T-Pain Is On A Boat: Re: [Electric Boats] 100kW hybrid installation

You are right about the self sustaining arc problem of high voltage DC. However any voltage above 48 is potentially lethal and even 12 volts at high current can make things go bang. We've accidentally turned a screwdriver into an explosive device at 48 volts.

However, the shock hazard of DC is, in some ways less than AC. AC causes fibrillation and DC defibrillates. With AC you can sometimes let go of a wire whereas DC can contract your muscles around a hot wire. The key thing is to make sure that you have the right safety systems. All wiring over 48 volts must be armored and the shields should all be connected together. There should be a detector to measure the insulation resistance between the shield and core on both the positive and negative side to assure that you never have a ground fault and to instantly disconnect all devices at the 48 volt level.

The other really big deal is cell balancing. If your cells are not in balance and you are charging the entire string, you can end up boiling off the highest battery and damaging it. Then your batteries are further out of balance and you can damage other batteries of start an internal arc which, since it's at high voltage DC can become self sustaining and start a fire. You have to control the wet corrosive environment any time you are over 48 volts. We just try to make certain that we do it in as foolproof and damned-fool-proof way as possible.

The thing about AC and three-phase AC is that the arcs are not self sustaining, the current over each conductor is a bit lower, and breakers are less expensive as a result.

- Bill

On Aug 17, 2011, at 2:38 PM, R Hampson (MottramGroup) wrote:

Wow.. you are so far ahead of me it makes my head spin! :-)

I have a pretty decent grasp of electricity theory, and can do basic residential wiring, however I need a recommendation on where I can learn the pros and cons of AC vs DC power when it comes to EV applications. Obviously cost is a massive factor from what you say.
I realize that higher voltage means lower amperage for the same power. The only thing that concerns me is the safety issue.. you are not concerned with having many hundreds of volts in a wet corrosive environment? Arcing is not more of a problem with the high voltage?
What are the benefits of using 3phase.. doesn't that add more cost/complexity?

I need your research material too! Where did you learn all your smarts? ;-)

I just posted my specs for my "sell everything and retire" boat which I was hoping to get going on late this year. Could you make some recommendations as to the direction you would go with this? The size of your projects make your knowledge invaluable. Any advice would be sincerely appreciated! See copy of email below…

My very best,
Bill

From: electricboats@yahoogroups.com [mailto:electricboats@yahoogroups.com] On Behalf Of Galstaf
Sent: Wednesday, August 17, 2011 1:08 PM
To: electricboats@yahoogroups.com
Subject: [Electric Boats] No sailed, solar powered cruiser (40-60 feet)

Hey folks,

I have posted occasionally but follow the discussions on the list with great interest in advancing battery and solar technology.
I am still looking to build my live-aboard cruiser in the 40-60 feet size range.
I know most of you guys are sailors, but the knowledge of solar and battery tech would be applicable.. so I am looking for recommendation on recreating this German solar boat on a budget. This is pretty much exactly what I want, a solar powered catamaran.. no sails, no regen, etc.
Please check this out

http://www.solarwaterworld.de/index.php?id=69&L=3
http://www.solarwaterworld.de/fileadmin/pdfs/SunCat-46-prospect-english.pdf

My current idea is to take a used aluminum or Fiberglass passenger ferry preferably with a blown motor(s) and strip out the engines and seats and convert it to a live aboard with electric power and a large solar array over the entire top of the boat.
This will be augmented with a larger genset when needed for emergency reasons.. but ideally the genset will rarely need to be started.
I would want battery storage to allow for 24 hours of cruising at around 5 knots.
The boat will be designed to hop between the islands in the Caribbean, and this should allow plenty of time for the array to top up the batteries if consumption has exceeded the solar array capacity.

So.. if this were *your* project, what would you recommend for brand and sizing the electric motors, what brand and type of batteries would you buy (Lithium or equivalent technology), what controller and what and where would you get the solar panels from?
How tall would you make the vessel, what should I consider in terms of weight and positioning of the array?
Is there a practical way to make an array of this size "directional", i.e. follow the sun.
The more detailed you can be the better. If you know of someone else that has put together a non-sailed cruiser in this sort of size range and has a blog, that would be awesome too.
I want to keep the cost of the whole project considerably under $100K. :-)

Many thanks!

Kind regards,
Bill

From: Bill Southworth [mailto:whs@gatesstreet.com] On Behalf Of Bill Southworth
Sent: Wednesday, August 17, 2011 1:53 PM
To: R Hampson (MottramGroup)
Cc: electricboats@yahoogroups.com
Subject: Re: [Electric Boats] 100kW hybrid installation

My boat was built with a design spec of 72 hp to achieve waterline speed in normal conditions. My experience with a conventional engine confirmed that it was about right. I know that many folks recommend using smaller electric power but I felt than the extra power is good to have when you are in rough conditions, a fast moving river, breaking inlet, etc. Admittedly, an electric motor has much more torque at low power, but that doesn't really help the top end.

On the other hand, my generator is only half that power, to get 50kW or 100kW requires either using all electric or syncing the generator voltage with the battery output to maximize the combined power to the motor while minimizing battery drain. My boat has a single battery bank and is charged at 352 volts.

We're doing the propulsion for a second boat which is a 110' schooner with twin screws. That system will be using two 480 vdc battery banks with 64 kW-Hrs of capacity in each bank. There's some more stuff about my boat at http://barbara-ann.com and about the design approach athttp://hybridpropulsion.com.

To a large extent what we've been doing is a research project so far. However, each iteration gets better and better. We're on our third go round on the battery management and we've reduced the size and cost by two thirds. Also, our all of our designs have been able to keep the batteries in balance to within millivolts. We've found that a very high percentage of the total system cost is wire, connections, and labor. Since all the DC cable must be armored and floating, cable costs can range from $7 to $23 per foot. Each connection and the manhandling of cable and hardware take an inordinate amount of labor. We're trying to eliminate most of this with our latest design. The telecom style batteries (like the Odyssey P1800) help this a lot. We've been very happy with our choice of using AC generators. At the current time, they are much less expensive and familiar to most installers. The only disadvantage has been the weight of the alternator versus a PMDC motor.

We are still ambivalent on the propulsion motors. We've used both the UQM and EVO motors. Both of these are great (EVO is a little better), but both are expensive. The drives, in particular, are optimized for automotive use and have more cost and features than we need. We are gravitating towards maintaining variable frequency AC in the system and only doing the DC conversions and the point of use. Try Googling 400 to 600 volt DC 200 amp circuit breaker and check the cost. Typically it's in the thousands of dollars, versus hundred for AC. Carrying around 3-phase greatly reduces the cost of breakers and safety electronics. Ideally, we'd like to stay at around 450 volts at 250 to 400 hz. This would be straightforward in the generator if we can find the right 12-pole motor, or maybe use a 400hz alternator. We try to stay at under 200 amps wherever possible for the same cost reasons. We're also interested in exploring induction motors for propulsion. The systems we are working on are right on the borderline where induction makes more sense than PMDC.

I'll post some more pictures next week. The contractor panel that I posted is the main DC bus. One connection goes to the battery bank, one to the generator, one to the motor, and the rest are various loads and sources like the shore charger, HV to 12VDC power supply, HV to 24VDC power supply, AC inverter, and a 10 kW induction motor for the hydraulics pump.

- Bill

On Aug 17, 2011, at 1:16 PM, R Hampson (MottramGroup) wrote:

Hey Bill,

Impressive stuff! It seems like a pretty huge power output in comparison to what everyone else on the list typically cites.
Why so much?

I am looking at to putting together a cruiser about the same sort of size (50ish feet), and am looking for all the advice I can get while I am in the planning stages.

Do you keep a blog or have a website with more details of your project and what you have done at each stage?

My best,
Bill

From: electricboats@yahoogroups.com [mailto:electricboats@yahoogroups.com] On Behalf Of Bill Southworth
Sent: Wednesday, August 17, 2011 11:35 AM
To: electricboats@yahoogroups.com
Subject: [Electric Boats] 100kW hybrid installation

I've included a couple pictures of the refit of my 57' sloop, the Barbara Ann, with 50kW continuous 100kW peak hybrid power. The installation includes a UQM HiTor propulsion motor with a 3:1 custom planetary gearbox, 24 Odyssey 2250 batteries with dissapative cell balancing and vacuum relays for each 48 volt group, ABB insulation resistance measurement, and multiple CAN bus electronic throttles. The whole system is managed by a CAN network connected to a small Debian Linux computer. The backup generator is a Westerbeke 34kW AC generator. The rectified generator voltage and current are controlled by the Linux machine by electronic control of the voltage regulator. High voltage inductive loads (generator and motor) are connected through a "soft start" circuit which brings the voltage on-line through a resistor before fully connecting the load.

- Bill

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