-----Original Message-----
From: Michael Ryan mryanqld@gmail.com [electricboats] <electricboats@yahoogroups.com>
To: electricboats <electricboats@yahoogroups.com>
Sent: Sun, Feb 25, 2018 10:42 pm
Subject: Re: [Electric Boats] Re: Direct Drive QS Hub Motors
Oh I forgot to address your question! Yes for a Nordic 17, 200ah at 48v, LiFeP04, will be a tremendous bank. Run time of course will depend on throttle setting as well as reduction ratio and prop size/pitch. But 15 hours at 10a will bring you down to approximately 25% capacity, which is not okay with FLA batts but as I understand is acceptable with LiFeP04 or other lithium types. 10a should push your Nordic along at close to 3kt I am guessing. Better have some deep pockets... that bank won't be cheap. You will want a good BMS and if you are going for that fancy a bank, maybe active cooling as well. Fuses between cells. You should never need more than 40a current through the pack, so I would fuse appropriately (50a? 100a?) unless you think you would ever want to show off a bit and run the motor at 300a to impress bystanders LOL. BTW, you can only do that for about a half minute before everything starts going north on you. I would guess your hull speed to be just a hair under 5kt? I am thinking you can get 80% hull speed at 40a or so. As you break 50% hull speed, the power/speed curve steepens up a lot. As you approach hull speed you start giving a lot of power and getting very little speed increase. Which impacts the range of your bank, or the size bank needed to make the desired range. At 1kt, you probably have close to 80 hr run time if you have no house loads other than nav lights and cell/vhf charging. Again, just a guess. For 6 hours run, you could probably go at around 22a I imagine. 1kw to be more realistically conservative.
The Nordic will carry the weight which is probably a little over 200lbs with mounting and stuff, (you will be down in the water a tiny bit but she will still go just fine. Think of it as another large-ish passenger.) but it will be a challenge to find the space. Especially if you allow proper spacing between cells. I really don't like the practice of installing high C capable cells chock a block like I see in so many pictures. I haven't heard of any thermal runaway catastrophes on electric boats yet, knock on wood, but you would not want to be forever immortalized as having the first one. Some "experts" will of course say it is perfectly okay to cram them together because of the ventilation ribs in the case. Whatevah. I'm not the expert, just a guy who would not want an uncontrollable, amazingly fierce fire on his boat.
Since your Nordic is not a sailboat, it is an excellent candidate for solar panels. About 500w of solar charging will greatly extend your range and probably give you well over 2kt without drawing the batts down, in optimum conditions while the sun is high. If you get stranded with dead batts, a sunny day at anchor and you should be good for getting back home.
Bottom line, yeah if you have the space, and the $, that would be a great bank for your boat.
---In electricboats@yahoogroups.com, <mryanqld@....> wrote :Hi All I have gone cold on the QS motors for a number of reasons. My plan now is to buy a 5KW Thunderstruck kit complete with a reduction unit and fit it to the Nordic 17. They seem to be the best value and are a popular choice for DIY. I am OK with the mechanical side of boat propulsion and basic 12 volt electrical systems but have a lot to learn about electric motors and controllers. I know this is dumb question and their are a lot of variables but what LiFePO4 battery bank capacity do I need to get a six hour run timeat 48v?... My budget could run to 16 x 3.2 Volt 200ah Calbs or Winstons is this enough? The motor used in the kit is a ME1305..
Posted by: Grant Perry <emmott@aol.com>
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