On Vacation -- Disconnect Car Battery?
 

How long does one have to be away in deciding to disconnect the car battery to keep it from running down? What is the prevailing thinking on this subject? Thanks

XFed2001 - a good question and will depend on the car technology and how much drain occurs in the "standby" operation. Will move this to the far more appropriate TravelBuzz forum for further discussion. Ocn Vw 1K, Moderator

Now that it's moved, it's recommended that for the '04 Toyota Prius with radio frequency remote entry, that that system be disabled in case of no planned operation in >10 days to 2 weeks.

IMHO a lot also depends on the age of the battery. I left a 2 year old battery connected and idle for 2 1/2 weeks last January here in MI and it cranked with no problem. Personally, I don't like messing with car batteries--when I do, I always seem to end up doing the 12 volt shuffle ;) .

Don't forget that disconnecting a car battery for any amount of time is likely to reset the engine computers to their default states - amoung other things this means that the tranmission shift points and diagnostics will need a run-in after the power is re-connected before everything is OK.

If your state uses OBD-II for emissions testing (parts of PA do) you will fail the inspection until the car has been run in following a battery disconnect.

That's not necessarily true, indeed I believe it not to be true for most cars. I used to disconnect my car's battery and leave it for months, then I'd come back and it would be running smoothly from the first second. I only had to set the time/date and make do with the trip computer not holding the older data.
If you want a general cut-off point, I'd suggest 7 weeks (providing your battery is in reasonably good condition).

That might be true for your car.

Generally, DON'T DISCONNECT THE BATTERY! pdhenry is correct! 1. You don't save a lot when you disconnect. 2. Your car may not run properly or not at all after you re-connect the battery.

If you're not driving the car for 2 months or more, then disconnect the battery. The computer, clocks, etc, will continue to draw a small current, and if you leave the battery connected you may get a dead battery when you come back.

Nothing wrong with resetting the computer of the car. Sure it may take a few days for it to "learn" your driving habits and set the optimum operating parameters, but there's nothing it will do to harm the car itself. More likely it'll run rich and use a little more gas (and probably not pass emission test). After a few days, you're fine.

And yes, you'll need to reset the clock, and there's any alarm or security system on the car, you'll need to punch in the correct code. So, know what they are beforehand.

If you have a radio with a anti-theft code, you will have to re-input the code.
Best to ask your dealer. (I get around this problem by using a trickle charger).

Totally depends on the car, age of the battery, and temperature. I would check with the dealer or service to see if there are issues (our car had a recall because some models (not ours) would go three days, then kick in the onboard computer, then kill the battery in another two days). Even if you have to jump start it when you get back, there is probably still enough power to keep the onboard electronics running for a very long time, even if it won't start the car.

If you are talking about months, then consider a trickle charger to keep it topped off if you plug it in, if not there are solar ones for very little money.

Thanks all. I have a '99 Audi A-6 Quattro with a 1.5 year old battery. I was gone for 4 months and returned to a dead battery. The starter wouldn't even turnover. I'll check with the Audi dealer about the short lifespan here. Thanks

Battery Manager II -- Griotsgarage.com
 

FYI: Finally found out via PBS' Goss's Garage that Griot's Garage website has all kinds of auto-related products, one of which is a battery maintainer (Manager) that addresses the issue that I brought up originally -- how to prevent a dead battery in a car that isn't driven for extended periods of time -- likke 6-7 months. The website (griotsgarage.com) displays two types of battery managers -- for motorcycles etc. and for autos. The warranty is a lifetime one and the price ranges from $40 to $60 with a $12+ delivery charge.

Incidentally, the trickler battery idea was given an overwhelming thumbs down!

Hmmm....I have an older car I drive only rarely and have both a trickle charger on it and gas stabilizer mixed with the gas in the tank. So what am I doing wrong, why is the trickle charger a bad idea? Everyone I've talked to among the local car gurus seems to like it.

My local BMW service advisor recommended a trickle charger, or in its absence disconnecting the battery, for my upcoming 31-day trip. I had a sense he would have come down more strongly in favor of the trickle charger had the trip been longer or if it took place in a colder season. (The car is a current-design 3 series, an E46 for you bimmer afficionados.)

You will cause a lotta more problems disconnecting it than leaving the battery connected. As mentioned disconnecting it zero-outs the many computers, radio, alarms etc. Dont leave a trickle charger connected to it either as they usually are cheaply made with cheap surplus parts (read: fire hazard). When you get back, if the car wont start call AAA or connect the trickle charger to it overnight. I often travel for 3 or more weeks and only once was the battery dead after a 6 week trip.

And forget about old wives tales such as draining the oil, putting the car on blocks and removing the tires, adding stuff to the gasoline etc. Just open the windows 1/4" for some circulation and go away happily.

MisterNice

I think the issue is with German batteries not lasting long in warm and humid climates. Our family in Hawai`i was a BMW/Mercedes/Porsche one for many years and the OEM batteries always died early. 18 months sounds about right. IIRC we used to get about 3 years or so out of the Die Hards we used to replace them with.