Battery voltage drop

[bruceb]

Recently the battery in my 2009 4.6 sedan, with 106k miles, died after I forgot to plug in my Battery Tender 1.25 amp battery maintainer overnight. I don't drive it much these days, so I keep the charger connected. After that incident, I monitored the battery and found it was losing .1 volt in 24 hours without the battery tender.

Since my battery was 37 months old, I bought and installed an identical new Interstate battery at Costco and monitored it. That battery also lost about .1 volt. Conclusion - parasitic draw.

Took it to my auto shop. They blamed it on the Costco Interstate battery, saying that they were getting a lot of those batteries back, that Costco has them manufactured elsewhere and they weren't any good. I found no such complaints online.

Auto shop tested the draw with a fluke and said it was losing voltage within normal limits, 35milliamps if I recall correctly. Blamed it again on Costco and charged me $50.

I reinstalled the old Interstate battery. That one now losing .1volt per 24 hours and the new Costco battery sitting on the floor lost .01v. In other words, both batteries lose .1v in the car, and .01v on the floor. Hmmm.

I don't want to test the circuits myself. Too much danger of me breaking something expensive. Any suggestions, other than taking it to a dealer who will charge me $100+/hour for a high labor diagnosis? Thanks for any help.

 

[fourthirteen]

Get a digital clamp meter, about $30 on Amazon, and clamp it around your positive battery cable and see what it says. Check it occasionally over a few days and see if the draw varies. You can pull fuses one at a time to see where the draw is coming from and go from there. Any Bluetooth devices, phone chargers, dash cams, etc. plugged into a power socket in the car? Also make sure no hidden lights are on, like glovebox, trunk, etc.

 

[bruceb]

Get a digital clamp meter, about $30 on Amazon, and clamp it around your positive battery cable and see what it says. Check it occasionally over a few days and see if the draw varies. You can pull fuses one at a time to see where the draw is coming from and go from there. Any Bluetooth devices, phone chargers, dash cams, etc. plugged into a power socket in the car? Also make sure no hidden lights are on, like glovebox, trunk, etc.

Thanks for the quick reply. That Amazon link took me to Genesis Motors, which is a collection of Genesis bling. I looked on Amazon and found this mid price one on sale.
https://smile.amazon.com/AstroAI-Mu...rds=digital+clamp+meter&qid=1669958147&sr=8-5

Reckon I don't need much for my limited use, i.e. one. I already have a cheap multimeter.

My mechanic said that likely something turns somewhere for some reason at some time, thus draining the battery. Sounds pretty vague, but I don't have a better answer. And 1-2 volts per day?

Thanks again.

Bruce

 

[mikec]

Next time you park the car at home, watch the CD/DVD slot for about 20 minutes after parking. The blue light at the top/center of the slot flashes a few times when the entertainment system switches from STANDBY to full OFF modes. If you don't see this flash within half an hour, your nav/entertainment system is staying in STANDBY which is a larger amperage draw. Why would it stay in standby you ask? The system does not fully shut down immediately - that way it can "wake up" more quickly if you return to the vehicle in a short time. Stopping at Starbucks or something... But it you don't return within that 20 to 30 minute window the car assumes "we really are going to stay parked for a while" and fully shuts down. Any open door, trunk lid, or open hood keeps the system in STANDBY regardless of that 20-30 minutes time: if everything is not fully closed then you "have not left" as far as the car is concerned. This also prevents the theft alarm system from arming. A common problem early on was a rubber bumper on the underside of the hood was missing or not big enough to actually press the button below it so the car thought "hood is open" all the time. There is a TSB about it: TSB number 09-BE-026. With the hood open, look on the driver side edge about half way between the front and back (windshield end) of the hood for a rubber bumper. If it's damaged or missing that is your bug. In the black plastic stuff surrounding the engine you'll see the switch this bumper is supposed to actuate. Make sure it hasn't become dislodged. Use the multimeter to test its operation too. The TSB replaces the rubber bumper with one that is a bit taller to make sure it presses the switch.

Note: there are other rubber bumpers in corners of the hood... ignore them. If your hood does not sit level with the fenders when closed these bumpers may be "unscrewed" too far; try twisting them in a bit. If they're holding the hood upwards too much the hood-closed bumper can't reach the switch to do its job.

mike c.

 

[bruceb]

Next time you park the car at home, watch the CD/DVD slot for about 20 minutes after parking. The blue light at the top/center of the slot flashes a few times when the entertainment system switches from STANDBY to full OFF modes. If you don't see this flash within half an hour, your nav/entertainment system is staying in STANDBY which is a larger amperage draw. Why would it stay in standby you ask? The system does not fully shut down immediately - that way it can "wake up" more quickly if you return to the vehicle in a short time. Stopping at Starbucks or something... But it you don't return within that 20 to 30 minute window the car assumes "we really are going to stay parked for a while" and fully shuts down. Any open door, trunk lid, or open hood keeps the system in STANDBY regardless of that 20-30 minutes time: if everything is not fully closed then you "have not left" as far as the car is concerned. This also prevents the theft alarm system from arming. A common problem early on was a rubber bumper on the underside of the hood was missing or not big enough to actually press the button below it so the car thought "hood is open" all the time. There is a TSB about it: TSB number 09-BE-026. With the hood open, look on the driver side edge about half way between the front and back (windshield end) of the hood for a rubber bumper. If it's damaged or missing that is your bug. In the black plastic stuff surrounding the engine you'll see the switch this bumper is supposed to actuate. Make sure it hasn't become dislodged. Use the multimeter to test its operation too. The TSB replaces the rubber bumper with one that is a bit taller to make sure it presses the switch.

Note: there are other rubber bumpers in corners of the hood... ignore them. If your hood does not sit level with the fenders when closed these bumpers may be "unscrewed" too far; try twisting them in a bit. If they're holding the hood upwards too much the hood-closed bumper can't reach the switch to do its job.

mike c.

Thanks so much Mike for your ideas. You know a lot about this machine.

I just looked at the CD, since the car has been sitting for about six hours now. No light. Then I hit the lock button on the remote and it locked. I unlocked it and popped the hood. Did not lock correctly until I then dropped the hood again. I found the TSB and it covers my car. I'll still check it out tomorrow.

 

[Gunkk]

Our cars should be less than 20mA when asleep. At 20mA a battery will drain from full to dead in about 4 weeks. One common culprit is the security system. Normally you get a beep+flash when system arms properly (entrances are closed and fob lock button pressed). If the system does not arm properly, it stays awake and draws high current (100mA or so) and will completely drain a battery in a few days. Missing/damaged/wrong-size rubber bumper on the hood is the usual suspect, there was a TSB way back when to swap for the larger part#.




You can test parasitic draw with fuses in situ (best way as nothing is shut down during the test), as there are a pair of contacts on the top of each fuse you can use to measure voltage drop with a basic voltmeter like the $20 unit linked above. BCM and IPM fuses are usually where you want to start, as they control the things that do draw power while asleep (or get restless and draw high current when not). Take that voltage drop and compare to the chart below to determine mA drain. If there's a current then there's a voltage drop (V=IR), but when I = zero there is no current thus no voltage drop thus no power draw on that circuit.

 

[Charlie1982]

Our cars should be less than 20mA when asleep. At 20mA a battery will drain from full to dead in about 4 weeks. One common culprit is the security system. Normally you get a beep+flash when system arms properly (entrances are closed and fob lock button pressed). If the system does not arm properly, it stays awake and draws high current (100mA or so) and will completely drain a battery in a few days. Missing/damaged/wrong-size rubber bumper on the hood is the usual suspect, there was a TSB way back when to swap for the larger part#.

View attachment 49883
View attachment 49884

You can test parasitic draw with fuses in situ (best way as nothing is shut down during the test), as there are a pair of contacts on the top of each fuse you can use to measure voltage drop with a basic voltmeter like the $20 unit linked above. BCM and IPM fuses are usually where you want to start, as they control the things that do draw power while asleep (or get restless and draw high current when not). Take that voltage drop and compare to the chart below to determine mA drain. If there's a current then there's a voltage drop (V=IR), but when I = zero there is no current thus no voltage drop thus no power draw on that circuit.


View attachment 49882

Thanks for posting this fuse reference chart, I've never seen this before.

 

[amartz]

I've just been dealing with a similar problem. It's looking like the ODB2 bluetooth dongle that I've had plugged in for years started drawing enough that it could run down the battery in a day or two. Pulled it out (after checking out other possibilities), and everything seems fine now. Got a new one coming next week.

 

[bruceb]

Wuzzat for? Some BT device or app to monitor your engine? I've used a Scangauge for years, left over from my prior F350 diesel tow vehicle.

 

[amartz]

I've just been dealing with a similar problem. It's looking like the ODB2 bluetooth dongle that I've had plugged in for years started drawing enough that it could run down the battery in a day or two. Pulled it out (after checking out other possibilities), and everything seems fine now. Got a new one coming next week.

Been running it with the new BT dongle I got thru Amazon. Everyuthing is working fine! Anybody want an old dongle? ;-)

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[bruceb]

Been running it with the new BT dongle I got thru Amazon. Everyuthing is working fine! Anybody want an old dongle? ;-)

Don't know what this is. Amazon link doesn't show a dongle.

 

[amartz]

Don't know what this is. Amazon link doesn't show a dongle.

https://smile.amazon.com/dp/B011NSX27A?psc=1&ref=ppx_yo2ov_dt_b_product_details

 

[bruceb]

https://smile.amazon.com/dp/B011NSX27A?psc=1&ref=ppx_yo2ov_dt_b_product_details

Thanks. I like this device. More compact than the Scangauge on my dashboard. However I don't use my phone when I drive, so I wouldn't see the display. I'll buy it and try it.

What all do you use? I looked at Carconnect, but I didn't like their data policy, which includes saving your location indefinitely. Keeping track of your travel.

Unnecessary.

Bruce

 

[amartz]

Thanks. I like this device. More compact than the Scangauge on my dashboard. However I don't use my phone when I drive, so I wouldn't see the display. I'll buy it and try it.

What all do you use? I looked at Carconnect, but I didn't like their data policy, which includes saving your location indefinitely. Keeping track of your travel.

Unnecessary.

Bruce

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