Charging problem...Again!!

[dave`12]

He we go again, man it seems I’m always fighting a charging problem!

So, I recently converted it to the SI12 alternator. It’s been running fine, being driven a couple of times a week since the conversion.

Here are the numbers that I have had since the conversion:

Engine off - 12.47v
Idle no accessories - 14.84v
Idle everything on - 13.04v
1500 rpm everything on 14.88v

The ammeter always jumps a little at first start and when I turn on the electric fans, then settles just over the 1/2 way position.

So, yesterday, I start it up (I had driven it 2 days before and all was well). The ammeter went to 3/4 and stayed there the whole time I drove, 20 minutes.

Got to where I was going, shut it off. The battery was just under 12 volts. Started it up again, volts only went to about 13.1 and stayed there (no accessories).

With everything on (fans, a/c) the volts were just over 12 at idle, goes up to around 13 at 2000 RPM.

So the gauge is staying at 3/4 and the charge is not going as high as it should.

It’s an optima red top that is about 2 years old and passed a load test when I did the upgrade.

So I believe the gauge is correct, but have no idea what may be going on. I would think alternator, but with the gauge at 3/4, I know it's charging quite a bit.

Any advice appreciated.

[dmjlambert]

Hmm, I don't know. Do you have another battery you can put in to see how it behaves? Are you actually having a problem starting or using accessories, or just worried about what is showing on the gauges? I would take the battery and alternator up to a car parts store and let them test both.

[franken]

My thought is normal battery voltage is ~12.6 and you're a bit low. Charging seems ok, but maybe a bit low when the revs are low.
The battery gauge is just a general indicator of charging and doesn't provide much real info. All you know is its on the C or D side. It tells that the battery or alt side is more + than the other. It's feed is voltage close to the battery and close to the alt; not current. Thus it's the difference between battery and alt voltage. Note that it has no units. That's why they switched to voltmeters.

What's bad things does it do? No start? Is there paranoia or an actual failure?

[dave`12]

Thanx, Lambert. I was considering those options myself. Luckily, my DD has the same optima battery. I switched it out today, and everything went back to normal. The gauge is back to the way it used to be, and the numbers as well.
I’m guessing the truck’s optima has bit the dust. In its defense, it has had a rough life, what with all the charging problems, being discharged and charged over and over and sitting in a project vehicle. I guess I can’t blame it for going south. Good news is, it’s still under replacement warranty. I’m hoping a new one will be ok.

@ Franken – maybe a bit of paranoia, the vehicle did start and run fine. But with my history, I would be a fool to ignore a gauge that suddenly tells me something has changed coupled with low readings on my voltmeter! 

actually, the numbers with my other battery are better than my initial with the old one when the gauge was showing all good:

12.6 off
14.2 idle and 14.4 at 2000rpm
14.2 idle all accessories on and 14.5 at 2000 rpm

I do have a couple of questions:
Franken, you say that all you have is C and D on my gauge - but there must be a difference between just north of C and 3/4's of the gauge - and all the way? I'm guessing more amps are flowing as it goes up? I mean, wouldn't you be worried if you had this gauge and it suddenly stayed much further up than it always has?

Opinion, how long should a vehicle be ok with the battery hooked up but not started? For example, if I know I won't be driving it for say 2 weeks, should I unhook it?

thanx

[dmjlambert]

I think the ammeter is interesting and somewhat useful. It is simply a voltmeter capable of reading either polarity, and measures the voltage drop across a solid piece of wire. Amount of voltage drop a voltmeter measures across a known amount of small resistance is pretty much the definition of current in amps. If you wanted to, you could add markings for the number of amps charging or discharging. Or you could add a voltage divider using resistors and calibrate it to measure voltage instead of current, although it would/should never go into the negative voltage range in that case.

I think keeping the battery connected or not depends on the environment and condition of the truck. A truck with unknown condition wiring (or known poor condition wiring) sitting around in a yard with rats and squirrels running up under it and having fun, and that drains the battery in a few days for no apparent reason, should probably be disconnected when it's not in your sight. (Mine has been there!) On the other hand, a correctly wired truck that is well maintained and sheltered, and that has been left for weeks at a time without it draining the battery, should be able to have the battery connected for a very long time. Perhaps over a year. And then there's everything in between.

[Andy4639]

The battery should last a month are more. The charging is doing what it's suppose to be doing by your numbers.

Do you have a volt meter hooked up inside the truck? If not, I would hook one up so you can see what it's doing.

[dave`12]

Thought I would update this. Turned out that when I converted to the 12SI, I had the 2 wires going into the alternator reversed.

It can sit for days now and not lose any juice.

Thanx for the help.

[El Dorado Jim]

Originally Posted by dave`12

Thought I would update this. Turned out that when I converted to the 12SI, I had the 2 wires going into the alternator reversed.

It can sit for days now and not lose any juice.

Thanx for the help.

cool, thanks for sharing