Out with flooded, in with AGM

The Coachman Crossfit came with a pair of no-name 100AH flooded lead acid coach batteries. For an RV with a compressor refrigerator, the 200AH of conventional lead acid battery wasn’t really enough. If the fridge ran too often I could barely make it through the night on the OEM batteries. To help extend our off-grid time, I added a Lithium battery – but retained the original flooded lead-acid’s. For our October trip we used the lead-acid batteries until they were depleted then switched to the lithium battery. As a general rule the 200 watts of solar was not able to fully replace the daily energy draw, so we could only run two days from battery – after which we’d have to either plug in, run the generator, or run the Transit engine and charge the batteries from the alternator.


The original lead-acid batteries are stashed up in the rear fender wells behind the rear tires where they are impossible to access without lowering them down to the ground. Because it’s a PITA to drop the the 70lb batteries down I left them alone and pretended they would last forever & never need maintenance. But I really wasn’t happy with their performance and figured I should see if they needed maintenance. That ended up being enough work that I decided to toss them out and replace them with new AGM batteries – partially because AGM’s would be better suited for RV use, and partially because AGM’s can be mounted sideways.

By side-mounting the AGM’s I could position them so the cabling is accessible from under the van without having to drop them down. The existing battery mounts were sized such that a Group 31 AGM would fit sideways, so I wouldn’t need major surgery to make this work.

To lift the AGM’s up under the fender wells I decided that instead of placing the battery in the mounting bracket and lifting the bracket with battery at the same time I would re-mount the battery brackets without the batteries and then lift the batteries up onto the brackets with a transmission jack or floor jack. But rather than wrestling a jack into place I ended up laying on my back under the van, setting each AGM battery on my chest and bench pressing it up onto the factory bracket.

To fasten them in place I bent up a new set of hold-downs using 1/2″ steel stock and galvanized bolts. The OEM baattey trays have a lip that keeps the batteries from sliding out to the side.

I now can access the battery terminals without dropping the batteries.

Coachman decided to position the plumbing drains and fresh water tank overflows directly above one of the batteries, so the battery got hosed down whenever I overfilled the fresh tank or drained the plumbing. The ugly plastic hoses above the battery are an attempt to fix that.

The OEM GoPower solar controller has an AGM charge profile, and the WFCO power converter’s profile is tolerant of AGM batteries (but not ideal), so I didn’t change out either of those.

Of course I could have decided to eliminate the lead-acid batteries entirely and instead add one or two more lithium batteries. That would mean either stealing more interior space or re-using the fender wells and having the lithium batteries exposed to the weather under the van. I decided to hold off on that until I have more experience with lithium batteries. The ultimate setup would be to remove the generator from under the campervan and use that space for a bank of 4 @100Ah lithium batteries in a sealed, insulated heated battery box. Maybe next year. 🙂

We’re set to leave for another road trip in the next few days and will get to see if the AGM’s perform any better than the OEM flooded lead acids.

[2020-04-05 – The ‘as built’ campervan electrical is described in detail on the Campervan Electrical page.]

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