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Charging the bow thruster battery in my 288?

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    Charging the bow thruster battery in my 288?

    Hi!
    So it seems like my bow thruster battery (mounted next to thruster) isn't connected to the rest of the system.
    There is a BEP DVSR there, but I'm not yet sure how it is used. There are no thick cables going to this battery, and I find it a bit weird.
    I don't even know if it has common ground with the rest of the boat...

    The previous owner has mounted a separate charger, plugged in the nearest outlet which of course only works when on shore power (which is most of the time though).

    So what's normal here? Checking prices on cables to run from the aft battery bank to the bow thruster battery seems like it'll set me back $3-400 for black and red 35mm2 cables...

    I've been thinking of adding another outlet (from shore power) next to the battery, and wire it to the "accessory" fuse on the shore power panel. It's not in use, and can provide up to 5A. That way I can switch the charger off separately. The charger will still be connected to the battery though, so hopefully that doesn't mean it'll draw power from the battery...

    Anyways - does this make sense rather than hooking it up to the aft batteries? Is it good or bad to leave the systems separated? I'm nervous of problems related to corrosion/ground issues etc.
    The bow thruster isn't really used that much, so in theory it is fine to just have it on its own charger. But at the moment it's the cheapest charger you'll find nearby, so I'd probably replace it to something that's made for being constantly connected.

    Thought: Would a DC-DC charger make more sense? One that's just 5-10A so I won't have to spend my summer budget on wiring?

    That way it would prioritize the thruster battery, rather than charging the rear bank THEN the thruster like a DVSR would (and require beefier cables). A smart DC-DC charger would also monitor the battery which it is charging from.

    #2
    It seems the previous owner was wrong.
    I took a look today, and there are wires there, probably 10 or 16mm2 (6-8 AWG)?

    The relay has a black thin wire connected to the battery, and the larger positive cable is going through the relay, which isn’t DVSR, but VSR. After tracing it I did find it behind the battery banks, looks like it has corroded and possibly been ripped out of a cable clamp. I couldn’t find any traces of a clamp, so
    it's probably been like that for ages. I secured and isolated the wire, and I’ll try hooking it up to the house bank when I got the tools.

    The other charger is gone, it’s now only the original.

    So is it safe to connect? The cables seem a bit thin to connect two batteries to each other IMHO.

    How about VSR vs DVSR, what’s the difference?

    Comment


      #3
      if there is a battery in the bow and its a short run to the thruster, a 10 gauge wire is probably sufficient... when the thruster is being powered by the batteries in the aft end of the boat, large wires are necessary to carry the amps needed, even though the thruster doesn't draw amps like a windlass...
      ...
      run an AC circuit, originating from where the main batt chargers connect in, to the front of the boat to the charger for the thruster battery.... then when one charger has power, they ALL have power... this will be the best, most efficient, and probably, most affordable way to do it....


      NU LIBERTE'
      Salem, OR

      1989 Bayliner 2556 Convertible
      5.7 OMC Cobra - 15.5x11 prop
      N2K equipped throughout..
      2014 Ram 3500 crew cab, 6.7 Cummins
      2007 M-3705 SLC weekend warrior, 5th wheel
      '04 Polaris Sportsman 700 -- '05 Polaris Sportsman 500 HO
      Heavy Equipment Repair and Specialty Welding

      Comment


        #4
        ...............
        Originally posted by DIYglenn View Post
        Hi!
        So it seems like my bow thruster battery (mounted next to thruster) isn't connected to the rest of the system.
        There is a BEP DVSR there, but I'm not yet sure how it is used. There are no thick cables going to this battery, and I find it a bit weird.
        I don't even know if it has common ground with the rest of the boat...
        The VSR would ideally be mounted in the engine bay where it would then take a divided portion of the alternator's charge rate and send it to the thruster battery.
        The thruster battery would require a negative connection to the System Negative Common.
        The cables from the thruster battery to the controller should be heavy enough for the thruster motor's Amp Load.
        .

        The previous owner has mounted a separate charger, plugged in the nearest outlet which of course only works when on shore power (which is most of the time though).
        IMO, that is silly.

        So what's normal here? Checking prices on cables to run from the aft battery bank to the bow thruster battery seems like it'll set me back $3-400 for black and red 35mm2 cables...
        I can't say what is "normal", but I will say that having a dedicated forward located thruster battery poses several issues:
        .... it adds one more battery to your system.
        .... it requires the need to receive a charge, and sooner than later.
        .... it does however, place weight forward of which is a plus.
        .... if using a wet cell battery, it may give off undesirable gasses into the forward area.



        I've been thinking of adding another outlet (from shore power) next to the battery, and wire it to the "accessory" fuse on the shore power panel. It's not in use, and can provide up to 5A. That way I can switch the charger off separately. The charger will still be connected to the battery though, so hopefully that doesn't mean it'll draw power from the battery...
        I would use the VSR (or an ACR) and take advantage of the engine alternator and/or the On-Board charger that you have for the other batteries.
        The charge leads (both Positive and Negative) running forward would need to be sized correctly..... probably 10 ga would do it.


        Anyways - does this make sense rather than hooking it up to the aft batteries?
        I see no reason why you could not eliminate the thruster battery, and run heavy cables up front that would be powered by your HLBB (house load battery bank).
        Your thruster operation will certainly not over-burden your HLBB Amp Hour capacity.
        It would be no different from that of a Windlass.



        Is it good or bad to leave the systems separated?
        Again, the weight forward is a plus.
        However, and as mentioned, it does add yet one more battery that needs to be charged and maintained, not to mention periodic replacement.


        I'm nervous of problems related to corrosion/ground issues etc.
        The thruster battery Negative Does NOT need to be in common with the rest of your Negative system.
        It will only need to be in common with the rest of the Negatives, if you use the VSR or an ACR in order to take advantage of the engine alternator or On-Board charger.
        Now, depending on how the thruster's controller circuit is wired, it may need to be connected to the ship's System Neg Common.
        I would need to see a schematic.



        The bow thruster isn't really used that much,
        Under that premise, that's all the more reason to power it from the HLBB.

        so in theory it is fine to just have it on its own charger.
        That becomes yet one item to maintain and/or replace.

        But at the moment it's the cheapest charger you'll find nearby, so I'd probably replace it to something that's made for being constantly connected.
        Keep in mind that the charger is only functional while on Shore Power or when you run your generator.
        Whereas with the HLBB, it will receive a charge while under way and/or via shore power and the On-Board charger.


        Thought: Would a DC-DC charger make more sense? One that's just 5-10A so I won't have to spend my summer budget on wiring?
        Bite the bullet and pick up the necessary cables and run them forward.
        Take the Negative to the engine block (system negative common).
        Run the Positive forward from the Common terminal of your MBSS.
        Either battery bank will power the thruster depending on which battery is selected.

        You'll do this one time only.... and you'll no longer need to worry about it.


        That way it would prioritize the thruster battery, rather than charging the rear bank THEN the thruster like a DVSR would (and require beefier cables). A smart DC-DC charger would also monitor the battery which it is charging from.
        I think that you lost me on that one!

        Here is an example of what I am suggesting.
        The ACR shown in my schematic will perform the same task as a VSR would by supplying the engine alternator charge rate to both battery banks.




        Click image for larger version  Name:	MBSS 2 batt system with bow thruster.jpg Views:	3 Size:	225.2 KB ID:	578755
        Rick E. Gresham, Oregon
        2850 Bounty Sedan Flybridge model
        Twin 280 HP 5.7's w/ Closed Cooling
        Volvo Penta DuoProp Drives
        Kohler 4 CZ Gen Set

        Comment


          #5
          The main problem with running large cables forward is the cost/size of them. On my 2858, I estimate that its about 35 feet (one way) from the battery switch to the thruster, with the thruster pulling somewhere in the neighborhood of 200 amps that's going to need 1/0 or larger. If you mostly use your boat going dock to dock, then having a plug in charger should be fine, the thruster battery will get charged up whenever you're hooked to shore power (this is how I currently have mine set up). The main reason to want to charge the thruster battery from the alternator is if you're spending days away from shorepower - in which case you can run smaller wires (I have the stock alternator). I'm not an electrician, but my read is that you need an isolator so that if the thruster battery is drained you don't accidentally pull 200 amps through the smaller wires.
          You mentioned the 12v-12v charger, but other items worth looking at are:
          https://www.sterling-power-usa.com/batteryisolator.aspx

          I'm leaning toward the
          https://www.sterling-power-usa.com/P...olator-12.aspx
          as it seems like it would simplify the charging system somewhat - wire the alternator to that box, then wires to the start, house and thruster banks, but it still needs decently large cables for the long run forward, I think that 4awg would probably be adequate but I might go 2awg if the cost differential isn't too bad.

          1998 Bayliner 2858
          7.4L MPI / Bravo III
          Harbour Village Marina - Kenmore WA

          Comment


            #6
            6 seconds of operation @ 200 amps = approx .333 Amp Hours.
            20 seconds of operation @ 200 amps = approx 1.11 Amp Hours.
            40 seconds of operation @ 200 amps = approx 2.22 Amp Hours.
            60 seconds of operation @ 200 amps = approx 3.33 Amp Hours.

            How many 20, 40 or 60 second bow thruster cycles will you use between battery charges via shore power and On-Board charger?
            Rick E. Gresham, Oregon
            2850 Bounty Sedan Flybridge model
            Twin 280 HP 5.7's w/ Closed Cooling
            Volvo Penta DuoProp Drives
            Kohler 4 CZ Gen Set

            Comment


              #7
              Thank you guys for the replies, learned a lot by some responses here.
              I think I’ll try reconnecting the VSR for now, and do some measurements, how much is drawn etc. I’ll try to measure the thickness of the current cables better as well before I do anything else.

              Comment


                #8
                Glenn, it would be very helpful if you were to put together a simple schematic (showing the VSR interface with the thruster battery) and post it here.
                Rick E. Gresham, Oregon
                2850 Bounty Sedan Flybridge model
                Twin 280 HP 5.7's w/ Closed Cooling
                Volvo Penta DuoProp Drives
                Kohler 4 CZ Gen Set

                Comment


                  #9
                  Will do once I've had time to double check the connections. Found some other wires hanging there as well, need to tidy up the electronics on this vessel.

                  Comment

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