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    Help with Charging Lithium Battery Pack from an E-Bike

    Sorry if it is in the wrong section but there is not a correct section and since many portable devices are charging lithium packs I put it in here.

    Please see the photos. The model is -> NKY341B2 (26v @ 8AH).

    Googling does not give much information. But I have established it is a nominal 26v pack when flat and 29.4v fully charged.

    I can buy a universal charger off ebay at exactly 29.4v, charging at 2A. It is the perfect voltage and current limits but has only plus and minus no data signals.

    On the photo you will see from left to right connections:

    T -> Measures 10K to ground approx and varies, not sure if it is a thermistor?
    - -> Ground/Negative connection.
    S -> Is open circuit to ground.
    C -> Positive via a 5amp car fuse.
    + -> Positive via a 30amp car fuse.

    Note that the C and + connections are soldered together after their respective fuses.

    If I connect + and - to the pack it will start charging for exaclty 60 seconds then stop.

    If I dis-connect the power leads and re-connect nothing will happen.

    If after it has stopped I short T to ground or S to ground it will start again and usually the gauge lights up also.

    If I leave those connections shorted in any combination it does not help. It always stops after 60 seconds unless I re-short them every so many seconds, the gauge will light after about 10 seconds so it acknoledges after waiting 10 seconds to re-short.

    Does any one know exactly what T and S are? And what is the pack expecting on those terminals?

    The S and T inputs are very sensitive, If I touch the metal tweezers to one of them but insulate my hand with paper it will still start charging, how is that so?? But only with a metal object.

    Could it be expecting a voltage on one of these terminals or a data signal?



    T goes to the board and is labelled ID.
    S goes to the board and is labelled Comm Pack. Maybe communications?

    The original charger is not available to buy any where and we do not have it!

    I do not have the bike here but I have thought maybe if it is left connected in the bike it will carry on charging if I hook up a socket on the side? It is my friends bike. I will try that when we have chance to get a lift with it.

    I suppose a circuit could be made that continually connects and dis-connects T to ground every 10 seconds!

    I tried using a resistor from T to ground but no difference.

    It will also start with me touching the T or S connection, no need to ground.

    I can charge it fully by bypassing the main board and connecting to the main cell terminals but this bypasses any safety and the gauge would not update so not ideal.


    Many thanks.
    Attached Files
    Last edited by reessi; 02-16-2020, 02:48 AM. Reason: mistake

    #2
    Re: Help with Charging Lithium Battery Pack from an E-Bike

    I am testing off my bench power supply. I also tested with different current limits from 0.5 amp to 2.5amp in case it was over current protection but no. I also tested with lower voltage than 29.4v but no difference.

    Cheers,

    Comment


      #3
      Re: Help with Charging Lithium Battery Pack from an E-Bike

      Well folks I have solved the problem, after wondering what to do for a week I worked it out simply by typing up this post! I connected a 1.5v battery from ground to T and now it charges continuesly and the gauge lights stay lit.

      Maybe this will help someone else.

      If anyone wants to add any info though then please do. I am wondering now if I can connect the 29.4v to the T input? Does seam to be via a resistor when measured to ground but the strange thing is it varies a bit from 10K to 11K?! I will try to look at the board but it is covered in clear rubber. Maybe I could add another resistor or be really safe and use a voltage regulator to 1.5v.

      Any thoughts?

      I'll report back what I come up with..
      Attached Files

      Comment


        #4
        Re: Help with Charging Lithium Battery Pack from an E-Bike

        Connecting the battery from ground to S does not work which is strange since simply touching a metal object to S does work!

        Comment


          #5
          Re: Help with Charging Lithium Battery Pack from an E-Bike

          I measured the current draw from the 1.5v battery via my multimeter and it is 350 micro amps (0.35ma).

          Comment


            #6
            Re: Help with Charging Lithium Battery Pack from an E-Bike

            T is a sensor, it sounds like a themister but your taking a big risk if that'as a LiPo pack,
            i presume you have an existing charger - lets see it.

            Comment


              #7
              Re: Help with Charging Lithium Battery Pack from an E-Bike

              We do not have it, hence why he asked me to make him one, well actually he asked if we could buy one as he did not understand what he needs, I think it is old as very little on google apart from this:

              https://www.tweezbike.com/batteries-...e-peugeot.html

              Looks like it is a Panasonic battery. All references to the battery come up on french websites so maybe it is just not sold in the UK.

              As you can see it is 200 euros!!! Anyway I can buy a universal charger on ebay for £20.

              I have now got it working with 12.7K (3 resistors in series) connected to the 29.4v input then to the T input, as you can see from the multimeter it only pulls 1ma. I believe this is safe. They do not heat up.

              It charges normally now. It has standard lithium ion 18650 batteries in it. What risk do you mean? Damaging the T input?

              Cheers.
              Attached Files

              Comment


                #8
                Re: Help with Charging Lithium Battery Pack from an E-Bike

                This might be the temperature sensor for the battery pack and if this is the case you might have a problem with the charger not turning off if the temperature of the battery pack get to warm

                Here is a way to find out if this is the case that this—>

                Hook a variable resistor pot that is 20k ohm and do the following

                Set 11k ohms and slowly increase the resistance and have a volt meter on the pack and see if the charger stops charging if dose not then slowly decrease the resistance until it turns off the charger if it does take note what the resistance at which it turns off the charger

                Then you will know if it positive or negative coefficient temperature sensor and replace it with the right temperature sensor and put it in the middle of the battery pack ( I would not recommend you using this type fast charger with out a temperature sensor )

                This is mine only personal opinion but charging this type of battery at a fast rate can be dangerous if not done right and not using the right charger for the BMS protection board controller can be some what dangerous depending on weather or not is a open loop controller or a close loop controller or it might not matter but not having the right charger to BMS protection controller board you have no way of knowing

                Here is a case in point of what I am talking about

                I have a battery operated soldering iron controller that has an option for battery power supply that uses 18650 batteries and uses a non loop controller dose not have a temperature sensor but it has a very complicated BMS protection controller board and it monitors the voltages of each cell and if any cell reaches the 4.00 voltage cutoff set point then the balancing part of controller kicks in and try to balancing the cells —>

                Which is what suppose to happen

                but if a bank of cells ( which is 3 cells and there are 2 banks ) reaches 4.2 volts then it stops the charger

                Which in turns keeps the batteries from being fully charged even with the right charger

                This is why you need to have the right charger for the right BMS balancing protection board

                Yes you can use different charger for this type of batteries but you have to understand what type of BMS balancing protection controller board you are using and you have to understand what type of charger you are using and how it works

                This is why I put how to tell what type of temperature sensor you have to use with the charger that you have
                and ( if it is really a temperature cutoff sensor circuit or not) then you need to know how this charger work to be able to use it correctly and safely
                Last edited by sam_sam_sam; 02-16-2020, 07:47 PM.
                9 PC LCD Monitor
                6 LCD Flat Screen TV
                30 Desk Top Switching Power Supply
                10 Battery Charger Switching Power Supply for Power Tool
                6 18v Lithium Battery Power Boards for Tool Battery Packs
                1 XBox 360 Switching Power Supply and M Board
                25 Servo Drives 220/460 3 Phase
                6 De-soldering Station Switching Power Supply 1 Power Supply
                1 Dell Mother Board
                15 Computer Power Supply
                1 HP Printer Supply & Control Board * lighting finished it *


                These two repairs where found with a ESR meter...> Temp at 50*F then at 90*F the ESR reading more than 10%

                1 Over Head Crane Current Sensing Board ( VFD Failure Five Years Later )
                2 Hem Saw Computer Stack Board

                All of these had CAPs POOF
                All of the mosfet that are taken out by bad caps

                Comment


                  #9
                  Re: Help with Charging Lithium Battery Pack from an E-Bike

                  My friend has took the battery to test it on the bike now since I charged it up for him. I will do your tests when I have it back in a week or so, thanks for response.

                  Comment


                    #10
                    Re: Help with Charging Lithium Battery Pack from an E-Bike

                    When I charged it as pictured with the resistors going to the T input it automatically stopped when full and the gauge lights went out and the bench power supply showed no current draw. It reached very little anyway as batteries do as they start to match the input.

                    Cheers.

                    Comment


                      #11
                      Re: Help with Charging Lithium Battery Pack from an E-Bike

                      Ok so I would like to try to understand how it might be working. When I had it apart I saw 2 temperature sensors taped to the cells, one at each end. Could the signals be routed to the T connection so that the original charger can know if it overheats and cut power? But why can't the pack deal with this itself? It cuts power when it has reached full capacity and when I remove the voltage input to the T input. But if so why does putting a small input voltage as I did turn on the pack for charging?

                      Is it just a way for the pack to know it is connected to a charger and an added safety mechanism so tell the charger to turn off in a overheat situation.

                      Can we presume the S connection is a readout of the gauge to the bike for the onboard gauge?

                      There is a huge board on the battery with alot of electronics, more than I've ever seen on a lithium battery, I believe it is trying to balance charge, there is a solid wire going to each bank (7 banks) and a big bank of mosfets presumably for cutting power from the pack.

                      As for the resistor test which I will do when I have it back do you mean hook up 11k pot from T to ground or as I did in the end from + to T after I found out that a 1.5v battery from ground to T turned it on?

                      I already tried the following tests:

                      10k (Ground to T) -> nothing.
                      20k (Ground to T) -> nothing.
                      2.7k (Ground to T) -> nothing.
                      470K (Ground to T) -> nothing.
                      470k + 470K (Ground to T) -> nothing.


                      10k (Positive to T) -> charges.
                      20k (Positive to T) -> charges.
                      2.7k (Positive to T) -> charges.
                      470K (Positive to T) -> nothing but charged when had a multimeter in series measuring current draw (Why can that be?).

                      470k + 470K (Positive to T) -> nothing.

                      Thanks.

                      Comment


                        #12
                        Re: Help with Charging Lithium Battery Pack from an E-Bike

                        And the T connection measures approx 10k for the T connection, when I get the pack back I could try un-taping the thermistors and warming up with the hot air station to see if it changes.

                        Cheers

                        Comment


                          #13
                          Re: Help with Charging Lithium Battery Pack from an E-Bike

                          They were just some loose resistors I had lying about. I didn't have a pot handy.

                          Comment


                            #14
                            Re: Help with Charging Lithium Battery Pack from an E-Bike

                            Originally posted by reessi View Post
                            Ok so I would like to try to understand how it might be working. When I had it apart I saw 2 temperature sensors taped to the cells, one at each end.
                            You have to check those temperature sensor to see how they control the charging circuits

                            Originally posted by reessi View Post
                            Could the signals be routed to the T connection so that the original charger can know if it overheats and cut power?
                            This is what I was talking about earlier that you really need the charger for this BMS balancing protection board


                            Originally posted by reessi View Post
                            But why can't the pack deal with this itself? It cuts power when it has reached full capacity and when I remove the voltage input to the T input.
                            It might but you have to take the temperature sensor off the battery and slowly warm it and see if it stops it charging or is function part of the charger circuit

                            Originally posted by reessi View Post
                            But if so why does putting a small input voltage as I did turn on the pack for charging?
                            What this pin seem to be doing is that it thinks it has the right charger but that does not mean that the battery pack temperature sensor turn off the charger it might be a signal to the charger controller

                            Originally posted by reessi View Post
                            Is it just a way for the pack to know it is connected to a charger and an added safety mechanism so tell the charger to turn off in a overheat situation.
                            Might be but the question is how does it exactly work and what is it really looking for in a signal

                            Originally posted by reessi View Post
                            As for the resistor test which I will do when I have it back do you mean hook up 11k pot from T to ground or as I did in the end from + to T after I found out that a 1.5v battery from ground to T turned it on?

                            I already tried the following tests

                            10k (Positive to T) -> charges.
                            20k (Positive to T) -> charges.
                            2.7k (Positive to T) -> charges.
                            470K (Positive to T) -> nothing but charged when had a multimeter in series measuring current draw (Why can that be?).

                            470k + 470K (Positive to T) -> nothing.

                            Thanks.
                            The 470k high enough resistance to turn off the charger controller but why does it need to be this high

                            Try this keep adding 10k ohm resistors until it turns off the charger controller
                            I would like to know just how much resistance do you have before it turns off the charger controller

                            This is tell me that this probably signals the battery charger to turn off but how
                            Last edited by sam_sam_sam; 02-19-2020, 06:47 PM.
                            9 PC LCD Monitor
                            6 LCD Flat Screen TV
                            30 Desk Top Switching Power Supply
                            10 Battery Charger Switching Power Supply for Power Tool
                            6 18v Lithium Battery Power Boards for Tool Battery Packs
                            1 XBox 360 Switching Power Supply and M Board
                            25 Servo Drives 220/460 3 Phase
                            6 De-soldering Station Switching Power Supply 1 Power Supply
                            1 Dell Mother Board
                            15 Computer Power Supply
                            1 HP Printer Supply & Control Board * lighting finished it *


                            These two repairs where found with a ESR meter...> Temp at 50*F then at 90*F the ESR reading more than 10%

                            1 Over Head Crane Current Sensing Board ( VFD Failure Five Years Later )
                            2 Hem Saw Computer Stack Board

                            All of these had CAPs POOF
                            All of the mosfet that are taken out by bad caps

                            Comment


                              #15
                              Re: Help with Charging Lithium Battery Pack from an E-Bike

                              Originally posted by reessi View Post
                              And the T connection measures approx 10k for the T connection, when I get the pack back I could try un-taping the thermistors and warming up with the hot air station to see if it changes.

                              Cheers
                              Yes this is something you need to do

                              But I caution you that do not over heat the temperature sensor or you might ruin it

                              The way to do this as follows

                              Hook up your charger and make it charge with the 20k ohm resistor on the ( T ) terminal and the ( + ) terminal

                              Then remove one temperature sensor and an slow heat the temperature sensor

                              Keep an eye on the charging current goes ( 0 amps )
                              Then do the other temperature sensor and see if you get the same exact results

                              If it does turn off the charger controller then it might not be that hard to get it work correctly

                              If it does not turn off the charger controller then you have a very big problem
                              Last edited by sam_sam_sam; 02-19-2020, 06:50 PM.
                              9 PC LCD Monitor
                              6 LCD Flat Screen TV
                              30 Desk Top Switching Power Supply
                              10 Battery Charger Switching Power Supply for Power Tool
                              6 18v Lithium Battery Power Boards for Tool Battery Packs
                              1 XBox 360 Switching Power Supply and M Board
                              25 Servo Drives 220/460 3 Phase
                              6 De-soldering Station Switching Power Supply 1 Power Supply
                              1 Dell Mother Board
                              15 Computer Power Supply
                              1 HP Printer Supply & Control Board * lighting finished it *


                              These two repairs where found with a ESR meter...> Temp at 50*F then at 90*F the ESR reading more than 10%

                              1 Over Head Crane Current Sensing Board ( VFD Failure Five Years Later )
                              2 Hem Saw Computer Stack Board

                              All of these had CAPs POOF
                              All of the mosfet that are taken out by bad caps

                              Comment


                                #16
                                Re: Help with Charging Lithium Battery Pack from an E-Bike

                                Many thanks for your help. I'll be back on here in a few weeks when the pack is back.

                                Comment

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