Neon conversion needs some help

I converted a 1995 Dodge Neon to a 144V electric. My problem is this:
When i first put the car in service, I was getting about 24 miles of driving range to 50% battery discharge. Now I’m getting about 6 miles and the vehicle is almost dead with a runing voltage of about 108V. I’m sure it has to do with battery charging (but I’m not sure). Here is a list of the cars assembly units:
Zilla Z1K-LV controller
Hairball HB2 interface
ADC 9" Series Motor
Zivan NG3 battery charger (setup for 144V series string 12 V batts.)
Universal Power Group UB121100 (12V. 110AH.) AGM batteries (quan. 12)
IOTA DLS 45 power converter (for charging the 12V accessory battery)

I have not measured each battery in the series string at this time, but hope to get to that next week.
If anyone has any suggestions, please let me know.
Thanks in advance…
Doc Paul