I'm in the planning stage of building a ROV. I'm gonna use three BLDC outrunners for propulsion and they're using lots of amps. The ROV will have a two-wire tether for both comms and power. I'm thinking of sending high voltage AC and Ethernet for control, feedback and video(s) on the same two wires.
The outrunners are rated with max power of 25A at 9V. This will give a max power consumption of 75A. In addition there will be several other systems on the ROV that will be needing juice. The outrunners doesn't need to be used to the full amp-range. I can control this by the Arduino, but it would be nice to be able to 8)
My plan now is to use a system of several NiMh battery packs for power. The packs will be of 8 D-size NiMh cells at 10000mAh. Ten of these packs will give me 100Ah. The Arduino will be used for managing the usage and charging of these packs. Each pack will be used by the ROV by the need. Idle packs can by charged. Lets say that I'm running the ROV forward at 25% speed. Then I'll be using two outrunners at about 12.5A. The ROV will then have a need for the power from two of the NiMh-packs. The remaining packs can be charged if its needed.
By using 100m of 0.75 sqmm wires in the tether I can easily pull 2A @ 230V (460W) and 50A @ 9.6V for the charging with 240V AC supply on the surface.
On the ROV missions I estimate that I will be using 30-40% of the max power of the propulsion system on average. This will give me hours and hours of running time. When running all thrusters on max, I'll have about two hours of fun.
My main objective in this project is to make the system very flexible, eg. that I can add more or bigger thrusters and other equipments. The charging system can not be limited in the number of battery packs, despite I don't think I will be needing more than ten. I'd like to start with 4 to 5 packs. I'm thinking that the "business end" of the system consists of a small pcb containing the charger and interface between one battery pack and the common charge controller.
Each battery pack will be an oil-filled tube with 8 cells in series and a ntc sensor.
What do you think will be the best way for an intelligent charging and power management circuit for this project? Is there anything out there?