T-Pain Is On A Boat: Re: [Electric Boats] Re: Proper battery capacity

Saturday, April 20, 2013

Re: [Electric Boats] Re: Proper battery capacity

Greenpjs, that's an excellent description you wrote; well said.

BTW, even if the units had been equivalent, I would personally consider a variance of 2:1 not bad at all for an empirically derived rule of thumb applied to such a broad range of boat, motors, & batteries.

One Watt*Hr per pound (per afternoon outing?) also has the advantage of being easily remembered......for a rule of thumb that's important too.

Roger L.

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----- Original Message -----

From: greenpjs04

To: electricboats@yahoogroups.com

Sent: Saturday, April 20, 2013 6:09 PM

Subject: [Electric Boats] Re: Proper battery capacity

Be careful not to confuse Watts (a measure of power) with Watt-Hours (a measure of capacity). The 1 KW per ton is a rule of thumb for the power required. The recent discussion of 1 Watt-Hour per pound is a discussion about what battery capacity is typically needed. Think of it as what size gas tank is needed rather than how many horse power is needed. Both usually go up as the boat gets heavier, but they are two very different things.

--- In electricboats@yahoogroups.com, RICHARD JAMES <dick.james@...> wrote:
>
> Hi all, I've been reading these posts to glean some info for my own project (more later) but I'm a bit confused over the units being talked about. seeing a lot of 1Wh/lb suggested and then 1kWh per ton as if they were the same. Surely 1Wh/lb is equivalent to 2kW/ton, there being 2000lbs in a ton (in the U.S.) or am I missing something.
> Anyway my project is probably an order of magnitude smaller than what you people are doing (apart from the guy with the canoe) but here goes. I'm planning a day boat for some genteel cruising on the upper reaches of the Thames (ie non-tidal). About six hours cruising a day at three to four knots. The hull form is pretty close to that of an inflatable, flat bottomed, rounded sides. All-up weight of boat, four people, batteries, motor etc approx 1500lbs. 350W 48v motor powered by four 110Ahr batteries in series. The question I have is this - does this all sound reasonable or is it way out. I would very much appreciate some advice.
>
> Richard James
> London, UK
>

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