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  • Mixed Battery Voltages and Mixed Charging Inputs

    I am strongly considering electric motors for my auxiliary power on my sailboat. I am planning to do some extended cruising, some of which will require motoring only, and not happy with my gas outboard. The motors are 48 volts / 4KW each and I plan to install two motors with a dedicated battery system of approximately 9216 WH each. I also have need of a house power at 12 volts. I plan to budget the house bank in two separate banks, both 4608 WH each. I currently have a 12 volt / 400 watt wind generator and approximately 100 watts of solar and about 6 KWH of SLA batteries, as well as a 2K gas generator. I plan to significantly increase my wind and solar capacity for this project. The total of nearly 20KWH should give me around 8 hours of cruise time at half throttle at 4-5 Kts, based upon vendor information.

    I plan to add an additional 12v/400w wind generator for a total of 800w of wind generation at ~12 volts charging capability. I have room for two 160w solar panels and plan a modification, in order to install 4 total solar panels. This would result in 1.6KW of wind and solar generators. This also does not include the motors themselves, which regenerate while under sail or at anchor in currents.

    My inclination is to setup all four battery systems the same with 3.2v LiFePO4 180AH batteries and tailor the all charging systems at 12 volts. My primary reason for doing this is shading. In order to setup solar panels for 48 volt charging I would need sun on port and starboard, which is only occasional. For 12 volts, I should get more consistent charging. I would run 12 volt to 48 volt step up regulators, one for each bank. (Initially, I would use the SLA batteries, which are currently setup in port and starboard banks until they became problematic.) Genasun makes a "boost" regulator that is even customizable, which may be what I get. The 56.8v Lithium is pushing the envelope for me, but also acceptable. The Genasun manual is located at

    https://cdn.shopify.com/s/files/1/00...87046331177433

    I would hope that the boost regulator is precise enough to keep me at or below 95%, and I would prefer 90%. If not, I will add a regulator.

    The BMS, below, should include LVD and HVD, but I am not too concerned about constant voltage. There is much hooplah about float charging LiFePO4, but I cannot buy into it. I agree that whenever you have different tensions, that there will be pressure to equalize, but this is the same with batteries in parallel because there is no perfection when it comes to batteries. The logic that I see is moderation, as with anything else. Longevity is probably my most important criteria. By keeping the systems at, or below 90% and at "float", I suspect that the tension is no worse than a parallel battery. That is my uneducated, in this arena, OPINION. I do have a BSEE, so I am not totally useless when counting electrons.

    The motors being evaluated are E-Tech 4POD and can be found at

    https://starboats.eu/electric-drives...h-pod-engines/

    I plan to use the outboard version in order to also use the engine as a tender motor, which will require another battery pack, engine controller, and throttle control.

    I plan on using LiFePO4 prismatic batteries for everything. I am currently looking at

    [LEFT][COLOR=#000000][FONT=Helvetica][SIZE=13px]https://www.dhgate.com/product/prismatic-rechargeable-lithium-lifepo4-battery/469834156.html[/SIZE][/FONT][/COLOR][/LEFT]

    which are CALB prismatic 180AH batteries. I would need 16 each (16S) of the propulsion systems and eight each (2P4S) for the house banks. I really won’t know until I get the first 16 in, but I plan to assemble them in groups of 4, or 12 volts, compression packs. This makes them more portable for me. I looked at the LiFePO4 pouches and they just do not appear durable enough for the environment that they will be in. I may "toy" with the 50AH dinghy pack with the pouches. The second, but significant part of this system is the battery management system.

    Since I will need a BMS for each system and plan to have five systems including a portable 50AH pack for the dinghy, I cannot rationalize $600 or $800 for each BMS. I found this at

    https://energusps.com/shop/product/t...6-150a-750a-36

    which does not include accessories, such as sensors and Bluetooth. I would like to have individual cell monitoring, balancing, and control, but that is not happening on my budget. I do plan on HVD and LVD on the four major systems and probably temperature sensors.

    [COLOR=#000000][FONT=Helvetica][SIZE=14px]I just ordered a prepackaged LiFePO4 battery last week for another application and evaluation from a reputable lithium distributor and their charger will both overcharge and float charge, with no instructions to do otherwise. I was very disappointed. It tells me that distributors either don't know or don't care how long your batteries last. Most only have a two-year warranty, which almost all LiFePO4 batteries should meet, so it is in their best interest for you to treat your batteries poorly. That is why I am here.

    Thanks for making to the end of my lengthy post and I thank you, in advance, for your opinions and advice.

    Regards,

    Jeff[/SIZE][/FONT][/COLOR]

  • #2
    If you can insure that you will daily monitor the health of the packs, you can research Top or Bottom balance systems, where you manually calibrate for the weakest cell, and use that cell as your guide. I'd repeat the balance every 6 months, as cells do drift over time. There are more things involved, like Hi Volt Disconnect and Lo Volt Disconnect, but that's the gist of it.
    Powerfab top of pole PV mount (2) | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister

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    • #3
      I do plan to have wireless connectivity to the BMS. The boat is not easily accessible, so remote monitoring is necessary. I currently have a cheap Walmart sensor that monitors voltage and it works remotely. The BMS will have LVD and HVD. THANKS!

      Comment


      • #4
        Originally posted by malabarmcgyver View Post
        I am strongly considering electric motors for my auxiliary power on my sailboat. .....
        ....... By keeping the systems at, or below 90% and at "float", I suspect that the tension is no worse than a parallel battery. That is my uneducated, in this arena, OPINION. I do have a BSEE, so I am not totally useless when counting electrons.
        Regarding your statement that you dont buy into the hoopla about floating Litjium batteries, you might want to review some chemistry regarding the growth of dendrites in Lithium batteries. Dendrites love to grow in an environment where the voltage is near the knee of the charge curve which is what float charging is all about. As PNjunction has said numerous times it is time that kills Lithium batteries whether you buy into it or not.

        .......
        ..... I was very disappointed. It tells me that distributors either don't know or don't care how long your batteries last. Most only have a two-year warranty, which almost all LiFePO4 batteries should meet, so it is in their best interest for you to treat your batteries poorly. That is why I am here.

        Your system sounds complicated and the complexity of multiple voltages may make it difficult to maintain while cruising.
        I honestly don,t think you are going to get much out of your solar panels while sailing and that was your reason for only going with 12v charging for your panels. Depending on the direction of the wind your sailboat will be heeling some what and that will put the weather side panels at a negative angle to the sun. As you mentioned the leeward side will be shaded. I would invest in a good 48 volt wind generator first. It could be running day and night depending on where you anchor.
        what part of the world are you cruising in.
        Last edited by Ampster; 08-02-2019, 12:04 AM.

        Comment


        • #5
          Ampster: I appreciate your feedback but I am still not clear about floating charge when it comes to LiFePO4. From what little I have read, it seems that most users get this confused with float charging SLA batteries, which would be at a higher voltage to promote absorption. This is not at all what I am proposing. Having a cell at continuous, 90%, or 3.45 volts definitely does not stress the battery as much as having at 3.6v or higher, so I was hoping that this moderation would help prolong the battery life. I have read that the LiFePO4 batteries like to be at lower SOC, but how does one accomplish this "in real life". Assuming that it will require 10 hours or so of charging to bring the batteries to 90 or 95%, I cannot add that into my plans every time I want to use the boat - it is just not practical. I am more than open to reasonable solutions that do not break the bank, but I cannot rationalize $800 for a BMS with all the bells and whistles for each bank. I am not attempting to be confrontational, but it gets real complicated real quick when all this charging power is coming in, but the SOC needs to stay at 50% UNTIL I need to use them. I want to do this right, and I am a novice, so I am taking your comments very seriously. I just don't understand an easy way not to "float" these batteries. If I have the voltage at 3.3 volts continuously - it could be considered floating, but now it is closer to 50% soc. Is this better for the batteries? Most of the BMS systems, especially when balancing, seem to float charge.

          I have strongly considered a 48 volt wind generator and I could be convinced in that direction. I am in Florida, so my panels receive a lot of power, BUT is often one side or the other - not both. A YouTube video with a $1.5M yacht (name - TOP SECRET) that converted to electric drives stated that was his biggest regret was having his charging systems at 48 volts because his series connected panels rarely reached potential to provide charge. I suspect that having consistent charging voltages is optimal and since 48 volts was not reliable for solar, I am proposing the 12 volt route. I also already have 12 volt panels, wind generator, and charge controllers, so it is cheaper to keep than replace. I do not have a monohull - I have a catamaran, so I am not heeling unless I am in big trouble. I only have room for 4 big panels, so I was planning on having two on port and two on starboard, but alternating banks that receive charge so if sun is on port, both port and starboard battery banks are receiving some charge. The 12 volt wind generator definitely produces more power than the solar panels currently, but it is supposed to since it is 400 watts and total solar is only 100 watts and the panels are 10 years old. New panels are planned in the near future. Once again, I sincerely appreciate your input. When I start looking at all the charge controllers, BMS, inverters, converters, and balancers it can really get overwhelming and I would prefer to keep it simple, which may not be possible.

          Comment


          • #6
            Originally posted by malabarmcgyver View Post
            Ampster: I appreciate your feedback but I am still not clear about floating charge when it comes to LiFePO4. From what little I have read, it seems that most users get this confused with float charging SLA batteries, which would be at a higher voltage to promote absorption. This is not at all what I am proposing. Having a cell at continuous, 90%, or 3.45 volts definitely does not stress the battery as much as having at 3.6v or higher, so I was hoping that this moderation would help prolong the battery life.
            Perhaps I was splitting hairs between Float and Absorb. Perhaps it would be easier to describe those in terms of what the battery sees, which is a constant voltage. Most Float charges can go on forever but Absorb charges usually have a timer. This part of my advice is only applicable when you are not using the sailboat and there is no draw on the batteries. In that case I would not suggest float charging the LiFePO4s. There is not as much self discharge with Lithium compared to Lead Acid and that is why Lead Acid batteries need to be floated especially if left unattended for periods of time.

            I have read that the LiFePO4 batteries like to be at lower SOC, but how does one accomplish this "in real life". Assuming that it will require 10 hours or so of charging to bring the batteries to 90 or 95%, I cannot add that into my plans every time I want to use the boat - it is just not practical. I am more than open to reasonable solutions that do not break the bank, but I cannot rationalize $800 for a BMS with all the bells and whistles for each bank. I am not attempting to be confrontational, but it gets real complicated real quick when all this charging power is coming in, but the SOC needs to stay at 50% UNTIL I need to use them. I want to do this right, and I am a novice, so I am taking your comments very seriously. I just don't understand an easy way not to "float" these batteries. If I have the voltage at 3.3 volts continuously - it could be considered floating, but now it is closer to 50% soc. Is this better for the batteries? Most of the BMS systems, especially when balancing, seem to float charge.
            The easiest way to accomplish lower SOC is to charge to a lower voltage.such as 3.45 per cell. That is enough below 100% SOC that there is less risk at that SOC of dendrite growth. They do not need to be at 50%. Just to be clear, BMSs do not float charge. They only monitor and in some cases balance the cells within a pack. What they can do is turn off the charger during the constant voltage phase when the current reaches a specified value. That ensures that there is no float voltage appled for a long period of time.
            You may wish to have two charging strategies, one for cruising and one when at the dock. When cruising you could charge to a higher state of charge because at the end of the day your night time needs will lower the SOC soon enough. When at the dock pick a lower voltage like 3.40 or 3.45 and control your charge controller or BMS to cut off charging completely.
            I have strongly considered a 48 volt wind generator and I could be convinced in that direction. I am in Florida, so my panels receive a lot of power, BUT is often one side or the other - not both. A YouTube video with a $1.5M yacht (name - TOP SECRET) that converted to electric drives stated that was his biggest regret was having his charging systems at 48 volts because his series connected panels rarely reached potential to provide charge. I suspect that having consistent charging voltages is optimal and since 48 volts was not reliable for solar, I am proposing the 12 volt route. I also already have 12 volt panels, wind generator, and charge controllers, so it is cheaper to keep than replace. I do not have a monohull - I have a catamaran, so I am not heeling unless I am in big trouble. I only have room for 4 big panels, so I was planning on having two on port and two on starboard, but alternating banks that receive charge so if sun is on port, both port and starboard battery banks are receiving some charge. The 12 volt wind generator definitely produces more power than the solar panels currently, but it is supposed to since it is 400 watts and total solar is only 100 watts and the panels are 10 years old. New panels are planned in the near future. Once again, I sincerely appreciate your input. When I start looking at all the charge controllers, BMS, inverters, converters, and balancers it can really get overwhelming and I would prefer to keep it simple, which may not be possible.
            Most of my experience sailing was racing on the West Coast. When we did race to Mexico and arrived at our destination I observed most cruisers had wind generators. Most of those cruisers were sailboaters so I assume they had 12 volt systems. I had once considered cruising there so I asked a lot of questions. You have already concluded that the wind generator generates more power than solar panels. In your case keep what you have and try the voltage converter. Eventually when you are upgrading to Lithium you will have some more data about how much energy you will need. That will dictate your battery capacity and your amount of charging capacity. At that point it may be easier to move to a single 48 volt pack and use a DC to DC converter to run your 12 volt accessories. Give it some thought and research the alternatives before buying the next wind generator. A catamaran gives you a lot more room for storage and solar panels. To balance weight you may need to split the pack and that may add more complexity. That is a topic for another time.
            Last edited by Ampster; 08-02-2019, 02:20 PM.

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            • #7
              Awesome! I think the answer was right there in front of me and you just pointed it out. I believe that it would be quite easy to cutoff charging after use at 3.45 volts per cell. As you stated, there is very little loss due to leakage or just sitting, so I think that answers my biggest concern. It also further supports my inclination to stay with 12 volts as the primary charging system. The 12 volt banks would be getting more routine use due to bilge pumps, lights, and other accessories, so it would require the routine charging. When I change my house banks to LiFePO4, that will be more complicated since they get constant use, but I have some time before the SLA batteries fail. Thanks so much! This was very educational and beneficial to me. Have a great weekend.

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              • #8
                Originally posted by malabarmcgyver View Post
                ............. When I change my house banks to LiFePO4, that will be more complicated since they get constant use, but I have some time before the SLA batteries fail. ......
                Long term when you get close to changing over to Lithium I would encourage you to look at some good BMSs especially if you go to a 48 volt pack. Ones that can report remotely via a bluetooth connection would be useful. I currently use an Orion BMS which is configurable but it does cost about $600 for the Orion Jr which is all you would need. I recently came across the smaller version of the EMUS, which is like the Orion Jr. It has bluetooth and built in contactors which would make it simpler to install. You would have to see if the Amperage limit on the built in SSR is enough for your electric propulsion. Years ago I used their larger system for a VW conversion.

                Another though about wind generation, In a catamaran you will be able to increase the apparent wind, especially on a reach and that even multiplies the advantage of wind generation when under sail.

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