Charging a 3.7 volt cell phone battery...

Use three "rechargeable" batteries rated at 1.27 volts @ 1650maH

That equals 3.81 volts if connected in series.

- + - + - + --- 3.81

The amperage push to fill the cell phone battery is enough to cause the

cell phone battery to 3/4 full charge in 2 hours.

You will need to solder two leeds out from plus and minus on the battery
Make each leed half inch long hard copper single strand at 22 awg gauge telephone wire for bending to hook to leeds from battery holder.
and damage might occure so this is in last resort or might be for reviving
a shorted battery which is fixed by a short charge cycle with higher amperage
which is what we might be doing here...
I am just guessing but this did charge a battery for me from 3.49 volts dead amperage
to 3.88 vdc. I checked another 3.7 vdc battery fully charged and it was 4.14 vdc at full amperage.

I don't think it will overcharge it will just equal out minus and plus below threshold.

The picture is the 3 AA battery holder. One wire 4 inches hard copper, one wire 3 inches multistrand, which is coming from the 3 battery holder to the cell battery leeds you soldered. Wire the 3 battery holder at plus and minus.

You will place a wire from where ever the batteries end at.
considering the batteries must lay out - +- +- +
and actually in the 3 battery holder will lay out
+~- +~
~- +~-

Cell battery leeds will need to be bent flat or removed so to close the cell phone battery cover.

I glued a plastic circle 1/4 in. spacer to protect the leeds onto the cover and then melted out the proper places where the leeds are then closed the cover over the leeds. That way I don't have to bother with the leeds.

Step 1: 3.7 Vdc Cell Phone Battery Alteration

You will need to solder two leeds out from plus and minus on the battery
Make each leed half inch long hard copper single strand at 22 awg gauge telephone wire for bending to hook to leeds from battery holder.
and damage might occure so this is in last resort or might be for reviving
a shorted battery which is fixed by a short charge cycle with higher amperage
which is what we might be doing here...
I am just guessing but this did charge a battery for me from 3.49 volts dead amperage
to 3.88 vdc. I checked another 3.7 vdc battery fully charged and it was 4.14 vdc at full amperage.

I don't think it will overcharge it will just equal out minus and plus below threshold.

Step 2: Battery Cover Alteration

Cell battery leeds will need to be bent flat or removed so to close the cell phone battery cover.

I glued a plastic circle 1/4 in. spacer to protect the leeds onto the cover and then melted out the proper places where the leeds are then closed the cover over the leeds. That way I don't have to bother with the leeds.

NOTE: Some batteries may become "not supported" by a process used by the cell phone company's.