T-Pain Is On A Boat: RE: [Electric Boats] battery cost comparison

Julian

Props – reverse engineer

Look at other boats and see what props they use.

Look at the rpms they are turning them and the power and torque needed to do that – in this case the torque

I assume you mean a 22kw input - 22kwhr? What is the output at peak efficiency?

I suspect something in the order of 17.65 kw depending on the manufacturers claims about motor efficiency?

Actually I recently worked out a genset powered twin system for a cruising cat, 22.5kw out per motor – that work has gone west with a computer glitch se la vie. But it looked viable – not economical but it was designed with a commercial end in mind.

The problem here is so many makers and styles (many like clover leaf pattern dating back to the 19^th century) and the lack of data logging.

The simplest way is to look at diesel setups running at similar rpms and torque levels (your outputs at motor's max efficiency rpm vs the diesel peak power rpm) – do a scattergram using the mass of the boat as the third variable and a start prop should be evident. Start with diesel of 18kw – and you can adjust the output rpm using a ratio which will enable you to see the prop which would reach the prop at its power peak.

See if you can get a modern design. Good luck. Submarine style props (very high aspect ratio scimitar blade shapes) are very efficient – more or less compatible with folders. Blades shapes like a variable pitch prop next best and variable pitch could give you more options still.

Use the props swept volume to roughly estimate the thrust (per second) – a ratio will emerge which may seem insanely small but it will be workable.

From: electricboats@yahoogroups.com [mailto:electricboats@yahoogroups.com] On Behalf Of Julian Webb
Sent: Monday, 10 September 2012 7:26 PM
To: electricboats@yahoogroups.com
Subject: Re: [Electric Boats] battery cost comparison - now long term cost too.

Hi Andrew

- Being an electrical technician by trade with 30+ years practical experience I too thought electric propulsion would be easy, and so when I was ready to convert a 36' steel cruiser from twin Diesel to all electric I did indeed join this forum hoping to tap into a vein of experience.

- I laid out all the boat specs and proposed a system, and asked if anyone thought I was on the right track. I think I got one heartening email from Eric................. and so far that's it as far as direct input to my project goes.

- I'm not criticising the forum or it's members, it's just there isn't a wealth of experience in planning a system built from separate components from different suppliers, which I guess is why Fischer Panda, Mastervolt etc can charge the prices they do, but I couldn't afford Panda and Mastervolt didn't produce what I wanted.

- The more I hunted down people who had tried to put together a hybrid system from off-the-shelf electrical components, the more depressing the tale became.

- The road was paved with mystery and repetitive failures that no one could solve, not even the manufacturers of the gear, giants like Allen Bradley and Siemens had all walked away.

- It took me 3-4 months ringing, visiting and emailing people kind enough to component list their failed systems for me , electricians that had been involved, and one really nice guy Arby who visits this forum who had himself had bad experiences in this exact field, before I thought I had worked out what had prevented people successfully using 3 phase induction motors, VSD/VFFDs, Diesel Gensets etc in a system.

- Working with a smaller Genset manufacturer, the electrical manufacturer WEG and the clever guys at Victron proved my theory, and has let me put a 22kW system together using components I can source/repair pretty much anywhere.

- So if you buy a smaller sailboat auxiliary or prepackaged system you are right, all you have to make sure of is that you have sized things correctly and you shouldn't have any problems and yes there are people here who can help with that, BUT if you either can't find or can't afford a larger hybrid system, then no, there is little to no help here or anywhere else, that I have found. Theory is fine and a good place to start but in the end it has to be empirical experience that rules the day, and this is what appears to be thin on the ground.

- I now have my system and it has been been dry tested under every load condition we could think of, with an in boat wet test hopefully in a month, and so while I appreciate your kind offer I think in this instance it might be me who can offer rare theoretical and practical experience.

- The one bogey I haven't gotten to yet is the props as you are dead right in that you can waste a major percentage of all your hard work with a wrong prop choice, so in this I humbly beg anyones advice?!?

Regards, Julian

On 10 September 2012 02:04, Andrew Gilchrist <andrew@fastelectrics.com> wrote:

Julian

You are thinking in the mode you use in your profiession, where you have a very comprehensive knowledge of the variables which produce successful outcomes in different situations and applying the subtleties of objective and subjective compromise.

Electric power systems are very simple.

Amps volts motor efficiency – determine the power in and outputs The hulls and water are givens.

Start with a very simple model. Replicate ICE systems – keep in mind their efficiency – vs electric. Duplicate other electric systems using component spec sheets and the real world experience of people here. They will give you real world Peukert effects – data which is hard to come by.

Battery makers (Panasonic have discharge graphs which are useful for avoid estimates of Peukert. Many of the lithium makers do too.

Use general models for hull forms.

The other thing you can look at it is props – so how much water do they move per revolutions – easy to estimate the thrust they are producing use volume of water; check out how it compares to motor outputs. Eg to accelerate a lt/kg of water from rest to X knots takes how much energy? Vs what energy is available? So what is the approximate correction factor you need to apply for a realistic power to thrust ratio?

People here have real world results.

Start simple focus on the new power system.

Andrew

From: electricboats@yahoogroups.com [mailto:electricboats@yahoogroups.com] On Behalf Of Julian Webb
Sent: Monday, 10 September 2012 7:14 AM
To: electricboats@yahoogroups.com

Subject: Re: [Electric Boats] battery cost comparison - now long term cost too.

Hi Eric

- Without getting metaphysical, 80% of mortals need their decisions validated by someone/somewhere they consider an authority figure, sadly usually T.V. or else someone more dominant than them in their network, but as this isn't a field of wide experience or with plenty of somewheres they can go to be reassured they'll waffle and over analyse, keep hunting for the "perfect system" or the next-best-thing until they give up or feel reassured enough to take the plunge.

- Sorry to sound cynical but sometimes you just have to go with good old fashioned common sense and appropriate technology with safety, comfort and practicality in mind.

- As you said, you can't take everything into account and in the end we all have to be sure for ourselves and doing your own research etc is often the best way.

Cheers, Julian

On 9 September 2012 16:11, Eric <ewdysar@yahoo.com> wrote:

Hi Julian,

You will notice that I rarely call anything out as the "best" choice, because the answer is so dependent on the particular situation. In this post I was trying to compare batteries "apples to apples" on initial cost, weight and range. It's up to each person to find the best fit to their own priorities. You may have noticed that buried in the midst of all that info, I did say "So for most boaters, I recommend AGMs as a good balance of price to range.". It's nice to hear that you came to a similar conclusion, even if for a couple of other reasons.

I also stated "Another point to consider is that the math is dependent on the load. Because of Peukert's Effect, higher load/capacity ratios favor Lithium, but lower load/capacity ratios make AGM and flooded look better.". This means that as uour battery bank gets bigger, your typical amp load becomes a smaller percentage of your capacity and the energy lost to Peukert's Effect is less. So lithiums have more benefits with smaller banks than larger ones. Hybrid systems (electric + ICE) can often use a smaller battery bank, and lithiums become a better choice. You can see that played out in virtually all hybrid cars on the market today.

Finally, before I converted my boat, like you, I was very concerned about my range under electric power alone. As a temporary solution, I bought a portable generator knowing that it could provide value to me off the boat as well. I have driven my boat at better than 4 knots for an hour on the generator and my regular shore charger alone as a proof of concept. But since I converted, I have never needed to resort to that under way. In fact I've never reached 30% DoD in a full day of sailing. Buying the generator was still a good idea, it's been run 10x as much on shore to provide emergency power to my house during a major blackout and to provide party lighting at a BBQ shore party or two at Catalina Island. In retrospect, I'm very glad that I didn't tackle the added cost, weight and complexity of a dedicated on-board diesel generator during my conversion. For the way that I use my boat it turns out that my fears about limited range were unfounded. A number of other sailboat owners in this group have said the same thing, range has not turned out to be the problem that we all imagined that it might be.

Just some food for thought.

Fair winds,
Eric

--- In electricboats@yahoogroups.com, Julian Webb <julian.proto@...> wrote:
>
> Hi Eric
>
> - Without sounding obvious, the D.O.D and cycle numbers are primarily
> determined by;
> 1) Usage
> 2) Recharging capacity
> 3) Available space for batteries
> - While Green/low impact recharging such as Wind, Sun and Drogue style are
> desirable, for safety and comfort sake you must have an "instant" power
> source, which at the moment is realistically limited to some form of I.C.
> Genset, and if you have such a power source (and fuel) you have complete
> control of D.O.D and cycle numbers.
>
> - I tortured for months over this one, getting more and more exotic as time
> went by as I tried to build what I thought would be the perfect system,
> until in the end I stood back and went for practicality, cost and
> "available technology", in that I want to able to go anywhere and be able
> to replace or repair any system component, and so a bank of A.G.M's and a
> silenced Diesel Genset seemed the "current technology best choice".
>
> - Aso there can be non system upsides too e.g. a bank of A.G.Ms can be
> useful ballast etc.
>
> Cheers, Julian
>
>
>

> On 6 September 2012 23:02, Eric <ewdysar@...> wrote:
>
> > **

> >
> >
> > Yep, I didn't include the lifespan in doing the cost comparison, because I
> > don't expect to put 500 deep cycles on my batteries in 10 years. Long term
> > costs (over decades) were not even covered in my analysis, so I'm not sure
> > what you're disagreeing with. I am certainly not counting on a lifespan of
> > more than 10 years from my LiFePO4 cells regardless of cycle count, but if
> > they last longer, it will be a pleasant bonus. But as I mentioned, if one
> > expects to delve into the upper ranges of deep cycle lifespans "replacement
> > costs may need to be factored in."
> >
> > For most of the people that are considering an electric conversion, the
> > up-front investment is a higher priority than costs averaged over a decade
> > or more. At least that's what most of them have said in posts in this
> > group.
> >
> > Given your typical usage, do you really expect to average more than 4 deep
> > discharges a week (greater than 60% depth of discharge) for the next 10
> > years? That usage is well within the projected lifespan of LiFePO4 cells.
> > If that is your actual usage than Lithiums will be cheaper than the other
> > chemistries. But for those that average less than two deep cycles a week
> > for a decade (like me), AGM might be cheaper in the long run.
> >
> > Fair winds,
> > Eric
> > Marina del Rey, CA
> >
> > --- In electricboats@yahoogroups.com, Robert Lemke <robert-lemke@>

> > wrote:
> > >
> > > Eric,
> > > I agree with your math and the Puekert, DOD, and weight short comings of
> > AGM and flooded. I respectfully disagree on the long term cost, asÂ
> > > LiFePO4Â is the hands down winner when cycle life is entered into the
> > equation. With proper care, 500 cycles is about it for AGM and less for
> > flooded, but at the present time you will get 2000 cycles fromÂ LiFePO4Â .
> > > Bob
> > >

> > > --- On Thu, 9/6/12, Eric <ewdysar@> wrote:
> > >
> > > From: Eric <ewdysar@>

> > > Subject: Re: [Electric Boats] battery cost comparison
> > > To: electricboats@yahoogroups.com
> > > Date: Thursday, September 6, 2012, 10:17 AM
> > >
> > > Hi Don,
> > >
> > > I'm not sure what physics lesson that you're looking for, but here is a
> > detailed comparison between battery chemistries by cost, weight and range.
> > >
> > > ---------------------------------------------
> > > This is what I posted on April 20 this year in post #21398
> > > "Hi Capt. Todd
> > >
> > > Perhaps you mean something like this post that I made back in Jan 2012
> > (post#20750) and reposted in this month (post #21237). I directly compared
> > the weight and cost of the same usable capacity of different battery types.
> > Peukert's has already been factored in. You can read the whole post here
> > http://groups.yahoo.com/group/electricboats/message/21237
> > >
> > > You said "Additional concerns are that the estimated Puekert
> > coefficients might be 1.0 for Lithium, 1.1 for AGM, and 1.3 for Flooded.
> > Estimated safe discharge levels might be 80% for Lithium, 60% for AGM, and
> > 50% for Flooded."
> > >
> > > In case you want to check my math, for my calcs I used a PE of 1.03 for
> > Li (no battery is 1.0), 1.1 for AGM and 1.25 for FLA. And you can see that
> > I used discharge levels of 80%, 70% and 60% respectively.
> > >
> > > -- Excerpt from post #21237 -----------------------------------
> > > Let's do the math for a battery pack that has a usable 2.5 hour range at
> > 2500W (6.25kWh used).
> > >
> > > FLA â€" 14.25kWh to 60% DoD at 2500W = 2.5 hours = 633 lbs, cost about
> > $1500
> > > AGM â€" 10.5kWh to 70% DoD at 2500W = 2.5 hours = 520 lbs, cost about
> > $2500
> > > LiFePO4 â€" 8.25kWh to 80% DoD at 2500W = 2.5 hours = 200 lbs, cost
> > about $3500
> > >
> > > So now the lithiums are 2.3 times the cost of the FLA T-105s but they
> > are less than 1/3 the weight for the same range at this load. So for most
> > boaters, I recommend AGMs as a good balance of price to range.
> > > ------------------------------------
> > >
> > > Another point to consider is that the math is dependent on the load.
> > Because of Peukert's Effect, higher load/capacity ratios favor Lithium, but
> > lower load/capacity ratios make AGM and flooded look better. Aiming for the
> > same amount of energy consumed, here's a similar chart at 4000W for 1.5
> > hours (6kWh used)
> > >
> > > FLA â€" 15.1kWh to 60% DoD at 4000W = 1.5 hours = 670 lbs, cost about
> > $1600
> > > AGM â€" 10.5kWh to 70% DoD at 4000W = 1.5 hours = 520 lbs, cost about
> > $2550
> > > LiFePO4 â€" 8kWh to 80% DoD at 4000W = 1.5 hours = 200 lbs, cost about
> > $3400
> > >
> > > Here's the another chart at 1500W for 4 hours (6kWh used)
> > >
> > > FLA â€" 12.5kWh to 60% DoD at 1500W = 4 hours = 550 lbs, cost about $1350
> > > AGM â€" 9.6kWh to 70% DoD at 1500W = 4 hours = 475 lbs, cost about $2350
> > > LiFePO4 â€" 7.8kWh to 80% DoD at 1500W = 4 hours = 195 lbs, cost about
> > $3300
> > >
> > > Looking at 6kWh usable at both 4000W and 1500W, we can see that FLA cost
> > 40% of Li at 1500W and 47% of Li at 4000W, mostly because of Peukert's
> > Effect. You can see where this is trending.
> > >
> > > I haven't even thrown battery life into the mix, but since I'm still
> > working I don't put as many cycles into my boat as I would like. With
> > proper maintenance and charging, I believe that I could get all of these
> > battery banks to last 10 years. But that's just the way that I use my boat.
> > For someone that cycles their pack more often, replacement cost may need to
> > be factored in.
> > >
> > > I hope that this helps.
> > >
> > > Fair winds,
> > > Eric
> > > Marina del Rey, CA
> > > -----------------------------------
> > >