So I just built a battery cart for this years build season (2019) I built it out of an existing cabinet that we outfitted with some 80-20 so that it could hold 12 batteries and the 4 chargers that we purchased so that a charger charges 3 batteries but It worked great was the only thing my team, 1939, took to the Einstein field in Huston. I would try to find a cabinet with a sturdy back because it fell over and now there is a large dent in the back for me to fix. I also Highly recommend some sort of charger that charges multiple batteries to save space. I also recommend that you don’t get different battery chargers so that it isn’t as confusing for your pit crew. Also whatever you go with make sure that it is sturdy and if you are doing a cart form a cabinet I would recommend reinforcing the bottom of the cart. Also not to say that the hand truck is a bad Idea but it is easier to push a cabinet than the hand truck like team 3572 suggested. We also give our team designs that were CAD of all 80-20 carts and they told us to go get a cart and modify it because it would use too much 80-20. Also make sure you have a hook on the inside for your battery tester so that is accessible and out of the way. And you should have a spill kit that is accessible.
These are the battery chargers that I was talking about. There might also be better options out there.
Good luck with the battery cart hope this was helpful
I will add a photo tomorrow (May 14th) in a comment
This was the cabinet that we got from Lowes
Then we got the wheels that work with it
Keep in mind that this is a garage cabinet that is meant to be pushed under a work bench not really roll like a normal cart with this setup the wheels that turn are in the back (back of cabinet) and the wheels that don’t turn are in the front (near the doors) so it is kind of hard to push it up an incline.