2009 (PQ09) precedent charging problem

[idontno]

I'm having problems with my cart reaching full charge. It has brand new crown batteries and cables with a power drive charger. Once plugged in it takes 3-5 seconds for charger to come on and then jumps to 15 amps. After 30 minutes or so it shuts off and will kick on and off again threw out the day. Pack reads 50 volts while charging and 48 volts when charger shuts off and each battery reads 8.1-8.2 volts. Cart has plenty of power but loses it after short rides which pack reads 47-ish volts. Any ideas why it not reaching the 50.93 volts for a full charge? Thanks