As a reminder, the point is that the solar panel gives ~ 22V, while the motors are rated 14.4V.
I thought a lot about it, and in my views, many strategies of reducing the voltage (like using a switching DC DC converter), will defeat the MPPT tracking using the motor as a load, one of the important point I want to check with the prototype.
So I thought even longer, and concluded: who gives a damn to the motor voltage rating ? They’re running in water (a dense medium), so at a much lower RPM than in the air, and with a very efficient water cooling.
So I just ran them at 22V for two hours. Everything went perfectly well.