Battery Dies Everyday: Testing For Parasitic Draw
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Date: 2020-12-13
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Comments and reviews: 9
Too-old
I disconnect the negative and positive cable from the battery, hook up the vom in ohm range to the end of the negative cable and a ground source on the body to look for good continuity. Then I move the vom to the positive cable to see what kind of resistance there is between the body ground and the end of the positive cable. That's how I found my last episode when my alternator grounded (long story during changing a radiator out) out and put a solid 4 ohm ground into the battery and killed the battery.
On another car, it wouldn't start in the morning only. The battery died overnight. The car ran and started alright in the morning and all day long after jumping it. Did the usual battery change and alternator change but the battery still died overnight. It turned out to be the wiring harness in the engine compartment. Apparently the full charge from the alternator wasn't making it to the battery even though I could read 14vdc at the battery while engine running.
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I disconnect the negative and positive cable from the battery, hook up the vom in ohm range to the end of the negative cable and a ground source on the body to look for good continuity. Then I move the vom to the positive cable to see what kind of resistance there is between the body ground and the end of the positive cable. That's how I found my last episode when my alternator grounded (long story during changing a radiator out) out and put a solid 4 ohm ground into the battery and killed the battery.
On another car, it wouldn't start in the morning only. The battery died overnight. The car ran and started alright in the morning and all day long after jumping it. Did the usual battery change and alternator change but the battery still died overnight. It turned out to be the wiring harness in the engine compartment. Apparently the full charge from the alternator wasn't making it to the battery even though I could read 14vdc at the battery while engine running.
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Russell
Just an intense and advanced DIY'er here. But, since it makes no sense to have expensive production-level kit for my situation, I find making little helpful aids key in solving the occasionally-encountered shade tree mechanic issues.
My multi meter has one of those expensive amp fuses for the low-scale portion of its useful range. I think it pops at around half an amp. Needless to say, I've smoked a number of them. However, before I get down to using the meter for tracing down a few milliamps, I use a DC amp clamp. But, DC amp clamps tend to be not very accurate at the couple dozen milliamp side of the scale.
So, to help the amp clamp along, I put a ten loop coil of 18 gauge or so wire together with zip-ties along with a standard 5 amp blade fuse. The amp clamp then goes on the 10-loop. Displayed readings need to be divided by 10, however.
One of these days, I'll sit down and build a 100 loop coil of varnish-coated armature wire.
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Just an intense and advanced DIY'er here. But, since it makes no sense to have expensive production-level kit for my situation, I find making little helpful aids key in solving the occasionally-encountered shade tree mechanic issues.
My multi meter has one of those expensive amp fuses for the low-scale portion of its useful range. I think it pops at around half an amp. Needless to say, I've smoked a number of them. However, before I get down to using the meter for tracing down a few milliamps, I use a DC amp clamp. But, DC amp clamps tend to be not very accurate at the couple dozen milliamp side of the scale.
So, to help the amp clamp along, I put a ten loop coil of 18 gauge or so wire together with zip-ties along with a standard 5 amp blade fuse. The amp clamp then goes on the 10-loop. Displayed readings need to be divided by 10, however.
One of these days, I'll sit down and build a 100 loop coil of varnish-coated armature wire.
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spelunkerd
More than a generation ago, I had an embarrassingly dumb habit of blowing the amperage fuse in cheap multimeters. Many could not be fixed, and some gave no indication of what I'd done. Some worked fine but would never again measure amperage. For those who don't want to feed current through their meter, you can use a 1 ohm 100 Watt resistor in its place. Then use a multimeter to measure voltage drop across the resistor. The cool thing about a 1 ohm resistor is that the voltage drop across the resistor is also the amperage going through it (i=V/1 ohm. Of course if current is more than 8 amps (=100W/12V) you can't leave it on for more than a few seconds, because you're exceeding the max current for the resistor.
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More than a generation ago, I had an embarrassingly dumb habit of blowing the amperage fuse in cheap multimeters. Many could not be fixed, and some gave no indication of what I'd done. Some worked fine but would never again measure amperage. For those who don't want to feed current through their meter, you can use a 1 ohm 100 Watt resistor in its place. Then use a multimeter to measure voltage drop across the resistor. The cool thing about a 1 ohm resistor is that the voltage drop across the resistor is also the amperage going through it (i=V/1 ohm. Of course if current is more than 8 amps (=100W/12V) you can't leave it on for more than a few seconds, because you're exceeding the max current for the resistor.
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Stephen
Amp clamps are often not very accurate. They usually measure rounded to 1/10th of an amp at best. A trick I learned a long time ago to increase the amp clamps sensitivity tenfold is to take a 14 ga wire and loop it 10 times. Connect each end in series to the circuit being tested and install the amp clamp through the loop created. This increases the magnetic field in the circuit 10 times. The amp clamp reading now reads 10 times the actual circuit amperage. Move the decimal point one spot to the left and voila, a 10x increase of amp clamp sensitivity achieved. 1/10th sensitivity is now 1/100th.
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Amp clamps are often not very accurate. They usually measure rounded to 1/10th of an amp at best. A trick I learned a long time ago to increase the amp clamps sensitivity tenfold is to take a 14 ga wire and loop it 10 times. Connect each end in series to the circuit being tested and install the amp clamp through the loop created. This increases the magnetic field in the circuit 10 times. The amp clamp reading now reads 10 times the actual circuit amperage. Move the decimal point one spot to the left and voila, a 10x increase of amp clamp sensitivity achieved. 1/10th sensitivity is now 1/100th.
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autos
Thank you for this method. It will really help me in the future. Sometimes when I get a current draw vehicle to fix I get really mixed up. I'm not ashamed to say I don't know to the customer, and that only really happens on current draw vehicles. I refuse to use the parts cannon, so I tell the customer I don't know. With the tips you showed in this video and the previous video, I'm actually looking forward to my next current draw customer. Thanks for taking the time to show people your methods. Merry Christmas.
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Thank you for this method. It will really help me in the future. Sometimes when I get a current draw vehicle to fix I get really mixed up. I'm not ashamed to say I don't know to the customer, and that only really happens on current draw vehicles. I refuse to use the parts cannon, so I tell the customer I don't know. With the tips you showed in this video and the previous video, I'm actually looking forward to my next current draw customer. Thanks for taking the time to show people your methods. Merry Christmas.
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Garth
Very sad that the car had that POS battery in there. Too small and a cheap low CCA model. Looks like that door lock/window switch had issues for a long time based on the scratch marks around it. Likely they had to use force on it to prevent whatever was happening with it which was likely not depressing and returning smoothly as plastics tend to wear then shavings cause them to stick. Oh dear, what will we do without crap plastic!
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Very sad that the car had that POS battery in there. Too small and a cheap low CCA model. Looks like that door lock/window switch had issues for a long time based on the scratch marks around it. Likely they had to use force on it to prevent whatever was happening with it which was likely not depressing and returning smoothly as plastics tend to wear then shavings cause them to stick. Oh dear, what will we do without crap plastic!
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Jim
While looking for the draw what about starting with fuse buddy that goes up to 30 amps they have ones for battery connection and fuse box connection. Then power could be monitored as your unplugging. Unfortunately I remember how low the display shows
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While looking for the draw what about starting with fuse buddy that goes up to 30 amps they have ones for battery connection and fuse box connection. Then power could be monitored as your unplugging. Unfortunately I remember how low the display shows
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Belux
I think that people asked you how to hook up for measuring current draw with a multimeter. I see people frying their meters by leaving the probes in the non fused com ports just like measuring voltage. Funny sight when you see one actually melt.
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I think that people asked you how to hook up for measuring current draw with a multimeter. I see people frying their meters by leaving the probes in the non fused com ports just like measuring voltage. Funny sight when you see one actually melt.
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Poot
More pinpointing please. so the switches were bad. they arent a source or a load. they merely open and close the circuits. Was the current draw from a constantly energized lock solenoid? Or just schmoo between B+ and ground?
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More pinpointing please. so the switches were bad. they arent a source or a load. they merely open and close the circuits. Was the current draw from a constantly energized lock solenoid? Or just schmoo between B+ and ground?
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