Low Battery

[Mattbchillin]

I rolled down my windows yesterday and kept the key in the ignition for about a minute turned to the 1st position, dash lights on. Well after about 1 minute I heard a weird BEEP and it said low battery. I figured I needed a new battery but I read somewhere that it could also be caused by a bad alternator not charging battery. I have had this car for 2 months now and have never had any battery issues. Should I start with the battery and see what happens? Anyway to check alternator without taking it off?

Thanks Again!

[oragex]

Not necessarily the alternator, it could well be a parasitic drain somewhere - that should be the first thing to check.

You need a multimeter, for battery and alternator alone a cheap multimeter will do. For parasitic drain you need a multimeter that measures 10A (will have three or four holes for the probes).

I'd start first by getting a new battery. Measure the new battery with the engine off 30 min. after driving, with all lights off (trunk lights off as well). Maybe unplug the trunk lights and open the trunk lid only with the remote. Measure the same the next morning. If there's a difference larger than 0.2 or 0.3 volts, there is a parasitic drain that's draining the battery overnight (which kills the battery after a few months).

To test the alternator it's a bit tricky because these alternators are 'smart': they put out some 13.5v most of the time when the battery is fully charged or 14.4v when the battery needs charged. Many say an alternator should put out 14.4v or it's bad - which is not true, most of the times a good battery stays fully charged while driving so the alternator only puts a lower voltage to power the car systems. What's more, if a battery is worn, the alternator will only put out the lower voltage even if the battery is discharged (around 13.5v).

The best way to test the alternator is to first discharge the new battery a little bit by leaving the headlights or radio on for some time until the battery voltage drops, then fire up the engine and see if the alternator puts out around 14.4v.

[difflock54]

Surely a load test of your existing battery to ensure it does not have dead or weak cells is a good starting point. Why go to the expense of buying a new battery if the current one is okay. Otherwise do as stated above.

[oragex]

The idea of buying a new battery is for two main reasons: when the old battery gets constantly discharged (such as from a faulty alternator or a parasitic drain overnight), the battery gets damaged and cannot be charged again to a reasonable level. Therefore, the chances are the battery is not longer any good. The second reason is, as mentioned, an alternator cannot be properly tested on a faulty battery - only with a battery that can accept a good charge.

If 30 minutes after driving the car, with all lights off, the old battery shows a voltage of 12.5v-12.7v, it may still be good. But the alternator can only be tested properly on a battery that is not damaged, so maybe get a new battery, test the alternator, and if it shows a good voltage, just return the new battery the store, and try to find out quickly where is the parasitic drain - before it damages the old battery to the point of need to replace it.

Here's my own issue with a parasitic drain which did cost me two batteries - before I properly diagnosed it was a drain issue

www.youtube.com/watch?v=A1xxHECS8as

[abscate]

I rolled down my windows yesterday and kept the key in the ignition for about a minute turned to the 1st position, dash lights on. Well after about 1 minute I heard a weird BEEP and it said low battery. I figured I needed a new battery but I read somewhere that it could also be caused by a bad alternator not charging battery. I have had this car for 2 months now and have never had any battery issues. Should I start with the battery and see what happens? Anyway to check alternator without taking it off?

Thanks Again!

5 years is decent life on a battery in New England - after that, you can expect cranking trouble in winter.

How old is it, and has it been on a daily driver for most of its life.

Deep discharge and non-use are the two early killers of batteries.