Hard wiring a solar trickle charger

[FST4RD]

Is there a way that you could hard wire a solar trickle charger without a switch?
One of my cars gets used very little, so I bought a solar trickle charger to keep the battery ticking over. The I instructions say not to turn the car on with it connected, fair enough, I was thinking of putting a switch inside so when I want to use the car I dont have to pop the bonnet and disconnect.
However is their a relay or something I could put between the battery and the solar panel that would recognize the car turning on or running and shut off? Like a 1 way power relay that allows power to run from the solar panel to the battery, but not the other way?

[whynot]

I would just wire up a relay from the accessory contact on the ignition so when you turn the keys on it turns the solar panel off. Should be quick and fairly easy

[FST4RD]

So a relay that's on when the car is off and off when you turn the key on?

[jondee86]

A normally closed (NC) relay that opens the charger circuit when
energised by the accessory output of the keyswitch.

Cheers... jondee86