Re: [electricboats] Motor stopped, then was fine…. Any thoughts?

Hi Myles,

The batteries are powerwall style but not Tesla brand, but in most respects very similar. They are linked together over modbus rs-232 and controlled by a built-in BMS. I think I can rule out that the batteries were my problem.  

Right now the theory I'm putting most money on is that I picked up something on the prop until the resistance was stopping the motor and then whatever it was came loose after some sailing. Bellingham Bay is busy enough that a stray rope or net is a possibility, and I had also earlier been skirting the shallows where there are a lot of kelp type things (I probably need a tidal biology refresher).  

On Aug 5, 2021, at 09:22, Myles Twete <matwete@comcast.net> wrote:



Did I hear it right that the batteries are a parallel set of Tesla Powerwall batteries?

How do these act in parallel?

What SW controls them and under what conditions will they just say "No"?

FWIW, a good contactor rarely temporarily fails OPEN.  They do weld CLOSED, and that can happen as a temporary "sticking".  Be sure to use appropriate suppression, either diode, resistor, snubbers and/or SW measures.  When I expanded my BMS controller to include controlling my charging power supply, it needed to OPEN an AC and a DC contactor when charging was deemed complete.  Worked great on the bench and first tests at my boat.  Then I left it to charge to a target voltage and shut off and came back in a couple days.  After coming back to the boat, the charger was OFF and the AC contactor contacts were OPEN, but the DC contactor contacts were welded CLOSED.  And that makes a little sense since all I had implemented to make sure the power supply output voltage was near the battery voltage on closure was to delay some amount of time…clearly got that wrong. J  Need to either actually measure the voltage or add circuitry to allow the controller to scale the power supply output as desired.

 

Anyway, black boxes are always a big worry…power wall, contactor, controller, etc.  And always read the specs on their limitations.  Power Inverters will drop out if they are not well connected to their DC source.  It could be that the motor controller in your case is on the hairy edge of being too distant from its source resulting in a bit too much voltage drop.  Having said that, I'd bet on the thermal cause.  Or software…it always can be software or some parameter that is wrong.

 

-MT