Caterpillar Batteries and alternator voltage

[Axekicker]

After experiencing wildly fluctuating alternator voltage issues, I took my truck back to the shop that rebuilt the motor last year and had them trouble shoot it. They said one of the Costco batteries had a bad cell (pass-side) and the ECM was bad. The alternator is original OEM (2004.5) and tested 'good'. The Costco batteries were put in new when the 5.9 was rebuilt last year and I could see that there was corrosion on the terminals and a damaged positive cable-clamp from rough-handling and over-tightening and was 'loose' even when tightened down. When the 5.9 was rebuilt I had them install all new battery cables & clamps so I decided to take the truck home and handle this issue myself. I installed two new Cat PHO (premium high-output) 31 series batteries...replaced the over-tightened & damaged bat-clamp...cleaned all terminals and connections. Success! When I first fire up the truck in the morning, the grid-heater pulls voltage down when it cycles on and cold-start voltage starts about 15.1 volts.....after warm-up it drops to 14.6-14.7 the rest of the day. When I come out in the mornings, resting battery voltage is 12.7-12.8 volts. These readings are from the dual battery gauges atop the steering wheel column as the photo's below show. They are hooked directly to the posts atop each battery. (Nice eh?) My question is.... what is the nominal voltage 'range' that our truck batteries should be showing me on my dual-gauges after engine warm-up? What is 'too-low' and what is 'too-high'? I know that the type of battery also makes a difference (lead-acid v. AGM etc) when it comes to allowable voltage-ranges. Your thoughts? (oh...and I don't think there's any problem with the ECM at present, based on what I'm seeing now).

 

[Prairie Dog]

Sounds perfect!
That's exactly as mine has behaved since new.

Scott

 

[Ozymandias]

Perfect Values, i see the same on mine.

 

[Wayne M.]

I guess those are the Cat/ Deka batts? Very nice. How do you control those meters? Do they stay lit all the time?

 

[Axekicker]

Wayne, hard-wired direct from meter to battery with an under-hood in-line fuse in the +pos line. Yes..they stay on all the time. That way I can look thru the drivers side window and see my battery voltages as I walk past and in the morning when I walk up to my truck. Let's me know my resting pre-start voltage. I'm not worried about the small amount of parasitic-draw they impose. I run the truck from 7am to 7pm weekdays and twice a month put it on a charger for 24 hours over an idle weekend to top-off their charges.

Thanks for the response Oz.

 

[Axekicker]

Oz: thanks.
Wayne: Yes. The meters are hard-wired direct to the battery terminals with an in-line fuse in the +line. They're on 24/7 so I can look thru the drivers window as I walk past the truck and see what my 'resting' battery voltages are...without having to get in the truck and flip a switch or turn the key. Its such a small parasitic draw it's almost negligible.

Ok...ignore the double-post. My first one disappeared for a while so I reposted....then it came back (wha?)