Battery charge level after running

[Doc]

I have battery tenders on most of my equipment that sits during winter months. I'll still start em up and run them for 5 mins or so every month.

When I check the battery charger both batteries on my tractor and excavator were at 100% charged.
After running for 5 mins or more I rehook the battery tender up and it shows that it is charging that the battery is below 80%.
If above 80% a different light blinks so I know both were showing below 80% after running.
In prior years I did not use the battery tender on them and had no trouble starting after they sat a month or so.
I simply do not understand why the battery would show that low after running a bit.
Scratching my noggin here.

 

[bczoom]

I don't think it's your battery, I think it's the tender itself.
It's probably just figuring itself out and where things stand when you first plug it in.
Within a minute or 2, does the greater than 80% light come on?

 

[Doc]

Very wise guess Brian. I think you are correct. I have not stayed around long enough to see the tender change from red to something else. But just today I was checking miles and hours on the Honda 1000 I have in the pole barn. I did not start it just turned the key on, read the hours, bumped the dial to the miles, then turned off the key. I checked the tender after that and sure nuff it was showing the battery below 80% and it was charging. I did not disconnect the battery tender while getting those readings but still It lost it's place when I just turned on the key for 60 seconds.