Down along the frame on the passenger side. Then in the back there is a little maybe 4"x4" plastic cover that allows access into the pillar (if that is what it is called) that goes up to the tail light. I had to drill 4 holes. Two in the plastic cover, then inside there was another plastic piece/divider at floor level. I was able to do this with a 12" long wood bit I think it was. Slight angle but easy to make the holes. It was recommended that I run both + and - back from the battery to my DC-DC charger and not use the chassis as a ground.

The cable I used was very flexible and easy to work with.
4 Gauge 4 AWG 25 Feet Red + 25 Feet Black (50 Feet Total) Welding Battery Pure Copper Flexible Cable Wire - Car, Inverter, RV, Solar by WindyNation

Are you thinking of doing something similar?

 

Similar, yes.

This is interesting to me. Was it explained to you why not use the chassis? If you were running a very high current, then yes absolutely I would run a separate negative. But your charger is only 20A so it shouldn't make much difference. All the other low current accessories in the vehicle use chassis ground.

 

The CFX65DZ is rated @ 115 kWh/yr . Your battery capacity is 200 Ah (2.4 kWh @ 12.0 V). You should theoretically get 7 and a half days out the batteries, running them completely flat, with no other loads. So you are doing really well, running well below rated power. Maybe because it's winter.

 

In the manual it says and shows hooking both +/- from the vehicle battery to the input side of the charger. I also probably watched or read a build from a person that does things way beyond necessary and it stuck with me. I do have my negative terminal block chassis grounded.

I'm just going off what I have seen on my battery monitor. Also you are correct in that I just got things working last fall, so haven't had it through a hot summer yet. I may also not have my fridge set at the same temp that the 115kWh/yr is measured at.

For my use though, I doubt I will ever sit more than 2 days without driving.

 

That's really good efficiency. Especially considering how compact those batteries are.

I just checked those batteries out online. Wow were they really $1,000 a piece?

 

haha yep, I paid $949 each. I also made sure to get insurance that covers all I have put in to my van.