Olson 40 with Electric Motor

[u4ea32]

I replaced the Yanmar 3GM30F with an Electric Yacht 10KW motor, and replaced the four Trojan 105 lead acid golf cart batteries (typical series-parallel for 5KWH at 12V) with four "12V" 100AH LiFePO4 batteries (series for 5KWH at 48V).

The weight savings is large: the total LiFePO4 batteries plus motor is about the same as 20 gallons of diesel in the diesel tank, so the savings includes everything related to the diesel engine and lead acid batteries, about 600 to 700 lbs.

Under normal use, where I just use the motor in the same way as the diesel -- to get in and out of the harbor, on or off anchor -- I end up with substantially more electricity available for house loads, simply because I can use all the LiFePO4 capacity, rather than just a small fraction as with lead acid.

Normally, I only power at about 3 or 4 knots, as I'm raising or dropping sails and dealing with anchors or moorings. So normally, I use very little power, usually a throttle setting of about 500 to 1000 watts.


While my motor can consume 10KW, or 200 amp hours, I don't want to have that level of battery or cables, so I de-rated the motor using the supplied motor controller, so the motor consumes a maximum of 95 amps, about 5KW.

On Sunday, I decided to actually measure performance across the power range.

Here are the results tabulated:

[u4ea32]

By the way: the 6.3 knots at 4.68KW is **identical** to the max speed I could achieve with the Yanmar 3GM30F, using the same prop, prop shaft, cutless bearing, and shaft log, also with a clean bottom and no wind or waves.

[OneKoolCat]

Interesting data Thanks! Do you also use the motor to charge your batteries when sailing?

[tkeithlu]

Ditto to OneKoolCat. Where are you getting your energy? Genset, solar, shore power charge-ups, regeneration?