One day we have to change the battery on Trident, is it possible or is it all embedded?
A quote from OpenROV Founder Eric Stackpole:
“To ensure reliability, the batteries and other electronics are mounted permanently inside the vehicle so that the seal can be professionally laid and tested in the factory. That being said, the electronics are being designed so that charging takes about the same time (~3 hours) as the vehicle can run. For major expeditions that have multiple vehicles, this would allow one vehicle to charge while the other is in operation. It’s also possible that an accessory could be made that would allow power to be sent down the tether, however the focus now is getting the core Trident design solid before developing accessories.”
There is more information about the reasoning behind this decision in this thread.