[dobermin]

Looking for opinion on cutting a gaping hole just to the front of the spare tire between the crossmembers which puts it between the wheel wells.

I'm contemplating 13" wide which would remove about half of the lip on both crossmembers (see diagram) and up to 32" wide. In this void would be an aluminum box to house batteries or whatever.....

Structural issue or not?

Thank you.

 

[keeponvaning]

Well, I wouldn’t do it personally but... 32" wide is a pretty big hole in the floor. I’m assuming you won’t eant to cover it over with anything so I gues your biggest problem is going to be with your layout. It depends on how much you want to/need to move out of the way to access the hatch door.

 

[phil]

"I" would not cut into the frame no matter what.

 

[Iron Tent Diesel 159 Ext.]

Looking for opinion on cutting a gaping hole just to the front of the spare tire between the crossmembers which puts it between the wheel wells.

I'm contemplating 13" wide which would remove about half of the lip on both crossmembers (see diagram) and up to 32" wide. In this void would be an aluminum box to house batteries or whatever.....

Structural issue or not?

Well, not much traffic on this. I'm currently thinking of doing the same thing and don't see an issue with it. What did you end up doing? I want to buy the same battery as the starter battery which is an AGM and put a relay switch so I can manually switch my alternator power over to the house battery "if desired". Very curious of your solution

 

[RnR]

I would not cut the lip of the cross member. Make the hole narrower so you miss the cross member.

 

[RnR]

I don't see an issue with it.

Are you a structural engineer?

 

[RnR]

I would find a good body shop that does customs and restos and have them frame in the hole.
Unless you are experienced with welding thin gauge steel and can do it yourself.

 

[Iron Tent Diesel 159 Ext.]

Are you a structural engineer?

No, on the structural engineer, I'm an RN.
I would not cut any crossbars for my build but the floor metal I would. I'd probably have a steel outline of the hole made that the recessed battery box would lay on top of and bolt the whole system together. Still trying to decide

 

[RnR]

If you don't cut into the cross members and secure a metal box to the hole as you describe, It should help restore some rigidity.
With a hole that size though, I'd feel better with it framed in, tied to the cross members.
Especially with heavy batteries.

 

[RnR]

I actually kinda like the idea overall.
Saves space and can easily vent flooded batteries.

 

[phil]

Well, not much traffic on this. I'm currently thinking of doing the same thing and don't see an issue with it. What did you end up doing? I want to buy the same battery as the starter battery which is an AGM and put a relay switch so I can manually switch my alternator power over to the house battery "if desired". Very curious of your solution

Since you are looking to add an extra battery that's the same size as the starter battery that a look at the starter battery box, you can see how they mounted it.

 

[KNDLKSTMS]

Or . . . . not cut the floor . Turn your AGM batts on their side mounted on a frame bolted to the bottom of the X members . There have been some under chassis mountings documented .

 

[RDinNHandAZ]

dobermin
For me it would be ONLY for a critical need NOT for "In this void would be an aluminum box to house batteries or whatever.....” I doubt it is structural to the extent of failure but any engineering I have done is loooong ago so ignore me or not.

 

[ginalolap]

I have a Winnebago Travato which is on a 2015 Promaster 3500 diesel. The 2 house AGM batteries are mounted where you suggested but only accessible from under the van. I was horrified when I saw the setup, thinking they would be covered in mud and road grime in no time. This spring, at 50,000 km I rewired the batteries with #00 cable to install a 2500 watt inverter. The batteries were clean as a whistle!. (I don't off road). Since there is no need to access the batteries I would live with this setup. It was a supreme fiddle to work on the batteries under there but it's done. If these AGM batteries need replacing I will go with Lithium which have to be inside in any case.

 

[Chance]

No problem if done correctly. I installed one almost 3-feet by 4-feet in my Ford van a long time ago (almost 15 years) and haven’t had a single issue.

One of the advantages I see to buying a ProMaster is that it would make it even easier to install similar boxes, although I wouldn’t need one so large in a PM. Even a smaller one can solve many design issues.

I wouldn’t go to the trouble and expense just to create extra space/volume, but if there is a valid reason like I had, it’s not that difficult provided it’s done right. I would do it again, and plan to unless I buy an already built camper van.

 

[Chance]

This is not mine, but I saved these pictures of batteries in a box accessible from above as reference. It took a while to find them.