Arbi offered: "95% of system failures are due to electro-mechanical
interfaces".
Maybe so, but that's not my experience.
And even IF so, 99% of those failures were likely due to operator error or
poor installation-
Yes, bad solder joints, bad crimps, unclean or corroded connections are
responsible for high resistance that can lead to poor performance or
failure.
But does that mean we stop using any of these techniques or only ever
connect electrical devices if within enclosures that meet arbitrary Federal
Regulations? No.
But let's get specific.
Speaking strictly of controller failures, as I've followed EV usage of them
since 1993, I'd estimate at least 95% of the failures that I have personally
experienced or read about were NOT due to electro-mechanical interface
issues at all.
Rather, the primary killers are:
. Non-existent pre-charge resistor circuit (sudden inrush into
controller kills bulk capacitor)
. Marginal or non-robust controller design (don't handle brief
overloads gracefully and outputs get fried)
. Insufficient thermal mounting of controller (controller overtemp)
. Incompatibility between controller and load or motor load profile
(eg. running continuously at controller peak rating)
. Blowing up controller by incorrect wiring on installation
I have been running now with a brush motor (ETEK), Curtis or Alltrax
controller, T-105 batteries and have had little or no corrosion issues (a
couple battery connections is all).
While I'm not operating in a salt-water environment, my boat has been
continuously moored on the Columbia since 1996 and operating as an electric
since about 2003. I haven't a clue about meeting any Federal Regulations as
regards enclosures--
I'd gladly use a Sevcon.and sure, it'd need to be protected from water (as
with my Alltrax), but seriously Arby, unless you are giving up on your
brushless motor and simple 24v brushless controller and instead packaging
Sevcons with brush motors, why are you concerning yourself with a housing
that meets Federal regulations for a controller in your personal private
boat when you can mount your Sevcon in part of the cabin? I'd be very
concerned about trading off good thermal design for putting a controller in
a housing to ostensibly meet some regulation that you already meet by
locating the electronics behind a control panel. Again, contact resistance
issues are only responsible for failures in cases where poor maintenance or
installation are concerned. And that's a tiny minority of brush motor
controller failures. The Sevcon and Alltrax (and other) brush controllers
are excellent controllers and are somewhat resistant to the primary killers
I mentioned above unlike others that are easily killed by mistakes.
-Myles Twete, Portland, Or.
From: electricboats@
On Behalf Of Arby bernt
Sent: Thursday, August 06, 2009 5:23 PM
To: electricboats@
Subject: Re: [Electric Boats] 4kw "Arby" motor?
Hi Cris,
I would like to test a motor using a 48v Sevcon controller. Brian has
suggested the same. I'll need to prepare a motor for an external controller,
and a housing for the Sevcon that meets Federal Regulations. Of particular
note is the 3/4" conductive sphere test...as well as the obvious corrosion
issues posed with the open header with its plated connectors. My experience
has been that at least 95% of all system failures are the result of
electro-mechanical interfaces. The plated spring bronze receptacles on the
Sevcon signal header and the contactor are fine for dry environments, and
will function fine for testing, but I would never consider them capable of
providing 10+ years of service-free reliability, even with an industrial
strength housing. There are a pair of Electric Wheel motors and controllers
on E-Bay. Have a look at them to see what happens when industrial enclosures
are used in a marine enviroment.
Arby
____________
From: Chris Witzgall <chris@witzgall.
To: electricboats@
Sent: Thursday, August 6, 2009 10:33:44 PM
Subject: [Electric Boats] 4kw "Arby" motor?
I would think a 48v version, perhaps that can run on 24v as well, would be a
hit. Our boat, 10k lbs on paper, and more in real life, would not be
suitable for a 2kw motor, but might get along with a 4kw version.
Arby - if you are reading this - have you looked into the possibility of a
4kw version of your motor?
Chris
On 8/6/09 10:17 AM, "aweekdaysailor" <aweekdaysailor@ yahoo.com> wrote:
>
>
>
>
> We had a sail-in to Treasure Island last weekend which included 4
e-boaters on
> 3 sailboats - mine, Hans K and Kevin brought his Erickson 27 powered by
Arby's
> [http://www.advanced marineelectricpr opulsion. com/] motor. Tomasz and
his wife
> came along on my boat (he's got an e-boat down in Monterey) so I got to
make a
> couple of new friends to boot.
>
> It was a great day for sailing and we hit the tides well (all coming from
a
> different spot on the bay). We'll hopefully get some pictures up soon.
>
> We did have a "watt race" - my boat and the Erickson running parallel and
each
> calling off watt (amp actually) readings. This was all very un-scientific
but
> we did calibrate the ammeters and had independent observers at least.
>
> Downwind, the 100% watt draw advantage (for example I was at 2KW, Kevin at
> 1KW) was pretty close to true. Upwind (about 15kts) it narrowed a bit to
about
> 50-60% fewer watts advantage (i.e. I was at 2KW vs 1.5KW for Kevin)-
making
> sense with that boat being about 30% lighter and a freshly scrubbed hull.
> (Kevin I'm going from memory, so please correct me if I mis-state). We
were
> nowhere near hullspeed - maybe 4kts down and 2-3 back.
>
> I'm still nursing a set of bad batteries, comparing very different boats,
mine
> needs a scrub, props, etc -- so unfortunately I don't place much faith in
the
> numbers - this was intended for fun more than anything else, though I'm
sure
> this will trigger some debates (what's the expected difference in those
hulls,
> etc...)
>
> That said...Arby' s motor is a very sweet package - very clean, compact,
and
> very robustly assembled (so much so I'm afraid pictures taken of my setup
are
> going to end up as "before" pictures like those diet ads in the
tabloids...) .
> In particular, I think the lack of exposed wiring will be a huge advantage
in
> long-term reliability in saltwater installations.
>
> I think more testing is in order before declaring it SF Bay ready for a
boat
> as large as mine (30' 9800lb), but it seemed to me a good fit for the
Erickson
> and for the very large number of boats up to that size/vintage ready for
new
> motors. The 24volt package has obvious advantages as well, though I would
love
> to see 36V and 48V options.
>
> YMMV, Caveat Emptor and all that - but all in all I think it deserves
> consideration as a legitimate option in appropriate sized vessels and
sailing
> conditions. What "appropriate" means will involve further testing,
experience,
> testimonials, etc.
>
> -Keith
>
>
>
>
>>
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