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Upgrading my E-bike. Building a battery pack

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    Upgrading my E-bike. Building a battery pack

    Good day folks. For a couple of months now, pretty much since summer has started and the weather allowed it, I've been trying to ditch my car as much as possible for an E-bike which I got a pretty good deal for at a local bike store because it had some cosmetic defects like some scratches and a broken metal piece holding up the rear rack. All these weren't enough of a dealbreaker to keep me from buying it and I managed to fix them myself eventually, so I now have a nice folding 20" E-bike. Getting more and more used to it, I started thinking of upgrading it, with one of these kits floating around on Ali.

    It's currently got a 250W Bafang rear-wheel motor on there and a 36v rack-mounted battery pack which I've yet to actually open up because it's still under warranty. The way it functions though is unlike what you'd expect when you hear the term "E-bike": you can't just hit the throttle and let the motor do the work, you have to actually pedal to get this to happen. Yes, that's right, there's no manual throttle control on this: the motor starts spinning when the sensor located in the pedal shaft tells it to, so it's more of an electric pedal assistant than a full E-bike. Still, better than nothing and it DOES make a huge difference uphill. It's got a small control panel on the handlebar to toggle between three different speed levels, basically how hard the motor tries to help you out, or you can disable it entirely if you want to conserve battery or you simply don't need it, like when you're going down a hill. Pretty fun stuff overall, BUT...we can do better than that

    I did a little research and found out that these motors are pretty universal and can fit every size tire and bike if you're careful and don't screw up the measurements. Of course I went for the most powerful one I could find, a 1500w one (though with this being China, you CAN expect that to be overblown by quite a bit, still...). Not the cheapest thing, but still cheaper than trying to source a new bike with an 1500w motor already on it, plus I still need it to be a folding type and I'll make up for some of the price by selling the current kit that's on it. These upgrade kits come with everything you need to get going, including the BLDC controller of course, but they don't come with one crucial item: the battery ! Some of them DO offer the battery as an option, but forget about it: too friggin' expensive ! I could buy a used car for the price of the battery ALONE !

    So being the resourceful chap that I consider myself to be, I started looking into building one myself, hopefully saving some $$$. The motor calls for a 52v battery, so I coincidentally found this video where the chap is building just that, except mine will lay flat on the rear rack where the current one is. We'll think of the enclosure later on... Seems simple enough: get some batteries, a BMS like these and start wiring......what could possibly go wrong right ? The choice of cells is the most important thing the way I see it. Also, since I don't have a spot welder and I don't want to solder directly to the batteries, I'm trying to source the same mounting brackets the chap in the video uses which have a screw at the top and allow you to use lugs to connect everything up, but can't find them - much quicker and safer than soldering, plus it allows you to (semi) quickly replace any dead cells, as opposed to soldering...what do you guys think ? You game ?
    Attached Files
    Wattevah...

    #2
    Re: Upgrading my E-bike. Building a battery pack

    make sure you cant touch the battery wires . 52v might be shocking to touch .
    does it have regenerative braking ?

    Comment


      #3
      Re: Upgrading my E-bike. Building a battery pack

      Originally posted by petehall347 View Post
      make sure you cant touch the battery wires . 52v might be shocking to touch .
      does it have regenerative braking ?
      No, the current setup doesn't have regenerative braking and I don't think the replacement one has it either, though that would be cool indeed

      Well I'll just use an XT90 connector to prevent the user for coming into contact with "live" wires...and be extra careful during assembly. You're right - that IS quite high voltage.

      Also, the website says the current battery is apparently 2800Ah.
      Last edited by Dannyx; 08-18-2019, 04:57 AM.
      Wattevah...

      Comment


        #4
        Re: Upgrading my E-bike. Building a battery pack

        get yourself some "705" silicone from ali, you dont want rain in those connectors or any other parts.

        Comment


          #5
          Re: Upgrading my E-bike. Building a battery pack

          Originally posted by Dannyx View Post

          Also, the website says the current battery is apparently 2800Ah.
          more like 28AH

          Comment


            #6
            Re: Upgrading my E-bike. Building a battery pack

            Yes, I too thought that's way too low - must be a typo.

            So 28Ah - that's what we're trying to achieve here, or better.

            Should I go with Samsung cells ? :|
            Wattevah...

            Comment


              #7
              Re: Upgrading my E-bike. Building a battery pack

              or samsung sleeves on trustfire cells???

              Comment


                #8
                Re: Upgrading my E-bike. Building a battery pack

                Originally posted by stj View Post
                or samsung sleeves on trustfire cells???
                Hey, whatcha gonna do ? Actually building my own pack might end up costing as much as a pre-assembled pack which I found, or thereabouts...
                Wattevah...

                Comment


                  #9
                  Re: Upgrading my E-bike. Building a battery pack

                  hope its quality cells .

                  Comment


                    #10
                    Re: Upgrading my E-bike. Building a battery pack

                    reminded me i have an old one that had burned out electronic controller . i was going to add a big resistor box like they use on fairground rides but never got around to it . was hoping to not have to pedal much .

                    Comment


                      #11
                      Re: Upgrading my E-bike. Building a battery pack

                      Meh...lots of these packs available. No way to know what cells you end up with inside though
                      Wattevah...

                      Comment


                        #12
                        Re: Upgrading my E-bike. Building a battery pack

                        hey yourself some lockpicks and come to london for a day, there are bikes with big battery-cases dumped all over the fucking place.
                        take the power-packs and run!!
                        btw, have a big aluminium box or metalised film bag to use as a faraday cage - they have 3G and GPS in them!!
                        Last edited by stj; 08-19-2019, 03:55 AM.

                        Comment


                          #13
                          Re: Upgrading my E-bike. Building a battery pack

                          Originally posted by Dannyx View Post
                          Meh...lots of these packs available. No way to know what cells you end up with inside though
                          They could bring a whole new meaning to the term crotch rocket !

                          Comment


                            #14
                            Re: Upgrading my E-bike. Building a battery pack

                            Originally posted by diif View Post
                            They could bring a whole new meaning to the term crotch rocket !
                            Thankfully it'd sit BEHIND my back on that rack thing so it'd act as a jet engine

                            Only one way to find out if they are any good or not by going for it....not that cheap though, so if for the same money I had the option of building something better, it'd take that option instead....
                            Wattevah...

                            Comment


                              #15
                              Re: Upgrading my E-bike. Building a battery pack

                              Sigh, finding cheap reliable batteries are hard... even when weight isn't a great concern. Would be nice to get a large bank of even lead acid batteries for energy storage...

                              Comment


                                #16
                                Re: Upgrading my E-bike. Building a battery pack

                                https://www.youtube.com/watch?v=BjDEY5Hh-_o
                                lol

                                Comment


                                  #17
                                  Re: Upgrading my E-bike. Building a battery pack

                                  Past few months Citi Bike, GoBike, Skip, Lyft San Francisco halted their e-bike programs, recalled their e-bikes.
                                  Mainly it's the battery packs burning up. From the pic and videos looks like most occur during charging.

                                  Is there a BMS in there, is it cheap batteries and over aggressive charging?
                                  Attached Files

                                  Comment


                                    #18
                                    Re: Upgrading my E-bike. Building a battery pack

                                    always a combination of things that go wrong at the same time and can't recover...

                                    Comment


                                      #19
                                      Re: Upgrading my E-bike. Building a battery pack

                                      ii bet they charge them like a bastard to get them back in service asap.

                                      Comment


                                        #20
                                        Re: Upgrading my E-bike. Building a battery pack

                                        Make sure you don't touch the battery wires.

                                        Comment

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