Hello,

My wife's Volvo's wouldn't start this morning, last night she'd said the battery was weak. I figured it was a problem with the alternator. I charged up the battery a couple hours with my trickle charger, it seemed ok. I drove it to the auto parts store, they hooked up the battery to a battery/alternator tester and then had me start the engine. It said the battery was okay, but needed a charge (agreed with what I thought), but they said the alternator was good too.

So it seems that I must have a battery drain. This car is driven pretty much every day. I have a couple cheapo multimeters that will supposedly handle up to 10 Amps DC. My plan was to disconnect the negative battery terminal (because it's easier to get to), and hook up a multimeter in between the negative battery terminal and the negative battery cable. I was figuring I'd see a a current of a few amps (certainly less than 10) and I'd then pull one fuse after another until I found the circuit where the drain was.

That was my plan. I hooked up my meter and got no reading. I tried my other meter (which was brand new) and also got no reading. I tried hooking back up my battery charger again, which says puts out 1.5 Amps. I hooked up the charger to the battery cables, and then hooked up the ammeter between the negative battery cable and the negative battery post, I also read no current. However, when I hook the battery terminal back up to the battery I see sparks, so it would seem there's a fair bit of current flowing.

So I'm wondering if I could have killed my meters? This would imply that the current drain is more than 10 Amps. A 60 Watt headlight would be 60 /12 = 5 Amps, so 10 Amps seems pretty huge.

-Eric

 

Hello, From your paragraph 3.
"However, when I hook the battery terminal back up to the battery I see sparks, so it would seem there's a fair bit of current flowing."

When you put the negative back on the battery was the charger still on? Get that battery fully charged. Don't over look a short in the alternator itself. Kira

 

Nope the battery charger isn't connected when I see the sparks.

-Eric

 

On most meters you have to plug the leads into different jacks to measure that high of a current; did you do that?

Also when you first connect the battery (after it has been disconnected) it will draw significant surge current initially; this is because all of the electronic control modules are being pwred up at once.

You will have the hood up so if you have an underhood lamp, make sure it is unplugged. The ignition key should be off and removed from ignition switch for several minutes before doing the test (i.e. let all the modules go into sleep mode). Loosen the negative battery cable but don't disconnect it yet. Connect the ammeter across the negative battery terminal connection; positive meter lead to the cable; negative meter lead to the battery negative terminal post (use big enough clip to be able to clamp onto the battery terminal). Make sure the meter is set to the highest current measurement scale it will go to initially. Carefully disconnect the negative battery cable from the battery terminal; now any current flowing from/through the battery will be going through the meter. Assuming your meter is not over-ranging (it should be under-ranging), turn the scale down until you're reading current within the readable range/scale.

BTW; you want to use a meter that has overload or fused protection for current measurments. If you hade the leads plugged in correctly before, open up the meter; bet you find blown fuse... (hopefully it is fused?!).

 

On the 10 Amp mode, the meter is unfused, which is why I'm thinking I fried it. I took it to a Volvo mechanic, he said the battery was fine, the alternator was fine, and the current draw was down in the milliamp range. He said he had a similar problem with another customer's car, they had to bring it to him seven times before the problem would reproduce for him. He said that it was a bad alternator that time. H said the V70 has some kind of fancy "free wheeling" alternator? I guess it's supposed to save gas by disengaging when it's not needed or something like that?

The first day back from the mechanic everything was fine. I hooked it up to a trickle charger overnight just to be safe. The light on the charger indicating the battery was fully charged was on in the morning. I had also bought a voltmeter that plugs into the cigarette lighter, it said everything was good. I hooked it up to the trickle charger that night again. The next morning the battery charge wasn't very good (barely 12 V). When my wife drove it around it seemed okay (close to 14V). It seemed that the battery voltage would be kind of weak (a little less than 12 V) after the car was parked. Then by the end of the day, the battery voltage was in the low 13s even with the car running. When she got home I tried revving the engine to a little bit over 4000 rpm, but the battery voltage wouldn't budge over 13.3 V or so.

That night, I disconnected the negative wire from the battery terminal and hooked up the trickle charger overnight, so the battery was hooked up to a charger, but not connected to the car's electrical system. The next day the battery was around 12.6 V (better than the day before, but not great). As soon as I connected the negative wire to the battery its voltage (measured across the battery terminals itself) dropped to around 12.1 V. She drove it around today with the voltmeter plugged in, I think it did okay.

Right now I've got the trickle charger hooked up to the battery jump points in the engine compartment, the battery has been charging for an hour, the voltage has come up to 12.7 V (measured across the battery terminals). It was 12.3 V before I hooked up the battery charger.

I think that what's going on is that I have an intermittent drain on the battery when the car is turned off. I don't think it's happening now, since the battery voltage seems to be slowly rising with the trickle charger hooked up and the negative battery cable is attached to the battery. What goes against this theory is that I'd expect the alternator to be able to get the system voltage measured at the cigarette lighter plug to go over 13.3 V the day before when the engine was revved over 4000 rpm, but maybe not if the battery was tired from the constant drain.

What I've observed with a different car with a known good battery and alternator was that the voltage would start around 12.6 Volts measured at the cigarette lighter plug and rise to close to 14 Volts after the trickle charger was hooked up to the battery for an hour or so. Also, the voltage readings I get across the battery terminals are about .1 Volts higher than what I see with the cigarette lighter voltmeter.

-Eric

 

Man, that's a long post! OK, one thing at a time...

Didn't know you had one of these "free wheelers" wondering if that couldn't be your problem right there. I am not familiar with these at all; do they some kind of clutch or something? How does know when to "release"?

BTW: What year is this and what's your mileage on odom?

From your Cig meter, what's the voltage during cranking? Monitor and log the voltage while driving, parked, etc.

After it dropped to 12.1, did you monitor it for another few minutes? It should have come back up to almost 12.6v.

If you alt was up to snuf, and the batt was low, you should see the system voltage rise to 14-16v. This is another reason why I suspect your "free wheeler" may not be engaging when it should be...

One more thing; may not be the most accurate way to measure system voltage at cig lighter. Would be better to use a good meter and run dedicated wires to the battery terminals for logging purposes.

Thought of something else; if you want to test your theory of intermittent battery draw, keep disconnecting the batt term when you park it overnight, but don't trickle charge the batt. If your alt and batt are working properly you should never have a problem, right?

 

It's a 2002, it has around 80,000 miles. It appears to still have the original battery, either that or the previous owner replaced the original with another genuine Volvo battery. I don't know anything about the freewheel alternator, other than the Volvo mechanic thought my car had one, and that they were a "stupid idea."

The cigarette voltmeter won't read while the car is cranking, but after the car started it read 11-something, but came up to 14 Volts after a few seconds.

When I charged the battery with it disconnected from the electrical system, the battery voltage dropped to around 12.1 as soon as I connected the battery cable, but rose back up to 12.6 or so when I disconnected the battery again for a few minutes.

I showed my wife how to disconnect the battery cables and she said it seemed okay yesterday as long as she did this. This is what I did on Sunday and it seemed okay when I did this, but I didn't have a meter hooked up.

This morning the "charged" light was on, on the battery charger. I'd left the battery hooked up to the car's electrical system. The battery voltage measured 12.5ish. This battery charger is meant to be left hooked up to a vehicle for long term storage, so it senses voltage and cycles on and off based on that. When the "charged" light is on the charger isn't charging. Soon after I measured 12.5ish volts, the charged light went off and the charger started charging the battery. After a few minutes the battery voltage read 13.8 volts or so and the "charged" light came back on and the charger stopped charging.

Contrast that to two nights ago when the battery voltage was around 12 Volts even, after the battery charger had been hooked up all night with the battery connected to the car's electrical system. The previous night I charged the battery with it disconnected from the electrical system and it read 12.6 volts, but I didn't wait to watch it cycle on and off.

I don't think that whatever is wrong with the car is currently acting up.

Thanks,
Eric

 

Put new battery in because drained three days in a row. New battery lasted two days before it also drained dead Friday morning. Charged then started car, disconnected neg battery cable to see if engine would cut out or hesitate or something. Kept running fine which would suggest alternator is functioning. Also, I seem to have a 3.56 Amp drain on the system with the ignition turned off! Were you able to get to resolve this issue?

Thanks, Shawn