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  1. #31
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    Quote Originally Posted by MLA View Post
    it requires 2 relays per pump to revers its polarity. This is too complicated considering that a standard Carling DPDT rocker will do this for you and carry the load. The pump only requires 12ga wire and has a continuous current draw of about 15A. I suggest passing on the relays, locate the pump's fuse block under the helm and feed it with with ample cabling from the battery.
    I agree 100%, that is what I did. No need for relays (Listen to MLA, he has helped me out on a few wiring single lines)
    Sent by the random thoughts from the voices in my head...

    Eric.

  2. #32
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    Quote Originally Posted by MLA View Post
    it requires 2 relays per pump to revers its polarity. This is too complicated
    Yes, 2 per pump but I disagree about it being too complicated, just a little more complicated. You trade off some cheap relays for the heavy/expensive wire. Overall, it's a less expensive solution. The relays are another failure point but they are pretty reliable - In 20 years, I've had one failure in my '84 Jeep and no failures in any other vehicles. I'm making the assumption that the engine will be running while filling so I'd rather take up to 80A right near the alternator instead of running that current on the battery cables.

    But... I have an ulterior motive. I'm dreaming up a geek project and would definitely need the relays for a control system.
    2007 Mobius LSV
    1989 Sanger Skier DX - sold

  3. #33
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    Oct 2010
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    Lake Wylie NC Area
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    When you quote only half the statement, it changes the entire context. 2nd, even with the engine running, you will actually be pulling the current through the battery cables, from the battery. As mention, that new fuse block needs to terminate directly to the battery. Therefore, you would not be pulling any additional current through the existing boat battery cables. The only other safe place electrically, to terminate that fuse block, would be on the main B+ starter post. So contrary to your vision, your setup would actually be pulling through the battery cables.

    If the batteries are in the port side mid-ship locker, then you are only looking at about 12ft of 4ga cabling to run the B+ and B- to the helm for that fuse block.

    Just a different approach, thats all.

  4. #34
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    Quote Originally Posted by MLA View Post
    When you quote only half the statement, it changes
    Sorry, it wasn't my intention to change the context, just reference my response. (OK, this time I intentionally loped it off)
    Quote Originally Posted by MLA View Post
    The only other safe place electrically, to terminate that fuse block, would be on the main B+ starter post.
    Right, this is my initial plan. I wasn't clear when I said "near the alternator" I meant electrically, not just physically. (But to be clear it's the + terminal of the starter relay not the starter.)
    Quote Originally Posted by MLA View Post
    even with the engine running, you will actually be pulling the current through the battery cables, from the battery
    Because the alternator isn't generating this much current at idle or based on connecting to the battery posts? I was thinking about this and I don't know any specs for the alternator. Any idea what it's generating at idle? From experience, if you run 3-4 pumps while at idle, does the system voltage drop to 12V such that you know you're getting everything the alternator has and the battery is supplementing the rest?
    2007 Mobius LSV
    1989 Sanger Skier DX - sold

  5. #35
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    Right, this is my initial plan. I wasn't clear when I said "near the alternator" I meant electrically, not just physically. (But to be clear it's the + terminal of the starter relay not the starter.)
    And to be a little more clear, boats often times use a starter relay in addition to the starter mounted solenoid. And when I reference the starter, I include the starter motor and solenoid together since this is a GM style v's an old ford style with a fender mounted solenoid, in which case the starter motor actually has a cable connected to it.

    The starter relay is on the starter solenoid side between the key switch and solenoid. That circuit was never intended to carry any other additional loads such as ballast pump. There may be a helm breaker in the engine bay that is fed directly off the starter's main B+ post. in theory, you could terminate to the starter feed side of that breaker, but not the helm side. But, you would have to consider the cable gauge. In many cases, its as little as 10ga, but can be as large as 4ga. So, this would bring us back to going directly to the starter main B+ that is connected directly to the battery B+ with possibly a 2/0 cable.

    Because the alternator isn't generating this much current at idle or based on connecting to the battery posts? I was thinking about this and I don't know any specs for the alternator. Any idea what it's generating at idle? From experience, if you run 3-4 pumps while at idle, does the system voltage drop to 12V such that you know you're getting everything the alternator has and the battery is supplementing the rest?
    Regardless of where in the circuit the load is terminated, the battery is the primary source and the alternator is there to keep up with loads and replenish lost battery voltage. In a practical sense, the higher the potential load, such as 4 pumps pulling 15-20 amps each, the closer you terminate to the battery, the better the entire circuit will be.

    The regulators output is based on load, but is also dependent on engine rpm. Even with a stereo pulling 120A, you wouldnt see a 60A alt peak, its just doesnt happen. if your battery drops below 12V with some pumps running for a few minutes, you need to test that battery.

    I dont want you to think im downing your use of relays. Its a sound practice and your system in theory, is sound, other then I would suggest terminating directly to the battery. But given thats its going to take 8 relays and somewhere to mount them all, I think its overly complicated, considering a switch with a labeled actuator is readily available.

  6. #36
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    Quote Originally Posted by MLA View Post
    So, this would bring us back to going directly to the starter main B+ that is connected directly to the battery B+ with possibly a 2/0 cable.
    I think we are really talking about the same thing just in two different places. I am talking about connecting to this same node of the circuit. It is the same as the battery + connection. I just want to connect on the engine side of the battery cable. The alternator and the battery connect together at the starter (relay, solenoid or whatever we call that point). That is the main +12V rail of the system, no fuses or protection, only limited by the supply of the alternator (or battery if not running).
    Quote Originally Posted by MLA View Post
    Regardless of where in the circuit the load is terminated, the battery is the primary source and the alternator is there to keep up with loads and replenish lost battery voltage.
    I disagree with you here. When running, the alternator is the primary source of a vehicles electrical system. It operates at ~14V and the battery is actually a load until it charges up and then it is neither a source nor a load in the DC system, it's basically invisible. (It is a capacitor so it will filter higher frequency signals but let's ignore that and say that everything in a vehicle is running DC/steady-state.)
    Quote Originally Posted by MLA View Post
    I dont want you to think im downing your use of relays.
    I don't think that at all. I appreciate your ideas perspectives. I came to these forums to bounce my ideas off of people like you.
    2007 Mobius LSV
    1989 Sanger Skier DX - sold

  7. #37
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    Below is the single line that MLA helped me with my current boat, didn't use relays and I am not sure what benefit you would get out of adding relays in.

    And I am not trying to argue any point, but more of being curious.

    Attached Images Attached Images
    Sent by the random thoughts from the voices in my head...

    Eric.

  8. #38
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    Quote Originally Posted by EricU View Post
    I am not sure what benefit you would get out of adding relays in.
    My main priority for wanting to use relays is to have a way to control the pumps using a micro-controller.

    A secondary benefit is to limit the bulk of large gauge cables. Using just the rocker switches, the 5 lines to the pumps need something like 12g wire and this runs from the rocker switches back to the pumps most likely in/near the engine compartment. If you mount the fuse block near the pumps and use relays on those lines, then you only need short bits of the 12g wire to go from fuse to relay to pump and little control wires to go from the rocker switch to those control relays - this could be sprinkler control cable (1 cable with 10 wires).

    Your drawing is spot-on. The only difference for me is that I will connect the fuse block to the blue box that represents the starter so that I only run a few feet of the 2 gauge cable. I would definitely rather run 5 pairs of 12 gauge wire from the helm/batteries to the engine than 1 pair of 2 gauge cable that same distance.
    2007 Mobius LSV
    1989 Sanger Skier DX - sold

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