is good in my opinion.
For short trips where the battery doesn't charge much between starts I've had the current hover around 15 A and then go to 10 A, then slowly but surely start to reach 1-2 A.
If you're really concerned about the battery or do lots of short trips, just put it on the charger one night a week. Otherwise the alternator does its job.