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Dan2 18th March 2008 12:48 PM

power consumption of "off" head unit.
does anyone know how much current is drawn from a head unit when it is off?? (just to keep the memory)

i want to run my head unit off a computer power supply, but i need to make a plan with (probably) batteries to hold the memory of the frontloader. it is going to be portable so it won't be plugged in all the time.

richie00boy 18th March 2008 01:17 PM

They may vary between models so why not just measure yours? Should take all of 30 seconds with a multimeter.

Travis Clarke 18th March 2008 04:11 PM

Yes, you should probably see somewhere between 25-50mA (.025-.050 A) on average. Just my experience with it.

That's one of the useful bits of information to have when troubleshooting a vehicle in which the battery keeps getting drained. Some customers would never believe it wasn't the head unit draining it until I proved it (and had a number to start with for the typical current draw).

Note: I do mean truly off, when ONLY the BATT wire has voltage applied, not the ACC wire too.

Dan2 20th March 2008 06:48 AM

ok thanks guys.

as i said i want to have a battery hooked up to keep the memory - i once did an experiment with a capacitor (my old car had a bad battery so the HU's memory would get lost sometimes when starting) connected to the batt wire. the cap dropped down to about 1V (in my test) and then i turned the radio on and the memory was still there.

So i want to parallel some rechargeable batteries (which will be charged when the radio is plugged in) and connect them to the radio. do you think it would work??

DigitalJunkie 20th March 2008 07:20 AM

Put a diode in series with the line to the radio/nicd's so that when you start the car,they don't drain-back into the starter motor,etc..
A big cap should work in place of the nicds.
Some kind of big Schottky diode,or fast-recovery type would be best (lower forward-voltage drop)

Dan2 21st March 2008 11:45 AM

well i had a different solution - i got another car!!! Actually the reason i sold my old Corolla was 'cos someone gave me a really good offer for it.

i still want to know what the lowest voltage is i can use for the batteries.

Dan2 23rd March 2008 08:38 AM

how would i build the battery charger?? cos i know you get nicd chargers, NiMh chargers etc. whats the difference and what goes into a charger??

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