one idea has sprung to mind, rather than go and have the spades removed everytime you want to charge, adapt the wires with two extra leads coming off the crimped battery leads, forming a Y, with a switch on each the feed to esc and a switch on the charge leads, you could then epoxy the spades off the charge-leads onto a spar, then when you want to charge, throw the switches over on the esc to off, plug the charging leads onto the charge leads, turn on the switch on the charge lead and charge the battery in the boat
that way your connections stay firm and wont fail because you've yanked them out. I fitted a tamiya plug to my gel cells and a tamiya plug on the charger of my gel cells. the spades now dont need to be disconnected :)