Electric outboard drive for small cruisers

  • 25 Mar 2020 10:45
    Reply # 8857430 on 8809939

    Good subject and lots of useful info.  
    I have to say that soldering wires is an art I have never mastered, copper pipe fitting I can do.

    Plain, un-tinned  copper will corrode at the joint, would solder tinning the wire ends before crimping be a good idea?  Likewise a copper strap.

  • 24 Mar 2020 19:25
    Reply # 8854329 on 8854277
    Deleted user
    Anonymous wrote:

    It depends... for making the cells into a battery, they provide copper straps which need no soldering (most other cells would be similar having screw on terminals). However, if you are going to make your own cables (which will probably be needed) most people like to use solder even with crimp ends to keep oxygen and water out of the join. There are others who say crimp only as the join may heat and the solder run out and the join fail. Certainly crimp first and solder after as the crimp is what gives a good mechanical join.


    A properly done crimp shouldn't need anything else.  With a proper crimp the wire "cold flows" into an airtight mass.   Add some glue-lined heatshrink and you should have a lifetime connection.  If you can't do or get a proper crimp done, then adding solder might help, but is definitely second best.  The problem most folks will run into is that by the time you get a part as large and heavy as battery cable hot enough to solder, it is very easy to have the solder wick along the wire.  This leads to a stress riser between flexible wire and hard solder that is prone to breaking strands and creating a high-resistance failure point.  If you solder you have to be very certain that you also restrain the cables well beyond the joint so that the fragile transition between solder and cable doesn't fail.  If you are going to solder do some test pieces and then destroy them and see how far the solder has moved along the wire.

    Crimpers for small wire gauges are cheap.  If you are doing lots of large wires then even a big crimper is pretty cheap spread over the job.  Also, online and locally it is not hard to get crimps done on big wires fairly inexpensively.  One of the great things about LiPO4 batteries is that they can provide and accept astounding currents.  However, this can also end up testing the reliability of your connections.

  • 24 Mar 2020 19:11
    Reply # 8854313 on 8853495
    Deleted user
    Anonymous wrote:

    Darren,

    Excellent tips regarding the charge controllers, thank you!

    Jami,


    As for LiFePo4 in general I really don't see any practical reason* for anyone to use lead acid batteries for anything anymore, so I would've switched even without converting to electric motor. When you factor in usable amp-hours and overall life expectancy, LiFePo4 is actually less expensive and a far superior battery technology.

    *) except short-term financial


    LiPO4 do have some problems, that mean they're not the best choice for everyone:

    1) They are damaged if charged below freezing temps.  This can be overcome, but if you have depleted batteries and can't use them to warm themselves you can get yourself into a pickle.

    2) They have a habit of destroying alternators if all you do is add them to an existing boat.  Their high charge acceptance rate will cause many alternators to kill themselves trying to supply the batteries.  This can be overcome, but it means LiPO4 is not a drop-in solution.

    3)  You have to have a functioning BMS to keep them working.  With lead-acid batteries you can charge them in all sorts of unsophisticated ways in a pinch.  Not so with LiPO4.

    4)  With LiPO4, a single error in over-discharge can destroy the batteries and leave them inoperable.  A BMS should prevent this, yet there are lots of examples of LiPO4 being destroyed this way.

    They're still a fantastic battery choice, but there are ways in which lead acid are better.  Something like Firefly carbon-foam AGM can offer a better compromise for someone who wants high-performance with fewer headaches.  For someone who is technically inclined, or with deep pockets, Lithium might make a better choice.



  • 24 Mar 2020 18:59
    Reply # 8854305 on 8809939

    The Haswing motor came with a short cable with crimped terminals and heat-shrink, to link two 12V batteries. It's not as large in diameter as the 25mm2 cables that are permanently installed in the motor; I think it's only 16mm2. I've assembled it for the moment, just for trials, but the right solution must be a short flat bar of copper, brass or aluminium, with the two batteries close together. Thanks, Len, for the idea of flattening some copper tube. I calculate that standard 15mm tube will give me more than 35mm2 cross sectional area.

  • 24 Mar 2020 18:40
    Reply # 8854277 on 8853569
    Anonymous wrote:

    Do I understand correctly: with those CALB cells you don't even need to solder to make a battery yourself? Soldering (which I just don't seem to master) is the main problem I've been afraid of so far, when thinking of a DIY lithium battery.

    To keep the budget down, one could make a 100Ah 24V battery first, and add another one later - right?


    It depends... for making the cells into a battery, they provide copper straps which need no soldering (most other cells would be similar having screw on terminals). However, if you are going to make your own cables (which will probably be needed) most people like to use solder even with crimp ends to keep oxygen and water out of the join. There are others who say crimp only as the join may heat and the solder run out and the join fail. Certainly crimp first and solder after as the crimp is what gives a good mechanical join.

    Copper straps are easy to make. Use copper water pipe pressed flat, cut to size and drill holes for the terminal screws. The shrink wrap is a nice touch but electrical tape will serve as well.

    Yes more cells can be added in parallel later. Most people suggest the exact same kind or at least the same AH but in practice with a slower charge rate that is not needed.


    Last modified: 24 Mar 2020 18:42 | Anonymous member
  • 24 Mar 2020 13:44
    Reply # 8853569 on 8809939

    Do I understand correctly: with those CALB cells you don't even need to solder to make a battery yourself? Soldering (which I just don't seem to master) is the main problem I've been afraid of so far, when thinking of a DIY lithium battery.

    To keep the budget down, one could make a 100Ah 24V battery first, and add another one later - right?

  • 24 Mar 2020 13:04
    Reply # 8853495 on 8809939

    Darren,

    Excellent tips regarding the charge controllers, thank you!

    Jami,

    The cheapest option (apart from buying second-hand cells, which would be a viable option) I've found would be CALB cells. Example:

    https://www.aliexpress.com/item/4000303299745.html

    With these 12V/100Ah would be about €400 (€800 for 24V/100Ah, €1.6k for 200Ah).

    In addition you'll need a BMS, which will set you back between €30-200 depending on type/features. If you aren't planning on sailing in freezing temperatures you don't need low temperature cutoff and a Daly would work fine, although it would be a good insurance to have it anyways (if you forget to unplug chargers when wintering).

    So for 24V/200Ah €1800 would be in the ballpark.

    If buying used cells (90% capacity) it could probably be closer to €1000 although I haven't looked into this extensively. Another cheaper option that some go for is to buy a used electric car battery pack. The problem with this is that they are mostly lithium-ion, which can be a fire hazard, so LiFePo4 is the way to go. LiFePo4 also has better discharge rate and is non-toxic.

    Another option (probably better but slightly more expensive) would be to get 200Ah cells.

    As for LiFePo4 in general I really don't see any practical reason* for anyone to use lead acid batteries for anything anymore, so I would've switched even without converting to electric motor. When you factor in usable amp-hours and overall life expectancy, LiFePo4 is actually less expensive and a far superior battery technology.

    *) except short-term financial

    PSA: You can find a lot of good information, reviews and tests in Will Prowse's Youtube channel.

    Last modified: 24 Mar 2020 13:04 | Anonymous member
  • 23 Mar 2020 17:22
    Reply # 8849999 on 8809939

    But now that lockdown seems imminent, and Scotland doesn't want visitors overloading its infrastructure, the project has to be considered as being on hold. It doesn't seem sensible to proceed with installing the solar panel. If I am spared, there might be a short cruise to be had in the Autumn, but nothing before then.

  • 23 Mar 2020 17:18
    Reply # 8849992 on 8809939

    Yes, I was thinking of something of the sort. The magnetic key comes with a lanyard and a clip which will attach to the pushpit, but I was thinking of an additional Velcro band or perhaps just duct tape, though it would be good to be able to remove the key easily to prevent unauthorised use.

  • 23 Mar 2020 15:13
    Reply # 8849687 on 8809939
    Deleted user

    I wonder if it might be worth gluing the kill switch in place?  I've never known anyone to use the kill switch as designed on a sailboat as large as Weaverbird.  However, I have experienced pulling the outboard start cord multiple times (longer than I care to admit) to no effect because the kill switch was not in place.  Also, with a standard red-outboard-button-kill-switch, should the "key" for the switch go over board or get lost, you can substitute anything that would lift the button of the kill switch.  With a magnetic kill switch it might be hard to find something on board to substitute.  In a dinghy a kill switch makes sense, but I think it might create more of a hazard on a larger boat. 

    Congrats on an other step towards freeing yourself of infernal combustion.

       " ...there is nothing - absolutely nothing - half so much worth doing as simply messing about in junk-rigged boats" 
                                                               - the Chinese Water Rat

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