Battery problems.

[Lil bastard]

You need to have a load test done on the alternator.

The alternator may have cooked the old battery, meaning that the alt. is the problem, not the battery.

It may just be that you haven't completed a drive cycle for the DME to relearn. Keep an eye on it over the next few days and if no better, check the alternator.

[FTD]

How does one test a sealed battery?

[Lil bastard]

Originally Posted by FTD

How does one test a sealed battery?

Most batteries are more than 12 volts. They have 6 cells, each producing around 2.1 - 2.2 volts. Wired in series, these cells combine to produce about 12.6 - 13.2 volts.

To test the battery, you want to disconnect one terminal and then using a multimeter (DMM), touch a lead on their respective battery post (- or +). If the battery is healthy, you should be seeing voltage in the 12.6 - 13.2 volt range.

Anything under 12.6 or over 13.6 says there's something not right, either low electrolyte, sulphur crytals built up on the plates, a cracked plate or cell. The battery may still work, but is on it's way out and is likely to make the alternator work harder, placing more strain on it's service life and reducing MPG slightly too.

It's also a good idea to test the alternator function while you at it. To do this, replace the battery terminal and start the car. With just the car running, placing the DMM leads as before, you should see somewhere between 13.5 - 14.5 volts (for the oem Bosche alternator) - this is the alternator voltage. Now, turn on accessories such as the headlights, radio, turn signals, fan (but not the AC), this is called a load test. The minimum voltage reading should now should be no less than 13.0 - 13.2 volts. If under this voltage (and assuming the battery tested healthy), or over 14.0 volts, suspect a problem with the alternator, usually the diode pack (one or more diodes may be faulty).

[FTD]

Originally Posted by Lil bastard

If under this voltage (and assuming the battery tested healthy), or over 14.0 volts, suspect a problem with the alternator, usually the diode pack (one or more diodes may be faulty).

How much over 14.0 = suspect a problem? 14.2?
And how does an overage indicate alternator weakness?
Thanks!

[Lil bastard]

Originally Posted by FTD

How much over 14.0 = suspect a problem? 14.2?
And how does an overage indicate alternator weakness?
Thanks!

There are a lot of variables at play, idle speed, belt tension/slippage, variances in each individual alternator, battery, and 'load' component.

Plus the alternator does degrade with time, while still having many useful miles left in it. So I wouldn't worry about a couple tenths.

But a wide variance, maybe 0.5 - 1.0 or more volts would concern me.

An large overage is a problem because the alternator alone, without the voltage regulator (diode pack), is capable of producing upwards of 40 volts which would fry the important circuitry in the DME, alarm, radio and other stuff, maybe even cause a fire.

[nefarious986]

Good news guys. Problem is gone. Car is running strong and idling smooth. It was probably the original battery's time to go ( it was 5 years old ) and not the alternator.

The funny thing is that it remembered my seat settings but not the engine settings. LOL.

Weird though because when the old battery died, I was still able to have stereo and lights and gadgets, so it wasn't completely dead, just not able to crank over.

It didn't give any warning though. I started it and drove it just fine 30 minutes before and when I got there, it just wont start again and just died. Oh wells.


Thanks guys.

[Boxtaboy]

Originally Posted by nefarious986

Good news guys. Problem is gone. Car is running strong and idling smooth. It was probably the original battery's time to go ( it was 5 years old ) and not the alternator.

The funny thing is that it remembered my seat settings but not the engine settings. LOL.

Weird though because when the old battery died, I was still able to have stereo and lights and gadgets, so it wasn't completely dead, just not able to crank over.

It didn't give any warning though. I started it and drove it just fine 30 minutes before and when I got there, it just wont start again and just died. Oh wells.


Thanks guys.

Good to hear all's well. My OEM battery left me stranded on its 5th year too. Same thing too- started just fine, and then after I stopped somewhere for a few minutes, tried to start her up and everything else worked but couldn't crank the starter. Replaced it with a Sears Diehard, and now I'm going to replace on the 4th year just as a precaution so I don't get stranded anymore.