Building Hints - Emergency Charger
If you've ever done any simple electrical work before this will be very simple. All you need in the way of tools are an inexpensive voltmeter, a soldering iron, some heatshrink and a little bit of solder.
You will also need to buy a short (6" or so) servo extension from your hobby shop. The pictures show a Futaba extension to fit the connector installed on this battery pack. You should get whatever type of connectors will fit the rest of your setup.
The instructions below are pretty sketchy because there's no way I could cover all the possible types of connectors and battery connectors. If you've not sure about any done any electrical electrical work before they should be sufficient since the procedure is pretty simple. HOWEVER, if you're not sure about your abilities find somebody to help you out. If you mess up you might fry your radio, your batteries or worse :-(
Start by cutting the servo extension in half. Also cut off the last 4-6" of the transmitter charging cord. The charger will likely be marked to show which side of the connector is positive.
Being careful not to start a short-circuit plug in the adaptor and check the ends of the wires to determine polarity. Attach the half of the servo extension directly to the AC adaptor so that the voltage polarity to the battery is correct.
Next, because you still need to be able to charge the transmitter, wire the other end of the servo extension the the plug that fits the tx so that when all of them are plugged in the polarity to the tx will be as it was at first.
Most chargers of this type supply about 50 miliamps which will charge a 150 mAh battery in 2-3 hours, a 270 mAh battery in about 6-7 hours and a 600 mAh battery overnight.
However, be aware that at the reduced voltage that a 6 or 7-cell battery will be drawing, the current output will be slightly higher and the battery pack will charge somewhat faster. A useful digital voltmeter can cost as little as $20 and would be a great investment to help you figure out what's going on in situations like this.
Also keep in mind that there's no voltage cut-off built into these chargers and it's possible to overcharge batteries (which will shorten their lifespan). This is not an ideal solution and if you have lots and lots of batts get a "real" charger.
The point here is just to get you going if you happen to receive one of these planes as a present or whatever and you haven't yet been able to, or haven't decided which "real" charger to buy.