Charge of Running Car Battery

[CKingsley08]

So i have 4 8s packs. I always go to the field with them fully charged. I have the astro flight a123 charger. It is a royal pain in the a$$ because it "detects" how man cells you have and frequently detects to little if you fly a bit too long. It will do up to 10cells and 8amps. I used to charge 4 to 6 times when i was running 7s packs. I now notice that while charging the 8amps the current slowly goes down with 8s packs. Kind of a pain. The charge time goes from 15 minutes to 30 when it does this. Will starting the car keep the amps pumping? My logic says yes but i don't want to burn out my charger. Mastech PS and generators look really cool but are just too much of an investment if my car will do the job. The vehicle is a ford edge 2008.
Thanks
Cameron