JD 135D excavator batterie(s) will not stay charged

We bought a 2011 John Deere 135D excavator a few months ago. Everything worked fine for a while. Then all of a sudden the batteries will not stay charged. Paw charges the batteries and it will run fine for a few minutes. We may run it while, stop it and then 10 minute later try to crank it. This has happened a few times. We keep thinking that maybe is leaving a switch on or something,. This is on our weekend farm and we haven't run the excavator but maybe an hour or so a week.
This morning we took the two batteries to the battery store and the guy put them on a tester and checked them and said they were fine.

POSSIBLE HINT? The only thing Paw can think back on is that the overhead light wasn't working and he wired it back in. After he realized we are having this problem he unwired it. But even after unwiring the light the batteries are not staying charged.

I need to ask Paw if he is sure it is both batteries draining down. I assumed that because he took both batteries to the battery store this morning.

Thanks for any help.

Granny DP
DP Forum Dog

DPForumDog said:

OH! I forgot to add that Paw ordered two "Battery Master Disconnect Switch Top Post Cut Off Shut Off Switches" this morning.
Granny DP
DP Forum Dog

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Should you want to verify the batteries and the charging system, there are BATTERY ANALYZERS you can buy for around $50.
The ANALYZER will tell you what the condition of the battery is, how much 'life' it has left, what the cranking condition is and what the charging system is putting out.

The battery 'internal resistance' is measured to determine condition. As a battery gets 'used' it's internal resistance increases so the 'life left' can be measured. The ANALYZER will also tell you the CA and the CCA of a battery (without needing to put a cranking load on it). They are quite useful and can save you money by making sure a battery is ACTUALLY BAD.

You could also put a volt meter on the battery posts while it is running. Let us know what the voltage reads.

A few questions come to mind.
Are you actually checking the voltage of the "dead" batteries or just figuring since she don't crank batteries are dead?

Is it only a problem when the machine is warm after running? Could be a problem of some component heating up. I chased this for months to a relay going bad that would heat up and a bad soldier joint on the board would create an open circuit till it cooled off.

If they properly load tested the batteries then it is doubtful they are bad. Look to the machine.

As asked what is the voltage at the posts when running and off?

Batteries should not drain in 10 minutes without a really large load. Consider that even leaving your headlights in you car on for 10 minutes won't kill the battery. You should see a spark when you pull a cable off the post.

1) battery voltage when it's running?

2) battery voltage when it's cranking?

3) is it cranking when you try? or is it not doing anything and you assume it's the batteries? or something else?

Two batteries on a 183 cubic inch engine in Alabama in late June, those batteries would be completely gone to not crank it fast enough to start in only ten minutes.