Does anyone know of a dual battery tray or how an extra battery can be mounted in an H3 Alpha?

 

Yes, there is a company out of Australia that makes secondary battery boxes that go in the back of a rig. You just wire the positive wire from a circuit under the hood and run it to the back. The negative is picked up off the frame. The circuit under the hood attaches to the primary battery and your done. There not cheap but very flexible and usable. Best part you can jump another vehicle from the secondary battery and be totally isolated from the primary. They come in multiple levels also. Probably can get them from here in USA also.

 

Artec use to make a dual battery tray for the H3 & H3T. Might want to contact them to see if they still have any or will make one.
It probably won't have the H3 or H3T cut into it. But it will fit!

 

Lased Designs makes a battery tray that looks very nice.

I have one sitting in my garage waiting to be installed.

 

those have been sold out for a long time now.