1997 850 sedan battery drains quickly

morgant · Post by **morgant** » 08 Jul 2015, 14:07

I drive my 1997 Volvo 850 sedan (base model) about 100 mi a day, 5 days a week, for my commute, plus a couple times a month I drive about 300 mi on the weekend.

About 3 weeks ago on the weekend, I drove for 3hrs, parked it for 4 hours or so (no lights or accessories left on that I know of), drove it another 30 mins, stopped for gas, then it wouldn't start (lights & accessories dimmed and it wouldn't even try to turn over). It jump started very easily, all accessories ran well and it even started charging the jump pack that was connected to it, so I assumed the alternator was fine. It has continued to drain the battery every couple of nights the past few weeks, despite not finding any accessories on and requires a jump start in the morning. Naturally, my 1hr commute usually seems to charge it back up.

I had the battery tested twice a couple weeks ago and it showed good (it's about 2.5yrs old and under warranty). Lately I've been finding it usually around 10.5V in the morning, which is very dead, but the last few mornings it's been 8.5V and I can't imagine I'll be able to recover it after such lows (from what I understand). It seems charged around 12.5V after driving, but the voltage quickly drops to 11.8V (which is still low), so maybe it's not charging up enough (esp. starting at 10.5V; I've heard it's hard to judge charge level by voltage on a battery that has just been under load & charge).

With the car running, the voltage is around 13.65-13.75V, so it seems like that means the alternator is working, correct?

It has been raining a lot in my area this spring and while the battery terminals never get corroded (I always coat with anti-seize to prevent corrosion & promote a good connection), the positive & negative cables, ground straps, and a couple ground points do have some copper corrosion. I sprayed them down with WD-40 & scrubbed to remove some corrosion and to expel any moisture. Could it just be a bad ground?

I read on another thread that you can test with a meter and that the draw shouldn't exceed .3 amps. My multimeter only has a mA setting, which I did test with between the negative battery terminal and the negative cable and it was reading -.02 mA. I pulled all the fuses one by one and it never dropped (I also reversed the order of the +/- sensors on my meter between the negative terminal & negative cable and it read much higher, around +.11mA IIRC).

I did try pulling relays and one of the "J" relays did cause it drop from -.02 mA to -.01 mA, but I wasn't able to determine what that was controlling or if I was even reading it correctly.

I was initially inclined to believe it was the battery, but have taken it out of the car and it doesn't drop particularly quickly. Yesterday, after performing a fast charge and driving it for an hour, it dropped from 11.88V to 11.52V over a period of 6hrs, but that was also with it cooling down, so it may not have really been at 11.88V.

Any suggestions for & corrections to my troubleshooting process would be greatly appreciated. I can't get the battery replaced under warranty without it failing on the tester and I'm not entirely sure I performed the draw test correctly with my multimeter (esp. since reversing polarity on the mA setting seemed to change by a factor of 10).

Post by **dcarlson12** » 08 Jul 2015, 16:13

My suggestion is to get the battery tested again.
Not sure if there are various ways that they do the test?????
Dwight

harryhendo · Post by **harryhendo** » 08 Jul 2015, 16:36

You should test the alternator, as an internal short in the alternator (a very common fault) will drain the battery overnight. A simple test is to disconnect it after you get home from your evening commute, and, if the battery is okay when you hook it back up the next morning, it is the culprit. Also, the 13.6 V output is kinda low... should be around 14.2.

Post by **tryingbe** » 08 Jul 2015, 18:56

Any auto part store should be able to test your battery for you, as a second opinion.

Post by **atucker1** » 08 Jul 2015, 23:46

A common problem on these 850s is the glove box light. The plastic glove box gets brittle and cracks, not allowing the door to fully close, and therefore leaving the light on. Its worth a check--leave your phone on camera in the glove box and shut it to see if the light turns off.

Post by **xHeart** » 09 Jul 2015, 08:19

A 3-years old battery becomes terminally ill -- gradually weakens.
Take off battery, and have it "fully charged" at local aZone or likes.
Make sure Cold Crank (CC) is at max -- 630-700.
Take volt-dc measurement, and then only monitor the tango between alternator and charged battery.

Alternator output should be consistent at idle and under load (close to 14.38 volt is best alternator output).

morgant · Post by **morgant** » 09 Jul 2015, 08:48

Thanks for all the suggestions, folks!

I should've noted that when I had the battery tested they did one test while it was in the vehicle and then I insisted that they do a full charge & test in the shop. The CCA was a bit lower than rated (562CCA vs 650CCA), but that's most likely due to the age and not low enough that it'd prevent starting.

I had read about the glove box light and had already verified that it does shut off.

Not sure why I was misremembering what the alternator voltage should be and I should've double-checked that before testing, but you're correct it should be 14.3V. I did more testing this morning and it's still only 13.6V either at idle or under load. So, at this point I have to assume it's the alternator and that it has not been fully charging the battery.

At this point the battery may need to be re-tested & replaced, but I should take care of the alternator first.

Post by **dcarlson12** » 09 Jul 2015, 10:34

See my starter/charging system thread:

https://www.matthewsvolvosite.com/forums ... =1&t=70662

RE your 13.6 volts across the battery i.e. from alternator, you may just have a higher than normal voltage drop across the wiring from the alternator to the battery. i.e. similar to what I had

You can find several voltage drop test 'how to' videos on Youtube.

Keep us updated what you find.

Dwight
97 850 T5

morgant · Post by **morgant** » 09 Jul 2015, 11:10

Hmm, I guess that would fit with the corrosion on the cables that I noted. Any good way to test that (other than the "hot" cable temperature that was mentioned in your thread?

I already ordered a rebuilt alternator, but I guess I can return it if it turns out to be wiring. Neither iPD or eEuroparts seem to have positive battery cables, only negative (and even those are about $100). I'll have to see if I think I can build my own replacement (don't have any cutting/crimping tools, solder, etc.), if it comes to that.

morgant · Post by **morgant** » 09 Jul 2015, 11:21

Looks like FCP does have non-genuine positive battery cables. That's probably the easier route to replace both positive & negative since they're both corroded, if it comes to that.

Any chance it's something like the voltage regulator?