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PanJH · 03-12-2018, 01:40 PM

I've been noticing that my 5 yr old batteries deplete their charge quicker than before,but I have no issues with running the refers ( 2 of them) and other things for several hours. Regardless, I've been looking to replace the batteries.. just not sure if I should go back to flooded or get AGM's

==== So here's the issue=====

About a month ago, I was in the coach and started up the genset for its exercise. I went to the bedroom are to do some stuff and after a few minutes, the genset stopped. Tried to restart it and it would fire,run about a second or two then stop. Code was a 36. For grins, I replaced the fuel filter, still the same symptoms. Then after a few more attempts, it wouldn't fire and cranked slow, even with the boost on.
I called Cummins to get an appointment ( have an extended service contract so not a big deal) . Had them move it out a month as we were going to be gone at a FHU cg, so the genset wasn't needed.
Got back and took it in. They replicated the issue even with their battery cart hooked up to it and thought they would have to pull the genny out to do further PD. Before pulling it out, they decided to unhook from it from the house batteries and try it off their battery cart. Well, they say it runs fine.

Their thought is I need new batteries. They don't sell them, so it's not a sales scheme. Panel in the coach says they are 12.6v Who knows how the electronic control boards in these things work with voltage/current issues.

My question is, since the batteries are powering the inverter fine and the appliances, it would seem that there isn't a catastrophic battery failure issue and that something else may be in the loop. Shooting in the dark, I assume there is a relay for the battery boost switch and mayne that's a spot to look into... maybe bad connection from the house batteries ? any idea where that is located ? The coach is still at Cummins, I'll hopefully pick it up tomorrow and get it back to storage where I can do some investigation. Just trying to get some ideas before I dig into it...
I'll probably go ahead and get batteries anyway, or at least shop seriously for them now.
Thanks ( yep long post)

twinboat · 03-12-2018, 01:52 PM

Your house batteries are deep cycle. When your starting your generator, your actually drawing 100 or more amps from them and in a start battery situation.

Deep cycle batteries can handle that, if they are in good shape and have the capacity, but your 5 year old battery bank may not. When your running your fridge, your only drawing 15 to 30 amps thru the inverter, so the effect on drawing down the battery bank capacity is slower.

A test would be to run a microwave for 5 minutes and see how much the voltage drops after that.

Buly · 03-12-2018, 04:56 PM

Another thing is, if one battery fails internally, it will draw down the rest. Sometimes you can tell, if you put your hand on each one, and the bad one will be hot. Best way is to load test them individually, but it is a more involved job.