I've got the Gerbing liner and think its very good - you need the temp controller by the way or it will get too hot for comfort. Bought mine about 3 years ago. You need to power it off the battery, not the accessory socket - it draws too much current for the accs socket (the canbus will then shut down power to the accs socket). I use a simple relay which is switched via a connection made to one of the wires on the diagnostic socket (this is the cylindrical device that lurks beneath the seat). Use a multimeter to find a lead that is live only when the ignition is on, then add a connection to this lead and use it to activate your relay. Or you could use the lead running to the accessory socket itself to switch the relay. A bit of minor bodging or a Scotchlok connector is required either way. You can buy a 12V relay from Maplin or Halfords for £2-£3. Get one that will switch at least 10 amps. There is a handy bracket under the RHS black plastic cover, by the air hose, that is ideal for attaching the relay to the frame (at least, there is on a 2004 GS)
If you can't be arsed with the relay, just connect the Gerbing lead directly to the battery. The lead is fused so it is reasonably safe if something happens to short the Gerbing socket when the jacket is not in use.
HTH
Forgot to say that I've had no problems with charging when using the jacket, but at low speeds through a city for example I'd turn my grips down to heat level 1. The jacket is usually running well under max even in sub-zero temps. The heat controller basically turns the jacket on and off for variable periods over a short cycle, so it goes from taking 70watts to nothing then back to 70watts, which is why the accessories socket won't cope (I think it is limited to 5 amps max so 60 watts)
