Having Similar issue with my 3GS and mintyboosy V3 which i got this week , Power Voltages are 5.05 V and data voltages are 1.98 V. I've tried 2 types of batteries , Alkaline AA and Energizer (NiMH) AA recharables.
Ive also tried 2 different OEM cables .
Tried shorting the data pins .
Keep getting " charging not supported with this accessory"
Iv'e plugged in my friends 4S , that seems to charge just fine.