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Electric outboard drive for small cruisers

  • 29 Apr 2020 23:24
    Quote
    Reply # 8936415 on 8809939
    Anonymous member

    With that price it's definitely not a pure sine wave inverter. Spent some time last night trying to find some decent information about it but wasn't able to conclude whether it's fine or not to use a modified sine wave inverter to charge laptops (or in general). My hunch is it should be fine. I know my dad's been using cheap ones without issues (mainly to charge his laptop) and the one I currently have that came with the boat seemed to work just fine both charging laptops as well as powering a small oil heater last summer. Should be good with that then, at least for the time being. Consensus from what I found seems to be that it's mostly delicate equipment (and especially equipment containing timers) that require pure sine wave inverters.

    I also just ordered the aforementioned 200A Daly BMS and a bunch of MC4 connectors required for my 4 panels to connect them in series+parallel - 2x100W 12V connected in series on each side of the cockpit (mounted on the lifelines*), which are in turn connected in parallel for 400W total at 24V. Pretty close to a complete setup now.

    If someone noticed that I bought two DC-DC converters it's because I got the cheap 360W one off Ebay first some time ago and then today when buying the Victron charge controller I happened to spot the 60W one for €25 and made an impulse purchase, justifying it with that I'd use the higher quality one for essential equipment (navigation and whatnot) and to have some redundancy. Although I believe a lot of nav equipment (at least my Garmin 152) can run directly off 24V as well?

    *) Mounted on stainless tube from pushpit to stanchion #1. It fits 2 panels perfectly and allows for adjusting the panels in one axis, which should give considerable gains while still at anchor. From the perspective of cost-effectiveness it's a pretty good solution I think. Will need to wipe salt stains off them more often than if they had been mounted elsewhere like on an arc or on top of the cabin roof (where the dinghy lives) but that I can live with

    Last modified: 30 Apr 2020 11:18 | Anonymous member
  • 29 Apr 2020 17:20
    Quote
    Reply # 8935556 on 8935375
    Anonymous member
    Oscar wrote:

    Inverter/AC is another question mark... I don't feel like spending money (€200+) on a pure sine wave inverter and I'm unsure how good a modified sine wave inverter would be for the longevity of anything connected to it. Both me and my SO have Macbooks which run off 14-18V so might just build custom power supplies for them. Don't really need AC for anything else. There are these DC supplies for Macbooks but the 1 star reviews there make me feel a bit cautious. Then again I also have a cheap Windows laptop purchased solely for running Delftship which I might want to be able to power... a but a cheap inverter would probably do the trick for this.


    I bought this Bestek 200W inverter, £33.10, and it does just fine for charging my Macbook via the Apple mains adapter and iPad and iPhone via the USB sockets.
  • 29 Apr 2020 16:24
    Quote
    Reply # 8935375 on 8809939
    Anonymous member

    Here's what I've purchased so far (shipping costs included):

    Haswing Protruar 5 hp electric outboard £615.92
    4x Flexible ETFE 100W solar panels €345.11
    Victron SmartSolar MPPT 100/20A €175
    8x LiFePo4 190 Ah cells €1180
    DC-DC 24V -> 12V converter 360W €29.90
    Victron Orion C-DC 24V -> 12V converter 60W €25
    AiLi Battery Monitor/ammeter €38

    Total: ~€2500

    Still need:
    - BMS (maybe a 200A Daly for €113, still need to do some research)
    - various cabling/fuses/whatnot/small bits and pieces (sourced locally)
    - 24V -> 5V converter for Raspberry Pi (with 7" display running Openplotter) and mobile devices, haven't been able to find anything good as of yet (tips are appreciated!)

    Inverter/AC is another question mark... I don't feel like spending money (€200+) on a pure sine wave inverter and I'm unsure how good a modified sine wave inverter would be for the longevity of anything connected to it. Both me and my SO have Macbooks which run off 14-18V so might just build custom power supplies for them. Don't really need AC for anything else. There are these DC supplies for Macbooks but the 1 star reviews there make me feel a bit cautious. Then again I also have a cheap Windows laptop purchased solely for running Delftship which I might want to be able to power... a but a cheap inverter would probably do the trick for this.

    Last modified: 30 Apr 2020 10:58 | Anonymous member
  • 20 Apr 2020 10:21
    Quote
    Reply # 8910454 on 8809939
    Anonymous member

    Yes, Will Prowse suggests putting a thermostatically controlled heater mat under the battery.

    Reading through that charging instructions PDF, it would seem that the safest way to charge 2 x 12V Relion batteries in series for longest life would be one stage bulk charging to 28V, putting it at 95% of full charge, and then no absorption. Will Prowse recommends cycling charge and discharge between 10% and 90% of full charge.

    Since there's also a high voltage disconnect built into the Haswing motor, it seems to make sense to set 28V as the maximum charge voltage, so that the charger can remain connected while the motor is running without fear of losing power at an inopportune moment.

    Last modified: 20 Apr 2020 10:28 | Anonymous member
  • 20 Apr 2020 09:41
    Quote
    Reply # 8910412 on 8809939
    Anonymous member
    LiFePO4 batteries can safely charge between -20°C to 55°C (-4°F to 131°F). However, at temperatures below 0°C (32°F) the charge current must be reduced, until the temperature is >0oC (32oF), as follows:

     1. 0°C to -10°C (32°F to 14°F) charge at 0.1C( 10% of the battery capacity)
    2. -10°C to -20°C (14°F to -4°F) charge at 0.05C (5% of the battery capacity)

    Source: Charging instructions (PDF) from RELiON's documentation page.

    So they don't cut off the charging completely but instead lower the rate. That's interesting, didn't know that was an option. But I would've thought that it would be healthier to instead do it as you suggested, by placing a heating element inside the battery casing. The power consumption of that would be miniscule compared to the gains in charging rate.
  • 20 Apr 2020 08:12
    Quote
    Reply # 8910231 on 8905396
    Anonymous member
    Oscar wrote:

    Horst, I haven't decided on a specific BMS yet but in important thing to look out for (if it applies to your cruising ground) is that it has a low temperature cut-off (usually configured around 5 deg C) as LiFePO4 cells are damaged if charged below freezing. You can test if it works by putting the temperature sensor in ice cold water and measure whether the charging stops.

    An alternative to low-temp cutoff on the BMS would be to have it on the charge controller instead, if solar is your only power source. For example Victron sells separate temperature sensors that you can hook up to their products. That said I think it's more sensible to have it on the BMS level so that you're protected whatever charging method you use.


    I'm puzzled about how my Relion batteries seem to get around this. The data sheet clearly says that the temperature limits for charging and discharging are -20˚C to 45˚C  and -20˚C to 60˚C respectively. Could there be some self-heating that cuts in at low temperatures? Nevertheless, I should look at the charge controller manual and see if I can set a lower limit.
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    Last modified: 20 Apr 2020 08:16 | Anonymous member
  • 17 Apr 2020 15:13
    Quote
    Reply # 8905733 on 8809939
    Anonymous member

    I've just watched Will Prowse build a 24V LiFePo battery

    https://www.youtube.com/watch?v=E4pN4DVPOcY

    I thought he was very clear and informative on the process and possible pitfalls. Particularly, I went back over the preferred charging profile several times, as I will need to set up a user-defined charge profile on my MPPT controller:

    Charge limit:   28.8V

    Absorption voltage for maximum battery life:   28.2V

    Float voltage:   27.7V

    Charge/discharge bandwidth for long battery life:   26.6V - 25V

    Last modified: 17 Apr 2020 15:37 | Anonymous member
  • 17 Apr 2020 10:26
    Quote
    Reply # 8905396 on 8809939
    Anonymous member

    Nice initiative David!

    Horst, I haven't decided on a specific BMS yet but in important thing to look out for (if it applies to your cruising ground) is that it has a low temperature cut-off (usually configured around 5 deg C) as LiFePO4 cells are damaged if charged below freezing. You can test if it works by putting the temperature sensor in ice cold water and measure whether the charging stops.

    An alternative to low-temp cutoff on the BMS would be to have it on the charge controller instead, if solar is your only power source. For example Victron sells separate temperature sensors that you can hook up to their products. That said I think it's more sensible to have it on the BMS level so that you're protected whatever charging method you use.

    And it's obviously worth being skeptic about super cheap products. There are a lot of good independent reviews of solar equipment (battery cells, BMS's, solar panels etc) on Will Prowse's channel. Electricseas.org as you mention is a good resource as well, many interesting project threads to read through, and the article you linked to seems like a good read, thanks!

    I'll try to post here when I figure out what I'm going to buy and why. So far, in addition to the cells, I've also ordered a 24V to 12V converter.

    Last modified: 17 Apr 2020 10:27 | Anonymous member
  • 17 Apr 2020 07:29
    Quote
    Reply # 8905230 on 8809939
    Anonymous member

    I've edited the heading for this topic from "Electric drive for Weaverbird" to "Electric outboard drive for small cruisers", so that Oscar and anyone else who is adding outboard electric propulsion to boats in the 18 - 23ft range can post here, on their own work, and we can keep all the info we gather in one place.
  • 17 Apr 2020 02:24
    Quote
    Reply # 8904999 on 8896661
    Anonymous member
    I bit the bullet the other day when I found a great deal for 8x 190 Ah aluminium cells for €1180, so will have a 4.5 kWh battery bank. Now I see further reduced the price slightly, those cells would cost €1108 today. Will take a while to arrive from China though (30-60 days from looking at the comments in the reviews).
    On the website it says "Customers should configure a BMS..." What are you going to use? How to decide which BMS is working correctly with these cells?

    electricseas.org is an interesting forum when it comes to electric propulsion on boats. And this appears to be a good read about LiFePo4s on boats: marinehowto - lifepo4 batteries on boats
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