I finally got around to installing my new Kelly 500A 24v-72v KLS7275D sine wave controller. Still have to program a few things but it is working. Operationally, the only difference is that with the system ON but motor stopped, controller only draws .15a or about 7.6w. The previous controller, a Kelly KBL48501EY 48v 500A square wave controller, pulled .25a at idle, or about 12w. Power vs RPM was almost identical. Statistically insignificant differences well within the slop of the potentiometer I an using for a throttle.
The noise level sounded to my ear about the same, but the sound meter told a different story.
KBL controller
72w 100RPM 28dB
100w 139RPM 30dB
250w 258RPM 40dB
500w 362RPM 43dB
1kw not recorded 44dB
KLS controller
72w 100RPM 17dB
100w 138RPM 21dB
500w 364RPM 30dB
1kw 486RPM 31dB
Sound readings are about 18" from motor. There is no sound shielding. My "sound meter" (Samsung Note3) was zeroed to the ambient noise level before testing. Boat was tied in the slip. Motor in both tests was the ME01014201 5kw BLDC motor driving a 14x10 prop through a Baldor 2:1 gearbox. Power readings are total system power, measured at the negative side of the 48v bank, comprised of 8 6v GC2 golf cart batteries. I recorded watts so that the voltage drop at higher power levels is not an issue. Seems like the right thing to do.
Out in the cockpit, with the drop board down and the hatch closed, at 1kw the motor noise was 8dB above ambient noise, with the new controller. Unfortunately I neglected to measure noise level in the cockpit with the old controller but cockpit noise, to my ear, is lower with the sine wave controller.
So basically the sine wave controller is no more efficient than the square wave device. Sound levels are somewhat reduced, but the difference is not a profound one. It is claimed that a sine wave controller will make the motor last longer, but of course this, while logical, cannot quickly and easily be proven.
My recommendation then, is if you already have a square wave controller installed, don't starve your kids to pay for a new sine wave controller, because the difference in sound levels is not great, and efficiency is about the same. If you are repowering from scratch, sure, go with the sine wave. It doesn't cost much more.
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