The stock operation would charge my iPhone to about 50%. I remembered that I could use Li-Po batteries in parallel without having to modify the circuitry, so I decided to add the battery from my first T-Max Heat unit to the second one to extend the battery life. I also never used the heat feature, so I could remove the heating pads to make room.
This was an easy mod:
- open up the device
- remove the heat pads to make room for the extra battery
- solder on the second battery
- close up the device
- discharge batteries
- charge batteries
I am not 100% sure that this can be used on all Li-Po battery circuits or with other types of batteries.