Originally Posted by biggoofball
I'd agree, just something generic. You can measure the voltage just to be sure. If it is a temperature sensor there won't be much voltage and there will be resistance that could be measured if you care. If there is the right voltage at black and red, change the end and tape up the blue wire.
You could remove the shrink wrap and see if there is a thermal resistor or remove the blue wire at that time but, I wouldn't be concerned.
Edit: my guess is it's just a wire splitting the pack voltage so they can use the pack with something else.
Cheers, i have just measured voltages : blue wire is 7.5v and red is 10.1v seems pack may be slightly over charged due to the charger having no sensing technology. it just says charge for 5-6 hours.
I have changed the connectors on the car, charger and the battery to double tamiya. pics below. I just need to decide what to do with the blue wire. may be handy to keep if i ever need slightly lower voltage for a project.
all negatives have been assigned to the circle and positive to the square.