T-Pain Is On A Boat: Re: [Electric Boats] 24 Volt Motor?

Tuesday, May 5, 2015

Re: [Electric Boats] 24 Volt Motor?

Motenergy is the new name of Mars Motors. http://motenergy.com
The motenergy site has several motor selections that support use at 24V,
including the ME0913 that was inlcuded with my drive system, the PM-20
from Electroprop.
There are also brush-type motors that will do the job.

The reason for 48V operation of many of our boats is a function of
maximum amperage for the cable lengths that are required to connect the
batteries to the controller. And the amperage is a function of the
power required to move the hull at a desired speed.

It's probably best to aim for around 100A continuous current.
At 24V, that limits you to around 2.5kW.
Using the 1kW/ton rule of thumb for displacement boats, that puts you
at boats displacing under 5000lbs. Provided your boat has a waterline
(LWL) of about 25' and displaces under 5000lbs, you should easily get
5kts at about 85% power.
My own boat is a Beneteau First 30, displacing around 8000lbs and has a
25' LWL. I draw 2459W at 5kts boat speed, according to my logged data.

Many of the Motenergy motors run at about 50rpm/volt, so your
hypothetical 24V system will be running at a max of 1200rpm. This is
good for a direct drive setup since displacement hulls are best moved
with a large, slow moving prop. So if we consider a prop with about 50%
slip, moving at 5kts at a target speed of 1200rpm will require a 10"
pitch. A 12" pitch should hit 5kts at 1000rpm, allowing a little
headroom for punching through a chop or river/tidal current.

Tell us about your boat and we can perhaps give you more accurate
information for your specific use case.

Cheers,

/Jason

On 2015-05-03 09:30, bob jennings sabre281@yahoo.com [electricboats]
wrote:
> It seems the majority of motors for EP are 48 volts.
> Does anyone make a 24 volt motor similar to the Mars that can be used
> for EP?
>
> Thanks,
> Bob
>
>
> Links:
> ------
> [1]
> https://groups.yahoo.com/neo/groups/electricboats/conversations/messages/26402;_ylc=X3oDMTJxaXRnbW43BF9TAzk3MzU5NzE0BGdycElkAzUyMTQzODIEZ3Jwc3BJZAMxNzA1ODg0MDkwBG1zZ0lkAzI2NDAyBHNlYwNmdHIEc2xrA3JwbHkEc3RpbWUDMTQzMDc5MTI0OQ--?act=reply&messageNum=26402
> [2]
> https://groups.yahoo.com/neo/groups/electricboats/conversations/newtopic;_ylc=X3oDMTJlYWhobGRnBF9TAzk3MzU5NzE0BGdycElkAzUyMTQzODIEZ3Jwc3BJZAMxNzA1ODg0MDkwBHNlYwNmdHIEc2xrA250cGMEc3RpbWUDMTQzMDc5MTI0OQ--
> [3]
> https://groups.yahoo.com/neo/groups/electricboats/conversations/topics/26402;_ylc=X3oDMTM2bHAybWFvBF9TAzk3MzU5NzE0BGdycElkAzUyMTQzODIEZ3Jwc3BJZAMxNzA1ODg0MDkwBG1zZ0lkAzI2NDAyBHNlYwNmdHIEc2xrA3Z0cGMEc3RpbWUDMTQzMDc5MTI0OQR0cGNJZAMyNjQwMg--
> [4]
> https://groups.yahoo.com/neo/groups/electricboats/info;_ylc=X3oDMTJlamhwdWMwBF9TAzk3MzU5NzE0BGdycElkAzUyMTQzODIEZ3Jwc3BJZAMxNzA1ODg0MDkwBHNlYwN2dGwEc2xrA3ZnaHAEc3RpbWUDMTQzMDc5MTI0OQ--
> [5]
> https://groups.yahoo.com/neo/groups/electricboats/members/all;_ylc=X3oDMTJmZGJmOGc5BF9TAzk3MzU5NzE0BGdycElkAzUyMTQzODIEZ3Jwc3BJZAMxNzA1ODg0MDkwBHNlYwN2dGwEc2xrA3ZtYnJzBHN0aW1lAzE0MzA3OTEyNDk-
> [6]
> https://groups.yahoo.com/neo;_ylc=X3oDMTJkcnQxZnFnBF9TAzk3NDc2NTkwBGdycElkAzUyMTQzODIEZ3Jwc3BJZAMxNzA1ODg0MDkwBHNlYwNmdHIEc2xrA2dmcARzdGltZQMxNDMwNzkxMjQ5
> [7] https://info.yahoo.com/privacy/us/yahoo/groups/details.html
> [8] https://info.yahoo.com/legal/us/yahoo/utos/terms/

--
Jason Taylor
--
S/V Fugu
1978 Beneteau First 30
Electroprop PM-20