Keep radio on for a few minutes after turning key off

[stumagoo]

Sooooo....I decided to bite the bullet and buy the Redarc TIM05 Relay with the "delayed off" timer.

I wired it into the standard ISO Aerpro harness (actually bought a spare from Supercheap for $25).
Using the relay, power to the ACC red wire is maintained (drawing from the yellow constant power line) and the radio stays on after the ACC key position is turned off - part one of the problem solved.

However, upon cranking the starter, my Sony XAV-AX100 dropped out and rebooted - which was not expected. Did some checking with a multimeter and the voltage drop on the line is from 12.4V to 10.4V while the starter is engaged. To make sure this is not a wiring issue, I wired the radio up to the battery and retested - same thing happens, drops out on starter crank when the battery voltage drops to 10.4V.

I am guessing that the radio needs at least 10.5V to stay on. I have it on charge tonight to see if the battery is on the way out...

The next challenge is then to figure out how to keep the voltage above the 10.5V mark....

Any ideas on next steps? Dual battery perhaps?

Josh

This is the reason ancilleries are turned off on startup..... Voltage drop, under powering many electronics can be bad for them but the bigger issue is providing the starter with the most current available, when a battery is getting a little long in the tooth, the starter is getting a bit iffy, or the car is older, things can have an issue starting, if you have your lights on an wipers and radio etc on a cold wet morning it can indeed draw enough for a modern computer controlled engine to not start, an those with high compression diesels are even more suseptible to low voltage issues. that is the biggest reason every thing turns off when you hit start.... of course they were not thinking of the practicality of car puters rebooting each time


As for electronics being susceptible I know its a possibilty but we have to protect our ecu when we weld or jumpstart due to this but it is running when we start the engine and it is more important than any other aspect of the vehicle when it comes to getting from a to b so while I acknowledge the possibilty I dont accept it as the main reason

[OldEmmGee]

Small battery

If you are realy concerned about this, you could run your head unit off a small battery (1.5Ah SLA for example) and have this connected to the existing BATT through a diode....the Head Unit woud run off this battery, and the diode (20A or 30A) would provide isolation.

As the head unit takes maybe 10A running, the diode needs to be of a reasonable capacity...

You could use a relay instead of diode, I guess....and check whether the head unit takes its power from the BATT (my guess) or ACC lines....

[craka]

If you are realy concerned about this, you could run your head unit off a small battery (1.5Ah SLA for example) and have this connected to the existing BATT through a diode....the Head Unit woud run off this battery, and the diode (20A or 30A) would provide isolation.

As the head unit takes maybe 10A running, the diode needs to be of a reasonable capacity...

You could use a relay instead of diode, I guess....and check whether the head unit takes its power from the BATT (my guess) or ACC lines....

Pretty much what ^ he said. (1) Either a backup battery with diode in circuit. Or
(2) A bloody big capacitor. Option one more doable.

Reason voltage comes down during cranking is the large current draw off the battery, during the high current draw the voltage across terminals will drop.

Figure2 on this link show an example of such "Adding a small 12V battery" http://archive.oreilly.com/pub/h/3649