Update on the install of the PowerMax, a few pictures below. Install is fairly straight forward, remove a few screws and slide out the old converter from the bottom section and remove a few more screws to remove the cover on the AC section at the top.
I removed the lid of the existing bottom section by drilling out the rivets and then removed the "guts" of the "old" Parallax so that I could reuse the tray. The PowerMax is held down with velcro but it could be screwed down easily.
Using a Dremel with metal cutting bit, I cut a lightly larger hole on the left for the PowerMax fan and a hole on the right to help with cable bend radius on the + and - 12V
cables coming from the PowerMax. I sheathed all the cables to protect and pulled them through existing holes in the tray. In hindsight I should have made a bigger hole for the 12V
+ and -. Space was tight.
The AC power cord (supply) to the PowerMax has a regular plug on it that must be removed to get the bare wires to connect to the AC supply in the top section of the existing unit. Make sure you mark the cable prior to snipping off the plug! The plug is marked for neutral. If you forget, the cable cores are colored so you can figure it out.........
I used some 4ga wire I had left over for the main 12V
runs, 4ga was a bit too big and hard to handle in the space available. I think 6ga is recommended - that would be easier to handle.
It took about 3 hours with some running around looking for wire to use.
Everything works as intended. The batteries charge at the higher voltage initially and ramp down per the chart in the PowerMax manual as they become charged. It sits at 13.2V once fully charged. I have not heard the fan come on yet although it has been very cold recently.
Pictures below are after the install, looks pretty much stock. Main advantage of reusing the tray is that you can use the existing mount for the fuse panel which mounts directly to the front of the tray via 2 screws.
Only downside I could see with the install as shown is that to replace the 2x30A fuses on the PowerMax would require sliding out of the tray and hence disconnection of a few wires. The fuses are on the right just in-front of the ground. Mounting the PowerMax with fuses at the front would have enabled replacement of the fuses without sliding the tray out since there is an access panel on the front of the tray (you can just see it in the photos). I think the rear of the existing tray would need removed to install the PowerMax lengthways.