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4S2P "12V" Accessory Battery Pack HELP!

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    4S2P "12V" Accessory Battery Pack HELP!

    I'm brand new to learning how to construct and wire up Lithium battery packs. After trying to charge a couple packs using a lithium-specific car charger (and frying cells each time), I bought a hobby charger and some BMS'.

    Today I built my first 4S2P battery to power the stereo on my electric scooter. I followed a DIY guide from the internet for building the battery and connecting the BMS (Images attached). After everything was connected I took my multimeter to test the voltage:

    B+ to B2 = 4V
    B+ to B3 = 8V
    B+ to B4 = 12V
    B+ to B- = 16V
    P+ to P- = 16V

    I also tested the voltage on each battery and each series, which were all 4V. I then connected the pack to my Hobby Mate Lithium Charger (for 1S to 6S lithium batteries) and ran several settings, but none would work. Not LiIo or LiPO, not Charge or Discharge. Every time I try and start the charging the charger beeps several times and displays "Battery Check Disconnect". Disconnecting and re-connecting the battery does absolutely nothing.

    I got frustrated and connected the battery up to a standard SLA 3A charger... It connected and began charging immediately until it reached "Fully Charged". I tested each cell and all were functioning perfectly; however the SLA charger does not achieve a full 16V and thus could never bring this pack up to its full voltage.

    I would appreciate any help some of you experienced battery builders can offer on why I am not able to charge this batter pack using my Lithium charger. I can't figure out what I'm doing wrong. Thank you in advance for your feedback :)
    4S2P BMS Wiring Diagram BMS Wiring Connections 1 BMS Wiring Connections 2 Lithium Charger Settings Charger Error

    #2
    Originally posted by LithiumNewbie View Post
    Every time I try and start the charging the charger beeps several times and displays "Battery Check Disconnect". Disconnecting and re-connecting the battery does absolutely nothing.
    1. Try to connect the battery pack directly, without BMS
    2. Try to make a balance socket (5-wire for 4S) and connect it too (there is a balancing port next to the output)

    Comment


      #3
      Originally posted by thunderheart View Post
      1. Try to connect the battery pack directly, without BMS
      This would lead to imbalanced charging which fries 18650 batteries.

      Originally posted by thunderheart View Post
      2. Try to make a balance socket (5-wire for 4S) and connect it too (there is a balancing port next to the output)
      The charger didn't come with any balance plugs or connectors. If you want to use the charger as a balancing charger without BMS there is an additional setting which is not the one I am using (which is bulk charging). Thank you for the reply but I'm still no closer to understanding why this charger keeps giving me errors when a Lead Acid charger works just fine.

      I should also note that I switched the position of the B2 and B4 wires to see if that would change anything (some BMS diagrams have B2 as the first connection after the negative, others have it after the positive). Nothing changed.
      Last edited by LithiumNewbie; 10-15-2018, 02:28 PM.

      Comment


        #4
        Originally posted by LithiumNewbie View Post

        I also tested the voltage on each battery and each series, which were all 4V.
        Your ahead of me with actual battery expertise... but the statement above doesn't seem to be correct. As a 4s reading should be 16 volts... I find your diagram difficult to follow. Is your battery and BMS wired as illustrated below?






        Regards,
        T.C.



        See my completed Magic Pie V5 rear hub motor E-Bike build HERE.

        Comment


          #5
          Originally posted by Tommycat View Post

          Your ahead of me with actual battery expertise... but the statement above doesn't seem to be correct. As a 4s reading should be 16 volts... I find your diagram difficult to follow. Is your battery and BMS wired as illustrated below?
          Each battery pair in parallel is 4V, all 4 pairs put together in series are 16V. Testing each set in the series connection yields 4V per "cell" or 2P. Yes my wiring is done as per the diagram you submitted, but my batteries are not arranged in that order. I don't do a string of 4 batteries in series and then connect two rows in parallel. Instead I connect 4 pairs in parallel and then wire those pairs in series.

          I see you're building an e-bike. This project got started when I bought an electric scooter. I decided to build my own lithium pack to replace the SLA batteries it came with, but decided to start small with some "12V" accessory batteries to run the stereo I put on it. Now I have a battery assembled that works as it should, it just doesn't charge with a lithium "hobbymate" charger, so I ordered a 16.8V, 3A Lithium bulk charger from Vruzend to plug it into.

          I've also been sourcing batteries for the project. Have tested samples from about 7 sources so far and have another 5 arriving this week. Most batteries on the market are junk and don't deliver anywhere near the rated capacity. Some people think they're building a 20Ah battery only to find they have 8Ah of capacity after it's built because the batteries were not even close to their advertised capacity. I have found two suppliers now who deliver a consistent 3200-3400mAh per battery.

          Comment


            #6
            Originally posted by LithiumNewbie View Post
            This would lead to imbalanced charging which fries 18650 batteries.
            If your cells are not worn out it would not. For healthy cells the balancing procedure is needed from time to time just to keep them well balanced.

            Originally posted by LithiumNewbie View Post
            If you want to use the charger as a balancing charger without BMS there is an additional setting which is not the one I am using (which is bulk charging)
            I know that. It's just for you to find out the bad working chain. If the charger does ok without BMS then you should replace the BMS, if not - the charger. Balance connectors are about one dollar so it's not that expensive i think.

            Comment


              #7
              Originally posted by thunderheart View Post

              If your cells are not worn out it would not. For healthy cells the balancing procedure is needed from time to time just to keep them well balanced.
              Yes if I connected them with balance wires to the balancing charger and ran the balanced charge setting, they would be fine. If I simply connected the battery to the charger on the bulk charge setting (as I have been doing) without the BMS, it will lead to frying the batteries. The BMS does the job of a balancing charger so you can charge the batteries direct from your alternator or other power source. People with e-bikes rarely if every disconnect the battery and hook it up to a balancing charger with balancing wires - it's simply not practical. The same is true of power walls, which is why we have BMS'.

              Originally posted by thunderheart View Post
              I know that. It's just for you to find out the bad working chain. If the charger does ok without BMS then you should replace the BMS, if not - the charger. Balance connectors are about one dollar so it's not that expensive i think.
              Bad working chain? That's why I used the multimeter. I have 16V of output on the P+ and P- wires. I have 16V on the B+ and B- wires. I have 4V for each individual parallel connection of 2 batteries. I've thoroughly tested this circuit to ensure there are zero shorts, faults or disconnects. And I've charged it using a standard lead-acid charger without any issues. In fact I built two of these and tested both on both chargers - both did fine on the SLA charger whereas the lithium charger keeps telling me to disconnect and re-connect. Charging this same pack with the SLA charger and no BMS results in dead cells. With a BMS the cells are fine. It's just driving me crazy trying to figure out the issue with this stupid hobbymate charger, which will charge my SLA batteries just fine. So I went ahead and ordered up a 16.8V, 3A lithium charger.

              Comment


                #8
                Frustrating for sure! What are the specifics of the cells you are using?
                See my completed Magic Pie V5 rear hub motor E-Bike build HERE.

                Comment


                  #9
                  Originally posted by LithiumNewbie View Post
                  If I simply connected the battery to the charger on the bulk charge setting (as I have been doing) without the BMS, it will lead to frying the batteries.
                  It will not (if your cells are healthy and not worn out)

                  Originally posted by LithiumNewbie View Post
                  The BMS does the job of a balancing charger so you can charge the batteries direct from your alternator or other power source.
                  Balancing is being done AFTER charging is finished. In fact balancing is just discharging individual cells using low current to equalize the voltage of cells in the pack.

                  Originally posted by LithiumNewbie View Post
                  Bad working chain?
                  ...
                  It's just driving me crazy trying to figure out the issue with this stupid hobbymate charger, which will charge my SLA batteries just fine. So I went ahead and ordered up a 16.8V, 3A lithium charger.
                  You answered your question.

                  Comment


                    #10
                    Originally posted by Tommycat View Post
                    Frustrating for sure! What are the specifics of the cells you are using?
                    I'm using NCR18650B (Panasonic) 3400mAh batteries. 3.7V standard output, 4.2V full capacity.

                    Comment


                      #11
                      Originally posted by thunderheart View Post
                      It will not (if your cells are healthy and not worn out)
                      Please stop spreading false information here. If someone else were to follow your advice they could blow up batteries, have a fire or end up in the hospital. Your words are careless. I have run several experiments charging lithium packs WITHOUT a BMS or Balance Wires - EVERY TIME IT FRIES BATTERIES. So don't speak of what you have no knowledge of.


                      Originally posted by thunderheart View Post
                      Balancing is being done AFTER charging is finished. In fact balancing is just discharging individual cells using low current to equalize the voltage of cells in the pack.
                      Balancing is done throughout the entire charging process to make sure cells never receive above 4.2V as it would damage the lithium cells. Again, please stop spreading misinformation. I may be new to lithium, but you seem to have absolutely zero knowledge on this subject.

                      Originally posted by thunderheart View Post
                      You answered your question.
                      Ordering up a specific charger does not answer the question. The other charger had many adjustments that could charge 4S batteries. If there were a ban or block from thread button I would use it, but instead I reported you for spreading information that could cause severe harm to another person if they were to follow your advice.

                      Comment


                        #12
                        LithiumNewbie, you're a funny guy))) Good luck)))))

                        Comment


                          #13
                          Just checking in to see if the new charger is working?
                          See my completed Magic Pie V5 rear hub motor E-Bike build HERE.

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