I have a 2011 6.7 with 16000 miles and it just turned 5 years old.Yesterday had hood up and notice driver side battery eye indicator was red, other battery was showing green, truck turned over and started fine. 15 degrees out this morning, truck started fine.Truck hasn't been ran for a couple weeks.What does the red indicate,battery needs charged or time for new batteries?

 

I was always under the impression that if eye was red, it needed water added to the battery cells

 

http://www.autoshop101.com/forms/elec03.pdf

Check this URL. It will explain the whole process.

 

Battery was bad, just got done installing 2 new BXT-65- 850 motorcraft.Got 5 years out of originals. Thanks for the info

 

I had corrosion on my passenger side battery. Noticed that the eye was black. Took the battery out to clean the terminals and such and why it was out had the autozone run a check on it. Came back good so I reinstalled. No issues with cranking. I'm going to try and get another few years out of them. Living in a northern climate ought to help them last longer as heat is your battery's biggest enemy.

 

Only checking one cell with that indicator

 

Yes, that eye is only to one cell. That is the most likely cell to need attention, but not always. If you waited this long to look at the rest, it is probably too late...

Depending upon where you live and how much you mind walking, I suggest 5 years and toss them, just like tires. Just not worth the risk.