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    Understanding your Lipo Batt

    Once awhile we get a "newbie" asking questions about Lipo Batt and can be frustrating for not knowing whatever causes it to fail or loose capacity prematurely etc..

    Therefore, I have decided to share this article with the forum members. The article explained some of the lipo characteristics. But feel free to throw question at it.

    Enjoy it


    #2
    Originally posted by X34
    Once awhile we get a "newbie" asking questions about Lipo Batt and can be frustrating for not knowing whatever causes it to fail or loose capacity prematurely etc..

    Therefore, I have decided to share this article with the forum members. The article explained some of the lipo characteristics. But feel free to throw question at it.

    Enjoy it

    Hey X34, is this article more on lion batt? Does not seem applicable to polymer type.
    Stop looking for a gyro in my plane, they are all in the head.

    Comment


      #3
      Originally posted by edmond22
      Hey X34, is this article more on lion batt? Does not seem applicable to polymer type.
      Hi Edmond22,

      You are right. The characteristics of the battery are the similiar. The "LIPO" batt we are using for our RC models are a cross between Lithium Ion and Lithium polymer = Lithium Ion Polymer.

      A true Lipo batt will need about 60 deg C to start discharging properly. Therefore, if we are using the real thing, we will have to pre-heat the batt before using it.

      We were often told to operate our batt not higher than 60 deg C and real Lipo needs at least that temp -- than what kind of batt are we using

      Cheers

      Comment


        #4
        Part Two, Lipo care

        Some sources suggest storing lipos at fully discharge state.

        IMO, that is a bit risky, lipo self dicsharge rate is relatively low,storing it for extended period of time, the voltage may drop below the min voltage. Many lipo manufacturers supply their batt at half charged. I would suggest storing the lipos at 10% to 50%. So any self discharging would not bring the cells voltage below the min.

        Physical handling of lipo - Almost all lipos use in RC are in soft packaging, individual cells comes in al pouches, lipo packs are shrink wrap together. So don't squeeze your cells with your hand or force it into the plane or heli. Squeezing on the cells causes the gel inside the batt to be displaced. Once displaced, the cell capacity will be reduced and it will begin premature aging.
        Transport the lipos in rigid containers, stuff some soft materials between the cells to prevent it knocking around.

        Use in model--Its is best to create a proper battery compartment in the model to hold the battery in a firm manner, use velcro strap to hold it in place instead of rubber bands or cable ties. In Gws airplane - the batt compartment is too tight for most 3s lipo, shave the foam to allow the batt to slide in easily and use velcro to keep it in place. Also make sure the battery compartment has sufficient airflow to prevent overheating the cells.

        I may not be conclusive in this area, pls share your experience with forum.

        Comment


          #5
          Lipo Care Pt3 Balancing lipos.

          Lots has been said about charging lipos, but not much about balancing them.

          Some brands of lipos are said to be able to maintain their balance better than others. Brands like Thunder power are now providing balancing taps, FMA introduce balancing taps.....

          A year ago, the lipo pack is deemed to be unbalance if the cell to cell voltage difference is 0.1v . Recently, the spec is 0.05v. So balancing is critical. Here is how I balance my lipos.. charge the lipos to full, use a voltmeter to measure individual cell, each cell voltage should not exceed 4.23v. If the individual is below 4.2v, i would charge that particular cell till 4.2v. If the cell voltage is greater than 4.23v, discharge it to below 4.23v. This usually takes about half an hour to rebalance a 3s pack

          To check the individual cell voltage, the wrapper will have to be removed to access the battery terminal. As for me, I would solder on some wires with connectors and rewrap the pack. This way I can check the voltage conveinently.

          Secondly, the voltmeter should be a good one with a tolerance of less than 1%.

          Balancing lipos can be tedious, it prevents premature demise

          Other balancing methods- charge the cells in parallel, charge the pack with lipo balancers.

          Comment


            #6
            Originally posted by X34
            Lots has been said about charging lipos, but not much about balancing them.

            Some brands of lipos are said to be able to maintain their balance better than others. Brands like Thunder power are now providing balancing taps, FMA introduce balancing taps.....

            A year ago, the lipo pack is deemed to be unbalance if the cell to cell voltage difference is 0.1v . Recently, the spec is 0.05v. So balancing is critical. Here is how I balance my lipos.. charge the lipos to full, use a voltmeter to measure individual cell, each cell voltage should not exceed 4.23v. If the individual is below 4.2v, i would charge that particular cell till 4.2v. If the cell voltage is greater than 4.23v, discharge it to below 4.23v. This usually takes about half an hour to rebalance a 3s pack

            To check the individual cell voltage, the wrapper will have to be removed to access the battery terminal. As for me, I would solder on some wires with connectors and rewrap the pack. This way I can check the voltage conveinently.

            Secondly, the voltmeter should be a good one with a tolerance of less than 1%.

            Balancing lipos can be tedious, it prevents premature demise

            Other balancing methods- charge the cells in parallel, charge the pack with lipo balancers.

            Is there a need to balance the pack? How often and if the voltage is equal, still need to balance? Thanks.

            Comment


              #7
              Mechplas,

              The pack cell voltage should be checked at full charge. The difference should not be greater than 0.05v (this is the latest recommendation). If voltage are within, don't need to balance. U would need a DVM with 2 decimal points to measure the batt.

              This is the procedure I adopted.

              1. After flight, take pack out and leave it to cool.

              2. 5 min later, measure pack voltage, if voltage avg =>3.7v. (pack not over discharge during flight)Let it continue to cool before re charging or storing.

              3. If avg voltage < 3.7v, measure individual cells voltage. Good chance some cells will be close to 3v or below 3v. In this situation, I would let the cell cool down and charge it with 10% capacity before storing. This is to prevent micro shorts when the cells are over-discharge. The micro shorts cause the cell to balloon.

              Usually, packs that goes below 3.7v avg. they tend to be inbalance.

              In my case, I charge every pack with balancers attached. Save alot of time.

              Cheers.

              Comment


                #8
                Originally posted by X34
                Mechplas,

                The pack cell voltage should be checked at full charge. The difference should not be greater than 0.05v (this is the latest recommendation). If voltage are within, don't need to balance. U would need a DVM with 2 decimal points to measure the batt.

                This is the procedure I adopted.

                1. After flight, take pack out and leave it to cool.

                2. 5 min later, measure pack voltage, if voltage avg =>3.7v. (pack not over discharge during flight)Let it continue to cool before re charging or storing.

                3. If avg voltage < 3.7v, measure individual cells voltage. Good chance some cells will be close to 3v or below 3v. In this situation, I would let the cell cool down and charge it with 10% capacity before storing. This is to prevent micro shorts when the cells are over-discharge. The micro shorts cause the cell to balloon.

                Usually, packs that goes below 3.7v avg. they tend to be inbalance.

                In my case, I charge every pack with balancers attached. Save alot of time.

                Cheers.
                I understand. Thanks for the TIPs.

                Comment


                  #9
                  Originally posted by X34
                  Lots has been said about charging lipos, but not much about balancing them.

                  Some brands of lipos are said to be able to maintain their balance better than others. Brands like Thunder power are now providing balancing taps, FMA introduce balancing taps.....

                  A year ago, the lipo pack is deemed to be unbalance if the cell to cell voltage difference is 0.1v . Recently, the spec is 0.05v. So balancing is critical. Here is how I balance my lipos.. charge the lipos to full, use a voltmeter to measure individual cell, each cell voltage should not exceed 4.23v. If the individual is below 4.2v, i would charge that particular cell till 4.2v. If the cell voltage is greater than 4.23v, discharge it to below 4.23v. This usually takes about half an hour to rebalance a 3s pack

                  To check the individual cell voltage, the wrapper will have to be removed to access the battery terminal. As for me, I would solder on some wires with connectors and rewrap the pack. This way I can check the voltage conveinently.

                  Secondly, the voltmeter should be a good one with a tolerance of less than 1%.

                  Balancing lipos can be tedious, it prevents premature demise

                  Other balancing methods- charge the cells in parallel, charge the pack with lipo balancers.
                  Hi,

                  Currently I am doing exactly the same as above on so-called "manual balancing" of lipos-using a volt-meter and a prolux 1-3 cells charger

                  Is it necessary to balance the lipos on every charge?

                  Can you advice on a quite way to discharge of a single cell when voltage is >4.23V.

                  Regards,
                  Lee

                  Comment


                    #10
                    Originally posted by Lee
                    Hi,

                    Is it necessary to balance the lipos on every charge?

                    Can you advice on a quite way to discharge of a single cell when voltage is >4.23V.

                    Regards,
                    Lee
                    One cheap and simple way is to use a light bulb to discharge.
                    Or use a resistor. Both these methods require monitoring during discharge.

                    Or buy one balancer to be use as a checker, discharger. The balancer will stop discharging if the cell is below the threshold voltage.

                    Cheers

                    Comment


                      #11
                      hi X34,
                      Is it ok for us to release the air that trap inside the al pouche of the lipo pack? eg. using a needle to lightly create (with care of course) a small needle hole to let the air come out from the al pouche.

                      Comment


                        #12
                        i don't think that is air... it is some liquid. Anyway, i think any lipo that is punctured is as good as gone.

                        Comment


                          #13
                          hi genexis, i had try to make a needle hole on one of the lipo.. it was air that came out.. didn't feel any liquid come out from the al pouche when i try to lightly press the lipo

                          Do the lipo cell needed to be vacuum sealed? Cause air will expend inside when the batt get heated up during flying...

                          Comment


                            #14
                            not so sure about being vacuum sealed. But one things for sure, you should stop using that lipo, wait for people with better understanding to answer your question. My guess is ... its gone case already. Too dangerous and risky to use.

                            Comment


                              #15
                              um.. in that the case, i will get this batt burn-off asap at the open flying field... to dangerous to thrown into the bin..

                              Comment

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