I have done this a couple of times, and there is no problem. Set the charger to less than an amp. The contact in the middle is just a temperature sensor, no need to connect it.
The only problem might be a suitable interface between the battery and your charge cable.
I suggest getting a piece of wood, hammer in 2 nails so that the backside of the battery has something it can rest at, and put two appropriately shaped pieces of music wire at the front, which press themselves on the contacts. Solder your charge cable to these wires.
I have stopped tinkering though, and got a charger with multiple bays for all my non-RC stuff.