Wireless charging system that consist in a trasmitter placed on the workbench and a reciever integrated to the battery pack, so you can charge your tools simply putting it on the trasmitter or when you are working you can put only the spare battery on the charging station.
A voltage booster is needed too into the battery pack in order to make the system working.
The steps of the project!
At first I’ve analyzed the drill and the original power supply.
The original charging system is very simple it consist in a wall transformer with the output of 15,3 V DC and the maximum current of 210mA. The power supply can be connected to the drill by a jack and it is almost directly connected in parallel with the batteries as you can see in the picture above: there is only a (hidden) diode that you can see in the schematic at the end of the article.
Since the step up converter behaves as a voltage ideal generator (keeping the voltage constant) the current supplied to the battery can be too high, so it is necessary to limit this parameter.
I’ve choose the simplest way to limit current: putting a resistor in series; I’ve mesured the open circuit voltage and the shortcircuit current (very quickly) of the original power supply and I’ve calculated its internal resistance by the Ohm’s law, R=V/I = 15/1 = 15 Ohm. So I’ve put a resistance of 15 Ohm 1W in series to the step up converter.
I’ve created two stl models with SketchUp in order to hold in place the static part and the mobile part of the circuit, you can download it for free at: http://www.thingiverse.com/thing:2057982
I’ve printed them with my 3Drag.
The base with the holes for the board, the coil and the battery (D shaped).
The “battery holder” with the hole for the reciever coil ad the left part with space for the other electronics.
The progect completet: you can recharg a spare battery….
or even the main battery without dismounting it, and without wires!
The scheme is pretty simple, into the dash-dotted box there is the original circuitery of the drill and outside only 5 elements
The 5V provided by the reciever module are elevated to 15V by the step up module and the resistor provide a limit to the charging current. No diode is necessary sinse the step up converter block the reverse current.
-Transmitter Module FT1235M with its coil
-Receiver Module FT1236M with its coil
-DC-DC step up module based on XL6009E1
-3d printed stand for the trasmitter module http://www.thingiverse.com/thing:2057982
-3d printed shell for the reciever module, the step-up converter the resistor and the battery of the tool quicklyhttp://www.thingiverse.com/thing:2057982
-R1 15 Ohm 1W