Help with LiPo safety circuit (not RC)

[ForrestGump]

Apologies for the off-topic, but maybe any of you can help. I've got a Compact Flash Sleeve for my IPAQ that has a LiPo battery on it. Original LiPo was ruined due to long period of no use and leaked destroying a small circuit connected between the poles of the LiPo batt.

I guess this circuit is the one used for overcharging protection / limiting and I've found some commertial ones but all of them are for 2S or 3S packs. I've not found anyone for just a single cell.

I've contacted the manufacturer but he does not even answer me.

Can anybody point me to a schematic or even better an already built safety circuit?

Thanks in advance.
FG

[warren52nz]

I charge my Li-Pos with a constant current, constant voltage source using two linear regulators such as the LM317 (maximum 1.5 amps). Use Goggle to find out info on these, they're really common.

That would probably be easier than designing and building a protection circuit.

You just make a constant current source with one LM317 and follow it with another LM317 set to 4.30 volts. You need a power supply to drive the circuit. You could use a 12 volt battery too. Each LM317 drops about 3 volts across it so you need to be at least 6 volts above 4.30 at the supply.

The current will taper as the battery reaches full charge depending on the gauge of the output wire so you can vary that to get what you want. Tapering is good.

The beauty of a one cell system is that you don't need to worry about balancing cells as you do in a multi-cell battery.

Email me on warrenh@woosh.co.nz if you want more help.

Cheers
Warren