Car batteries and infrequent driving

[John Lanciani]

... AMPS. If it is more than a few AMPS you have short some where. I do not know how many AMPS to expect but would guess only 4 - 6 AMPS computer and the clock...

George

4-6 amps is going to kill the battery in less than a day. An optimistic guess on the reserve capacity of a car battery would be 80 amp-hours. (deep cycle batteries for an RV or trolling motor are +/- 100AH) I would expect to see less than 100 milliamps doing the test that George suggests. I also agree with George, disconnecting the battery on a modern car is not a great idea due to the computer having to re-learn all of the operating perameters every time you re-connect it.

[George Bokros]

4-6 amps is going to kill the battery in less than a day. An optimistic guess on the reserve capacity of a car battery would be 80 amp-hours. (deep cycle batteries for an RV or trolling motor are +/- 100AH) I would expect to see less than 100 milliamps doing the test that George suggests. I also agree with George, disconnecting the battery on a modern car is not a great idea due to the computer having to re-learn all of the operating perameters every time you re-connect it.

Thanks for correcting me John. I have no idea what the computer might draw but you are correct the draw should be in milliamps. Now thinking about it 4-6 is a healthy draw.

George.

[Jessica Pierce-LaRose]

Just an aside - I had some battery problems in my car - turned out at some point (probably before I bought the car from what turned out to be a bit shady used car dealer, but who knows) someone had put the wrong battery in the car. Every time I had the battery checked after having problems, it checked out okay, and replacements wouldn't last as long as I would like. Finally dug up the Ford manual for the vehicle on their website, and realized I had an incorrect, smaller, battery in the car than required. When I had it replaced in the past, I had just taken the old battery down the shop and gotten the same. Getting the proper battery for the vehicle, I haven't had any problems since.

Not saying this is your problem at all, but might be worth checking out - one screw up in replacement could easily lead to a long line of improper replacements if someones not paying as much attention as they should.

[Bill Huber]

I guess I still have a question, is the battery going dead and the car has to be jump started or is the battery just going bad and will not take a charge?

[Curt Harms]

The problem with completely cutting off the battery in the newer cars is the computer will always be in a re-learn mode which takes about 15 - 30 minutes while you drive. Can be troublesome, and inconvenient.
<snip>

George

I guess that's the advantage of drive near-antiques. We have two Ford 4.0 V6s early 2000s vintage and no issues with drivability after disconnecting the battery. I guess they're pretty low tech by today's standards.

[Greg R Bradley]

I guess that's the advantage of drive near-antiques. We have two Ford 4.0 V6s early 2000s vintage and no issues with drivability after disconnecting the battery. I guess they're pretty low tech by today's standards.

It is very low tech by today's standards but is still probably new enough to have some issues. It just is not having enough issue that you are noticing it. They were going to those systems starting well before 2000 but started slowly and mostly in the higher tech systems.

It probably has enough of those systems in it that you could generate enough of a fault to turn on the check engine light if you did silly things with the throttle during the first few minutes of running. Many modern cars are still recalibrating functions for around an hour after the battery is disconnected and will flunk a smog test during that time.

[Bruce Page]

Firestone replaced the battery at no charge.

Bill, the previous 2 batteries just slowly lost their oomph when the temps started dropping into the teens. I would put the charger on it overnight and it would fire right up. I don't know what is causing the problem. I will have the dealer look into it at the next service.

Thanks for the advise.

[Jim Koepke]

After sitting for months, my truck is sometimes a touch cranky, but it will start on the second try without battery problems. I moved it a few days ago and first had to wash off all the pine cones and needles so I could see out the window.

This kind of problem is where an amp meter comes in handy. My bet is you will get a good spark when you connect and disconnect the battery cable. The amount of spark can be an indicator of the amount of current draw. In the old days I would remove fuses one at a time to identify the circuit where the problem was located. Now days a lot of items have inline fuses with which to contend. An alternator can produce a charging voltage yet still have a diode that bleeds current to ground when the system is off.

I used to use a simple automobile light in a socket with test leads as a poor man's meter. Mostly for setting my distributor points. (that tells my age, eh?)
If this is placed between the battery and the cable a bright light tells you there is a heavy draw on the battery. The higher the draw, the brighter the light. If you are interested in more info on this PM me and I will post a reply here.

Some culprits could be the lights in the engine, trunk, glove compartment or other "courtesy" lights not turning off when they should. Many of these draw more than an amp.

The clock in the radio and other parasitic voltage eaters shouldn't be enough to drain a battery in a few days.

We sometimes do not move our going into town vehicle for as much as two weeks. (we love our hermit lifestyle) It fires right up. I let it run easy for a few minutes to let the oil get back to the places from where it drained.

Your mention of the side mirror also makes me wonder about how the repair was done. There could be a bit of sloppiness in the wiring that has a wire (or wires) making a current path to ground. This seems off to me since most cars I am familiar with do not have these controls enabled with the key off. But then again I am not a wiring engineer who designs this stuff.

Any place that changes a battery should be able to put a meter on and tell you what the "key off" load is on your battery. The worst would be if you have something intermittent. Also note the alternator may be attached directly to the positive cable. This is why it is best to check the load on the ground cable side of the electrical system.

jtk

[Kelly Craig]

Remotes, radios and clocks drain batteries, but shouldn't do it quickly.

If you removed the negative battery cable and connect a 12 volt light between it and the battery, it will come on, in most instances. This is because the radio and/or circuit provides a path for current flow. If you doubt that, after you connect the test light, turn your head lamps or parking lights on and the test light will come on. If it does, but goes off when the lights are off, you have no drain.

If the light is on when all switches are off, you can remove fuses to the radio and clock. If the light goes out, that was the only draw. Otherwise, remove fuses [then replace them] until the light goes off and that will tell you which circuit is the problem child. It could be, for example, a glove box light, or a trunk light.

Sixty-eight dollars is absurd for a battery swap. I could buy a NAPA battery for a little more than that. That aside, my Gruman step van was doing that and I just installed a battery kill switch inside. The switch kills everything and I go up to six months between starts. That would be a bit complicated, but you can get knob type shut-offs that go on the battery that are pretty easy to install. You have to open the hood for each run, but nothing will drain.

If your car is a late model, this may mess with some electronics, so check around to see if this is a viable option. If not, the trickle charger would be your best bet. You could secure it so the cord was outside the car for quick connections.

[Duane Meadows]

Or... if you are starting the engine, driving a block to the corner store, shutting it off. Coming out of the store and doing the same thing, driving home. Do this enough, you will eventually kill that battery as it doesn't have time to recharge. Just a thought. If you drive it for several miles should it should be ok. If you are doing this with lights, heater/AC, radio, etc on, may happen even more rapidly.

My wife killed one doing garage sales that way... granted it was old anyway, but that finished it!

[Bruce Page]

Or... if you are starting the engine, driving a block to the corner store, shutting it off. Coming out of the store and doing the same thing, driving home. Do this enough, you will eventually kill that battery as it doesn't have time to recharge. Just a thought. If you drive it for several miles should it should be ok. If you are doing this with lights, heater/AC, radio, etc on, may happen even more rapidly.

My wife killed one doing garage sales that way... granted it was old anyway, but that finished it!

I do that a few times a week. I also drive across town 8-10 miles about once a week, sometime more and sometimes less.
Since retiring I'm only driving my car 3 to 4 K a year.

[Jerome Stanek]

My new truck sits for long times I had to take it yesterday and id started up ok the last time I drove it was Dec 23 and we have had some below zero weather here.

[Chris Parks]

All modern cars have constant battery drain and if you disconnect stuff like radios you have to either forget about using them or re-program every time you use the car. Something stupid like a trunk light might be staying on if a switch fails in the on mode but it could be anything really. with the high output alternators these days frequent stop start driving is not such a problem but it sure destroys exhausts quickly.