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Never used li-io batterys

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  • Never used li-io batterys

    So i have been looking on here a lot and found some good info but im looking for more ideas.

    I have a bunch of li-ion batterys i would like to use. They are 36v @8ah i have about 50. I have a charge controller i would also like to use if possible. Its variable voltage an li-ion compatible. I havent bought panels yet but looking to get 800-1000watts(3-4panels)

    My questions is how would you guys use these batterys in a set up and what panel size(12v/36v) would you use?

  • #2
    A 36 volt lithium battery is a probabbly a pack made up of perhaps 10 or 11 individual cells in series. There could be buddy pairs of cells in parallel to get that Amperage. Do you have any more information about the chemistry, nominal voltage and whether it has a Battery Management circuit board attached?

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    • #3
      It does not list nominal voltage on this battery but it does have bms on each battery. Each battery looks to be made of 3 groups of 10-18650 batterys.

      Battery listed info 36v/7800mah/280wh
      Battery voltage limit 42v
      Last edited by Lerknerd; 04-20-2019, 01:36 PM.

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      • #4
        Originally posted by Lerknerd View Post
        It does not list nominal voltage on this battery but it does have bms on each battery. Each battery looks to be made of 3 groups of 10-18650 batterys.

        Battery listed info 36v/7800mah
        Then you are probably safe connecting them in parallel. Do you have a photo? That will help in figuring out the best way to connect them.
        if you dont know what the chemistry is then you wont know the correct voltage to charge them to. That information would be needed to figure out the charging parameters which would determine the panels and other equipment. Even your inverter choice might be determined depending on the low voltage cutoff.

        Do you know what your loads are or are you just trying to charge all your bunch of batteries over a day or two?
        A bunch of 7800 mWh batteries may be a bunch of Watts. Unfortunately electronic equipment isn't sold in bunches so it also might be helpful to know exactly how many you have? 7800 mWhrs sounds like a lot but it is probably only 5 Watt hours of usable capacity.

        NB The actual capacity is 7,800 mAhours which at 36 volts is 280 Watt hours.
        Last edited by Ampster; 04-20-2019, 02:33 PM.

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        • #5
          Specs are 7800mah/280wh...... Where does 7800mwh come from? Only info on manufacture site thats not on battery is 42v limit and 7.8ah @36v

          I have 50 of these batterys
          Attached Files
          Last edited by Lerknerd; 04-20-2019, 02:21 PM.

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          • #6
            Picture of B.m.s. on a smashed/bad battery block

            Red circle is power out.
            5 wire: red/black is ac charge source. White/yellow/green is 6v dc grounded
            Also seen is 5a fuse (right side/white)
            Attached Files

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            • #7
              Originally posted by Lerknerd View Post
              Specs are 7800mah/280wh...... Where does 7800mwh come from? Only info on manufacture site thats not on battery is 42v limit and 7.8ah @36v
              My mistake about Whrs. I will correct that on my post.

              7.8 Ahr time 36 volts nominal is 280 Watt hours per pack with perhaps 200 usable for longest life. If it says 42v max for 10 cells then that is not LFP snd a max cell voltage of 4.2 volts which are the more dense (and more dangerous) chemistries. I have some of those from a Nissan Leaf and I never take them above 4.1 per cell or below 3.0 per cell.

              I have done all I can do to help you identify the battery type now you need to answer the questions about your loads and the application you are using them in. That way others can help you with panel, inverter and charge controller sizing.

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              • #8
                Originally posted by Ampster View Post
                My mistake about Whrs. I will correct that on my post.

                7.8 Ahr time 36 volts nominal is 280 Watt hours per pack with perhaps 200 usable for longest life. If it says 42v max for 10 cells then that is not LFP snd a max cell voltage of 4.2 volts which are the more dense (and more dangerous) chemistries. I have some of those from a Nissan Leaf and I never take them above 4.1 per cell or below 3.0 per cell.

                I have done all I can do to help you identify the battery type now you need to answer the questions about your loads and the application you are using them in. That way others can help you with panel, inverter and charge controller sizing.
                I will be using a 50a mppt rated for lithium an is variable voltage 12/24/36/48. I will be using 2 inverters(switchable)1000w and 2500w the smaller inverter will be primary power source.

                Does this help with anwsering what voltage panels i should get?

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                • #9
                  Originally posted by Lerknerd View Post

                  I will be using a 50a mppt rated for lithium an is variable voltage 12/24/36/48. I will be using 2 inverters(switchable)1000w and 2500w the smaller inverter will be primary power source.

                  Does this help with anwsering what voltage panels i should get?
                  I am a grid tie guy, so I can't give you the best answer. However it may be useful for others to know your loads in kWhrs. In other words how much are you planning on consuming in 24 hours? I assume this is off grid? Where are you located? Any shade? How much flexibility do you have to face the panels due south and tilt them to the optimum tilt?

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                  • #10
                    Wow all the just to get told you cant anwser my question. Thats more frustrating then searching for info on here for a week. I figured this would be more of a dircet way to find info on here. I hope someone can help with my question.

                    Yes i have full sun,south facing san diego california an i plan on running about 600w after sun goes down for a few hours. Hope that anwsers all your questions

                    Again im just looking for what volt size panel i should use with these lithium batterys

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                    • #11
                      I hope some one can help you. For whatever reason they have not responded yet.
                      Sorry I disappointed you. I know more about Lithium batteries than many on this forum but less than most about charge controllers. Hopefully the answers you provided will now get you some useful answers. All is not lost. Think of this as be just prologue to getting the answers. In any event you would have had to answer those questions any way.

                      If my calculations are correct, you conservatiely have 10kWhrs of Lithium batteries. Obviously that amount of storage should easily get you through the night. You didn't answer the question if you were off grid and what your daytime loads were. That would be useful information to determine what size panels to use. Most experts here view panels and batteries as part of a system to serve a load. Therefore the question would probably get you a better answer by framing it differently.
                      Last edited by Ampster; 04-21-2019, 04:54 PM.

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                      • #12
                        Originally posted by Lerknerd View Post
                        Again im just looking for what volt size panel i should use with these lithium batterys
                        That's pretty easy. You need a panel that will deliver at least 45 volts under worst case conditions of temperature. The charge controller will then drop it to 42 volts (3 volts is decent headroom for most controllers) and charge the battery.

                        ALWAYS use MPPT controllers.

                        You can count on about .6 volts per cell at normal temps, so a 96 cell panel will give you ~57 volts. Then you look at the tempco to see if it will drop to 45 volts under your use case. With a 96 cell panel you are probably safe. Two 60 cell panels in series will also work.

                        If you are looking at a larger system you can put as many in series as the controller can accept. Most controllers will allow up to 150 volts or so. For this you have to use open circuit voltage and calculate the LOWEST temperature you will see.

                        For example:

                        Panasonic VBHN330. 57.6 volts Vmpp. Let's say worst case temp is 60C. So (60-25)*.174=6.09 volts. So lowest voltage you will likely see is (Vmp-6.09) = 51.5 volts. So that is OK; the system meets minimum voltage requirements.

                        Let's say lowest temp is 0C, so (25-0)=25*.174=4.35 so highest voltage is (Voc+4.35) =74.05. So that's OK; system will not exceed maximum voltage limits. Two in series is 148.1, which means you'd be _just_ under the max voltage limit for a 150 volt controller.

                        I would also note that 36V inverters are a bit harder to find than 24 or 48 volt controllers but not impossible. There are several sources out there.

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