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Thread: SHTP Electrical Seminar

  1. #1
    Join Date
    Sep 2007

    Default SHTP Electrical Seminar

    Was October 19, 2009 at KKMI's Boathouse . . . thanks to all who attended!

    Race Co-Chair Rob Tryon is working on this one and needs your questions! We want to keep this relevant to the race, and questions from YOU will help us do that.

    I'll "prime the pump": My engine panel is installed low in the back of the cockpit. If it gets soaked, the key may not work and I won't be able to start my engine to charge batteries. I made a cover for the panel but it still isn't completely watertight. This leads me to my question:

    Having grown up in East Oakland, I know you can hotwire a car pretty quickly. If necessary can I start my diesel that way? How?

    Please send your electrical system questions to Rob or me at:

    Also, be sure to put the seminar on your calendar.

    Last edited by BobJ; 10-20-2009 at 12:57 PM.

  2. #2
    Join Date
    Sep 2007


    I'll add this to the problem - even if you jump-start the engine, you may still not be able to charge the batteries because power to the regulator may come off the failed ignition switch! (At least it does on mine..) Now what do you do?

    Oh, and here's another one. If you don't have an energy monitor installed, how can you tell how many amps your alternator puts out to charge the batteries?

    - Mark
    Last edited by Alchera; 10-04-2009 at 04:34 PM.

  3. #3
    Join Date
    Sep 2007


    Hmm, my regulator is also wired to the key switch - I hadn't thought of that.

    I have a 35 amp alternator (and a battery monitor) but the monitor rarely shows the batteries getting anywhere close to 35 amps - sometimes it shows as little as 3-4 amps. Is my alternator not working?

  4. #4
    Join Date
    Sep 2007


    I'll add an alternator question.

    We all know we musn't switch off the electrical system while the engine is running, because it can blow out the alternator diodes. But is this supposed to be instant irretrievable disaster, or is it just a risk, and how big a risk?

    A couple of times I've absentmindedly switched off when I intended to pull the fuel cutoff, and my alternator still seems to work.

    Has anyone thought of wiring a relay into the system so that as long as the engine is running you can't switch off the electrics? What would you tap into to energize the relay? Any risk in doing this, eg fire hazard?

    I know I could add a Zap-Stop. Is this a one-time sacrificial fix, or is it good indefinitely? And what exactly is a Zap-Stop? Can I scrounge a cheap substitute, or do I have to pay the ~$30 for the real thing?

    OK, I guess that's several alternator questions.


  5. #5
    Join Date
    May 2009

    Default Charging batteries

    Okay, several pretty basic questions I think.

    I have 2 house batteries, and I typically use one to run the systems while keeping the other in reserve for starting the engine or for emergency. Both are AGM, deep cycle but rated for starting also. (I would prefer a dedicated, third starting battery, but I'm hoping not to add that project to the list.)

    Using the engine to charge the batteries:
    1. If one battery is fully charged (or very nearly full) and one is 50% down, should I charge both or each one separately?
    2. If I leave them both in the charging circuit, do I risk damaging the full one, and how could the regulator possibly know the difference?
    3. Will it take longer if I leave them both in the circuit, or perhaps will one not receive a full charge (because of how the regulator works, perhaps)?
    4. I have a wired-in voltmeter and ammeter, nothing sophisticated, and with these can I determine when (let's assume) a single battery is fully charged? (I have read that the voltage on a battery should be read after it has "rested" following a charge--something to do with equilibrium between the electrolyte, cathode and anode?)
    5. Wishing it were not true, but guessing it is... related to the last question: obviously the output of the regulator is above the battery's present voltage, so while charging, the reading on the wired-in voltmeter must be higher than the battery's voltage, right? so would I need to turn off the engine (or take the battery out of the charging circuit) and wait until the battery is rested before using the voltmeter reading to assess state of charge?
    6. The simple question is, how can I know how long I should charge? and one at a time or both?
    7. What RPM is best?
    8. Can I switch from 'Battery 1' to 'Battery 2' on the fly, while the engine is running, without damaging anything (the switch does not pass through 'off' to go from '1' to '2'... I think it passes through 'both'.. i'll have to check this)
    9. If it is recommended to add a monitor for state of charge, is there one that does the trick while charging? high, med, or low install challenge?



  6. #6
    Join Date
    Sep 2007


    I'm dyin' to answer some of these but I don't want to steal Rob and Ron's thunder!

    Great real-world Q's - keep 'em coming!

  7. #7
    Join Date
    Sep 2007

    Default some good deals...

    If you are planning your electrical setup I might have some good deals for you....

    I have 2 8G31DT Gel batteries, 98Ah each that I'm happy to part with (only used for 1 Transpac Race)

    I also have a never used Balmar 712-80 alternator with the MC-612 regulator. I had to do a full repower prior to my Transpac and the alternator didn't fit the new engine.

    All combined should be upwards of $1200, first $500 can take it all!!!

  8. #8
    Join Date
    Oct 2007
    Alameda CA

    Default Solar panel pulse charging systems

    I am curious about the possibility of an adverse interaction of solar panel pulse charging systems and the electronics systems in use during the race.

    A small power example of such a system is found at the link

    Anybody using a pulse charging sytem?

  9. #9
    Join Date
    Sep 2007


    For aspiring SH TransPac'ers who are racing to Vallejo this weekend: Ragtime! will be available for inspection up there. Her electrical system is closer to the "minimalist" end but has most of the components recommended at SHTP Electrical Seminars over the years. Maybe I'll install the solar panels too so the whole system will be in place.

    I'll be somewhere in the VYC basin so just track me down.

  10. #10
    Join Date
    Oct 2008

    Default Solar Panels

    I saw "Black Feathers", a Cal 20 equipped for ocean voyaging that competed in last years Transpac, parked at the South Beach Marina a couple weeks ago. This has gotten me thinking that I might actually be able to equip Tinker with what is needed for the Transpac in 2-3 years.

    My general question about electrical systems is: "Typically, how many solar panels and how many Amp hours of batteries are needed on a small boat without a generator?" If this is too general of a question or the answer requires a specific watt by watt accounting of everything electrical on the boat, I understand.

    Black Feathers has a couple nice sized solar panels bolted to his stern railing that looks like more than enough. I've seen similar setups on Starbuck, Mirage and other boats that have done the Transpac. Is there any general rule of thumb on the number, size or wattage output on the solar panels needed for the Transpac?

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