RE: wall wart charger
your 9V wall wart should work OK for the 1500 mAh pack. should take about 15 hours. if possible, check the current through the system while it is charging. this requires a servo extension with one of the wires cut so that you can put an ammeter in series with the circuit. If you don;t have an ammeter, get a friend to help you with this. Just because the wall wart charger says "100mA", doesn't mean it will actuallyput out that much. depending upon how many volts the battery has, this can go up or down from its rated output.