Just a question?
Does anyone know how much current is being drawn from their batteries when the car is off?
I know the radio will chew a few milliamps(for the memory store), the alarm(in off standby state), a clock maybe or whatever other accessory you may have connected, but what is considered too much, 50mA , 100mA, 200ma ......?
Battery Usage when car is off.
Started by
fuzzypumper
, Jul 07 2009 12:22 AM
5 replies to this topic
#1
fuzzypumper
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Posted 07 July 2009 - 12:22 AM
#2
_torbirdie_
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Posted 07 July 2009 - 01:40 AM
Just a question?
Does anyone know how much current is being drawn from their batteries when the car is off?
I know the radio will chew a few milliamps(for the memory store), the alarm(in off standby state), a clock maybe or whatever other accessory you may have connected, but what is considered too much, 50mA , 100mA, 200ma ......?
Too much depends on the size of your battery. A largish battery may have a capacity of 100Ah, can produce 100A for an hour, or 1A for 100 hours, or 0.1 for 1000hours.
If you want the car to start after sitting for 2months, 100mA draw would be pushing it. Ive had toranas start after 3 months with the clock, radio(memory) and flashing led going. Never measured the idle current, but a flashing led is at least 10mA.
#3
_evilsim_
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Posted 07 July 2009 - 08:22 AM
I fitted a new stereo (HU) and then I was having trouble with battery going flat after around 3-4 days. The HU was wired so I could listen to tunes will ignition was in the off position, measured the current draw with ignition off (Fluke meter) and it was pulling 250ma.
Rewired HU now so it goes off with ignition (memory still connected) and re-measured current draw at 0ma. I have no clock or other accessory that should draw power other than HU memory. Sorted ...
Simmo
Rewired HU now so it goes off with ignition (memory still connected) and re-measured current draw at 0ma. I have no clock or other accessory that should draw power other than HU memory. Sorted ...
Simmo
#4
fuzzypumper
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Posted 07 July 2009 - 02:26 PM
Torbirdie, thanks forthe reply, I understand the Ah equation, but the question isnt so much how many days or weeks can I leave the car before it wont start as opposed to what are the long term detramental effects of high drain trickle current on a car battery?
Simmo, then I suppose 250mA was too much in your case.
Incidentally, I have always used batteries >500cca in my car and currently have a > 2 year old 550cca atm. I had changed my old but still working 85amp alternator to a VN 85amp alternator a few weeks ago. Now, batteries in my car have never lasted more than 2-3 years in the past and this one was beginning to show signs of giving up the ghost, not lasting more than 3 days after a full charge on the charger. Since the VN alternator went in I can now get about 5 days outa of it.
So now I have done an idle current measurement and got 140mA of drain with car off.
Through a process of pulling fuses I figured the alarm seems to be chewing about 10mA, another 10mA is being wasted by something yet untraced and the rest about 120mA by the radio and possibly something else on the same feed(unsure atm).
Is 140ma too much in the long term?
Simmo, then I suppose 250mA was too much in your case.
Incidentally, I have always used batteries >500cca in my car and currently have a > 2 year old 550cca atm. I had changed my old but still working 85amp alternator to a VN 85amp alternator a few weeks ago. Now, batteries in my car have never lasted more than 2-3 years in the past and this one was beginning to show signs of giving up the ghost, not lasting more than 3 days after a full charge on the charger. Since the VN alternator went in I can now get about 5 days outa of it.
So now I have done an idle current measurement and got 140mA of drain with car off.
Through a process of pulling fuses I figured the alarm seems to be chewing about 10mA, another 10mA is being wasted by something yet untraced and the rest about 120mA by the radio and possibly something else on the same feed(unsure atm).
Is 140ma too much in the long term?
Edited by fuzzypumper, 07 July 2009 - 02:27 PM.
#5
_torbirdie_
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Posted 07 July 2009 - 05:47 PM
Yes, I think 140mA is quite high and could cause significant battery drain, that's going to flatten a normal battery completely in 3 weeks or so. Not good to even leave it 2 weeks, discharging past 25% causes significant damage and the longer a battery is left in a state of less than 80% charge the worse of it will be.
I realise the typical battery selection at the moment pairs high CCA with high RC(reservere capacity) or Ah. However, it doesnt have to be the case and batteries with higher CCA may not last longer as they are built with thinner plates to get more surface area with the electrolyte to get the fast reaction/high current, and are typically overkill for starting conditions in our climate.
For all the info you can take in have a look at :
http://jgdarden.com/...aq/carfaq11.htm
I realise the typical battery selection at the moment pairs high CCA with high RC(reservere capacity) or Ah. However, it doesnt have to be the case and batteries with higher CCA may not last longer as they are built with thinner plates to get more surface area with the electrolyte to get the fast reaction/high current, and are typically overkill for starting conditions in our climate.
For all the info you can take in have a look at :
http://jgdarden.com/...aq/carfaq11.htm
Edited by torbirdie, 07 July 2009 - 05:47 PM.
#6
fuzzypumper
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Posted 07 July 2009 - 06:21 PM
Thank Torbirdie, I did some more investigating today on where the 140mA is going.
A majority of it was being lost down the STOP Tail fuse which my CD/radio unit runs is connected to as well. However I was getting a couple of random readings. When i first tested with fuse inline I radio was only taking 30ma which would them drop to less than 10ma after awhile. But as I continued to test, with and without fuses the meter jumped up to between 110-130ma a few times.
I worked out when I pulled the interior light it went down to 30mA, put the light back back and went up again.
It them dawned on me that the current may be flowing back into the alrms input circuit as I had attached the alrm detection wire to the white door switch wires in an attept to share the switch. I cut this wire and all is good.
The total current being drained from the battery now is only 30mA and not 140mA.
Now I have to put seperate switches on the doors for the alarm or see if a diode to sufficient to stop the back flow.
I will also thy and figure out where the remaining 30mA is going.
A majority of it was being lost down the STOP Tail fuse which my CD/radio unit runs is connected to as well. However I was getting a couple of random readings. When i first tested with fuse inline I radio was only taking 30ma which would them drop to less than 10ma after awhile. But as I continued to test, with and without fuses the meter jumped up to between 110-130ma a few times.
I worked out when I pulled the interior light it went down to 30mA, put the light back back and went up again.
It them dawned on me that the current may be flowing back into the alrms input circuit as I had attached the alrm detection wire to the white door switch wires in an attept to share the switch. I cut this wire and all is good.
The total current being drained from the battery now is only 30mA and not 140mA.
Now I have to put seperate switches on the doors for the alarm or see if a diode to sufficient to stop the back flow.
I will also thy and figure out where the remaining 30mA is going.
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