Many Thanks newbie for this very helpful post. My battery was held in the Mayday Unit by tamper proof screws which I managed to undo with an allen wrench. I bought a replacement battery pack from Battery worked. It was not a Toyota unit but just a generic 7.2V nicd pack. I think that the design is poor. Not only is the battery under constant charge causing poor battery life but it is the very dickens to replace as you quite rightly point out. I got longer leads with my replacement battery so I can mount it outside the box. That way, next time the battery fails I can replace it easily from within the boot. I don't mind paying $30 every couple of years and doing a 10 minute replacement myself rather that paying Toyota $300 have having to pay one of their blokes to do the tedious replacement process. BTW, my battery volts had fallen to 6V indicating that one cell had gone short circuit. Toyota Link had not detected to low volts yet but the red led had come on. Also, be warned that as soon as you unplug the unit, Toyota Link will phone you to say that there is a security alert from your car.
