Keeping unit powered while starting engine.

[ablackformula]

I know this has been a topic of the past, where time-released capacitors were used not to keep power to the unit (necessarily) while cranking, but to keep power to the unit for a short time after it's been removed. I have an idea that I wanted to run by you guys before the labor of trying it, although I'm pretty sure it'll work...

 

I attached a quick diagram to help explain, but basically:

 

The red wire of the navigation, which usually is connected directly to the car's acc/run wire, would be cut and wired in series with the normally closed contacts of a SPDT relay. At this point, nothing should change, the same two wires are connected as long as the relay is not energized. The normally open contact, as well as one side of the low current circuit, are connected to the starter wire (the other side of the low current circuit to ground.) When the key is held to the start position, the relay energizes and maintains 12v at the navigation system, preventing a re-boot.

 

This relay would keep the starter circuit and the rest of the cars 12v system isolated, so when the relay is energized, the 12v doesn't back feed and supply the entire run/acc circuitry. The only additional load to the battery while cranking is the navigation.

 

While I'm sure this will work, my question is if the fraction of the second it takes the relay to energize/de-energize, the lack of 12V to the red wire would cause the navigation to restart. I'd guess not, but am not sure how sensitive the power supply of the navigation is. Any ideas?

[rgarjr]

The time it takes the relay to switch probably will shut down the AVIC. I think u need some type of delay unit that will keep 12V a few seconds after it has been turned off.

 

PAC TR7 maybe. U can contact PAC tech support and ask them if it will work.

[mtimmy]

put a big enough capacitor in it.