2005 Club Car DS slow uphill

[JB in VA]

Looking for some help. I've searched the forums and tried the typical fixes but haven't had any luck.

I recently picked up a 2005 Club Car DS that needed new batteries. I replaced the 4 24 volt batteries with 6 new 8 volt batteries. At the same time I replaced the pack wiring as well as the wiring to the motor and when running the positive I was sure to run it through the sensor. (I used good quality wiring the same size as stock) I am still in the break in period for the batteries where I am running them down to about 50% and then charging them completely. When they are fully charged I am getting a reading of 52 volts across the pack and the meter on the dash shows that they are fully charged. The cart runs well on flat ground including being quick to accelerate from a stop. The issue that I am having is that when I go up even the slightest of grades the cart slows to around 8 or 9 mph and the volt meter on the dash drops to almost half. I have replaced the speed sensor and added the upgraded magnet which has increased the flat ground speed from 13 mph to 16 mph and downhill to 23 mph but did not improve the speed going uphill. Any advice on what to try next would be greatly appreciated.