any 4.2 volt charger will charge your 3.7
batteries.
And DONT use the charger that came with the kit- MY
batteries MELTED AFTER BEING ON THERE FOR 20 MINS.
The light was red, but I smelled burning. Took them off (they really fell right out as the springs are crap) and burnt my fingers.
OK, DH came home from out of town and had a look at my set up (he's a gorgeous techie guru).
He says:
The charger is junky but fine. Mine just had broken springs (he fixed mine). The light didn't work correctly on my charger. It showed red, however, he tested the 3.6V batts that came with the unit, and they measured at 4.0V.
They were fully charged on the charger and were not placed correctly on the charger because of the springs. This is why the charger had a burning smell.
I explained to him that the batteries were super hot and I thought I needed to throw them away. He said no need to.
OK moving on to the mod for the space within the SP2:
1. Screw the bottom cap onto the tube.
2. Put battery in tube.
3. Place
Black O Ring Size 10 from Home Depot onto top cap threads.
4. Screw top cap with Oring tightly onto tube.
5. Screw 501 adaptor onto top cap.
6. Screw on 501 atty/carto.
The best placement of the O-ring is between the top cap and tube because you won't be unscrewing that portion as much as the bottom (i.e. replacing the batts).
He said do not place an O-ring between the atty/carto and the adaptor. I don't know what his reason was because I stopped listening.