Look at the image on the right.
The BLUE one is the powerchairs charge socket.
The black one is your chargers plug, or your new phone connector XLR / Neutrik plug.
You need pin 1 and 2 only.
On MOST chairs 1 is positive. So it goes to the centre pin on the car cigar lighter plug. And pin 2 is negative and goes to the outside.
My HTC phone, its USB charge lead, and the adapter (top left) that converts the powerchairs charge socket, to a 5v USB phone charge socket. Small enough to keep in a pocket or your wallet.
Take one of these car cigar lighter USB things apart as below.
The "Belkin" cigar lighter / USB socket designed for a car. £3 from eBay. Obviously dismantled here! Throw away the shell, cut off the steel "wings" (this is the negative). The spring in the middle is positive. It is a mini inverter. It changes 24v to 5v efficiently with nearly no loss or heat.
Here I have already added a 2 core cable to the Neutrik "charger" socket. These are £3 on eBay too. The cable needs soldering, and any old bit of cable will likely do here. This is a bit that came from an old hair dryer. My hair is long gone! The bit on the right is the tiny inverter taken from its case, and changes the 24v to 5v for the USB.
Now has the cable attached. This is the POS side. (the spring.) Its soldered to, and runs in the spring for added support!
This is the NEGATIVE side. Note the heat shrink tube... Add a much larger size over the top of the complete thing will protect it when completed. As below.
When you plug in to the powerchair's charge port there will be an LED that lights up. At least on the Belkin version. This is ready to use. Works great. Its that simple.
DON'T GET THE PLUS AND MINUS MIXED UP! It will fry the circuit board most likely. And waste £3... If unsure of powerchair charge plug polarity just test it with a volt meter. But the vast majority are as per the diagram above. Tiny bit of simple soldering, and £6 worth of bits! Now I can use sat navigation, display maps on screen, and the phone battery doesn't die. It charges up instead.
Works for any 24v powerchair. Runs and charges iPhones, HTC, Blackberries, Tablets, or anything that normally needs power or charges from a USB port.
There's a thread on my forum discussing this here And contrary to some peoples opinion it will not damage your powerchair. That socket can supply 8 amps+ Quite safely. If you worry about these things, its also a good idea to add a 1 Amp (1000mA) fuse in the cable.