Car battery charging questions

[apocrypha]

Can I ask a car tech question in here? Well I'm gonna anyway.

I don't drive very often any more cos of my back yadda yadda, so my car battery keeps going flat. Usually the bloke next door gets me started with one of those battery starter thingies, which is awesome of him, but he's not always there and I can't afford to get one of them myself at the moment.

Is there anything I can do while I'm driving (I manage about four 15-20 min drives per week roughly) to increase the rate at which the battery charges? Like, not play the stereo or drive in a lower gear or rev the engine when idling at lights etc? I know shit all about cars so I am aware that those may be utterly stupid questions!

[Trippy]

I'm not a car tech so you should probably "fact check" what I say but here are my observations and suggestions.

Depending on your alternator and the electrical load it might help to rev the engine slightly at idle. Some alternators don't charge well or charge at all when idling too low. Not using electrical stuff should help speed up the battery charging but I couldn't begin to tell you how significant the difference is.

The fact that your battery has run down multiple times means your battery most likely doesn't hold a charge very well anymore. I had my initial battery in my current car run down because of an electrical short somewhere and despite my best attempts I could never get it to hold a significant charge anymore and was constantly having to jump start it (which I'll explain more in a bit). In contrast, I'm currently taking care of a friend's car and that one I drive once a month for 60 - 90 minutes and so far after 8 months or so the battery hasn't died yet. And this is a modern car with a car alarm, electronic door locks, etc. so it's always drawing a small amount of current when turned off.

If you park your car in a garage overnight you could get a battery charger and keep your battery charged up that way. It's a bit complicated cause properly charging a car battery requires a charger with more "smarts" than your typical consumer one but it's still better than nothing. Another car I used to take care of I wouldn't drive at all for months and months and then when I knew the owners would be coming back soon I would charge it using a battery charger and that worked fine.

For my car when I had the bad battery/electrical short I would carry around a portable "jump start" kit until I had a chance to take my car into service and have them figure out where the short was and replace the battery. The portable battery plugs into a standard wall socket to charge up and it has built in cables and I would carry it around in the trunk with me. You could just carry an extra battery but a kit is more convenient/nicer.

[Hawkbit]

The fact that your battery has run down multiple times means your battery most likely doesn't hold a charge very well anymore.

This.  Unless you're parking it consistently in sub zero temps all year long, it's time for a new battery.  You can keep using a charger to give it a boost, but you run the risk of it not starting when you're out and about. 

Been many years since I've bought one, but it should run $50 and take the old one in for $10-15 core credit.  Should save you a potential hassle from getting stranded somewhere. 

[Oban]

Why not just sell the car and use a car sharing service like http://www.zipcar.com/ ?

[Numtini]

Four twenty minute drives a week pretty much matches how often I drive in good weather now that I have a Vespa and my car has no trouble holding a charge. You need a new battery.

[Salamok]

if you park outside they make a solar trickle charger, I think it even feeds your battery via the cig lighter

[Murgos]

New battery or, possibly a new alternator.

Don't freak out though, you can replace your alternator with a wrench and some elbow grease and rebuilt alternators run pretty cheap.

Go to a car parts store and ask them to test your battery, they have a little hand cart they can drag out to the car and use.  Takes 5 minutes.  They may be able to test the alternator at the same time but maybe not.

If they say the battery is shot then replace it, if it's not the battery then it's probably the alternator.  It can quite easily be both though, a bad alternator can kill a battery pretty quickly so if you want to be sure get a Chilton's or look up on the internet how to take out your alternator and take it into the car parts store and they will have a tester there in the back that you can hook it up to.

It's pretty straight forward.

[TheWalrus]

Better news. If you continue to use your alternator to charge up your dead battery, you'll get to replace that too. They are meant to maintain charge and provide enough output to run things like stereo and a/c etc. Have a complete system test done so you know if you have a bad batter, alternator, or a parasitic drain on the system thats kicking your ass. You'll regret it otherwise. Have a nice day!

[bhodi]

If your battery is dying that fast it's not holding a charge and there's nothing you can do about it because as soon as your car turns off bye bye juice.

A cheap car battery is $50. Buy a new one. If that one dies too, you'll probably need a new alternator.

Taking your car to the shop and having diagnosis on it will cost more than a new battery which is what it probably is anyway.

[Engels]

I'm having a similar problem, and my first thought was bad alternator. Turns out that some modern cars (mine included) have additional parts related to the electronics that can affect the efficiency of battery recharging that is -not- the alternator. So mine's going into the shop.

[apocrypha]

OK cool, thanks folks, new battery it is then probably.

It's way overdue for a service anyway, like 2 years overdue... I'll sort it out next week :)

[Murgos]

Taking your car to the shop and having diagnosis on it will cost more than a new battery which is what it probably is anyway.

No.  What I suggested is entirely free.

[Selby]

Before *I* can give any serious advice, I need to know the car we're dealing with.  Older cars vs. modern cars vs. domestic vs. foreign (European vs. Japanese vs. Korean vs. Russian vs. etc) all play a different role.  More information is better to get accurate answers.

That being said, like others have stated your battery is likely toast.  How old is it?  How is the water content in it (assuming you can check)?  Does the car have any gauges or does it have lights for the charging circuit and what are they saying?  If you continue down this path the alternator will eventually give up the ghost too due to high current output for long periods of time.  Your 15-20m drives per week, are they at highway speeds or are they in stop and go bumper to bumper traffic?  All of this plays a big part in how long it takes to charge a depleted battery and whether the battery is truly charged for the long haul or not (assuming the battery isn't dead).

[WayAbvPar]

I would suggest spending the extra $30 for a good battery instead of going bare bones cheap. Some places (like Costco) will even give you a warranty IIRC.