I had a problem with my portable XM radio shutting off when I started my truck. I would then have to push the power button to make it come back on again.

I found a device at a local specialty electronics shop. It uses a very small 12v sealed battery (about the size of a pack of cigs) and a small electronic device. I sits inline from the trucks power. It keeps the small 12v battery charged and if/when it sees a voltage drop (starting truck) it cuts off inline power and switches (2ns) to small battery. So whatever device is hooked to it keeps power and stays on while cranking.

It could be used for gps's, xm and any other device that shuts off when starting the truck.

And yes I did try hooking it up straight to the batteries before I did all this. It seems the cranking drops battery voltage to 10.33v and its not enough to keep devices running.

If anyone needs one let me know. They are my cost 50.00. You need to get a small battery at a local elec. shop.

Do yourself and your accessories a favor. Turn them all off prior to shutting down the truck and don't turn them on again until after starting it and allowing the voltage to increase to normal levels. The electronics will live longer.

It's not always the voltage drop that causes the problem, but the surge that comes when the rig starts and you release the key. We sell GPS equipment for agriculture use and it is a common problem. The battery backup is a good solution.