What's the longest a car can sit without running before its' battery needs a jump?

[SilverBack]

Tried searching this first but got nowhere, so here goes:

I just replaced the car battery in my landlady's Accord after she couldn't start it. This was due to her being out of town for 3 months straight. AAA guy was afraid to jump it because his tester showed it was sitting around long enough to explode if it was jumped.

Anyways she's going out of town again next week and I convinced her to leave her keys with me and another roomie so we can take turns firing-up the engine every so often to keep the battery alive. My initial thought was this should be done once a week, but I can't help to think it could go at least an extra couple weeks longer without running.

I can try to make the time to run the engine for a few minutes every other week, but I won't always have time to switch-out the battery just because it sat around for too long, so any thoughts and experiences would be a great help!

[CTScott]

It depends on the car and the options (alarm, remote entry, etc.) If you have a meter that can measure amperage, you can measure the draw with the car powered off.

Here's an analysis I did a while back on the Yaris:
http://www.yarisworld.com/forums/showpost.php?p=405121&postcount=119

[SilverBack]

I suppose I could search for a meter. I'll check a few local hardware and auto parts stores to see if they got any. Thanks Scott.

One more question since you mentioned options (and I did see your link): Would it drain slower if I disconnected the battery altogether so that not even the clock's memory would work? Or would I still get the same result?

[cali yaris]

it should store better disconnected, there won't be any draw on it.

starting it up for 10-15 minutes once a week will guarantee it's fully charged.

I've had cars sit for 6 months and fire up, so I think it's pretty variable.

[CTScott]

^Exactly. The only downside to disconnecting the battery is that it some ECMs clear the short term values when the ECM is disconnected from the battery, and the car may run a little rough for a few minutes when the it's initially restarted.

[DevilGirl]

I may be wrong here, but I do believe how long they can sit also depends on the type/brand of battery that's in the car...

[Kal-El]

There's way to many factors to give a straight answer. Tons of different batteries (brands and types). And every car places a different load on batteries. Even when parked, there's different amounts of power draw from different cars.

[Yaris Hilton]

From past experience, I start getting antsy when a vehicle's been parked much more than a week. They need regular running.

[SilverBack]

^I think I might be going down that road myself lol.

15 mins of idling every weekend will have to do.

[STC]

I remember as a kid growing up in Miami, my dad charged the boat battery every other week when we did not use the boat for lengthy periods of time.

Charging (starting and running) the car battery every other week will assure charge... :smile:

Cheers!

[silver_echo]

agreed on about fifteen minutes per week... that way the oil is kept moving... but a possible suggestion for next time would be to have her pick up and install a battery tender... plug it in to power and leave it... then when she gets back, unplug and drive away... would still recommend at least brought up to operating temp once every two weeks though...

[severous01]

just go buy one of those little solar panels and put it on the dash, wire it into the cig lighter or put a cig adapter on the end...

at 2 amps all day it dont matter how long it sits there, it'll always be charged.

to answer your question, you'll be doing more harm that good by just starting it up and letting it run for 10 min. it takes more than 10 min to recover from starting the car and start actually charging the battery above use from starter.

there are several voltage maintainers and small chargers for home/garage use at walmart or autozone.

[Yaris Hilton]

it takes more than 10 min to recover from starting the car and start actually charging the battery above use from starter.

7 seconds is an often quoted figure given by those recommending shutting off the engine at stops for fuel conservation. I don't know how that was determined, and I'd imagine it differs from one car to another, but surely it doesn't take 10 minutes for the alternator to replace what the starter drew if the engine starts normally quickly. People who mostly drive short trips would quickly have their batteries run down if that were the case.

[GrimlockGT]

I park my other car for winter (about 5 months) and it always starts right up when spring rolls around.

[Yaris Hilton]

Count yourself blessed!

[severous01]

10 seconds...10 minutes...either way, you're doing more harm idling than you would driving it around a few times a month.

if you dont want to drive it a charger of some sort is your only other option. i like the solars because you dont have cables everywhere, you can plug it in, lock the car and forget about it...and if you know anyone with a volkswagen they get them free from the factory and they probably dont use it.

[SilverBack]

Well, she had the car put into non-operational status, so it's not going anywhere (not even around the block due to high cop presence). If it breaks down then it's on her. I only agreed that my job is to just run the engine every other week, alternating weekly with my roomie. And that's all I'm gonna do.

[Kaotic Lazagna]

Have a notarized contract saying that you and your roomie are not held liable for any damage on her car while under you guys' supervision, and get all parties to sign.

[cali yaris]

surely it doesn't take 10 minutes for the alternator to replace what the starter drew if the engine starts normally quickly.

+1. It doesn't.

And starting up a car once a week does no harm whatsoever. Such nonsense!

[severous01]

battery disco switch???

[SilverBack]

Have a notarized contract saying that you and your roomie are not held liable for any damage on her car while under you guys' supervision, and get all parties to sign.

I would've, but she's a good friend so a contract would be awkward. Plus she already left before I came back and saw your post. I'll remember for next time though in case something happens and I need to appear on People's Court lol.

[why?]

i think it is easier to just disconnect the battery. And that guy that was afraid to jump start it was a moron.