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I fixed a parasitic drain on my car in 408 days

davidmuller.github.io

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Re: I fixed a parasitic drain on my car in 408 days

#41

Post by SoftTalker »

kybernetyk wrote: post #29
kccqzy wrote: post #7

Earlier quoted context omitted.

> it's normal for the battery to die if you don't drive it for 3 days I've heard this nonsense a couple times now. I was incredulous at first but everyone seems to say this. What are anyone's suggestions for a weekend-only car? (I bike to work so I don't need a car on weekdays.) Trickle charge the car battery on weekdays?

There's battery kill switches you can install onto the battery pole to effectively disconnect everything from the battery. This should work for older cars. For newer ones you may experience hiccups like reverse camera not working for a few hours until it has re-paired itself with the head unit.

Also the engine and transmission computers may go into "learn" mode if they are cold-starting having had no power for a while, and so you may have stuff like a wandering idle speed for a little while.

Re: I fixed a parasitic drain on my car in 408 days

#42

Post by mysql »

I used to be a computer engineer working on embedded systems for automobiles. Quiescent current is what the normal proper draw is called for these systems when the car is off. We worked very hard getting these numbers in spec but it was hard to catch everything especially in this case where the issue is probably due to software missing the sleep state for that module. This could be from bad code or your CAN/LIN bus is messed up in your car. 99% of mechanics (and engineers) have no idea where to start with debugging these issues and the answer will be "replace the module".

Re: I fixed a parasitic drain on my car in 408 days

#43

Post by everybodyknows »

Anecdata: Some Hondas (e.g . 2010 Element) exert enough parasitic drain to put the car into a chronically undercharged state if a door is left ajar overnight.

The wrong thinking turned out to be: Car is safe in garage, interior lights go off, and my hands are full now -- why bother going back to the door to shut it completely?

Re: I fixed a parasitic drain on my car in 408 days

#44

Post by markdoubleyou »

overthrow wrote: post #3

Well this is timely. I have a parasitic draw on my NC Miata. The first mechanic just replaced the battery. The second told me it's normal for the battery to die if you don't drive it for 3 days (because "cars have computers now"). It seems like mechanics really don't like digging into the electrical part of the car... but these days that encompasses more and more of what can go wrong. Without time to dig into it myse…

My last car, a 2007 Acura TSX, had the same problem--it wouldn't start after 4 or 5 days (maybe 2 or 3 during the winter). This model was from the first wave of touchscreens and bluetooth. Mechanics shrugged, pointed to the tiny, underpowered battery, and told me to drive it more.

Thankfully there are a lot of car enthusiast forums out there that have been plugging away on vBulletin for years. Someone on an Acura forum had figured out that the bluetooth module was always on and looking for a connection. I tried disconnecting it, and the problem was fixed.

Re: I fixed a parasitic drain on my car in 408 days

#45

Post by red-iron-pine »

tecleandor wrote: post #30
kccqzy wrote: post #7

Earlier quoted context omitted.

> it's normal for the battery to die if you don't drive it for 3 days I've heard this nonsense a couple times now. I was incredulous at first but everyone seems to say this. What are anyone's suggestions for a weekend-only car? (I bike to work so I don't need a car on weekdays.) Trickle charge the car battery on weekdays?

Really nonsense. It's true it might be more common due to all the additional modules and computers cars have now. If one goes crazy, it might drain your battery. But this is only in case of a failure. Edit: cold weather can accelerate that. If it's 'weekend only', battery should be no problem. If sometimes you leave it a couple months unused, that might be a problem. Depending on how ready you would like to be when y…

> Edit: cold weather can accelerate that.

My Honda HRV dies anytime it gets below -7C. Outside, inside, driven a bunch a day or two before -- once it's cold that battery taps out.

Probably a vampire drain but I suspect it's just a small battery. My old 2013 Mazda 3 starts in -25C without fail.

Re: I fixed a parasitic drain on my car in 408 days

#46

Post by ghaff »

tecleandor wrote: post #30
kccqzy wrote: post #7

Earlier quoted context omitted.

> it's normal for the battery to die if you don't drive it for 3 days I've heard this nonsense a couple times now. I was incredulous at first but everyone seems to say this. What are anyone's suggestions for a weekend-only car? (I bike to work so I don't need a car on weekdays.) Trickle charge the car battery on weekdays?

Really nonsense. It's true it might be more common due to all the additional modules and computers cars have now. If one goes crazy, it might drain your battery. But this is only in case of a failure. Edit: cold weather can accelerate that. If it's 'weekend only', battery should be no problem. If sometimes you leave it a couple months unused, that might be a problem. Depending on how ready you would like to be when y…

I don't have extensive experience with my current car bought last summer but 2 weeks in warmer weather definitely wasn't an issue.

I agree colder weather is always a bigger issue and at 1-2 months I'd definitely be thinking of a trickle charger if at all possible. An older car I didn't drive in the winter would definitely end up with a dead battery if I didn't keep it on a charger.

Re: I fixed a parasitic drain on my car in 408 days

#47

Post by maccard »

_ea1k wrote: post #23
maccard wrote: post #19

Earlier quoted context omitted.

No car I've owned in the last decade has actually drained in a few days. Any car that does has a problem.

I have this problem, but it really only becomes an issue when a few days becomes a few weeks. Do that a few times and the battery will lose capacity too.

Weeks, sure. 2 weeks is probably on the lower end of acceptable though. My car is often left for 2 weeks and is completely fine, but most of the time it's weekly.

Re: I fixed a parasitic drain on my car in 408 days

#48

Post by KMnO4 »

kccqzy wrote: post #7
overthrow wrote: post #3

Well this is timely. I have a parasitic draw on my NC Miata. The first mechanic just replaced the battery. The second told me it's normal for the battery to die if you don't drive it for 3 days (because "cars have computers now"). It seems like mechanics really don't like digging into the electrical part of the car... but these days that encompasses more and more of what can go wrong. Without time to dig into it myse…

> it's normal for the battery to die if you don't drive it for 3 days I've heard this nonsense a couple times now. I was incredulous at first but everyone seems to say this. What are anyone's suggestions for a weekend-only car? (I bike to work so I don't need a car on weekdays.) Trickle charge the car battery on weekdays?

You should see if there are carshare options around you.

Even if you’re spending $50/weekend (which is a fair amount of driving — Communauto is as low as $3/hr), that’s still quite a bit cheaper than owning a depreciating asset with lifetime maintenance costs (not to even mention insurance and fuel).

Re: I fixed a parasitic drain on my car in 408 days

#49

Post by discardedrefuse »

Thanks for this timely post. I'm literally in the middle of running down a parasitic drain on my Nissan Xterra.

I tracked mine down using a different method which helps when your fuses don't all have test points (and no conversion table needed).

- Disconnect negative battery cable

- Switch your multimeter to 10A (don't forget to swap lead ports)

- Connect the multimeter in-line between the negative cable and negative battery post

- The readout on the multimeter should now tell you how much drain you have

- Start pulling fuses one by one until you see the amps drop to normal

Re: I fixed a parasitic drain on my car in 408 days

#50

Post by AlexandrB »

voldacar wrote: post #36
rozap wrote: post #9

Earlier quoted context omitted.

It's fairly straightforward if the car is unmodified, as everything should be fused. Multi-meter between positive terminal and positive lead and pulling each fuse to see when the drop goes away will isolate the circuit. Then you've narrowed it down pretty far and can go from there. The horrible thing is if the car is modified, and you discover an un-fused circuit.

Ammeter in series, not across the terminals! Unless you are trying to weld something :]

Realistically, you'll just pop the fuse in the ammeter. If it's a nice ammeter the fuse might be pretty expensive.
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