Today I added the AC plug, XT60 plug, and the large relay for the low voltage cutoff. I am really liking how it is looking.
I'm still debating adding some other features. Things I'm thinking about adding are an on/off switch for the dc/dc converter. There is a switch on it already, so I'd just have to wire in a new one and connect the leads. I'm not sure how essential that would be though as you could fairly easily just unplug it too. The other thing I'd like to have is some form of indicator that tells me when the batteries are charged... This is way more complicated as I've essentially created a constant current / constant voltage charger. A voltage indicator wouldn't really suffice as it'll only tell once its reached the constant voltage stage of charging. Ideas are welcome, but I'm thinking that I'll probably just omit these features for now.
You can see the large relay behind the AC plug in this image.