T-Pain Is On A Boat: Re: [Electric Boats] Any larger electric boat owners out there?

Sunday, May 24, 2009

Re: [Electric Boats] Any larger electric boat owners out there?

Generally electric motors are rated at continuous HP and combustion at
peak, so most sources I have seen recommend multiplying the electric
HP by 3 to approximate the HP of a combustion engine. The battery bank
will not be effected by the Peukert Effect (or to a much lesser
degree) as I will not be using lead acid batters. Now that quality
(Sky Energy) LiFePO4 batteries are in the $1.50 per AMP hour range
delivered to your door (1) I think you would have to be an idiot to
use lead. No offense if you disagree but face it A good set of Lead
Rolls now cost more per unit of useful energy (mostly due to the
Peukert Effect and short life time, and 50% discharge limit) then
lithium now, over the useful life of the packs.

My current plan is to have a 200-400 AH pack at 144 volts, So at 7 or
8 knots I'm pretty sure I could get at least 60 miles with out using
the generator or the solar array. Just because I have larger motors
does not mean they will be wide open all the time, hell most cursers
never cruse over 10 knots because they can't afford the gas anyways!
A 144v 200 AH pack with BMS will run me about $10,000 Not exactly
cheap but should be the last pack I ever by.

I have been watching closely a few car conversion using 100AH packs
with these batteries getting 100 mile range at highway speeds, So with
a pack 2 to 4 times as large I think I will get expectable range. Or
so I hope, if not a bigger generator then 7.5 KWH will be in my future
purchase list. A least I'll only have one combustion motor to deal
with instead of three, as I do now.

But I guess you answer my question in a round about way, I will be the
first to do a conversion this large. So I'll keep good notes and
take lots of pictures to help the next guy out. :-)

1. http://www.evcomponents.com/SearchResults.asp?Cat=33

On May 24, 2009, at 7:27 AM, dennis wolfe wrote:
>
> James,
>
> HP is HP, whatever the prime mover. The continuous (not max or peak)
> power rating of your motor is the number to use.
>
>

> The battery bank is the real power constraint anyway, not the motor.
> You want to consider speed and range. Not much sense setting up an E
> boat that will go fast but drain the batteries flat in 5 or 10
> minutes. Start the design process by defining the speed and range
> you require, select a possible motor/battery system, evaluate cost,
> weight, performance. Repeat until you are confident you have the
> best compromise.
>
> Get Dave Gerr's "Propeller Handbook" to figure the prop size and rpm
> best suited to your boat.
>
> Google the "Peukert Effect" to see how rapid discharge affects
> battery capacity.
>
> You will be removing around 2500 - 3000 lbs from the boat. You new
> installation needs to maintain the original center of gravity or the
> boat won't float level and if it floats bow down maybe hard to steer.
>
> Good luck.
>
> Denny Wolfe
> www.wolfEboats.com
>
> ----- Original Message -----
> From: James Sizemore
> To: electricboats@yahoogroups.com
> Sent: Sunday, May 24, 2009 3:25 AM
> Subject: [Electric Boats] Any larger electric boat owners out there?
>
> I see a lot of traffic on this list for smaller conversions replacing
> A4's and such on 20-30 foot sail boats. Are there any folks that have
> replaced larger motors on cruisers/trawlers?
> I will be replacing two 427 fords (350hp gas engines) on a 41 foot
> Chris-Craft. This if for a number of reasons including not wanting
> the ongoing expense of buying gas, second I really hate the monstrous
> complexity of combustion engines. I have a computer science/
> electrical background so I am much much more knowledgeable and
> comfortable with electrical systems. And not to mention the smell and
> noise of combustion engines. The knowledge I lack right now is boat
> related: prop size pitch ...etc...etc. I don't need the boat to plane
> at 17 knots or anything like that, although if it does all the better.
>
> My current thinking is to replace the fords with a pair of (Netgain
> Warp 11'' or Transwarp 11'')'s. The part I can not rap my head
> around is if I go direct drive with the Transwarp's will they spin the
> props to fast? Or should I keep the transmissions that the fords are
> bolt to now and go with the Warp's. I would prefer not to have the
> extra complexity of the transmissions. The Netgains can move a large
> truck at freeway speeds 70+ MPH. My understanding of the conversion of
> electrical hp to combustion hp is at 144v these motors should be about
> the equivalent of a 150-200 hp gas motors with considerable more
> torque at the low end.
>
> The boat will soon have a fairly large solar array and already has
> 7.5 KWH generator. So keeping the battery bank feed should not be a
> problem. I know finding a solar charger/inverter for a 144v battery
> pack will be a real challenge. Any recommendations are welcome. I
> would also be very curious of other conversions of larger plaining
> hull boats, and what motors you use and performance you get now. Also
> any recommendations on motors/charges/controllers or kits for boats
> this size would be most welcome.
>
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>
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>
>

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