car charging at 13.2

[chpr1972]

I have an Optima battery that is about 4 years old. I usually charge at about 14.8 V. Today it started charging at bout 13.2. My gauges are Dakota Digital analog/digital . I checked the system with my 30? year old Snap On digital tester. All 4 lites didn't come on so alternator is good. I then put the battery on a regular charger and in less than a half an hour at 10 amp it was charged. I then switched it over to 2 amp and in about half an hour it was charged. Still charging at 13.2 V. Took it up to Auto Zone and had them check it. He said the regulator was bad. But the battery was good at 12.4 V. I then took it to Advance Auto Parts and had them check it. Everything including the alternator was good. But the battery was also at 12.42C. Voltage went down to 11.35 cranking. Charging system at no load was 13.39 and loaded at 13.0. What gives. I have always considered a battery at 12.4 as discharged or bad.Tomorrow I'm going to pull the alternator and take it down to have it checked. It is a 100 Amp and I have to call Vintage Ait to find out whom made it

[TheJDMan]

You did not specify what car or alternator you have but based on your description of a reduced charge rate, I would suspect a bad diode in the alternator. If you have a GM 10SI or 12SI a replacement diode trio can be purchased for around $12-$15 from any auto parts store and replacing it is a simple 10 minute job. I would also recommend you read through some of the tech articles on Mad Electrical for some great background information on charging systems.

http://madelectrical.com/electrical-tech.shtml

[chpr1972]

I'm not sure what alternator it is and who manufactured it. It is a GM alternator of later design. It came with the Vintage Air front runner system. It is in a 66 Lemans conv with BBC. I have had it for 4/5 years. It is the battery voltage that kills me. I'm use to a 14.8 to 15.2 charging and a 13.6 battery voltage. Is this normal for a Optima battery? Darn new technology!
....................................lost in the 60's .......................................

[TheJDMan]

Your problem has nothing to do with the battery, IMO. The scenario you describe is typical of a popped diode in the alternator. As you stated in your first post remove the alt and have it tested off the car. It will likely generate voltage but I suspect it will fail a load test.

[DT69Cam]

Def sounds like an alternator problem. I thought the front runner set-ups used 140 amp alternators ??

[dontlifttoshift]

It's a 1 wire CS130 manufactured by TuffStuff. Make sure your alternator has a good ground path back to the battery. If that is all good, replace/rebuild the alternator.

[chpr1972]

It is about 5/6 years old and I had TUFF STUFF rewire it to a 3 wire a couple of years ago. I got out my receipts last nite cause I need to know. That is why it is a 100/105? amp alternator. No one has given me an answer about the Optima battery which only charged to about 12.4 V on my charger. Should it not be 13.6. I tried to call Optima Batteries this afternoon. 21 times and it was busy! Never did get thru!

[ULTM8Z]

My Optima red top measures out to be between 11.5 and 12V with the car off. But I never have any problems with it (have had it for about 3-4 years now). I charge at 14.2-14.5V with a 105 amp GM CS-130 alternator off a 1990 Camaro.

[dhutton]

What kind of charger are you using? Optima needs a special charger. I use Odyssey batteries and had to buy their charger.

Don

[ULTM8Z]

I don't use a charger. The alternator keeps it charged and it'll retain that charge on its own. I sometimes don't drive the car for a few weeks and it'll start right up.

I measured the current draw with the car off and it pulls about 25 mA... radio, keyless ignition RF TX/RX, ECM, etc...

[blitzer454]

I use a Deltran battery tender on my red top that charges at about 13V. Without the charger the battery will eventually drop down to about 12V. The alternator will charge around 14V.

[ULTM8Z]

I don't get it... you guys are saying that 12V is a bad thing in terms of the battery output?

[blitzer454]

I didn't say that. 12V is normal when not charging.

[chpr1972]

I took the alternator down to a local alternator repair shop and had it checked out. It was putting out 14.8 V and well over 100 amps. I'm going to try another battery and see what happens. I called Optima today and talked to tech. The guy I talked to could not give me any type of an answer. I asked him what the voltage reading was on a new Optima battery. He had to look it up! You would think that they would know that. It appears that a new red top is 13.6 to 15? something.

[DT69Cam]

I took the alternator down to a local alternator repair shop and had it checked out. It was putting out 14.8 V and well over 100 amps. I'm going to try another battery and see what happens. I called Optima today and talked to tech. The guy I talked to could not give me any type of an answer. I asked him what the voltage reading was on a new Optima battery. He had to look it up! You would think that they would know that. It appears that a new red top is 13.6 to 15? something.

What actually prompted you to investigate the battery and or alternator ??? Are you having trouble starting because of a weak battery ???? You just checked the voltage because you wanted too ?? If your not having any staring issues you may just be fine. Just a thought.

[ULTM8Z]

Also make sure the sense wire is showing the right voltage at the alternator.

[chpr1972]

what happened was the car usually charges at 14.8. Last time I took the car out, it was charging at 13.2. As an older than dirt person, if a battery did not show 13.6V it was bad or discharged. But this battery was at 12.4V and had 900 cranking amps out of a 800 rated battery, I wanted to know how that happened. When I get it back together with a different battery I will check the sense wire if I still have a problem.

[DT69Cam]

what happened was the car usually charges at 14.8. Last time I took the car out, it was charging at 13.2. As an older than dirt person, if a battery did not show 13.6V it was bad or discharged. But this battery was at 12.4V and had 900 cranking amps out of a 800 rated battery, I wanted to know how that happened. When I get it back together with a different battery I will check the sense wire if I still have a problem.

Your Dakota Digital dash gauge was showing 13.2 I take it ?? Hmmm....

[Warthog5]

I have always considered a battery at 12.4 as discharged or bad.

No......a settled 12V battery will have 2.1V per cell...IE: read 12.6. This is when the surface charge has worn off.

The regulator in your alt. is the control device that regulates the alt. It should be 13.8 to 14.2V

Do a Voltmeter test direct to the battery.

Crank the motor.....turn on the headlights ....turn on the heater blower motor.....bring the RPM to 2000 and test battery voltage.

[Doug1]

See the next to the last entry on my thread on Dual AGM batteries. It has Optima's required charging voltage that must be measured at the battery.

[Warthog5]

For AGM batteries you should get an advanced regulator. It will do multi step charging. An old style regulator doesn't and will wear the battery out prematurely.

I Totally disagree.

[MonzaRacer]

OK so charging system 101, class is in session.
Been working on cars as profession for 30+ yrs and I am pretty good at electrical.
First of all a common car battery is full charge at 12.6. Making 2.1 volts per cell. As for testing batteries they are testing with a capacitance tester and for the most part they DO a fairly accurate test.
Most current systems for testing then use a no load "float" charge test with only car running but no accessories, THEN have you run lights, blower, rear defogger etc for the added load looking for a voltage RISE.
This can also be checked with good digital multimeter (not cheapy from tool bin at gas station if at all possible) and a carbon pile tester. One that loads battery and system with heavy load.
The old hand held Snap On 100amp testers take much more to spot actual system faults.
This is what I have for old school battery load testing and IT WILL MAKE A WEAK BATTERY HEAL to the load.
https://www.tooldiscounter.com/ItemDisplay.cfm?lookup=ASC6039&source=froogle&kw=ASC6039&gclid=Cj0KEQjw3PLnBRCpo8PCoaGM99MBEiQAppRuC3JOsWgS acYJuYjocoVC1KUrhtBwy9DlL7JD8HtEG58aApgr8P8HAQ


I also use Midtronics ED18/3 at work

But my personal unit I just got last fall from Matco is:
https://www.matcotools.com/catalog/product/MBT1015/DIGITAL-BATTERY-TESTER-WITH-PRINTER/


It tests starter, alternator, ground plane and diode ripple as well.

One way to see if you have a weak diode is using a quality digital multimeter with at least 5 mega ohm or 10 mega ohm impedance you attach it to both terminals then turn on low beams and watching multimeter on AC voltage blink your high beams or turn on another high amp surge device and watch the multimeter.
The industry spec is 0.070V AC or 70 mV AC if you get more than low 80 mV AC you have a diode that isnt clamping the AC current properly and WILL destroy the battery forthwith.

I have seen systems flashing well over 1V AC into batteries trashing them and it will make computer systems act up as well.
A sharp load taxes the diode a heavy load that comes on with less speed may not flare the diode clamping BUT still may allow damage to happen but over longer period of time.


NOW, the CSI130/133/144 alternator either internal or external fan has a digital regulator which give the alternator a much sharper and cleaner charge pattern under loads.
Older 10/12 SI simply have two or three steps depending on what the second regulator wire senses(that would be the larger wire that clips to regulator plugs.
The newer CSI alternator do not need a sensing wire BUT ARE EQUIPPED with that circuit.

On either alternator you wire a 12 key on run source through a light(preferably a bulb similar to a 194) to the turn on circuit.
They also have a sensing wire you can run to different areas of the electrical system.
But its not required.

Generally if an alternator that has been in service starts charging lower try looking at worn brushes. This allows the spring tension to lessen and reduces brush connection on slip rings. Also if the rings are not concentric the weaker springs allow the brushes to hop and reduce power output regardless of what the regulator is trying to produce.
My money is look at brush wear, MAYBE a weak diode and also if you tear it down change the bearings for insurance.
OR buy one with extended warranty.