Why is my electric club car stalling uphill?

ive noticed going downhill the engine doesnt brake like its supposed to and going uphill the accelerator completely cuts out and i have to let off the accelerator and then press it again to go. i have brand new batteries. i did hook up my multimeter to watch the voltage when it kicks off...going uphill it drops to 42 to 45 volts depending on how steep the hill is...but when the accelerator stops and i stall it jumps to 47 volts. i dont know what else to do at this point.