I'm going to use a 18.5v lipo in my bot, what's the size of the battery (dimensions)? or do you have a link where you got them from?

Those crews you used to hold the battery down, are they just screwed into HDPE? or did you place some sort of threaded insert into the HdPE first?

I take it your charging th ebattery whilst in the robot? would the foam around it not great a fire hazzard issue?