GoldenMotor.com Forum

General Category => Electric Boat Conversions => Topic started by: Almex on March 24, 2025, 04:15:23 PM

Title: Questions about continuous regen
Post by: Almex on March 24, 2025, 04:15:23 PM
I am planning a conversion to electric of my 39ft Catana sailing catamaran with old, smelly 18hp diesels I am considering using two 7kw 72v axial flux  motors to  drive the existing sail drives directly, without gear reduction or the existing transmission  as the rated speed of 1950 rpm a good match for the prop speeds of 800-2000 rpm.  So two HTM07KW motors, one in each hull. Will these motors be okay operating for hours at a time? The motors will usually be operated at low power setting to extend the range, usually less than 2000 watts combined.  Usually the motors will only be used for a few minutes, to get the boat out of the marina unless there is no wind and we need to get somewhere..

So my main question is that I would like to know if using a third HTM07KW motor attached to a 12hp Kutoba diesel as a 72v generator with the same EZKontrol 800A controller as I am using for the drive motors. Can the controller handle regenerating  continuously? can the motor?  I hope for around 5-6kw from the 9KW (12hp) diesel at 1800- 2400 rpm.  The diesel is at it's tq peak from 2000-2600 rpm, so I would drive motor directly as it matches the rpm range  of the HTM07KW.  I already own the diesel engine.

I like that I would have three of the same motors and controllers as I'll be sailing long passages and could swap them if one failed. Keeping the generator light as possible is another reason I am considering this set up instead of a regular brushed alternator that would be much heavier. This generator would not be used too often, probably only a few times a year as the boat also has 1200 watts of solar, a hydrogenerator,  a wind generator and sails..  I am planning to use a 72v 300ah Lifepo4 battery for the motors.

Title: Re: Questions about continuous regen
Post by: Bikemad on March 25, 2025, 06:09:26 PM
Hi and(https://i.imgur.com/evDSMvT.png)to the forum.

Unfortunately, I have no experience with either the HTM07KW motor or the EZ-A72400 controller so I don't know what sort of regen current output you might expect to see, or whether continuous regen operation would cause any problems.

The EZ-A72400 has a rated motor power of 3-6kW, but the HTM07KW is rated at 7kW with a peak of 18kW therefore the EZ- A72500 rated for a 4-7kW motor (or even the EZ-A72800 rated for 7-12kw motor) might be a better choice of controller if more power is likely to be required occasionally.

As the HTM07KW motor is rated for 92A @ 72V (6.624kW @ 1,950rpm) I'm guessing that it might produce a regen output of ~78A @ 84V maximum charging voltage (6.552kW @ 2,275rpm) if the regen efficiency is somewhere near the motor's power output efficiency.

I also noticed that the 7 and 11kW motors are both described as having "Natural cooling" yet they both appear to have liquid cooling pipe connections. ::)

Alan