My Wife’s 2016 Subaru Outback has all the bells and whistles. There seems to be a parasitic drain on the battery. The battery will go dead in a week. It has had the original battery, and now two more batteries replaced by Subaru when this has happened.
Subaru can’t locate the problem, and tries to blame us (left the dome light on ect.). This is NOT the case.
My question then is in the title. Is it common, or getting common for new cars that have a LOT of electronics to always have some sort of drain on the battery?
I would not be surprised if there where some tiny drains, but having the battery die in just one week is a bit much.
I suspect the batteries they have been putting in the vehicle, as well as the original battery are not the best you can get.
And this question may be related - The last time this happened, we jump started it. It idled fine for about 10 minutes but when we drove it, it seemed (to me) like the fuel mixture was way off. It would lurch and stumble when accelerating. After letting it sit for a day, it was fine. Perhaps the computer or other controller had to reset itself?
This doesn’t surprise me. If you have a REALLY dead battery or it you disconnect the battery cables to change it then the computer can lose its stored memory. It will then default into a safe ‘limp home’ mode for a few miles while it relearns how to run everything.
All cars do have parasitic drains but going dead in a week is out of line. Most likely cause is some interior light (trunk, lighted make-up mirror, under hood light, could be almost anything) that should be shutting off but isn’t. You can try selectively pulling fuses to try to narrow it down.
IANAMechanic, and your example seems a bit extreme. However, I suspect that modern cars are shipped with marginally good batteries with very little extra capacity. (Not unlike the original tires, which the dealer told me have about half of the capacity of good quality replacements.)
I left my radio on for about an hour as I was packing my 2015 car for a trip, and the battery ran down so far the car would not start. Once charged, the battery tested fine. I’ve never had that kind of minimal drain on a car battery result in that drastic an outcome.
You need to measure the drain.
On my wife’s 2008 Jetta, the sleep current is supposed to be less than 40mA. I measured it at 7mA after 2 hours (it takes a LONG time to go to sleep).
If the drain is more than 100 mA or so, it’s going to deplete your battery quickly. All kinds of things can cause mysterious parasitic current draw - door lock sensors being one of the biggest ones.
Most modern cars from the early 1990’s up use something called IOD (Ignition Off Draw) or a similar system which pulls a bit from the battery at all times to keep the PCM/Computer powered, your radio stations set, clocks, etc. In theory, as more and more things are digitized and computerized it can take more power to keep everything. As mentioned above, after a dead battery the car will lose what it has learned about your driving habits, timing and sensor calibration and will take up to 50 miles or so of driving to ‘re-learn’.
All that being said, a week and the battery dying seems more like a shorted or damaged cell in the battery. Make sure the battery is secured in the compartment and doesn’t move and make sure the terminals and ground connection to the chassis are clean and not corroded. If it is a damaged cell, just get a new battery with a CCA rated for your vehicle since too high can damage an alternator/generator (though i’ve never seen it happen). Another option is that if you are going to leave the battery connected and let the car sit, go under the hood and find the PDU (power distribution unit) or fuse panel and look for one labeled IOD. It doesn’t fully come out but pops up. In most cases it will leave the car computer/PCM alone but you still will not have radio stations/configurations/clock set.
Yeah, this was the first time it died at our house (11,200 feet elevation) so I immediately thought computer/mixture.
It died twice at the Denver airport, but that’s only ~ 5280 feet. And the drive out of the airport is flat ground and doesn’t work the engine very hard (at least for the first 30 miles or so).
The finding the leak by pulling fuses is a bit problematic, as we can’t let it sit for a week, try again, let it sit, try again… Well, I suppose we could but it would be quite the pain in the ass. I have checked it at night, and can’t see anything on.
My personal data point: I bought a new Toyota Rav-4 last October. I left it parked outside for about six weeks when I went south last winter. The battery was fine and I had no problems starting it up when I returned.
That’s not how you test it.
You put an ammeter in series with the battery cable, and let it sit for a few hours. If the reading is high (greater than 50mA or so), you start pulling fuses until it drops to something reasonable, and note which fuse caused the drop. There are plenty of articles on how to do this on the web.
Yeah but you wouldn’t be able to tell if the trunk, glove box, or even the hood light are staying on when they’re not supposed to unless you put a video camera in there (fairly easy to do with a smartphone, except perhaps under the hood if it’s tight). You wouldn’t be able to see if your rear window defogger was stuck on, but I bet that would drain the battery much quicker. It could be the ECU or another computer not shutting down properly as well.
Good point about the lights. And especially the heated rear window, and using a cell phone. When I’m working on stuff, I always take a picture before taking complex things apart.
As long as we are all here… I plan to go to Lowes tomorrow (the only place ‘close’, only an hour each way.) to get an ammeter.
I believe either could do this job. Would I be correct? I’m leaning towards the Fluke as I always buy good stuff. And it is more automated. I also have some vision problems (cataract surgery in a month) But I doubt I will be using this much, and 100 bucks difference is a 100 bucks.
You don’t have to actually close the trunk, glovebox, hood etc. You just have to make the car think they are closed by actuating closing the latch with a pencil or screw driver or something
My wife has a 2015 Outback with half the bells and whistles, no EyeSight. We have had no issues with the battery dying. We have had multiple instances of not driving the car for more than a week.
Can you even do that anymore? Old fashioned plunger switches like you find on your refrigerator have been replaced in many cases with hinge switches or electromechanical relays built into the latch mechanism and out of reach. Hoods and trunks might even use tilt switches.
The Fluke is a 6,000 count meter, while the cheaper one is 2,000 count. That would be important if you were doing serious electronic testing, but probably wouldn’t matter to you.
Yeah I’ve done quite a few of those tests when I worked at a VW dealership up until around 2013. The switches are built into the latch, but you can manually close the latch with the door/trunk/hood in the open position and it will stay locked in that position
I’ve also heard 50 mA is the (more or less) threshold.
And another thing… I have a theory that the residual current draw is different for the following two scenarios:
Turn off car.
Turn off car. Disconnect battery. Reconnect battery.
When you measure current, you are performing it under scenario #2. But the current draw in scenario #2 may be different than the current draw in scenario #1. And you really want to know the current draw in scenario #1, not scenario #2.
Measuring the current draw in scenario #1 can be done, but it is tricky to do.
My sister claims that the battery in her new VW goes dead if she does not drive it at least once a week. She told me that the dealer said that’s just how the car is designed, what with all its great deluxe electronic features and all, and that she should just be sure to drive the care every few days.
I’ve also heard 50 mA is the (more or less) threshold.
And another thing… I have a theory that the residual current draw is different for the following two scenarios:
Turn off car.
Turn off car. Disconnect battery. Reconnect battery.
When you measure current, you are performing it under scenario #2. But the current draw in scenario #2 may be different than the current draw in scenario #1. And you really want to know the current draw in scenario #1, not scenario #2.
**Measuring the current draw in scenario #1 can be done, but it is tricky to do.[/**QUOTE]Bolding mine. Yeah. That sounds right. Scenario #2 might shut down the computer and any draws might not show up until the car is started and computer reset I suppose. I guess I would need a jumper wire between negative terminal and cable while I set up the multi-meter and then pull off the jumper wire?