i have a 300E diesel 1995 had alternator rebuild about 3 wks ago did fine except battery charge light would come on when first cranked. then this week went to start it would turn over but not start. when we got it home put the charger on it it was below 40% so we charged it, started fine a couple of days happen again took it back where they repaired the alternator they said it was the battery but in new battery started fine that night. next morning same thing went to charge new battery it was below 50% please help.