Electrical Mystery-Battery or Parasitic Draw or ?

[BIC]

2012 Acura MDX 65,000 miles. Slightly over 3 years ago put in OEM Acura battery with 3 yr free replacement and 8 yr prorated. I would get about $90 towards a $155 OEM battery if it was defective just beyond 3 yrs.

Car wouldn't start. Fully charged battery--no go. Fully charged again and hand carried to Acura dealer. They did two tests and said battery was OK. It did fall short of some specs like CCA but no replacement offered.

I put Fluke multimeter on car and it showed parasitic drain of 275mA. Took it to Firestone. ASE certified mechanic in Electrical Systems said parasitic draw was OK at 40mA and battery was toast.

Bought an Interstate battery from Costco. Running for a month OK. Don't know why the parasitic draws are so different, it's a pretty simple test.

During this past month, resting battery voltage is usually between 12.5 and 12.7. Sitting quietly over a 24 hr period, it typically loses anywhere from 0.01 to 0.08. Is this a normal daily sitting loss, say about 0.04v?

If the daily voltage loss is normal, guess the mechanic was correct with the 40mA parasitic drain and for whatever reason, my Fluke is wrong at 275mA. BTW, I disconnect negative cable and put black lead on negative post and red lead on disconnected cable. Thanks.

 

[tnt31]

2012 Acura MDX 65,000 miles. Slightly over 3 years ago put in OEM Acura battery with 3 yr free replacement and 8 yr prorated. I would get about $90 towards a $155 OEM battery if it was defective just beyond 3 yrs.

Car wouldn't start. Fully charged battery--no go. Fully charged again and hand carried to Acura dealer. They did two tests and said battery was OK. It did fall short of some specs like CCA but no replacement offered.

I put Fluke multimeter on car and it showed parasitic drain of 275mA. Took it to Firestone. ASE certified mechanic in Electrical Systems said parasitic draw was OK at 40mA and battery was toast.

Bought an Interstate battery from Costco. Running for a month OK. Don't know why the parasitic draws are so different, it's a pretty simple test.

During this past month, resting battery voltage is usually between 12.5 and 12.7. Sitting quietly over a 24 hr period, it typically loses anywhere from 0.01 to 0.08. Is this a normal daily sitting loss, say about 0.04v?

If the daily voltage loss is normal, guess the mechanic was correct with the 40mA parasitic drain and for whatever reason, my Fluke is wrong at 275mA. BTW, I disconnect negative cable and put black lead on negative post and red lead on disconnected cable. Thanks.

Your Fluke may be correct. Are you waiting until everything goes to sleep? Which I have seen take up to 20 minutes. Some vehicles may take longer.

 

[BIC]

@tnt31, yes, I wait hours to do the parasitic draw test, even days. Always the same, 275mA.

 

[berniedd]

What tnt meant was that when you remove batt cable for a few minutes or hours, some electrical modules/system are reset, then draw a lot more current when they restart as the cable is reconnected. Some systems may take up to 20 minutes to settle down.

Try this: Wait 2 hours or more after reconnecting the battery. Set your Fluke to DC milliamps, loosen the neg batt clamp but do not remove it yet. Have somebody assist you to push firmly your Fluke negative test prod on top of the negative batt post. You hold firmly the positive test prod onto the batt clamp, then slowly raise the clamp off the batt post. At no time allow even a very momentary interruption of electrical flow anywhere. Your meter is now showing the true reading.

 

[twX]

Make sure the car doors are closed. If the hood latch has a sensor, do the test with the hood closed. If the car has push button start with a remote fob, even having the fob too close to the car might keep the computers awake.

Also, when measuring the voltage drop over 24 hours, if you open the car doors to pop the hood, it will load the battery and the voltage will be depressed for a while.

 

[Trav]

The cable and post must be disconnected from each other to perform an accurate test. Close every door, trunk, you can close the hood latch with a screw driver buy pushing down on the middle of the latch when finished pop the hood release. Move the key fob far away from the car, make sure the auto headlight and any interior lights including the glove box is turned off before disconnecting the cable.

It is normal to have a higher draw for about 20 sec to a min then it should drop. If not it is time to pull fuses one at a time to locate the draw. I am doing a loaded BMW X5 yesterday and today trying to locate a battery killing draw, this one is a real treat, just get too near it and it wakes up some systems and the battery is on the trunk.

How to test for a parasitic draw - Innova Electronics Knowledge Base

Parasitic Draw Test Sometimes, a battery may experience significant drain long after the engine has been shut off. It might not be a faulty battery causing this

innova-electronics.helpscoutdocs.com

 

[Elektrishun]

My son's 2010 Mazda 6 has a parasitic draw. It only becomes a problem when temperatures drop to around minus 30 Celsius (we live in the Great White North). If the car sits for a few days during these cold snaps it might not start. The easy solution is to go for a short drive before it sits too long. Once the temperature warms up it's no longer a problem. Narrowed down the source by pulling fuses but it would still require a lot of effort to find the exact cause. Short drives, if needed, will suffice for now.

 

[SC Maintenance]

Even my extremely simple Nissan's take more than an hour to go to sleep. However when they finally get there they only draw around 10mA.

Often its some aftermarket thing - alarm, stereo, etc.

Even a 275mA parasitic draw would take a couple days to kill a battery. Thats like 6.6Ah per day. I think a decent lead acid starting battery has like 50Ah. So it would take like 4 days to cut it in half. What are your actual problems? It might be something else.

 

[Number_35]

My son's 2010 Mazda 6 has a parasitic draw. It only becomes a problem when temperatures drop to around minus 30 Celsius (we live in the Great White North). If the car sits for a few days during these cold snaps it might not start. The easy solution is to go for a short drive before it sits too long. Once the temperature warms up it's no longer a problem. Narrowed down the source by pulling fuses but it would still require a lot of effort to find the exact cause. Short drives, if needed, will suffice for now.

Our 2009 Mazda5 had a parasitic current draw of c. 290 mA (if I recall correctly). It was on the ROOM fuse, which unfortunately supplies many accessories.

The problem turned out to be the Bluetooth unit, which I disconnected. It was behind the glove box.

Dark current dropped to around 30 mA.

Apparently this is a common problem.

 

[Elektrishun]

ROOM fuse - yes, same fuse I found that eliminated the draw. Never looked further into it yet.

 

[Marcozi]

Once the car is asleep start pulling fuses.

 

[Sequoiasoon]

2008 CRV was a bad AC relay that was discussed on many forums. It kept the AC clutch engaged when car was off. New relay, draw was gone.

Others had problems with the bluetooth unit in same vehicle.