Is .18A normal parasitic drain?
02-18-2018, 07:44 PM
#1
Member
Thread Starter
Is .18A normal parasitic drain?
I tested by removing each fuse in the driver's side and trunk boxes one at a time, with the car locked, doors closed, armed and in sleep state, and the draw observed on the meter (in series between the trunk batt -ve post and ground cable) was 0.18A (180 milliamps). Is this normal draw for an '06 E55? Or should it be much lower in the .05-.07A range?
02-18-2018, 09:09 PM
#2
Junior Member
Should be much lower. .03 -.05 amps (30mA - 50mA) preferred. Current Drain. The following chart is from GM. It is for a battery with approx. 690 CCA and 110 min Reserve Capacity
GM says the battery run down time will vary depending on cold cranking amperage (CCA) and reserve capacity (RC). If the CCA and RC are higher, then the battery run down time would be longer. If the CCA and RC are lower, then the battery run down time would be shorter. The graph below indicates roughly how many days a 690 CCA battery with at 110 min. RC (60.5 AH) starting at 80 percent state of charge will last with a constant current draw until it reaches 50 percent state of charge. Differences in battery rating and temperature will affect the results.
Current Drain Days
25 mA / 30.5
50 mA / 16.5
75 mA / 11
100 mA / 8.25
250 mA / 3.3
500 mA / 1.65
750 mA / 1
1 A / 0.8
2 A / 0.4
GM says the battery run down time will vary depending on cold cranking amperage (CCA) and reserve capacity (RC). If the CCA and RC are higher, then the battery run down time would be longer. If the CCA and RC are lower, then the battery run down time would be shorter. The graph below indicates roughly how many days a 690 CCA battery with at 110 min. RC (60.5 AH) starting at 80 percent state of charge will last with a constant current draw until it reaches 50 percent state of charge. Differences in battery rating and temperature will affect the results.
Current Drain Days
25 mA / 30.5
50 mA / 16.5
75 mA / 11
100 mA / 8.25
250 mA / 3.3
500 mA / 1.65
750 mA / 1
1 A / 0.8
2 A / 0.4
Last edited by GrumpyDad; 02-18-2018 at 09:12 PM.
02-18-2018, 11:10 PM
#3
Member
Yes, that's a bit high. A general rule of thumb is that parasitic draw shouldn't be higher than 50 miliamps (although most cars are much lower than this: 5 to 30 miliamps is pretty typical). I haven't tested a 211 recently, but I'm guessing it will be towards the top of what's normal (still, it shouldn't be nearly 180 miliamps).
Testing by monitoring the draw while pulling fuses used to be the best way to approach this type of problem, but due to the proliferation of computers in modern vehicles, it is no longer the best approach. When power is disconnected and reconnected to a control unit, the control unit will generally "wake up" for a few seconds up to a few minutes, and may wake up all other control units on the same CAN network, causing a significant draw. Also, when one computer shuts down due to a pulled fuse, it may affect the current draw of other systems on other fuses. The best way to find a draw in modern cars is by measuring the voltage drop across the fuse with an accurate multimeter (manually set the range to the smallest milivolt setting, and touch the two leads to either side of the tiny terminals on the back side of the fuse. All fuses with any current flowing will have some voltage drop, but the one with the parasitic draw will have a much higher voltage drop. The problem is that different size fuses will also have different voltage drops with the same current so you can't just pick the highest number. For example, with 185 miliamps, a standard 30 amp fuse will have a voltage drop of 0.3mV, while a 5 amp mini fuse will have the same 0.3mV voltage drop with only 18 miliamps. There is a chart on this page that shows approximate voltage drops for different fuse sizes: https://us.autologic.com/news/testin...e-voltage-drop.
With a draw of 180 miliamps, before spending too much time checking fuses, I would check for any aftermarket devices connected (phone chargers, alarms, remote start, audio equipment, dash camera, radar detector, etc). Most systems in a car will draw much more power than that if something is wrong (although sometimes failing and/or wet control units can cause a draw like that). Another possibility for a draw like that is a relay that is remaining powered. A typical relay coil draws about 150 miliamps so if you add in 30 miliamps normal draw, you get 180. This is not terribly likely because usually a relay that is powered will result in some other component running which will draw much more power, but there are exceptions (or the component powered by the relay could be defective or have failed or blown a fuse due to the excessive runtime). If this is the case, it's not the relay that's the problem, but rather, whatever switch or control unit powers the relay coil.
Good luck.
Testing by monitoring the draw while pulling fuses used to be the best way to approach this type of problem, but due to the proliferation of computers in modern vehicles, it is no longer the best approach. When power is disconnected and reconnected to a control unit, the control unit will generally "wake up" for a few seconds up to a few minutes, and may wake up all other control units on the same CAN network, causing a significant draw. Also, when one computer shuts down due to a pulled fuse, it may affect the current draw of other systems on other fuses. The best way to find a draw in modern cars is by measuring the voltage drop across the fuse with an accurate multimeter (manually set the range to the smallest milivolt setting, and touch the two leads to either side of the tiny terminals on the back side of the fuse. All fuses with any current flowing will have some voltage drop, but the one with the parasitic draw will have a much higher voltage drop. The problem is that different size fuses will also have different voltage drops with the same current so you can't just pick the highest number. For example, with 185 miliamps, a standard 30 amp fuse will have a voltage drop of 0.3mV, while a 5 amp mini fuse will have the same 0.3mV voltage drop with only 18 miliamps. There is a chart on this page that shows approximate voltage drops for different fuse sizes: https://us.autologic.com/news/testin...e-voltage-drop.
With a draw of 180 miliamps, before spending too much time checking fuses, I would check for any aftermarket devices connected (phone chargers, alarms, remote start, audio equipment, dash camera, radar detector, etc). Most systems in a car will draw much more power than that if something is wrong (although sometimes failing and/or wet control units can cause a draw like that). Another possibility for a draw like that is a relay that is remaining powered. A typical relay coil draws about 150 miliamps so if you add in 30 miliamps normal draw, you get 180. This is not terribly likely because usually a relay that is powered will result in some other component running which will draw much more power, but there are exceptions (or the component powered by the relay could be defective or have failed or blown a fuse due to the excessive runtime). If this is the case, it's not the relay that's the problem, but rather, whatever switch or control unit powers the relay coil.
Good luck.
