power consumption of "off" head unit.

Dan2 · 18th March 2008, 12:48 PM

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.

MartyM · 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??

18th March 2008, 12:48 PM	#1
Dan2 diyAudio Member Join Date: Sep 2005	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.

18th March 2008, 01:17 PM	#2
richie00boy Did it Himself diyAudio Member Join Date: Nov 2003 Location: Gloucestershire, England, UK	They may vary between models so why not just measure yours? Should take all of 30 seconds with a multimeter. __________________ www.readresearch.co.uk my website for UK diy audio people - designs, PCBs, kits and more

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18th March 2008, 04:11 PM	#3
MartyM diyAudio Member Join Date: Oct 2006 Location: Monroe, North Carolina, USA	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.

20th March 2008, 06:48 AM	#4
Dan2 diyAudio Member Join Date: Sep 2005	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??

20th March 2008, 07:20 AM	#5
DigitalJunkie diyAudio Member Join Date: Apr 2003 Location: Portland,Oregon Blog Entries: 4	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)

21st March 2008, 11:45 AM	#6
Dan2 diyAudio Member Join Date: Sep 2005	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.

23rd March 2008, 08:38 AM	#7
Dan2 diyAudio Member Join Date: Sep 2005	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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