Battery keeps loosing its charge...at times.

Post by **jmmxc** » 29 Oct 2011, 23:11

Hi every one:
I would be driving the car for weeks ( to work, parked during the day, errands evenings). Then I would leave the car parked a couple days then all of a sudden the battery would discharge to the point where it can not turn the starter. But during the time when it would drive OK, the car starts right up with absolutely no indication of an imminent indication of a weak battery condition.
Measuring the battery voltage during engine idling shows about 13.97V, dropping to 12 after engine isturned OFf. That seems to indicate that the alternator is working.

In one occasion I took the battery to Sears, they tested and recharged things would work fine and the issue repeats itself if left parked for a few days..They want to charge $200+ to check for shorts...

Any idea what may be causing the battery to loose charge?
Or is there an alternator problem?
I checked all around for current leaks, radio, cabin lights etc...no significant current draw from radio and no short I can find.
I would hate to change battery or go to an expensive alternator w/o knowing the root cause.
Your suggestions and insights are welcome.
Thanks,
jmmxc
Volvo 850GLT, 1996

Post by **Juan62** » 30 Oct 2011, 09:16

When your car sits for a few days, that's when I would test the battery. When the car is running and IF the alternatoris bad, it will draw current from the battery, not charge it.
How old is your battery? What brand? Take the car to autozone and have them test both for free. If battery is more than 3-4 years, it maybe time for a new one. I have went through 3 Volvo batteries since 1998. The original lastest the longest=7 years, the other 5 years. That's why i buy Volvo batteries...I can get at least 5 years out of them ($23.00) per year.

Post by **erikv11** » 30 Oct 2011, 09:43

This could be a problem with a dead cell in the battery but it usually is not, and the battery was tested already.

Very common: check for "parasitic" current draw. That just means something is drawing current when the car is off. The most culprit is the light in the glove box not shutting off even though the door is shut. Does that light work now? Does it go off when the little button is pushed (and does the glove box door close all the way)? Even so, it can be hard to tell. So the way to figure it out is with a hand-held multimeter (voltmeter). It can be tedious to do but is not difficult.

To test for parasitic draw, when the key is off the spec draw should be between 25 - 45 mA. If it is anything more than 100 mA (0.1 Amps) then you definitely have a parasitic draw problem. Pull the fuses one at a time until you see the amperage drop, that tells you which circuit has the draw.

After the glove box light, other possibilities are any aftermarket electronics, e.g. stereo or alarm system. Or the alternator, it could be putting out too few volts (should be up around 14) or a bad diode can cause it to draw when off. An auto parts store will test the alternator for free, but you might have to take it out and bring it in.

Post by **Pauloil** » 30 Oct 2011, 11:27

search for "voltage drop" and test your cables under load read up also how to test your grounds and consider replacing starter cable, if there is not a parasitic draw.

Post by **jmmxc** » 30 Oct 2011, 13:24

First of all, thanks for the advices....
I went through all your suggestions, except concentrating on the alternator possiblility.
I had removed the glove compartment lamp long time ago (in 2000) after the dealer found out that was the cause of a dead battery back then. As an aside their previeous diagnostic, which was wrong, pointed to a bad alternator: $600 parts and labor down the drain. But I digress...
* I used a multimeter to check for "parasitic current". Baseline current measured with everything off was 29mA~31mA.
* I pulled all fuses one nby one, no change. Small change of 1mA when I pulled the radio fuse #7. Still have origninal stock radio.
* All cabin and rear trunk lights are off. Summary: I am seeing only 30mA.
I am thinking the alternator might be start going bad as some of you suggested. Nevertheless the charge voltage goes up to 13.78V from battery voltage of 12V nominal at rest.
Question: Is there a way to test the alternator w/o removing it from the car. I have an oscilloscope that I can use if you guys know of a procedure to follow.

Oh by the way, the battery is barely 2 year old. It is a Sears battery.
Thanks again.
jmmxc

Post by **Pauloil** » 30 Oct 2011, 20:23

before you test alt, test your cables...... if you read the volvo alternator/starting eval, it starts out with testing the cables.
once again, search voltage drop

Post by **Pauloil** » 30 Oct 2011, 20:27

here's post with link in it to the volvo advise. i'm only persistant because I went thru 2 alts. before I found out my starter cable was bad.

https://www.matthewsvolvosite.com/forums ... p+#p190328

Post by **jmmxc** » 30 Oct 2011, 22:59

before you test alt, test your cables...... if you read the volvo alternator/starting eval, it starts out with testing the cables. once again, search voltage drop

OK Paul, I appreciate your insistence on this. And there can be something going on in the cables, considering the car is aging.

!
I am looking at the "Charging System Wiring Diagram" and I will follow the troubleshooting guide for voltage drop as discribed.
I may have some problem getting an ammeter to read the current as mentioned in the Output Test section. My multimeter is only good for 10A.

By the way, if I want to check the alt. cable lug itself do I have to remove the manifold? Or is there another way to get there?

I will keep you posted, hope to do some tshooting sometimes Monday afternoon.
I really appreciate your input and thanks again.
jmmxc

Nuttydriver · Post by **Nuttydriver** » 31 Oct 2011, 17:05

A simple way to test your alternator is to start the car and unhook your positive battery terminal. If the car stays running and everything seems normal then your alternator is doing it's job. If the car shuts off then it's time for a new one. Sound like it might be your starter cable to me, I've heard of that problem several times now with many different vehicles. Good luck.

Post by **jmmxc** » 31 Oct 2011, 21:27

Thanks to both of you Pauloil and Nuttydriver.
I am starting to think it might be something like the alt. or starter cable acting up.
How do I get to replace the alt. and starter cables w/o removing the intake manifold though, which seems to be in the way?
And can you indicate where to get a replacement calbe for the Volvo 850GLT?

Weather is starting to get bad, I would like to get to this at the earliest before the temperature dips further.

Thanks again.
jmmxc