I am having trouble with intermittent battery issues. Sometimes there isn't enough power to start my 6.0 diesel van. I haven't found a clear pattern but sometimes I cannot get enough juice to start. Couple things:

1. I currently have a solar panel to keep the battery "topped off" as this is an occasional use van. It has a good quality charge controller (https://www.renogy.com/renogy-advent...w-lcd-display/) and I set the battery type to flooded.
2. I have replaced the starter motor as it had some bad windings. BTW used a high output starter from CNC Fab and I love it. Starts very strong when there is juice.
3. Unknown battery condition. I had them out and tested a year ago and they were good. A lot can happen in a year though. Especially when they've been treated so rough.
4. I thought that I had a parasitic current draw, but it tests OK. See this thread: https://www.ford-trucks.com/forums/1...rent-draw.html

Yesterday I started it, idled for ~5min, then drove (~5mins) to fuel it up. I left the headlights on while fueling and it would not start. 10 mins with the alternators isn't a lot of time, but with everything working properly I would think that screwing up and leaving the lights on while fueling is something it should handle.

I believe I have either bad batteries or bad cables. Leaning towards bad cables because this is an intermittent problem. I am thinking that sometimes I am getting a high resistance connection, other times it is OK. Or both, that is a theme with this van. It has duel batteries and dual alternators.

Can anybody recommend some trouble shooting procedures? I've got a clamp on style DC current meter. Should I pull batteries and have an auto parts store test them? Just throw new cabling in?

 

How old are the batteries and how many times did they not start the van? Each time they are zapped bad, it takes a little life out of them. If they are old anyway, and they have been run down 5 or more times, they may be done for.

You can monitor the voltage on the battery terminals with a meter as you try to crank it. If the battery voltage drops a lot, the battery is down. If the battery voltage stays up, you have a bad cable somewhere, or a bad connection somewhere.

 

Put a volt meter across the batt terminals and take readings with the engine off (to get a sense of the battery condition) and with the engine running (to get a sense of the condition of the charging system.

Also, assuming both ends of the batt cables are accessible, an ohm meter test for continuity will tell you if there is an open in the cable. Might what to jiggle them a bit with the the ohm meter attached to see if continuity is lost when doing so.

 

Yeah I was thinking about it and believe I've got bad batteries. I monitor the voltage from the charge controller and sometimes it just drops (>11V) during a start. Often it will tank from the glow plugs before the starter motor. The charge controller has cabling completely separate from starter motor.

Not sure what to make of how intermittent the problem is. But I think I should replace the batteries and go from there. These have been deep discharged 5+ times. I think I've fixed enough that new batteries wont get destroyed. It's a lot of money for a couple of those big boys!

 

Cheapest place I have found is Walmart, and they seem to be doing ok, I have had them on my diesel for about 6 years now. And I don't drive it much either.