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Repowering a 55' sailboat
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I just removed a frozen Borg Warner Diesel engine from my 55¡¯ sailboat, and am in the process of repowering it with electric.? I¡¯ve spent a great deal of time on this site and others trying to understand many of the trade-offs and ways to approach the conversion.? I wanted to post my tentative plan here for feedback from people who¡¯ve been through it before. ANY and ALL feedback is welcomed and greatly, greatly appreciated!? ? Boat details: ¡¤??????? Former motor: 120 HP diesel engine (substantially more power than needed, even at hull speed). ¡¤??????? Length: 55¡¯ (49¡¯ at waterline) ¡¤??????? Beam: 16¡¯ (14-15 ft at waterline) ¡¤??????? Hull speed: 9.4 knots (calculated, and seems about right from experience) ¡¤??????? Prop: 24¡± diameter, feathering, with adjustable pitch (currently 24¡±, I believe) ¡¤??????? Transmission: 2.57 reduction (inline gear reduction), also acting as thrust bearing (I believe) ¡¤??????? Moorage: Washington state (but need to move from Columbia River to Puget Sound) Planned usage: ¡¤??????? Electric motor primarily for moving in and out of marina ¡¤??????? Mostly day sailing, but with occasional trips to Hawaii / South Pacific ¡¤??????? Potentially add a 5kw diesel generator for continuous motoring at 4 knots (calculated guess) ¡¤??????? I¡¯m planning on keeping the feathering prop, as I don¡¯t intend to attempt regen until I¡¯m beyond day sailing and will be taking her to Hawaii or the South Pacific. ¡¤??????? ? The Plan: ¡¤??????? Motor: Hyper9 HV or AC-51/35 running at 144V o?? I can¡¯t figure out how to get enough power running at 48V ¡¤??????? Transmission: Keep the existing 2.57 reduction in-line transmission o?? Ideally a 5:1 reduction would allow the motor to run at higher speeds and I could use the entire motor range at existing 24¡± prop pitch (but I have the existing 2.57 reduction) ¡¤??????? Prop: Lower to 14¡± pitch o?? Minimum¡± recommended¡± OK range (from Propeller Handbook, Dave Gerr), (0.65 pitch ratio), but could go as low as 13¡± with additional efficiency loss) o?? Assumes 45% slip (calculated based on Propeller Handbook, not measured) ¡¤??????? Battery Bank: 45 CALB 3.2V 100Ah cells, in series o?? 100Ah & 144V = 14.4kW o?? Alternatively, buy a used Nissan Leaf battery and tear it apart. (Same 14.4kW assuming batteries are only at 60% - but extra work and an extra hundred pounds or so. Savings is substantial, though. Price goes from $7-8,000 for batteries to around $1500.) Details and Calculations: ¡¤??????? Range on batteries (given the current plan of 14.4kW and stopping at 10% remaining charge): o?? At 4 knots approx. 2.5 hours of runtime = 10 nautical miles o?? At 9 knots approx. 20 minutes of runtime = 3 nautical miles ¡¤??????? Range with 5kW Diesel generator: limited only by diesel (at 4 knots) o?? Anything above 4 knots will take > 5kW and will use battery o?? Anything below 4 knots will charge battery ¡¤??????? Prop pitch will influence motor RPMs o?? 24¡± pitch at 4 knots requires 1100 motor RPM (9.4 knots = 2700 RPM) o?? 18¡± pitch at 4 knots requires 1500 motor RPM (9.4 knots = 3600 RPM) o?? 14¡± pitch at 4 knots requires 2000 motor RPM (9.4 knots = 4600 RPM) ¡¤??????? Motor efficient RPM range: o?? Hype-9: 1000 ¨C 6000 RPM o?? AC-51: 1000 ¨C 6000 RPM Hopes and Dreams: ¡¤??????? My Dad, Uncle and Grandpa bought the hull and custom built the boat. It¡¯s beautiful! I took over the boat a few years back.? I¡¯d like to repower the boat partially to make it easier for me (I¡¯m more comfortable with electric motors than diesel), and partially to add sweat equity into the boat in order to share in the family effort to build the boat. One of my sons will also be joining me in the effort. ¡¤??????? It¡¯s in the Columbia River now, and I¡¯ll need to move it out the mouth of the Columbia, then up and around the Olympic mountain range, and into Puget Sound. I have a slip for her in the southern part of the Sound. ¡¤??????? Although likely use is day sailing for the next few years (once or twice a month), eventually I¡¯d like to take her to Hawaii, and beyond. But that will likely be several years from now. Questions: These are all my current questions. I¡¯m looking for answers for any or all, but even an opinion on just one would be very valuable.? Also, what questions am I missing?? ¡¤??????? Is changing the pitch to 14¡± (on a 24¡± prop) a good or bad idea?? o?? It would give me closer to the full range of the motor (4600 RPM at hull speed vs effective top range of 6000 RPM for the engine) o?? I¡¯d lose a little efficiency of a higher pitch, but wouldn¡¯t have to buy another inline gear reduction, or figure out how to do a belt system or the like. It just seems simpler, and the gear reducer is attached to the driveshaft already. ¡¤??????? Is the 3.2V CALB 100Ah battery the correct choice?? ( ) o?? Can I put that many in series (45 ¨C 48 cells) to get 14.4kW hours at 144V? If so, do I need to use any special connector bars since I¡¯ll be pulling 500 Amps, or are the thick copper ones they ship with sufficient? o?? Should I buy them on Alibaba for less than $5,000 for 50 batteries or get them from someplace a more traditional store (EV West, Stealth EV, etc ? o?? Should I go with an OEM battery and just rip it apart? ¡¤??????? Which BMS should I use?? I¡¯m thinking the Orion BMS2, but they are expensive. () ¡¤??????? Which motor should I buy? o?? Netgain Hyper-9 - o?? HPEVS AC50/51 - o?? HPEVS AC34/35 - o?? Or should I do something completely different?? I¡¯m not wanting to use a brushed motor, and would like something more plug and play than doing my own build from a forklift motor. I¡¯m comfortable with working with electronics and electricity, but for this build I¡¯m looking for more simplicity. ¡¤??????? Should I add a 5kw diesel generator for cruising longer distances? o?? By my calculations I can push the boat approx. 4 knots with 5kw. ¡¤??????? I don¡¯t have any idea on a charging system. At all. ¡¤??????? Oh, my. What am I missing?? When I started writing this thread I felt like I knew a lot more than I feel like I do now!? :-O Everyone, thank you so much for your help in the forums. I¡¯ve read so much, and I¡¯m so pleased to have this resource available.? So, even if you can¡¯t help with these particular questions, I still want to say ¡°Thank you!¡± |
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Hi Steven,
Welcome to the group! ?I can see that you¡¯ve done your homework and come up with a plan based on traditional sources. ?What we (the people in this group) have found over the last 10 years, is that the traditional powering models and calculators aren¡¯t quite right for electric conversions. ?The Dave Gerr book is a great resource, and I respect him greatly, but we¡¯ve seen time and again, that our end results are not close to his predictions (typically we need much less power than his formulae suggest). ?In conversation with Dave, he accepted that his work is more applicable to power boats operating at faster speeds. What we have found is that displacement is the most accurate indicator of how much power a boat needs. ?A rough rule of thumb for a properly designed electric marine drive is that 1kW/ton of displacement will deliver 90+% of hull speed, 1kW/1000# of displacement will deliver hull speed. ?Another observation is that increasing speed by 1kt (while staying under the 90% hull speed, the flatter part of the speed chart) requires twice the power. ?Conversely, halving one¡¯s power should slow one down by about a knot. Since you did not provide a displacement for your boat, I did a quick search and found that many 55¡¯ sailboats come in between 40,000 and 55,000 pound displacement. ?Given that, I did some quick calcs based on an assumed displacement of 50,000 pounds, or 25 tons. ?Personally, I am in the 1kW/ton camp (my boat achieves 95% hull speed at that power), so that would indicate a 25kW system for your boat. ? Working further with my displacement assumption, I would predict the following results:
Given these numbers, we can start sizing the motor, batteries and wiring. ?Most of the folks here have stayed with 48V systems for safety, ABYC considers up to 50V as low voltage, and greater than 50V as high voltage, ?High voltage systems should follow the additional requirements listed in ABYC TE-30. ?But with your max power draw of 25kW, a 48V system would pull 520A which isn¡¯t very practical or safe. ?Going to 96V brings your max load to 260A, getting better. ?And choosing 144V should keep your max power below 180A. ?144V components are readily available, i.e. motors, controllers, chargers, the DIY electric car guys have been running around this voltage for decades. ?Given your boat, I would choose 144V too. Personally, I find that 100Ah traction banks are pretty much the minimum for electric boats, and you may find that a pack that size gets worked harder that you might like. ?My pack is 160Ah and seems pretty good. ?But going with your planned 14.4kWh bank, we can see that 90% discharge could drive your boat for 8 hrs at better than 4kts, giving a battery only range of more than 30 nm. ?Even at 6kts, you should be able to run for more than 2 hrs on batteries alone. Ok, this response has turned out longer than I expected, but it should give you some new info to digest. ? I converted my boat to electric in 2010 and have been very pleased with how it has turned out. I have posted here extensively with detailed performance observations and predicted performance of other boats.Feel free to contact me here or off-list for more, if you like. Fair winds and following seas, Eric 1964 Cheoy Lee Bermuda 30, 5.5kW drive, 8kWh LiFePO4 battery bank Marina del Rey, CA PS. ?I am not a vendor, just a hobbyist/satisfied owner. |
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Hello Eric,? Thank you for the technical info. Every bit helps. I converted my 40ft sailboat with out any real investigation. I bought the 10kw thunderstruck kit. I ended up with a 3 to 1 reduction to keep it in a good power to rpm.? ?It turned out well. I started with 4 agm 12v 220ah? universal lead batteries which we connected in series. This was good but not enough range. I then built a 48v 360 ah battery lifepo4? I used 90ah 3.2v cylinder cells 4p4s? with appropriate sized bus bars. I use the ant bms to monitor during charge/ discharge. I am very pleased with the range and performance. I did have to add some lead to replace some of the weight to keep my water line from changing.? ?I would not go back to diesel to power my boat. We are building 48v systems for our own projects and friends. Not available commercially. but always willing to share what we know and absorb what we don t? ?best regards Larry
?Terminalift LLC 9444 Mission Park Place Santee, CA 92071 Ph: (619) 562-0355 F: (619) 562-2060
On Sunday, September 13, 2020, 09:34:48 AM PDT, Eric via groups.io <ewdysar@...> wrote:
Hi Steven, Welcome to the group! ?I can see that you¡¯ve done your homework and come up with a plan based on traditional sources. ?What we (the people in this group) have found over the last 10 years, is that the traditional powering models and calculators aren¡¯t quite right for electric conversions. ?The Dave Gerr book is a great resource, and I respect him greatly, but we¡¯ve seen time and again, that our end results are not close to his predictions (typically we need much less power than his formulae suggest). ?In conversation with Dave, he accepted that his work is more applicable to power boats operating at faster speeds. What we have found is that displacement is the most accurate indicator of how much power a boat needs. ?A rough rule of thumb for a properly designed electric marine drive is that 1kW/ton of displacement will deliver 90+% of hull speed, 1kW/1000# of displacement will deliver hull speed. ?Another observation is that increasing speed by 1kt (while staying under the 90% hull speed, the flatter part of the speed chart) requires twice the power. ?Conversely, halving one¡¯s power should slow one down by about a knot. Since you did not provide a displacement for your boat, I did a quick search and found that many 55¡¯ sailboats come in between 40,000 and 55,000 pound displacement. ?Given that, I did some quick calcs based on an assumed displacement of 50,000 pounds, or 25 tons. ?Personally, I am in the 1kW/ton camp (my boat achieves 95% hull speed at that power), so that would indicate a 25kW system for your boat. ? Working further with my displacement assumption, I would predict the following results:
Given these numbers, we can start sizing the motor, batteries and wiring. ?Most of the folks here have stayed with 48V systems for safety, ABYC considers up to 50V as low voltage, and greater than 50V as high voltage, ?High voltage systems should follow the additional requirements listed in ABYC TE-30. ?But with your max power draw of 25kW, a 48V system would pull 520A which isn¡¯t very practical or safe. ?Going to 96V brings your max load to 260A, getting better. ?And choosing 144V should keep your max power below 180A. ?144V components are readily available, i.e. motors, controllers, chargers, the DIY electric car guys have been running around this voltage for decades. ?Given your boat, I would choose 144V too. Personally, I find that 100Ah traction banks are pretty much the minimum for electric boats, and you may find that a pack that size gets worked harder that you might like. ?My pack is 160Ah and seems pretty good. ?But going with your planned 14.4kWh bank, we can see that 90% discharge could drive your boat for 8 hrs at better than 4kts, giving a battery only range of more than 30 nm. ?Even at 6kts, you should be able to run for more than 2 hrs on batteries alone. Ok, this response has turned out longer than I expected, but it should give you some new info to digest. ? I converted my boat to electric in 2010 and have been very pleased with how it has turned out. I have posted here extensively with detailed performance observations and predicted performance of other boats.Feel free to contact me here or off-list for more, if you like. Fair winds and following seas, Eric 1964 Cheoy Lee Bermuda 30, 5.5kW drive, 8kWh LiFePO4 battery bank Marina del Rey, CA PS. ?I am not a vendor, just a hobbyist/satisfied owner. |
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Eric,
That is an incredibly helpful reply! I'm going to spending some time reading more of your posts on the channel.? Your guess on displacement is spot on. With full fuel tanks and the diesel motor in place, it was a bit under 50,000 lbs. It's been as low as 45,000 pounds, and I'll likely shed a bit of weight as I draw down the diesel. But 25 tons is great for calculations. As I get it running, I'll be sure to feed back all the technical details to you and the group for one more set of data points. :-) I'll be digesting this info and starting to include it in my future calculations and plans.? Once again, thank you so much for your wonderful reply. I pray I'll be able to be as helpful on this list sometime in the future with some conversion experience under my belt! :-) Steve |
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Steve,
I came up with a different calculation than Eric.? Without more details not sure I can share anything else.? She is a big boat and I am aware of several of that size that have been converted to electric. Note I am a vendor.? Mike? Electric Yacht These where my assumptions: LOA???????????????????? 55ft LWL???????????????????? 49ft Displacement??? 50000lbs (1000lbs per foot) ? Speed & Power QuietTorque 60.0LC 96V PMAC Motor System???????????????? ????????????? Kts???????? Amps??? Watts?? (Calm Seas) 2.8???????? 10????????? 960??????? 3.4???????? 20????????? 1920????? 4.0???????? 40????????? 3840????? 5kW generator to support this speed 4.5???????? 60????????? 5760????? 5.1???????? 80????????? 7680????? 5.7???????? 110??????? 10560?? 6.2???????? 150??????? 14400?? 6.8???????? 200??????? 19200?? 7.3???????? 240??????? 23040?? 7.9???????? 310??????? 29760?? 8.5???????? 370??????? 35520?? 9.1???????? 460??????? 44160?? 9.6???????? 550??????? 52800????????????????? Hull speed????????? 9.38?????? |
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Thank you for this information?
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Best regards, Larry Schmitz On Monday, September 14, 2020, 10:53 AM, Mike Gunning <mike@...> wrote:
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Thank you so much, Mike!? This is very helpful. I actually looked deeply at the QuietTorque 60.0LC. It looks like one of the absolute best solutions for my boat. The professional look, ease of installation and excellent reviews really led me to consider it. Really, the only reason why I didn't end up going down the pre-build route is that my boat was built from the hull up by my father, uncle and grandfather over 12 years of effort. Everything has been hand built and designed. In order to fully participate in the experience and make the boat mine, I wanted to deeply dive into all the technical details of an electric conversion and then build from as close to scratch as I could. That said, I was recently in a rush and almost bought the QT60, but decided, in the breach, that I could lose another sailing season and build it myself.
I really like the breakdown, Mike.? I've actually created a graph with the estimates created from Gerr (from his book), Eric's feedback-based calculations from this list, and your experience-based calculations from building production systems.? I built a quick non-linear regression to fit a simple curve, then used it to predict a set of common values.? (I couldn't embed it and the normal upload to the forum isn't working. I was able to add it as an attachment, but can't find the attachment. So, there's a simple link below.) Thanks again, Mike! |
Mike Gunning