Electric outboard drive for small cruisers

  • 02 May 2020 00:24
    Reply # 8940497 on 8809939

    For my camper set-up, I got a DC-DC converter. The easiest and cheapest way I found for my laptop, which uses a USB-C tip, was a USB-C car charger (for the cigarette lighter socket). For my cellular signal repeater, I got a DC-DC converter brick from Amazon. This saved a lot of power lost in the DC-AC-DC conversion.

    Last modified: 02 May 2020 00:30 | Anonymous member
  • 01 May 2020 18:18
    Reply # 8939799 on 8809939
    It will also be harder on your AC power brick, which is likely to run hotter, whether or not this will cause it to die earlier, who knows.

    Better to be safe then, given that my (remote) job depends on having a proper working laptop.

    If you use your laptop a lot (like a navigation computer) it might be worth sourcing a DC-DC converter for it.

    During periods when I work it'll be running probably 10+ hours per day. For navigation I'll use a Raspberry Pi to keep the power requirements low.

    I've never tried this with a Mac.  Apparently their Mag connectors have an extra wire to see if the power supply is "valid".

    Yes, the middle pin is for this and apparently there's some electronics in the plug so I would just cannibalize an existing charger (I have a couple of spares) and hook it up to DC.

  • 30 Apr 2020 18:52
    Reply # 8937859 on 8809939

    A modified sine wave inverter should work.  It will be less efficient, on the order of twice or more the power loss of a DC-DC converter.  It will also be harder on your AC power brick, which is likely to run hotter, whether or not this will cause it to die earlier, who knows.

    If you use your laptop a lot (like a navigation computer) it might be worth sourcing a DC-DC converter for it.  We've used boost DC-DC converters for years to power our 20V laptops from 12V batteries.  They seem happier if they are somewhat oversized.  I've used cheap ($5-$10) 150W converter for our 90W laptops.  In an aluminum enclosure with external heatsinks, they have lasted for years, but run warm to the touch.  We have a newer commercial model, but haven't used it enough to know how long it will last.  We also have a very beefy model for running a 3D printer (I have a teen and preteen son, as well as never fully grown up myself :-)  

    I've never tried this with a Mac.  Apparently their Mag connectors have an extra wire to see if the power supply is "valid".   With a 24V battery, you would also need a Buck Converter rather than a Boost Converter.  I think a fair number of commercial trucks use 24V, there must be some kind of Mac solution for long-haul truckers.

    I did some back-of-the-envelope calcs.  Using an inverter vs a DC-DC converter, you will probably see about 0.4Ah additional power consumption per hour of laptop use from your 24V house bank.  Not enough to worry about if you have a single user and limited laptop use.



    A modified sine wave inverter should work.  It will be less efficient, on the order of twice or more the power loss of a DC-DC converter.  It will also be harder on your AC power brick, which is likely to run hotter, whether or not this will cause it to die earlier, who knows.

    If you use your laptop a lot (like a navigation computer) it might be worth sourcing a DC-DC converter for it.  We've used boost DC-DC converters for years to power our 20V laptops from 12V batteries.  They seem happier if they are somewhat oversized.  I've used super-cheap ($5-$10) 150W converter for our 90W laptops.  In an aluminum enclosure with external heatsinks, they have lasted for years, but run warm to the touch.  We have a newer commercial model, but haven't used it enough to know how long it will last.  We also have a very beefy model for running a 3D printer (I have a teen and preteen son, as well as never fully grown up myself :-)  

    I've never tried this with a Mac.  Apparently their Mag connectors have an extra wire to see if the power supply is "valid".   With a 24V battery, you would also need a Buck Converter rather than a Boost Converter.  I think a fair number of commercial trucks use 24V, there must be some kind of Mac solution for long-haul truckers.

    I did some back-of-the-envelope calcs.  Using an inverter vs a DC-DC converter, you will probably see about 0.4Ah additional power consumption per hour of laptop use from your 24V house bank.  Not enough to worry about if you have a single user and limited laptop use.

    Last modified: 30 Apr 2020 19:01 | Anonymous member
  • 29 Apr 2020 23:24
    Reply # 8936415 on 8809939

    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
    Reply # 8935556 on 8935375
    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
    Reply # 8935375 on 8809939

    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
    Reply # 8910454 on 8809939

    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
    Reply # 8910412 on 8809939
    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
    Reply # 8910231 on 8905396
    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
    Reply # 8905733 on 8809939

    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
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