Looking for 2008 E250 aux battery fuse

[flyr6105]

I have been busy converting my 2008 Quigley E250, 5.4 gasser to a camper/beach surf fishing buggy. In its earlier life, the van might have been equipped with a wheel chair lift using the second battery under the side barn doors. I plan to use the auxiliary battery box to house a BB 100A Lithium house battery. I have traced the charging wire back from the house battery to a wire bundle in the engine compartment but am having difficulty locating the fuse. I have the manual and used a volt/ohm meter to test which fuse it might be. There are a couple of 50A/60A circuits that are labeled with promising names, but I can’t get a continuity reading on any of them (#s 18, 19, 20, 21 or 22). Can anyone tell me what circuit fuse connects to the auxiliary battery? I didn’t test any of the inside under dash fuses, just the box in the engine compartment.
If I were using just a lead/acid house battery, I wouldn’t care about the charging circuit amp rating as much, but the 100A Battle Borne lithium can take a much higher charge rate and am not sure if the circuit can take the higher rate. The wire to the aux battery is stout, but may not be good enough to handle a high charge rate. It’s kind of difficult to guess the wire gage, but it is nowhere near the size of battery jumper cables. Does anyone have any experience using this circuit to charge lithium batteries? Thanks for your input.

[winmag4582001]

A few more photos would help, aux battery location, wire bundle under the hood, ect.

The last van I worked on that had a wheel chair lift had the fuse secured to the radiator brace right in front of the fuse box under the hood. Had a 4ga red wire going from the main power going into the fuse box up to the fuse, then to the aux battery. If that makes sense. LOL

Personally I would run a charge line from the positive side of your start battery- to a 60amp fuse-to a VSR and then to your aux battery. On charge lines I use 4ga OFC wire, on the usage side I would run what your inverter recommends.

[flyr6105]

Thanks for the information on where you found the lift fuse. I'll check that location tonight. I have ordered 4 gage wire and plan to use your suggestion to run a new fused circuit from the start battery to the house battery. I already have a Blue Seas 120 A ACR. I guess under the hood is the best place to mount the ACR since the house battery is in Ford's box mounted to the frame under the side doors. I don't think it would be good to mount the ACR under the van and exposed to the elements.

[winmag4582001]

https://youtu.be/M7xJr-NDK5c