Intermittent Charging issue - opinions?

[dieselbigot]

Guys,

A few weeks ago I was sitting in my truck waiting for my wife...I had the stereo on for about 40 minutes. When I went to start the truck, it turned over very slowly (like weak battery slow), then started. I drove home without incident, checked the battery w/ my DMM and it was 12.3v. I decided to test it again by keeping the stereo on for 40 min again....it did'nt knock down the battery this time and started fine.

Fast forward to last weekend...went camping @ Pismo and after parking the truck I was running my ARB fridge and LED dome lights...a few hours later the truck would'nt start again. I jump started it and drove to town and had the Napa guy throw his battery tester on it. When shut off it was at 12v, then I started it and the needle didn't budge (so seems the alt was charging at 12v rather than 13.8 - 14.1 like it should).

I drove home 5 hrs and when I got home I tested the battery again w/ the DMM:
12.3v off and 13.8v running....so it's charging again. I looked at all the obvious things:

Grounds and connections all clean & solid
The 7.5A fusible link from the alt to the battery is fine
Alt charging over 60A @ 13.0v to 14.1v
Battery output 250-300 for 10 sec while above 10.5v

So it seems the charing system is healthy. My battery (single) is a 1yr old Optima red R34 on my 99 100 w/ 85k.

Anyone have any idea's here? I'm heading to Death Valley in 2 weeks and really don't want to deal with any issues like this...

Thx

Brett

 

[Jim_Chow]

Voltage regulator?

 

[hoser]

I would first test the Optima battery as they have a reputation of dying unexpectedly. I would charge it up with your home charger. It should read between 12.6-12.7V on a full charge. If successful, then "Load Test" the battery. If checks out, then move onto vehicle charging system.

 

[dieselbigot]

The voltage regulator is built into the alt on these trucks...so since the charging system tested ok, one can assume that the voltage regulator is ok.

Also, the battery was load tested and showed up ok. The key here is "intermittent"...that's where I'm drawing a blank

 

[hoser]

Okay, but curious, have you been able to get a reading higher than 12.3V since this problem started?

 

[dieselbigot]

Okay, but curious, have you been able to get a reading higher than 12.3V since this problem started?

Nope...12.3 has been the highest reading since this started

 

[mobi-arc]

You might consider having the battery tested on the more eleborate testing setup that they have at Sears. Sometimes the instant load testers that most shops have won't indicate a faulty battery. The more elaborate testers have a stepped program of charge and discharge cycles and can fail a battery that normally tests fine on quicky testers. The test takes about 40 minutes.

 

[dieselbigot]

You might consider having the battery tested on the more eleborate testing setup that they have at Sears. Sometimes the instant load testers that most shops have won't indicate a faulty battery. The more elaborate testers have a stepped program of charge and discharge cycles and can fail a battery that normally tests fine on quicky testers. The test takes about 40 minutes.

Scott,

I think you're right...I called my guy at Lehr Auto electric where I bought my Optima from...he said the battery should have done way better on a load test than 250-300 @ 10.5v. He thinks it's just a crappy Optima red top (wouldn't be the first), and said he'll replace it no problem.

Thanks again for taking so much time to talk to me today when i ordered my Power-Gate. As soon as I talked to you I called Ben @ Slee and ordered my battery tray and called Westcoast batteries and ordered a new Odyssey PC1700 MJT....dual batteries and a fresh odyessy for my main ought to fix me up just fine

 

[hoser]

Nope...12.3 has been the highest reading since this started

12.3V is considered half discharged. If it won't register higher than that after charging, there is something wrong internally.