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Throttle quickly the power cuts off, help pleas :)

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    Throttle quickly the power cuts off, help pleas :)


    I finally managed to get my bike together :) Yesterday I was out on a short test ride. I drove both fast and slow and everything worked perfectly and I was really happy.

    But today when I took the bike out of the garage to go for a ride, it did not work well anymore.

    it starts up and indicates that the battery is fully charged. It's no problem to ride away and everything works as it should until I throttle quickly the power cuts off If I go easy on the throttle the bike will power up to full speed.

    The power don't die completely,What happens is that the power disappears and the battery icon starts flashing like the battery was out. it also losing the contact
    to the temp sensor,and the temp value just flashes.

    After about 3-5 seconds, everything returns to normal, until i I throttle quickly next time.

    What could be the problem ?

    This is my setup:

    Battery is : 52v 14s 7p Panasonic NCR18650PF 2900mAh - 10A


    51.8V lithium ion battery bms 3.7V 14S 30A BMS with the balance function Different charge and discharge port
    Brand Name:ANN
    Model Number:14M30AFK
    Application:Lithium ion battery
    Type:Lithium ion battery BMS
    Product name:14S 51.8V 30A lithium ion battery BMS
    Rated Voltage:51.8V
    Charging voltage:58.8V
    Continuous working current:30A
    Over-Current Discharging Protection:100A
    Maximum charging current:15A
    Balanced Current:50mA
    Charge and discharge:Different charge and discharge port
    Composed Type:14S

    And This kit from :

    Kind regards

    My guess is the motor may be drawing more current than the BMS or the motor cobtriller feel it is safe. They likely detect a voltage drop below some limit or the temp sensor is faulty or too sensitive and reduce power.

    Before your second ride, did you fully charge your battery? If not, fully charge the battery again and immediately after the charge competes ride and see how it works.

    Is your pack charged to 58.8v immediately after the end of charge? If lower, you likely have some cells that are not fully charged and need to be balanced. If that is the case, avoid full throttle and full discharge until you balance the pack and determine it has no issues.


      A poor connection in the main power cables, such as a dry solder joint or weak crimp, it a partly connected connector, could cause low voltage under load, too.
      Fabrication is fun! Build something today. Show someone. Let them help. Inspire and share. Spread the desire.


        Hi !

        First, I would like to thank you for taking the time to help me, much appreciated.

        I recharged the battery again to 58.8v and plugged it in again and everything worked perfectly again :)

        I went for a short ride to my parents' house, I turned off the bike and went in and visited them for about 10 minutes.

        After the visit i I turned on the bike and drove home (5 min) everything still worked prefect.

        Then it became the same problem again after standing in the garage overnight.

        something happens when standing overnight even though the bike is completely off .

        strange error, anyone have any idea ?

        Feels almost like something wrong happens with the battery when it is not used for a few hours.

        Kind regards


          I'm with JPLabs in that the first place I would touch is all the power connectors/connections - this is a good excuse to redo them and make sure they are really solid!


            I had a similar problem, under no load and minimal throttle it would spin all day. As soon as I went to half throttle it would cut out and have a error code. I would disconnect the battery and the code would disappear and the same thing would happen. For me it was the plug for the motor not seated all the way in. Bafang fatbike 750watt hubmotor. Maybe check inside of plugs for bent pin.


              Thank you very much for the answers !

              I'll try to review and check all the power connectors/connections.

              A reflection I have is just that,, if that would be a bad connector/connection the problem should be more constantly present.

              I find it strange that the problem disappears every time you plug in a newly charged battery and comes back every time it's left in the garage overnight
              It feels like if there was one dry solder joint or weak crimp then the problem would occur more irregularly or be constantly present.

              or am I way off track ?



                I originally misunderstood, I thought the problem went away over night, but see now that you said it developed when sitting overnight. I will remove related comments. Sorry if I confused anybody beyond myself! :)

                I saw a post elsewhere, from ykick, which reminded me to double check the basics, so I went back up and re-read your problem statement. Oops, I got that wrong. How basic. (Blush).

                [ 2nd edit: now ykick is already below, with similar advice to you, beating me to the above. Hilarious! Nice job, ykick. You must have started sipping coffee faster than I did this morning. ]


                You don't have problems with a full pack, right? Only as the voltage of the pack drops with use?

                Just make really sure your pack is charged up all the way. Now, to me, that sounds like a good potential cause.

                Wiring issues could still exacerbate such issues, and (power) wiring improvements could thus help.
                Last edited by JPLabs; 11-18-2017, 07:02 AM.
                Fabrication is fun! Build something today. Show someone. Let them help. Inspire and share. Spread the desire.


                  Even if in the end you find there's something else going on outside the wiring I completely agree that you should go through it all and ensure it's solid, especially the power connectors, or it will always be suspect and it's really important that it's good or things can burn/arc/etc...


                    If you're not using volt meter to view battery level you're not seeing an accurate representation of SOC (state of charge). Those % meters and battery icons are a waste of time, IMO. They try to decipher and average between voltage at rest and voltage under load and they're simply not up to the task.

                    Color dash/display usually have option for volt meter - enable it. Then read up on SOC resting voltages for 52V battery pack. Above 58V resting is full SOC. Below 50V resting is practically empty.

                    Charge your battery fully and ignore all of the 80-90% "your battery will last forever" talk. The pack must be charged 100% on regular basis. In addition, it should be left connected to the charger for 12-24 hrs from time to time to insure good BMS balance function. Even if the green LED comes on and fan stops, that's not always a fully charged pack because the BMS may be balancing and it will resume bulk charging once the higher voltage cell groups have been reduced internal to the battery pack.

                    Please check the battery knowledge base for more tips and troubleshooting information.


                      Hi I'm back :)

                      Now I have charged the battery for 12 hours.

                      when I use the volt meter to view the battery it shows 56v

                      As usual, the bike worked well on my first 10 minute ride after full battery charge. I measured the battery after the ride and it showed 55.3v
                      I took the battery from the garage to make sure that the cold would not be a factor.

                      The next day I took a trip again, The bike worked well for about 1 min, then the usual fault returned.

                      Then i used a clamp meter to see how much current the bike would like to pull from the battery. I noticed that it cuts every time it pulls 37.5 Amp for
                      about 2-3 sec.

                      it makes me start wondering if the BMS is to weak , could that be the problem ? it is specified to Continuous working current: 30A


                      • ykick
                        ykick commented
                        Editing a comment
                        Fully charged 56V for 52V pack indicates a problem imo. Probably a cell group is in poor balance and the high current 37A sags the weak cell down to ODDV (over discharge detection voltage).

                        Probably need to open it up and measure each of 14 series groups and see if one is much lower than the others?

                        As I said earlier check the battery knowledge base and make sure you're leaving it on charger for days to ensure it's balanced as much as possible. In balance and good health 52V pack should be over 58V fully charged. Does your charger output over 58V when not connected to the pack?

                        Sorry I'm typing on phone or would grab and paste the links but they're in the forum index.
                        Last edited by ykick; 11-21-2017, 04:30 AM.

                      Hi ykick !

                      Thank you very much for your response and for your help,much appreciated .

                      Excuse that I am not so well informed on this electronic stuff, I'll do as good as I can.

                      Maybe a stupid question ,Is there any way to measure cell packages as the battery is now or do I have to separate all cell packages ?


                      • ykick
                        ykick commented
                        Editing a comment
                        Do you have a picture of the pack? Does it have a plastic housing?

                        Try leaving the pack on the charger for very long period of time? Couple days perhaps since it can take a very long time for BMS to balance a pack that's significantly out of balance? If the full charge voltage climbs up to over 58V that's a good indication the BMS has balanced the cell groups. But, if it doesn't you'll need to look inside and measure the 14qty cell groups and look for one lower than the others.

                        You don't need to separate cell groups (packages?) to check their voltages but you will need to open the enclosure enough to access wiring to the BMS sense wires. Then carefully measure each cell group looking for what I suspect will be a group with lower voltage than the others.

                      I have built the battery, it is Panasonic NCR 18650PF 2900 mAh 10A (new cells) setup 52v 20,3Ah 14s 7p .
                      I have already removed the package and the shrink wrap so there is no problem to access and measure the volt .

                      I will try leaving the pack on the charger for very long period of time but I thought I would try to measure it first.

                      I upload some pictures,, I would be very happy if you wanted to tell me how to measure each cell group with the volt meter .


                        Please be very, very careful (not that you aren't... but just in case! ;-} ). When these are open and exposed there is a very lethal shock hazard presented and a huge danger from fire/burns if anything should get shorted. When you are directly on the cells there is no protection (not that 30A or more current limit offers much more than short circuit fire prevention) and it's way too easy to have a screw or other bit of metal come in contact - definitely consider insulated gloves!


                        • Tuna
                          Tuna commented
                          Editing a comment
                          Thank you for your concern, I will wear gloves and be careful

                        • max_volt
                          max_volt commented
                          Editing a comment
                          There is no documented case of electrocution from 50v dc. If you go to the bms you should see equal steps of voltage on each wire.
                          Last edited by max_volt; 11-21-2017, 10:14 AM.

                        • AZguy
                          AZguy commented
                          Editing a comment
                          There have been fatalities with 12VDC. It's much harder to do. =] 50V is generally considered the "safe" threshold for *dry* skin exposure but sweat can bring this down and very hard water like we have here can bring it down a lot (first hand here!). At a job several decades ago I was knocked on my butt by 75V (back in the tube days) and while not apples and oranges that was dry skin and it was *extremely* unpleasant even though low current.

                          The issue is the enormous amount of energy these can deliver. If you do manage to get conduction across your hands, it is likely to be lethal. If you short something and all you get is a big pow you are way ahead of the game. These are *dangerous* batteries and you have a fellow here that's admittedly not terribly experienced with these sorts of volts, amps and watts. There are plenty of ways to hurt yourself inside one of these...

                          Better to approach with caution (although in my book there's a difference between healthy and unhealthy paranoia)!

                          Just sayin' ;-}


                        I'm pretty ashamed to say that I made a real mistake last night.

                        I read in the book: DIY lithium batteries that a test can be to measure both the charge and discharge wires. I usually always be careful about electricity and usually always have plastic gloves that you also talked about here in the thread I guess I was a little tired yesterday and I was supposed to just measure the contact a little fast with voltmeter. I'm embarrassed to say that when I measured the Male XT60 plug I turned my upper body to see that result on the display then I slipped with one stick and there was short circuit. it was not a pleasant experience , I have to put it on the learn account.

                        so now it does not feel so nice ,, I do not know if I destroyed the entire batteriety :(

                        I disassembled the whole battery again to try and get to the bottom with everything.

                        I measured all cells individually and they were all at about 3.8V.

                        The only positive is that I may have found the error :) I found a cell in the middle of the package that had no contact , could it have caused the whole error?

                        Now I have to try to start over. I was thinking about buying a new BMS with a little better quality and changing the XT60 connector, and redo all connections.

                        someone who has recomendations on a good BMS ?

                        would this work ?


                        Kind regards


                        • max_volt
                          max_volt commented
                          Editing a comment
                          Nothing to be ashamed of. That's human nature. A quick short should not destroy anything. Just start from scratch and make it better this time.

                        • Tuna
                          Tuna commented
                          Editing a comment
                          thank you for your support :)

                        • max_volt
                          max_volt commented
                          Editing a comment
                          You say one cell wasn't connected. I would think that would throw the whole thing out of whack.