Tony whichever route you choose I'd suggest taking some time to play with the different battery sizes using stencils, cardboard etc.. It's can be fiddly and time consuming but I think it's something that needs to be done if you have any care for the looks of the build. That frame is pretty awesome IMO and deserves some respect for it's figure
The wiring can take up significant size and of course the padding + outer casing takes up a good 1/3 inch in itself. I know when I did my case it took a few builds to get right and hours of laying out batteries in different configurations. The wiring in particular took up more space than I imagined, partially because I used Sermos / Anderson connectors which are a little larger than bullets.
Some of the factors you may like to consider (for battery layout) are:
- Space for wiring
- Case material / strength for worst case scenario (i.e. crashing)
- Ability to remove / install the batteries as a single pack (often overlooked IMO)
- Ease of charging. i.e. put batteries into parallel then series them so they can be broken back into parallel easily.
- The routing for cables running from the throttle, voltage meter and e-brake to the battery and the cables running from the batteries to the controller. The length of the latter cables can have a surprising impact on efficiency.
- Space for the controller and whether it will sit inside your battery case or not. Need to consider airflow / vents if it's inside.
- Space for a battery disconnect relay or switch which can be quite large depending on the power draw.
- Some way to mount the battery box to the frame without having any screws, cable ties or other sharp things rubbing against the batteries inside.
- Perhaps room for a BMS such as methods' ( viewtopic.php?f=31&t=36414
) if you're going the LiPo route.