mysterious power loss

[chrome730]

Im pretty sure i may have left the light on or door slightly open but my battery died last week . So i jumped it, like any normal person would do. Then last night my brother in law drove my car and the battery died again. Again could've been the door slightly open or the light or markers may have been on. But has any one had a case where the battery has just lost power. Im sure i just left something on but wanted to know your opinions.

[Newfie_dan]

if the battery dies on its own there are 3 possibilties;

1) bad battery, its not holding its charge and that can happen over time, remove and clean all connections to the battery make sure all conenctions are clean and free of corrosion, that will help to eliminate part of the issue, also make sure all connections to the battery are tight. Use rubbing alcohol and help remove it along with a battery terminal cleaning brush.

2) there is a drain on the battery, either a light or some other item which is drawing current with the car turned off. This can be determined by using a ammeter, disconnect the negative terminal of the battery then put the ammeter inline with the positive lead on the negative cable and the negative lead to the battery.

3) The alternator is not putting out good voltage, and to most people's knowledge an alternator is not meant to fully charge a dead battery you can in fact do serious damage to an alternator if you just boost a car and then allow the alternator to charge the battery. It can overheat the alternator and damage the voltage regulator. So precharging the battery if its lower than 9 volts is a good idea. To test the alternator's output use a voltmeter with the car running at idle you should see 14-14.4 volts at the battery if all connections are clean and free of corrosion.

A cheap multimeter from canadian tire or other parts stores which read amps and volts will suffice for these tests provided that its not a total crap multimeter. Make sure you read and understand how to use it properly before you attempt to use it so that you don't risk frying the multimeter you just bought. With that said there are a lot of other isues which can contribute to the problem but check these first then get back to me and I will attempt to help you troubleshoot the issue.

[Inodoro Pereyra]

Pretty much what Newfie_dan said.
By design, car batteries are dimensioned so, when everything is new, they should be able to start the car after leaving the headlights (low beams) on for 10 hours.
Take your battery to your nearest auto parts store and have it checked. If the battery has a voltage of less than approx 10 V, or less than 80% its nominal CCA, have it SLOW charged. That will take 24 hs, but will be much less damaging to the battery than a fast charge.
If the battery tests good after a slow charge, you can either do what N_D said in his point 2, (let us know if you don't know how to use a multimeter), or you can take your alternator out and also take it to the auto parts store for testing. I would test the alternator first, out of the car, to make sure it's working, before checking for current draws.
Also, one test yo can run is, with the car running and the multimeter set in "DCV", put one of the MM leads on the positive lead on the alty, and the other on the positive on the battery. You should read "0V" or maybe a few mV. IF you have a reading higher than, let's say 100 mV, you need to check/replace your "MAIN" fuse, and/or check/replace your alty/battery positive lead.
Also, it's not a bad idea to check your grounds, especially the battery negative lead.

[chrome730]

Thank you for the info. Today I made sure everything was off and if it dies on me. Im gonna check what you guys have stated.

[Mx3Kid16]

take the battery out of your car and hook a battery charger up to it...

let it charge for a few hours... if it still dies get a new batt.

[chrome730]

im ruling the battery out as it is only two months old.

[Inodoro Pereyra]

Don't rule ANYTHING out until you've tested it. I've seen batteries gone bad after 48 hs of use, and it's not as rare as you may think.

[chrome730]

ok ok ok. i how ever am still waiting to see if it will end up dead so far its day two and no problems. thank you for your help inodoro and newfie.

[Inodoro Pereyra]

Anytime.
Let us know what happens...

[chrome730]

ill keep ya posted

[Mad Cow]

I've had a battery die in a week or 2, so it could easily be that.

[Newfie_dan]

the more times you drain the battery below 9v the more you decrease the batteries life time. I have seen a typical car battery die after 5 times of drain to complete charge cycle.

[93vtecklr]

I've had 2 yellow top optimas for my datsun fail completely within 24hrs of purchase.

[Inodoro Pereyra]

Optimas are especially delicate (besides the fact that they're a piece of cr@p), because they don't accept any kind of fast charge at all. That means, if by any chance you leave anything on in the car and drain the battery to, let's say, less than 10V, you should take it off the car and slow charge it. If you start the car with it, and and charge it with the alternator, it's toast.

[Newfie_dan]

yeah gel cell batteries like the optima are inferior when it comes to being able to drain and recharge them for any great amount, however the advantage to a gel cell is that they far outweigh the comeptition when it comes to vibration resistance and temperature variance. The best battery overall is a dry cell which a new technology being used in the commercial sector. You can mount them in any positions even upside down, they repsond very well to vibration, and last through several drain/charge cycles. The down side to them is cost, they are very costly at this time.