EBike Battery Pack || DIY or Buy || Electric Bike Conversion (Part 2)

EBike Battery Pack || DIY or Buy || Electric Bike Conversion (Part 2)


in the last episode of this video series I showed you how to create your own sensored ESC in order to power an electric bike wheel with low voltages but since the achieved rotation speed was too slow and not many people want to create their own ESC for an E-bike conversion let’s rather switch back to the controller which was included in the kit to test it I got myself a new lab bench power supply which can output up to 60 volts so I connected its outputs to the input of the controller and slowly started raising the voltage and approximately at around 40.6 volts the controller started working how it was supposed to now by cranking up the voltage even more the wheel started rotating continuously faster until I reach the limit of my power supply that means we will need a battery pack which can cover a voltage range of at least 40.6 volts to a maximum of 61.5 volts a suitable choice of batteries would be 18650 lithium ion cells since they offer a great volumetric and gravimetric energy density can deliver enough current and let’s face it everyone uses them for E-bike battery packs but while searching for a compatible battery pack on eBay I noticed the rather high prices which got me wondering whether DIY-ing your own E-bike battery pack would be cheaper so in this episode of DIY or BUY let’s find out what goes into creating your own lithium ion E-bike battery pack and whether it is truly cheaper in the end LET’S GET STARTED [INTRO] this video is sponsored by JLCPCB one fact about them JLCPCB was the first PCB company that cut the price from $70 to $7 on 2-layer PCBs 10 years ago upload your Gerber files to order 10 professional PCBs for only 2 dollars when inspecting the data sheet of most lithium ion cells then we can find out that they got a nominal voltage of 3.6 to 3.7 volts and maximum charging voltage of 4.2 volts and have almost no capacity left when they got discharged to 3 volts that means we got a voltage range of 3 volts to 4.2 volts per cell thus for our controller voltage range it would make sense to put 13 cells in series to create a battery voltage range of 39 volts to 54.6 volts with a nominal voltage of around 48.1 volts which not surprisingly is the advised voltage of the controller next we need to know the maximum required current of the controller sadly though my dry test with the lab bench power supply did not present an exact answer and the product page does not mention the current as well but luckily it states 1000 watts at 48 volts which would equal a current of around 20.83 amps the next best common lithium ion cell which can output 20 amps continuously was the Samsung INR 18650-25R with a capacity of 2500 milliamp-hours but just to be on the safe side and to double the capacity of the battery pack I decided to use two of those cells in parallel which thus ultimately equaled a 13S2P lithium ion pack with a capacity of 5 amp-hours and nominal voltage of 48.1 volts and a possible constant output current of 40 amps so I went ahead and ordered 30 of those cells from a trustworthy German seller how do I know that they are trustworthy? well after receiving the cells and visually inspecting them I measured the voltage of all of them and noticed that they were all very close to one another which was not only a very good sign but also indispensable since we want to connect two cells in parallel if they would have a big voltage potential difference a parallel connection could result in a large current flow and the destruction of the cell but anyway to turn 26 of those cells into a nice looking battery pack I will be utilizing those plastic spacers which can hold 2 cells each so I connected 13 of them in series through the help of the interlocking system place two batteries with the same orientation in the first row and alter the orientation of the next two cells continuously while filling up all the spacers once that was done I added the remaining spacers to the top of the battery pairs and connected them as well through their interlocking system to connect the cells to one another I got this 7mm wide and 0.3mm thick nickel ribbon which can handle up to 30 amps so I started creating 26 smaller pieces of the nickel ribbon which were long enough to connect all the parallel cell pairs now to create the actual connections I wanted to avoid soldering this time but as you might know I recently failed at creating my own battery spot welder thankfully though a viewer sent me a solution to this problem the so called kWeld which is basically a pretty advanced battery spot welder after doing a bit of assembly it can be powered by a LiPo battery and therefore can create suitable welding spots without a problem according to its manual it is recommended to use an energy of 100 joules for 0.3mm nickel strips which I use as a standard value for all my battery pack welds and as you can see creating the welds is really not that complicated simply press the electrodes onto the metal with a distance of roughly 3mm to one another push the foot switch and THERE YOU GO! 😀 now I created two welding spot pairs for each battery terminal which resulted in a total of one hundred and four welds and once that was done it was time to measure and cut another 24 nickel strips for the series connections which need to get connected to the parallel batteries in the here shown arrangement so I created another 96 welds for the series connections in pretty much the same manner as I did it for the parallel cells and with that being done our 13S2P battery pack is basically complete and should deliver us a voltage within the previously calculated voltage range which it did 🙂 the only remaining question is: how to charge it up? the data sheet of our utilized lithium ion cells states a constant-current constant-voltage method with 1.25 amps and 4.2 volts if we multiply those values for the 13S2P battery pack we would get 54.6 volts and 2.5 amps this means I can set my lab bench power supply current limit to 2.5 amps the voltage limit to 54.6 volts and simply hook it up to the battery terminals to which I soldered thicker 10 AWG color-coded wire beforehand and not surprisingly the charging process worked like a charm but as soon as I got closed to the target voltage I interrupted the charging process to measure the voltage of each battery pair and as you can see the voltages are still pretty close to one another but let’s imagine we repeat such a charging process several hundreds of times since no two batteries are completely the same the voltage gap between the cell pairs will grow and grow until one will eventually give up what we need to prevent such an event is this a BMS aka a Battery Management System not only it keeps all cells at an equilibrium voltage at 4.18 volts but it also adds an overcharge over-discharge and short circuit protection to use it we simply must solder its balance connector wires to the battery according to its label that means B1- to the ground potential B1+ to the 3.71V potential B2+ to the 7.4V potential B3+ to the 11.1V potential and so on and on… until B13+ connects to the 48.1V potential finally we simply connect the ground wire of the battery to the B- terminal and add two more black wires to the P- and C- terminal now to charge the battery pack we reconnect the positive supply voltage but connect the ground potential to the C- terminal this way the battery now charges like before but simultaneously the battery charges itself through the BMS and once all the red LEDs lit up the charging process was complete and thus we can connect our load through the P- terminal and the usual positive voltage wire of the battery pack and just like that the creation of my DIY E-bike battery pack was complete 🙂 but one question remains… was it CHEAPER? well according to eBay prices it was in fact cheaper! but only a tiny bit 🙁 but then again if you add labor costs and the cost of a battery spot welder then it would only be cheaper if you plan to create more than just one battery pack and care for customization so all in all I hereby declare that both DIY and BUY are the winner of this episode! and with that being said I hope you’re looking forward to the final chapter of the E-bike conversion project! as always don’t forget to like, share, and subscribe STAY CREATIVE AND I WILL SEE YOU NEXT TIME!

100 thoughts on “EBike Battery Pack || DIY or Buy || Electric Bike Conversion (Part 2)

  1. There is a type of holder that holds the welder's terminals at the correct distance, you can download the sketch to print it on the 3D printer.

  2. Update!!! I ordered 8 premade 12 volt lithium packs from "Wish" for a little over 2$ each. Total 60$ with shipping.

  3. The other benefit of building over buying is that you know you're getting genuine cells. As long as you buy from a reputable place anyway.

  4. I need Help for the BMS: i need 10S6P Pack, but i cant find a Management solution and i dont know how to Charge the whole thing

  5. Have a look at the "VRUZEND – Battery building made simple" – vruzend.com.
    Seems a good idea. Cheers and thanks for sharing this well documented tutorial !

  6. Ein sehr gutes Video! Als Leihe ohne viel technisches Verständnis habe sogar ich alles gut und sicher verstanden. Jetzt kribbelt es in den Fingern, etwas basteln zu wollen, um im Anschluss ein hoffentlich positives Ergebnis zu generieren.

  7. To anyone trying to assemble ebike battery i would reccomend lghg2 but most are fake especially littokala there 2700mah and the can only do 15a max. most ebay sellers buy them but heres where i got mine they just restocked lol https://www.ebay.co.uk/itm/382894811723

  8. Very interesting. So, if you only need one battery you might as well buy it in already made up. Thanks for make it all clear

  9. Hey, I was wondering if anybody could give some advice, I may potentially need to build a battery to replace the one in a Seabob F7, the current battery states, 2.1 KW/h, 56v, 40ah.. would this be possible to make from 18650 cells and would I be able to use the original BMS from the old battery pack with the new 18650 cells once they’re wired together?

  10. Used battery packs from ebay very often have suspiciously unreadable manufacture dates. If you know where to look, you can get good-as-new 18650 cells for under 2€ a piece. I just bought 2kWh worth for 300€, that's where ebike batteries with a chance to actually work just get started.

  11. why would 415 people dislike? maybe its some of those bench power supply people that this project hurts them? did the thumbs down just become a game? or are there that many idiotic morons that have some interest in electronics? maybe it is many other youtubers that do same type projects and this project made 'their' project look bad?

  12. problems with buy is that you don't really know the quality of the batteries used, coming from china you cant guarantee a quality battery or even if they are not just recycled batteries or rejects so buying would be best to spend the extra money and buy from a reputable seller and not the 'cheapie' from overseas

  13. Hey @GreatScott! ich habe diesen akku nachgebaut und er funktioniert auch… ich lade den akku mit einem 48v 2a netzteil aber selbst nach 5 stunden laden "jedenfalls denke ich dass… das netzteil wird zumindest warm" blinkt nicht eine rote lampe des bms… es sind 2600mah zellen die ich verwendet habe… soweit habe ich alles richtig verschweißt und verlötet… kann es sein dass es einfach nur sehr lange dauert zu laden oder das der akku garnicht lädt?

  14. though the expense of plastic spacer holders could be eliminated, as well as a balance charger (BMS is internal) you find over 30% cheaper for DIY than buying retail. in real world, you'd have ~$300 invested DIY vs. ~$450 retail.
    tape and shrink sleeve are fine for battery packs, and you can make any shape you wish! if you buy 50 18650's at a time (or 100!) you can get name brand quality at under $3 each

  15. Most good quality battery packs are 10 to 14Ah so your 5Ah one wouldn't last long. Also $250 to $300 for a battery pack is very cheap. A 36V Bosch battery pack (which uses Samsung cells) of 500Wh (13.88Ah) costs around £700 ($887.94) in the UK.

    Also using a lithium battery pack/charger without BMS is a quick way to burn down your house!

  16. A very few videos which shows throughly making of a battery pack. Make more videos like this. And also manage to show every little little things.

  17. I am very surprised to see 800,000 people interested in ebike batteries. Just a week ago I was exposed to, and bought my first Ebike only because I’m old, out of shape but want to enjoy the bike trails with my family and 1year old granddaughter. Makes me think this is the future, for sure

  18. Cheap Chinese e-bike Batteries do not have Panasonic, or Samsung etc batteries in them.. They can even be wrapped in cardboard! I have to repair by e-bike battery as the batteries got pounded with no vibration protection have shorted and won't fully charge. THIS is how I will repair the pack because at least I know how the batteries are built and what the quality is…

  19. can someone help on how to install the bms. I still dont understand where to place each cable from the bms.

  20. NONONO … DIY is much better!
    ebay batteries are in fact cheaper. but it is unreliable batteries… when you diy it yourself you uses trusted or at least …safe batteries
    think would you make your own burgers at home even it cost more and time OR just go restaurant and buy and eat cheaper but they uses mystery meat.

  21. If I'm building a 24v pack with a 2×7 layout, what specs of BMS would I need? 24v 20A? Or more current?

  22. The difference between DIY or BOUGHT battery packs is that by buying a ready made pack the cells are most likely the cheapest cells with the lowest amount of mAh & discharge rates, the BMS is one of the cheapest & light duty BMS's you could buy.

    If you are using a 13s Battery @ 54.6v @ 10amps 546w or 20amps 1092w or 30amps 1638w or 40amps 2184w electric motor then you will be draining such a high current from the battery pack that without knowing specifications of the battery pack it may not provide the power you really need. Plus most importantly lets say you only have a 1500w motor that requires 30amps continuous, if your battery can only supply 30amps maximum then your battery pack will overheat very quickly. To get around this you would need a battery pack that offers more amps maximum so that you are not putting much strain on the batteries.

    This is why most people who buy DIY rear wheels with much higher watts than standard will design their own DIY battery packs & specialty BMS with more features & greater control.

  23. Hi, Scott. Very informative video. I just have one question. At 3:41 you said the current for each 18650 25R cell is 20A. If I use other versions cells such as 8A max, is it possible to use 3 of that in parallel to match the 48v 1000w controller? Thank you.

  24. So putting batteries in series only increases voltage and putting them in parallel only increases current.

    In your example you put 13 in series to get 48V but then added to each of these 1 in paralel to get 5Ah. I'm new in this and would be amazing if someone could educate me but isn't that way capacity of added batteries wasted? You will get 5Ah from the first pack and then add 12 more batteries just to keep that same capacity. I guess when connecting batteries in series they will retain the lowest of the available capacitities meaning if you only added 1 battery the total capacity is still 2.5Ah.

    So my question is: Is it possible to have 48V while still drastically increasing capacity by perhaps having 13 batteties only in parallel and the rest separated in series and then somehow combing them to get 35Ah. Thanks

  25. hi,
    if i have this BMS attached to the battery, can i charge the battery with constant voltage? or ill have to set it up with constant current?

  26. I would have liked to have seen it compared with price of targeted prebuilt battery pack an it's specs such as capacity and output. But overall nice video.

  27. Awesome Project….. you get those original SAMSUNG INR18650 25R battery for around 4$ but in India, it is about 10$ and sometimes it's fake. Please tell us the seller's website so that we can also get it for cheap.
    hope you tell us soon…

  28. Hi very good video, I have a question, you used batteries with 20amps discharge current max and 3.7 volts, wouldn't have been better if you used an higher max discharge current battery so that the battery could work more efficiently?

  29. Would it be possible to power the bike with a typical Lead-Acid Battery? (Given that the battery has the same voltage/Max current/Ah ratings)

  30. you can reuse LION cells from laptop battery, test it and reuse… then you will get LION cells for free 🙂

  31. i highly recommend buying sony vtc6 nmc batteries (nmc is same kind used by tesla and tesla power walls and are the best chemistry in the world right now). You can buy them for $4/cell at liionwholesale.com which is where I bought mine. I'm not affiliated with them but they have great reviews on reddit and with the vaping forums communities.

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