Mr. Kaufman,
I believe your client may have a misunderstanding regarding electric power as the primary propulsion. No one using a gas engine would ever travel with the expectation of ending at the dock with no fuel left in the tanks. If it were me I would use the manufacture's run time at full discharge as the maximum run time for the boat. It is a much better result to arrive home with power to spare than the opposite. It is the inherit issue with battery power. The alternative would be to carry a small generator aboard for emergencies.
Mark
--- In electricboats@yahoogroups.com, "pottererer" <john.starkie@...> wrote:
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> Mr Kaufman,
>
> I'm new, too. I'm not a lawyer; I'm a retired scientist.
>
> You and your client need a series of experiments.
>
> For each experiment, start fully charged, note the readings and time and then run the boat at constant discharge on flat water in no wind until it stops. Note the time and readings. Repeat three times.
> Then repeat at different discharge rates.
> Plot the results on a graph of range against predicted range.
> Get a qualified medical statistician to look at the graph.
> Get a biological research scientist to supervise the experiments: these people are familiar with experiments having many variables.
> Let your client operate the experiment.
> I wish I were close enough to help.
>
> My son and I are running this experiment on my Torqeedo.
> There is a temptation to maintain constant speed by changing the discharge rate: this will skew the results.
> There is a temptation to change the discharge rate to change speed in order to give way to traffic.
>
> From our experience we would expect your client to be changing propeller revolutions significantly, for very short periods of time, when leaving or returning to the dock and when changing direction. This significantly and rapidly reduces the expected run time. In one experiment I asked the engine for 3 seconds of full ahead before returning to the standard discharge rate. During that 3 seconds the expected run time fell from 59 minutes to 43 minutes.
> With a diesel or petrol (gas) engine this is standard practice, and it has exactly the same effect.
> The difference is psychological. The diesel tank has greater capacity than the battery, it is easier to refill and it is familiar. The diesel tank gauge is imprecise: a reduction of 10% capacity over a few minutes of high revs is hardly noticed. The battery gauge is very precise: 10% loss of available energy over a few minutes is scary. The diesel tank contains far more available energy than the battery: your client may feel (as my son and I did) that (s)he's running on a nearly empty tank.
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> It's not that 'time-remaining' gauges don't work: they do. When it says he has 2.5 hours remaining, he should: provided that he does not alter the discharge rate! If he alters the discharge rate, then the time remaining will change, exactly like a diesel or gas engine.
> It's true that there are very many variables.
> Run triplicate experiments for each variable and don't let anyone touch the throttle (accelerator, control switch, discharge valve, whatever) until the experiment is over.
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> Do let us know what happens.
>
> John
>
> --- In electricboats@yahoogroups.com, Kevin Pemberton <pembertonkevin@> wrote:
> >
> > Time remaining gauges don't work!
> > Because the variables are to great to figure precisely. In a gas
> > powered car without a sensor that meters the fuel in the fuel line and
> > an accurate way to put the information into the computer the amount of
> > fuel will depend on; level of car, analog float level in tank, Throttle
> > position, incline plus or minus. It will also depend on the mood of the
> > driver and load of the vehicle. Point is condition is everything. The
> > gauge is nothing more than a tool to help the driver make an educated
> > guess, and to believe it is anything more if folly.
> >
> > With a boat condition, loading front to back and overall weight can
> > change how far you might go. Other factors include head wind, current,
> > water surface i.e. glassy or rough. Number of cycles on the battery
> > bank. Temperature of motor and controller i.e. system resistance.
> > Throttle position, and speed of travel all change the drain on your
> > resources. No manufacture would claim that battery condition means
> > nothing when range or time is concerned. No one that has a battery in
> > any device expects that battery to run forever so should not consider
> > them to last forever in a vehicle. I would guess your search on the net
> > has not found the same complaint because no one else is trying to fill
> > their pockets using a frivolous lawsuit.
> >
> > Such lawsuits only serve to reduce the number of useful tools that could
> > be put to use by people with a little common sense, and make these
> > people safer because they are better informed.
> >
> > I am one of those people that hates people that spend their time trying
> > to take advantage of the system, and the lawyers, and politicians, that
> > help them do it.
> >
> > Kevin Pemberton
> >
> > P.S. May I suggest a testing laboratory that would verify there is no
> > real problem with the equipment? Of course at the expense of the
> > complainer. You may find this man (you say gentleman) unwilling to have
> > a "real" third party involved in the issue.
> >
> > >
> > > On Dec 17, 2010, at 7:58 AM, barristerla <no_reply@yahoogroups.com
> > > <mailto:no_reply@yahoogroups.com>> wrote:
> > >
> > >> Rick,
> > >>
> > >> I like a good lawyer joke as much as the next guy, perhaps more, thanks.
> > >>
> > >> Thanks also for pointing out, not so subtly, that blanket profiling a
> > >> group of folks for the purpose of ridicule is not appropriate or
> > >> wise. Picking on lawyers per se, while an ancient art, is akin to
> > >> picking on my wife for being Chinese, picking on my daughter for
> > >> being a dwarf, picking on my relatives in Germany for being
> > >> Vietnamese or picking on our President for being African. It's an
> > >> ugly can of worms and simply should be avoided.
> > >>
> > >> As noted prior, my purpose here is to find out whether this potential
> > >> claim is a worthy one. After all of the feedback received, it seems
> > >> to me that it's borderline at best.
> > >>
> > >> I thank all of you who have offered positive and constructive feedback.
> > >>
> > >> Scott K.
> > >>
> > >> --- In electricboats@yahoogroups.com
> > >> <mailto:electricboats@yahoogroups.com>, Rick Campos <rick_1211@>
> > >> wrote:
> > >> >
> > >> > THE OLD SAYING A 1000 LAWYERS CHAINED TO THE BOTTOM OF THE OCEAN IS
> > >> A GOOD START.........is usually what most people believe is a good
> > >> start once they feel an attorney gets in...somehow.
> > >> > Â
> > >> > What everyone should believe as true is that it is true!...but a
> > >> nessesary truth. Civil trial attorneys would be out of business in a
> > >> heartbeat if they had regulations restricting what a manufacturer may
> > >> claim or state. Of course "they" would be them...who are they ...your
> > >> government!
> > >> > Â
> > >> > So lawyers attack! Afterall, even if this particular manufacturer
> > >> cannot correct the problem because of unknown variables (ie:
> > >> charging, battery displacement, etc) they should extend every
> > >> possible consideration regarding a customer who was just buying a
> > >> boat. This electric engine 'conversation' posted on this forum, and
> > >> many others, are for tinkerers and alternative thinkers. Not a main
> > >> and commonly believed understanding..such as a car!
> > >> > Â
> > >> > We all know a car's gauge(s) will only let you drift to a halt or
> > >> stall....a situation not dangerous and easily corrected.
> > >> Notwithstanding a possibility of ...let's say running out of gas as a
> > >> tractor trailer is dead on your bumper....NOT AT ALL. But a boat that
> > >> stalls...lets say in a lane.....can be extremly dangerous! A boat
> > >> who's power cuts out docking may create a dangerous situation....to
> > >> themselves or other's.
> > >> > Â
> > >> > We have seatbelts, airbags, energency brakes....all adopted after
> > >> trial attorney's did thier thing! Not the manufacturer, not the
> > >> government....these were implemented not for your safety..really! If
> > >> the price was high they never would have been implemented.
> > >> > Â
> > >> > IN BOATS....THERE ARE NO REGULATIONS REGARDING LOW POWER
> > >> PROPULSION, thats why many people opt for a 48 volt system. Staying
> > >> below a certain voltage requirement does not require coast guard
> > >> approval.
> > >> > Â
> > >> > MANY 'SO-CALLED' MANUFACTURER'S are racing for market share and the
> > >> simple truth is THERE IS NO BASE LINE. If they stressed this
> > >> IMPORTANT INFORMATION regarding batteries, gauges, boat design, etc
> > >> BEFORE SELLING IT......they probably would cut thier sales in
> > >> half...if that
> > >> > Â
> > >> > As I stated a long time ago on this site, I designed my own system
> > >> (48V) generator backup on an older 30 ft. Hunter. It works because I
> > >> am a scientist who wanted the diesel mechanic to go away. I am a
> > >> tinkerer in this field. I have loved it...BUT BE REAL....I know what
> > >> will and can go wrong. Never should a company state anything it
> > >> cannot prove or at least service and educate.
> > >> > Â
> > >> > My suggestion to you is to have the batteries and gauges verified
> > >> by a service person who works in the golf cart or better forklift
> > >> type industry.
> > >> > Â
> > >> > Best of Luck
> > >> > Rick
> > >> >
> > >> > --- On Thu, 12/16/10, barristerla <no_reply@yahoogroups.com
> > >> <mailto:no_reply@yahoogroups.com>> wrote:
> > >> >
> > >> >
> > >> > From: barristerla <no_reply@yahoogroups.com
> > >> <mailto:no_reply@yahoogroups.com>>
> > >> > Subject: Re: [Electric Boats] New member, Q re: Duffy Boat
> > >> > To: electricboats@yahoogroups.com
> > >> <mailto:electricboats@yahoogroups.com>
> > >> > Date: Thursday, December 16, 2010, 11:51 PM
> > >> >
> > >> >
> > >> > Â
> > >> >
> > >> >
> > >> >
> > >> > Dear Rick and Mark,
> > >> >
> > >> > Thank you for your insight.
> > >> >
> > >> > I think the main issue with this gentleman is that the gauge always
> > >> seems to be inaccurate, even when fully powered, so, when it says it
> > >> has 2.5 hours remaining, he is never sure what he's got. The
> > >> representation from Duffy as to the efficacy of the gauge was quite
> > >> different.
> > >> >
> > >> > That all said, it seems like you are saying one can never rely on
> > >> their gauges? If that's true, these craft seem quite dangerous by design.
> > >> >
> > >> > George, as to the advice re: a qualified technician, the boat
> > >> manufacturer warranties the boat and this item, but refuses to fix. I
> > >> should note, your tone is not appreciated...
> > >> >
> > >> > Regards,
> > >> >
> > >> > Scott Kaufman
> > >> >
> > >> > --- In electricboats@yahoogroups.com
> > >> <mailto:electricboats@yahoogroups.com>, GeoMar Logistics
> > >> <geomarlogistics@> wrote:
> > >> > >
> > >> > > *Go away. Tell your client to suck it up, stop whining and get a
> > >> qualified
> > >> > > electrician to trouble shoot the problem. *
> > >> > > On Fri, Dec 17, 2010 at 7:16 AM, barristerla
> > >> <no_reply@yahoogroups.com <mailto:no_reply@yahoogroups.com>>wrote:
> > >> > >
> > >> > > >
> > >> > > >
> > >> > > > Hi folks:
> > >> > > >
> > >> > > > I'm new to the group. As you may have guessed by my "handle" I
> > >> am an
> > >> > > > attorney. I am NOT, repeat, am NOT looking for business here.
> > >> > > > I could use some input from you folks though.
> > >> > > >
> > >> > > > I currently have a client who claims to have issues with
> > >> his2008 Duffy 18
> > >> > > > Snug Harbor craft. More specifically, he claims that he has
> > >> issues with the
> > >> > > > readout on his Digital Energy Gauge. It does not appear to show
> > >> the proper
> > >> > > > time remaining even when initially charged and going forward,
> > >> during use. He
> > >> > > > feels he cannot depend on it and if he did he may end up
> > >> stranded at sea.
> > >> > > >
> > >> > > > I have searched the net and not really seen any other folks
> > >> having these
> > >> > > > problems. Are any of you experiencing this issue or do you know
> > >> anyone who
> > >> > > > is? Usually I expect at least some smoke before I believe there
> > >> is a fire...
> > >> > > >
> > >> > > > Thanks in advance for your thoughtful responses.
> > >> > > >
> > >> > > > Regards,
> > >> > > >
> > >> > > > Scott Kaufman
> > >>
> >
> > --
> > Ubuntu10.04, Acer AspireOne, Virgin Mobile 3G Broadband2go.
> > Doesn't get any better than this!
> >
>
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