I noticed that the system voltage was a little low when I started the car to head home last night. When I turned on my lights and fan it was riding on the edge of the red zone on the voltmeter. I made it home but the lights were getting pretty dim. I charged that battery overnight and when I started it the voltmeter went well up towards the red zone on the other end of the scale.

The battery light comes on with the key on, engine off. Nearly 0 ohms (cheap DVM) between the alternator case and the intake manifold. After charging, engine running, the voltage measured at the battery was 14.7V. Turning on the lights and fan dropped it to 12.4V. Specific gravity was low across the board and more 50 points between cells. Not great, but not exactly fatal either.

My question is - Will a bad battery make it so the alternator won't be able to operate the car ( yellow headlights, EGR light on, low system voltage) ?

Thanks

Greg

The battery had two dead cells and the rest of them weren't great. A new battery spins it over noticeably faster. A significant part of the problem was that the alternator belts were loose. NAPA belts, about a year old, retensioned, etc. Either NAPA belts are not so good anymore or the bushings may have pooped out. Charges on the high end of the scale (~14V) with high beams on and blower at full tilt. 30mV between the alternator case and the intake manifold. It's supposed to warm up so I can give the bushings a look.

Greg

Measure the voltage at the battery while starting the engine, if it drops below 12 replace the battery. I suspect it will drop even lower.
Dan

Hi,

A dying battery is very possible with the unevenness of the electrolyte weight reading but it’s not the last word as it is “variable” with the state of charge and so is with a winters temperature dependency.
When a battery is getting its charge the acid is being pushed out of the lead plates and back into the solution.
The capability of this rise and fall of acid does indicate some health of the battery but ultimately it comes down to the have good lead availableand not being sulphate.
Sulphate gets dropped into the bottom of the battery and can short the cells plates from underneath. Eventually over time the charging current never gets into the plates and goes straight through or across the cell.
At this point, the battery has a short life of holding or doing anything worthwhile.


When you went from the alternator case to the engines intake manifold using an ohmmeter is only going to say that they are grounded like their suppose to be.
Using a voltmeter and reading the same side of polarity is a better method for checking the ground. With something on in the car you want see 0.000 to 0.02 volts. This is the best indicator.
Seeing anything resembling a rise in voltage is a bad ground or a “resistance” within, somewhere!
With Big cables, the ohmmeter cannot define a small wire strand or from one big wire with many strands of them!
Same with the engine case to the alternator case. The little battery’s voltage and it’s meter current goes everywhere or which away!

It is very good you have a voltmeter connected into the cars system, so you know what’s happening and exactly when. Flickering lights or a gauge needle is the same.

It would be best to first have the battery test loaded and also determine its age!
If the battery has been abused by limited use and long periods of idleness, then yes, suspect the battery.
After that, one has to take the same thoughts on to the alternator’s condition!
This includes having good battery cables with good clean connections.

You never mentioned at what RPM’s the engine was turning over when you had a full electrical load.
12.4 volts indicates a load beyond the alternator’s output. It is saying the battery/system was under a high discharge or load condition. Could be slipping belts but Something not good for a long term.

If the battery is fully up to par with charge, the alternator should be able to hold 13.2 volts. This is a minimum output or the battery may not be maintained as it should for short trips.

14.7 is saying that the regulator is sensing or has sensed the system need for a lot more input.
“Ideally” the regulator shoots for one volt over standing or rested battery voltage or 13.65 volts with a plus or minus 0.5 volt margin.
A few tenths each way shifts the alternators “current” output appreciatabley.

The battery takes any leftover that the system is not using. A battery is like a shock absorber or bucket to catch or dispense as needed.

If a battery goes south by having a shorting cell it can take out an alternator.
As again, a battery can drain itself internally.
In some cases the alternator can develop a shorted diode and it will drain a battery.
Sometimes a shorted diode happens during a jump start is done from another car!

Connecting cables up wrong is the biggest killer!
The next thing, it jumps to trying to start a totally dead car before the battery gets some charge built up in it.
I believe it’s recommended to keep the one car running and reved slightly during a cranking of the dead car.
Many schools of thought have fallen out from the owners manuals of different cars!
Some want the car stopped and even recommend doing a disconnect. In affect, using only using the battery available. But there goes your radio memory and the computers adaptive driving settings?

My advice is to test more and observe more if you suspect the battery’s age.

Phil

Hi Phil,

It looks like I'm going to have to give up on this battery. I charged it Friday night ( didn't want it to freeze), all day Saturday, started the car and put it in the garage, topped up the cells and charged it overnight last night (10Ahr rate). The end cells are 1.100 and 1.150. The rest are in the 1.250 range. It was a good battery, it was the original out of Mary's '04 V70.

I'll warm up / charge up another battery and stick in it and see what happens. '

On a somewhat related note, the alternator that I had sitting on the shelf (working, recent brushes and regulator) is seized up. It was cold but now it is in the warmish garage. Still stuck. Thoughts ?

Thanks

Greg

Hi Greg,

The alternators rotor should spin freely unless the bearings are bad or super dried out. There should be a very slight dragging sound coming from the brushes and possibly the bearings depending on their age. If you can shake in any kind of play out of the pulley shaft, but not turn it, then the bearings are usually done!

I would remove the regulator by removing two screws.
If you had just changed the regulator and brush pack it might be that the brushes are cocked onto the slip rings. If the slip rings are badly grooved it’s possible they or one brush is not seated down deep enough. The brushes can be tricky.

If you tried to replaced the regulator, while still in the car and later took it off, this can most likely be the case.

The when inserting the brush pack the brushes need to be held up as far as they will go to get them onto the slip rings. Any Grooves in those rings do not help the situation.

There are also two flat spring fingers or contact shoes that must allow the regulator in.
Maybe one is bent up or down in some way. To lock a rotor up something has to be bad or in a pinch.

I would start by opening up the brush pack and inspect that location.
Otherwise, it’s a complete tear down to check out the inside particulars.
Match mark the outer housings before a tear down is always wise no matter if it looks like it goes only one way! Same for electric motors.

It’s a nice cold day job to do on the bench!
Luck to ya!

Phil

Wait so your saying the battery in question is 14 yrs old ?

Yes, it was a Volvo branded battery, made in France. A good one.

Greg

I always bought the battery from Volvo lasted 8 trouble free yrs to the month. because they made the battery . They don't make batteries anymore went to the Die hard international and again 8 solid yrs. Sears discontinued that as well. Using Bosch now so time will tell.

the thing that will drain the battery after the car is started it is a problem with the Alt. Have you checked the Brushes. Found in that Regulator/Brush unit in the rear of the Alt.

That was my first thought but it didn't act like worn brushes with the dim / flickering warning lights. The lights that were dim the other night were the headlights. I'm going to try another battery and if that isn't the solution I'll put in a set of brushes and VR.

Greg