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  1. #1
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    Default Power budget calculations

    At https://www.sfbaysss.org/forum/showt...2209#post32209 DavidH posted a link to the power budget spreadsheet used in his seminar.

    >> Also Also, many have asked for a link to the electrical budget document... that is located here I have attached this as a link as the forum does not like excel as an attachment. Let me know if there are issues downloading this

    I found the following to be useful additional resources, especially the second one as it has something I found I needed - "modes" of use (credit for the second reference is the first reference):



    Mike / EOS
    Last edited by GBR3068; 01-05-2023 at 11:13 PM.

  2. #2
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    Here's a completed energy budget spreadsheet for my boat EOS. I would submit this as my example. I think it is complete enough, but note:

    1. Massive variability in what happens every day, with ram autopilot use etc.
    2. What might be useful to others is to use the first tab "offshore" as a template, then you can see the pie chart of the second tab change showing power hogs. I find that very useful.
    3. Some of the references for the consumption of various bits of equipment I found may be useful to you.
    4. Credits for the sources of various bits are on the last tab. Keep that tab if you pass your version on. The other "mode" tabs are from the original sources, but I have just focused on offshore tab. I may get to the other "modes" at some point, but I think I would just keep everything on one tab and have "mode" columns rather than having separate tabs.
    5. I was going to include things like duty cycles on some equipment, but honestly what's here is good enough. You can just play with current draw (use an average) and hours on to get an effective duty cycle
    6. I found this detailed spreadsheet was very useful for not only sobering reality on the power war you go through every day, but what if on the use various bits of equipment knowing here most of the power goes.
    7. I tried to make it useful for others, so there are "spare" rows and multiple rows if you have multiple iPhones, iPads, laptops.
    8. Excel spreadsheet attached as .zip

    Thanks!

    Mike/EOS
    Attached Files Attached Files

  3. #3
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    Here's what my energy budget pie chart for typical daily power consumption looks like, I made the spreadsheet above so you create your own … (I added my Echomax radar transponder that I had forgotten in the spreadsheet I posted above)…
    Attached Images Attached Images  

  4. #4
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    Default

    Surprise Electrical Budget.pdf

    Mine for the Pacific Cup on Surprise! is attached. The biggest mistake I see skippers make is with the alternator output. It may be a 50 amp alternator but you'll never see 50 amps from it, especially with all those other sources. Even without them, as the batteries fill up the alternator output drops off quickly. Also, if the alternator is your primary charging device (as it is for most boats with inboards), you need to run the calculations all the way out to fuel consumed.

    Nice job though. Are you kidding with the washer/dryer, hair dryer, etc?

  5. #5
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    Thanks BobJ for valuable advice. I am going to use your PacCup template for a summary report if thats OK. Your report is way easier to understand than the spreadsheet. Can I start by asking you about alternators and charging since you brought up some great points?

    1. I have a Balmar 170A https://balmar.net/product/alternator-xt-sf-170-ir/
    2. Its on a strengthened KKMI bracket (Brian has warned folks that brackets are often the limit to charging, I think DavidH repeated that at the seminar)
    3. I have a Balmar Max-Charge https://oceanplanetenergy.com/wp-con...anual-RevC.pdf This is the one before the MC-618 that has Bluetooth, I'm thinking of upgrading just so I can more easily change field settings
    4. I have 300Ah Relion LiPO as my main. I currently have my alternator charge settings dialed way back to about 70A.
    5. I have a UNIVERSAL M-40B at 37.5 HP (or about 37.5/1.34 = 28 kW)

    So

    1. I dont *think* I am acceptance limited, especially with LiPO, but help me out. I start charging at about 70A and ramp down to about 40A over 30 minutes I *think* due to heating. Do I check this by putting a big load (like my electric kettle) on and watch to see if I increase output (acceptance limited) or stay same (heat limited)? I wish there was an easy way to understand what the MC-614 is doing and why but its not easy.
    2. If I'm charging at 70A or 70A * 13V or nearly a kW and my alternator is 50% efficient (is that fair?), then I have a 1kW heater next to my engine, right? I haven't shot my alternator with an IR gun but I will. There's not much I can do about that.
    3. If my alternator is 50% efficient and I'm putting 2kW into it from the engine, then the engine is running at 2/28 or less than 10% of maximum capacity. Does that seem about right?

    I am kidding about the hair dryer.

  6. #6
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    If you'd like Surprise!'s energy budget in Excel, send me an e-mail: BobsailsSF at yahoo

    I'm not able to sort out your data and questions - maybe others can chip in. Equipment-wise, both boats had/have Balmar's ARS-5 and despite the goofy magnetic pen to program them, they've been fine. There are temperature sensors for both the alternator and house batteries. I've not been able to get the battery temperature sensor to work on Surprise! but the alternator sensor does its job to cut back the output when the alternator gets too hot. It's Balmar's 100A unit and I've never seen more than 40A out of it. I think I'm using a lot less juice than you are and the batteries just never get that low.
    .
    Last edited by BobJ; 01-09-2023 at 03:20 PM.

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