Hi guys,
My first post here after watching Dave's exploits for about 2 years, I finally needed some EEV assistance and there was clearly no better place to turn! Apologies if this isn't how this forum works, or is in the wrong place, but let me know if so
Basically, I have purchased a car GPS tracker, specifically I was looking for one without an internal battery as they all seem to be something silly like 1000mah which only gives a few days of runtime. My car can be parked up for a week at a time or longer so these were useless.
The tracker itself takes a standard ~12v from a car battery, but in the box it also includes a little magic black box which contains a boost converter and it lets you power the thing from a 5v USB power bank as the boost converter steps this up to 12v.
What I'm looking to do, it provide a system whereby when the car if off, the included boost converter powers the tracker from a USB battery bank, however, when the car is on, it needs to instead draw 12v power directly from the car (which I will provide), and start charging the USB battery bank itself. Once the bank starts charging, output is terminated anyway. I was going to accomplish this step by hacking up a standard car cigarette lighter USB charger thing as it already does the 12v to 5v step down which I would need to charge the USB bank, but its the switchover which has got me confused. . .
My initial thought was to try and do it through relays, but I soon got lost down a rabbit warren from which io couldn't recover. I'm a optimistic amateur when it comes to this stuff, I can do basic breadboard work, possibly down to soldering IC's as long as they come with sockets if this helps.
I'm sure in my head its probably a simple circuit, but not being my field of experience, I cant wrap my head around it!
Any replies at all would be amazing, thanks