what would be a good alternator to use to keep battery fully charged while all accessories are on? electric fan pulls 18.5 amp,water pump 6 amp,fuel pump 5 amp and ignition box pulls about 3 amp at 2000rpm. with all accessories and head lights on the battery is pulled down to 11.3 volts after idling 10 minutes and you have to drive a few miles to get back to full charge. using a duralast 72 amp alt. going down the road it works fine,but stop and go it sucks. is there an alt. i can use that will keep bat. fully charged at idle with everything on?