Help Please! Parasitic Battery Drain
02-29-2012, 06:11 PM
#16
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Precision Motion, 2805 Chicago Ave., Riverside, CA 92507 (951) 784-0425, is a good independent Porsche shop. Ask for Donny Kravig, the owner.
02-29-2012, 06:16 PM
#17
Rennlist Member
Alex is right...Just get a DMM. Disconnect the neg. battery terminal and connect one of the DMM's leads to the Neg. lead and the other to the Neg. battery terminal. You now have the DMM in series. Allow the DMM to be outside the trunk, then close the trunk on the leads and wait for the trunk light to go out after supposedly 15 sec. If your current draw is more than 35-50 milliamps, something's not shutting off. Open the fuse box near the passenger side cowl and start pulling fuses one at a time in a logical manner, closing the trunk each time. If that fuse doesn't eliminate the drain, replace it and go to the next one. Keep this up until you find the one that stops the drain. Now you have a general idea where to look for a solution. I'm betting on a) a sound system amp that's not shutting down or b) the microswitch under the trunk latch needs adjusting or replacement.
02-29-2012, 07:03 PM
#18
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Thread Starter
Get yourself a digital multimeter and be done with the guessing. You can get this one at Walmart for $12. I keep one in my roadside repair kit.
Dan, find a local RLer that knows what they are doing. They can do some simple tests in a matter of minutes.
Although unlikely, just because you installed a new battery does not mean it can't be a dud. With the engine running, your battery voltage should be 14.0 to 14.4V, provided the battery is health and fully charged. An on-board voltmeter is a handy device.
Dan, find a local RLer that knows what they are doing. They can do some simple tests in a matter of minutes.
Although unlikely, just because you installed a new battery does not mean it can't be a dud. With the engine running, your battery voltage should be 14.0 to 14.4V, provided the battery is health and fully charged. An on-board voltmeter is a handy device.
Alex is right...Just get a DMM. Disconnect the neg. battery terminal and connect one of the DMM's leads to the Neg. lead and the other to the Neg. battery terminal. You now have the DMM in series. Allow the DMM to be outside the trunk, then close the trunk on the leads and wait for the trunk light to go out after supposedly 15 sec. If your current draw is more than 35-50 milliamps, something's not shutting off. Open the fuse box near the passenger side cowl and start pulling fuses one at a time in a logical manner, closing the trunk each time. If that fuse doesn't eliminate the drain, replace it and go to the next one. Keep this up until you find the one that stops the drain. Now you have a general idea where to look for a solution. I'm betting on a) a sound system amp that's not shutting down or b) the microswitch under the trunk latch needs adjusting or replacement.
02-29-2012, 07:07 PM
#19
Rennlist Member
Thread Starter
02-29-2012, 09:52 PM
#21
Rennlist Member
Dan, since you're not a DIYer, just a couple of tips.
To measure current, the red lead plugs into DC 10A (left) and the black lead plugs into COM (center).
Since you do not know how much the current drain is, set the rotary selector to DC 10A. You start high so as not to blow a fuse. If the reading is less than 0.2A, then you can switch the selector to 200 mA (you also need to plug the red lead into V Ω mA (right).
The above applies to the meter I pictured. Note, the 10A setting does not have a fuse, but it is limited...see note on meter.
Ask if you are in doubt.
To measure current, the red lead plugs into DC 10A (left) and the black lead plugs into COM (center).
Since you do not know how much the current drain is, set the rotary selector to DC 10A. You start high so as not to blow a fuse. If the reading is less than 0.2A, then you can switch the selector to 200 mA (you also need to plug the red lead into V Ω mA (right).
The above applies to the meter I pictured. Note, the 10A setting does not have a fuse, but it is limited...see note on meter.
Ask if you are in doubt.
03-01-2012, 11:45 AM
#22
"Disconnect the neg. battery terminal and connect one of the DMM's leads to the Neg."
Ideally the best way to measure a draw, especially on cars with a lot of
electronics, is to:
1. Connect one of the meter leads to the chassis ground. With a digital
meter it doesn't matter which one.
2. Loosen the negative lead while still allowing it to make connection
to the battery post.
3. Place the other meter lead on the center of the negative post.
4. Now carefully remove the negative battery cable from the post.
The meter will now 'carry' and measure the draw current.
This method will prevent a surge current from damaging the meter and
not cause some electronics to draw their normal operating current
after application of the battery voltage and prior to their 'sleep' mode,
i.e. 'off' state.
Ideally the best way to measure a draw, especially on cars with a lot of
electronics, is to:
1. Connect one of the meter leads to the chassis ground. With a digital
meter it doesn't matter which one.
2. Loosen the negative lead while still allowing it to make connection
to the battery post.
3. Place the other meter lead on the center of the negative post.
4. Now carefully remove the negative battery cable from the post.
The meter will now 'carry' and measure the draw current.
This method will prevent a surge current from damaging the meter and
not cause some electronics to draw their normal operating current
after application of the battery voltage and prior to their 'sleep' mode,
i.e. 'off' state.
03-01-2012, 09:14 PM
#23
Rennlist Member
Thread Starter
Dan, since you're not a DIYer, just a couple of tips.
To measure current, the red lead plugs into DC 10A (left) and the black lead plugs into COM (center).
Since you do not know how much the current drain is, set the rotary selector to DC 10A. You start high so as not to blow a fuse. If the reading is less than 0.2A, then you can switch the selector to 200 mA (you also need to plug the red lead into V Ω mA (right).
The above applies to the meter I pictured. Note, the 10A setting does not have a fuse, but it is limited...see note on meter.
Ask if you are in doubt.
To measure current, the red lead plugs into DC 10A (left) and the black lead plugs into COM (center).
Since you do not know how much the current drain is, set the rotary selector to DC 10A. You start high so as not to blow a fuse. If the reading is less than 0.2A, then you can switch the selector to 200 mA (you also need to plug the red lead into V Ω mA (right).
The above applies to the meter I pictured. Note, the 10A setting does not have a fuse, but it is limited...see note on meter.
Ask if you are in doubt.
"Disconnect the neg. battery terminal and connect one of the DMM's leads to the Neg."
Ideally the best way to measure a draw, especially on cars with a lot of
electronics, is to:
1. Connect one of the meter leads to the chassis ground. With a digital
meter it doesn't matter which one.
2. Loosen the negative lead while still allowing it to make connection
to the battery post.
3. Place the other meter lead on the center of the negative post.
4. Now carefully remove the negative battery cable from the post.
The meter will now 'carry' and measure the draw current.
This method will prevent a surge current from damaging the meter and
not cause some electronics to draw their normal operating current
after application of the battery voltage and prior to their 'sleep' mode,
i.e. 'off' state.
Ideally the best way to measure a draw, especially on cars with a lot of
electronics, is to:
1. Connect one of the meter leads to the chassis ground. With a digital
meter it doesn't matter which one.
2. Loosen the negative lead while still allowing it to make connection
to the battery post.
3. Place the other meter lead on the center of the negative post.
4. Now carefully remove the negative battery cable from the post.
The meter will now 'carry' and measure the draw current.
This method will prevent a surge current from damaging the meter and
not cause some electronics to draw their normal operating current
after application of the battery voltage and prior to their 'sleep' mode,
i.e. 'off' state.
