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Thread: Power budget calculations

  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.

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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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    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.

  7. #7
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    With a 170Ah Balmar you should be able to get 100-120A without overheating. With a Belt Slip Manager (Balmar-614 term) set at (70'ish% output) it shouldn't overheat. The alternator temp sensor should be used so the 614 regulator will back off the charge level if it does overheat.

    Do you have a serpentine belt kit? Also you talk about a LiPO, which would be a huge no no.... but I imagine you mean LFP (iron phosphate).

    You say "main".... what is your 2nd battery for the house as I recall the rule wants 2x batteries. I would never use just a single LFP battery with a built in BMS for any offshore boat. If ANY internal connection, sensor, or CPU were to fail the batteries would shut off the contactor and you couldn't get to your amps in the pack. An external BMS is what is recommended as you can bypass it if it fails and still use your amps (Victron, Lithionics, etc). If you have to use a pack with an internal BMS you should have multiple.

    Do you know that the 300Ah Relion only recommends a 10-50A charge (their BMS is the limiting factor) with a MAXIMUM of 100A? That means you shouldn't be charging near 100A, period, and shouldn't go over 50A as it may overheat the BMS. If you have two of those batteries your max charge rate for the pair should be 100A. Sorry to step on toes but I would not go offshore with that battery with such a limited internal BMS.

    Also, how are you charging your starting battery....? usually a lot of mistake in the setup here as most have a non LFP starting battery mixed with LFP house bank.
    Last edited by solosailor; 01-10-2023 at 11:19 AM.

  8. #8
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    I risk diverting this thread but I'm getting so much great information...

    Thanks BobJ !

    >> send me an e-mail: BobsailsSF at yahoo
    I did. Thanks for the continued assistance, on all threads, it is much appreciated.

    >> despite the goofy magnetic pen to program them, they've been fine.
    I think your Balmar unit and my MC-614 are similar and I too have that goofy programming system. Balmar claims its to avoid an intrusion point. I called Balmar and the new MC-618 for example allows smartphone programming except you also need to buy their shunt and their battery monitor and then wire all that up in addition to the shunt and battery monitor that you surely already have (Victron in my case). That just seems plain daft design engineering to me.

    >> I've not been able to get the battery temperature sensor to work
    I have a battery temperature sensor for the Victron monitor and I never see anything much happening at the battery with the charging currents I presently use. I *think* though have yet to confirm, thats its all about the alternator temperature. I will find out.

    >> It's Balmar's 100A unit and I've never seen more than 40A out of it.
    I will be interested to see what I can get out of my 170A unit if I tried.

    >> I think I'm using a lot less juice than you are and the batteries just never get that low.
    I am doing worst-case analysis or trying to, but I'm still surprised how all the devices add up, how much you forget (like charging the handhelds), and how poor solar is. I do need not only modes for use but modes for what happens when things fail, such as losing one solar panel or a battery. I need to construct a "vital systems only" mode for example.

    and thanks Solosailor!

    >> With a 170Ah Balmar you should be able to get 100-120A without overheating.
    I will find out. I think I have a big engine and big alternator in a small boat. I do have a way to extract some heat, but not sure I want to build a power station inside the boat. We'll see.

    >> Do you have a serpentine belt kit?
    Yes. I have a 410J10 with the Balmar red and blue pulleys. I am struggling to get just the right belt tension which I gather is key. I do have a Belt Buddy. I just bought a couple of gauges, the Gates Krikit and the Amazon standard 10 lb push gauge. Never used one before but that might help figure out what is going on in some quantitative way instead of the qualitative look and feel which is what I'm doing now.

    >> Also you talk about a LiPO, which would be a huge no no.... but I imagine you mean LFP (iron phosphate).
    Yes. I have a Relion RB300 Lithium Deep Cycle Battery LiFePO4 (or LPF) main battery. My bad. I was researching battery fires and just typed LIPO. Fire is one of my concerns with these batteries. I think Brian or David told me one of the SSS members works with fire issues for DoD and I looked at some of the research on Li battery chemistry fire suppression but not sure there's much you can do. I have read https://www.coastalclimatecontrol.co..._Coastal_2.pdf carefully (and cant find this at the Relion site). I have a ceramic firewall but what good is that going to do.

    >> what is your 2nd battery for the house as I recall the rule wants 2x batteries.
    Yes. A 100Ah Relion, same chemistry, same everything as main, different capacity. Starter battery can be paralleled (combined) to the main. I have a Sterling Pro Batt Ultra BB1230 between the two batteries as the charger on the Victron MultiPlus Compact 2000 inverter is a bit too small. I have never seen the issue of throwing the Blue Sea battery switch to combine two big batteries discussed in detail. I do see Relion specifies 50mV (https://relionbattery.com/blog/how-t...lion-batteries) which is not going to be practical in the emergency situation for which you would typically use combine. I have tried combining at 500mV separation and it worked, just because I cant live with the uncertainty that it might not. What are you going to do? bleed the high battery? I do have a third completely separate rechargeable battery for emergency system use and I may get a fourth. I do worry about the complete reliance on someone's BMS design. I have this weird feeling that relying on products that have a niche market (such as marine where B&G would be an example) is much worse than relying on a mass-market product (like Li battery technology). I'd rather not rely on anyone, but if I have to risk assess I think thats how I place my relative worries.

    >> Do you know that the 300Ah Relion only recommends a 10-50A charge (their BMS is the limiting factor) with a MAXIMUM of 100A?
    Yes. Those figures are front and center at https://relionbattery.com/products/lithium/rb300 for example and the same values for the 100Ah battery. The Relion FAQ does say 1C (https://relionbattery.com/resource-center/support/faqs). Some of their documentation says the lower of 100A and 1C. Also watch https://youtu.be/oHJ3UdQLnOs?t=78 (at that time point). I haven't sorted all this out with them yet. LMK if you have! I don't think I would want to go above 100A charge current as that puts me at a 1.3kW dissipation (assuming a 50% efficiency) in the engine compartment. Does that sound right?

    >> If you have two of those batteries your max charge rate for the pair should be 100A.
    I have to think about that. You might think you can charge at a maximum of 200A on combine, but who knows which battery wins and in any case I wouldn't want to do that. Again, if you have got into this with Relion LMK. You are right and it may be worse, the conservative charge current for either one or two batteries in parallel would be 50A. I currently start at about 70A and reduce to 40A. After I do some more work on what my alternator is doing, I will call Relion and see what they say.

    >> I would not go offshore with that battery with such a limited internal BMS.
    Please step on my toes. Thats how I learn. I am learning so much from the SSS Forum and a lot from just this thread and especially from you! Thanks!! I have what I have at this point and have to learn to live with the problems and limitations of what I have. My boat is small enough that it would be really hard to swap out the current electrical system, especially the batteries, and honestly I'm not sure how much better I could make it. I do absolutely worry about losing one and then both batteries. If you had a blank cheque what would you do?

    >> Also, how are you charging your starting battery....?
    The Sterling. Another wonky programming system.

    … and thanks again to everyone. Keep the great comments coming!

  9. #9
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    Starter battery can be paralleled (combined) to the main.
    You would be bridging together a good battery with a dead battery. Starter should really have a choice of starting from the house or starting battery, never combine using "both".

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    >>> Starter battery can be paralleled (combined) to the main.
    >>> You would be bridging together a good battery with a dead battery.

    You sort of skipped from two batteries one of which might need help to a dead battery. I don't think those are the same. Good is good, bad is bad (for a number of reasons), and dead could be any number of things but ...

    1. I wouldn't combine a bad battery with a good one, nor charge both a known bad battery and good battery in parallel.
    2. I use a standard Blue Sea switch in a standard 2-battery system. See https://www.bluesea.com/support/arti..._Battery_Banks and https://www.bluesea.com/support/arti...Battery_Switch for the Blue Sea combine switch at https://www.bluesea.com/products/pro...witch/featured Let me know if you think thats bad practice.
    3. Battery terminals are fed out to posts so in the event that I did have one bad (or dead in some cases) battery it can be isolated / disconnected and the other battery substituted. It's not going to be as easy as throwing a bunch of switches but I think thats as good as can be reasonably done. I know I can easily recover from a 500 mV differential.
    4.The system was checked by Jeff Cote at Pacific Yacht Systems, see https://www.pysystems.ca and he recommended the Blue Sea system, so not sure what else to do here
    5. I probably got the most help from this post at this great site: https://marinehowto.com/1-2-both-bat...onsiderations/ that has both detailed recommendations as well as detailed practical explanations. Let me know if you disagree with them.

    Thanks!
    Last edited by GBR3068; 01-12-2023 at 09:04 PM.

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