I have little knowledge on electronics apart from following a few guides. I have made a few 7 segment displays, nothing complicated.
Recently my girlfriends car was stolen and she has an insurance style GPS tracker, but only gave the road that the tracker was down. We spent hours looking for clues and eventualy we found the car and it had been chopped up into bits with the tracker striped out.
Now these GPRS trackers are good but useless if the battery is pulled out.
So my question is:
How do I create a circuit so that when the car battery is dead/removed, a small 12V battery hidden away kicks in and powers up the tracker.
Now I have done my research and all I can come across is complicated circuits that involves the 2nd battery being charged up aswell.
I don't need this, all I need is a few good hours out of the second battery so charging the second battery is not needed.