🔋 DIY Electric Bike Battery 🔋

In today's world, battery-powered electric vehicles are becoming more and more popular. Thus, the number of electric bicycles is also growing. Therefore, the problem of batteries is very relevant. I am a supporter of ecological transport. My opinion is to maximize the potential of battery recycling from used gadgets. By doing this, we can influence the ecology of our planet! Making such a battery from lithium-ion batteries with your own hands will not be difficult or costly. It can be used for various purposes, both for electric vehicles and as a powerful power bank for charging various gadgets. You can also use this homemade product for a small home solar power plant.To make a battery for your e-bike, you will need used (or new) lithium-ion batteries. Unfortunately, buying new lithium-ion cans is not always possible, not only because of their high cost but also due to delivery difficulties in some countries. Therefore, for these purposes, you can use old cans from various gadgets: laptops, old batteries from electric vehicles, and other home devices. From my own experience, I can say that about 30% of the batteries removed from laptops are still quite functional and show good results.

Supplies

⚡ Materials:

• Li-Ion battery 18650, 3.7V/2000-3000 mAh x 40pcs
• BMS 10S 4P 36V/10-15A PCB Board Balance
• Electric Bicycle Brushless Controller Kit with S866 electronic display, 250W/350W, 36V/48V
• Throttle Accelerator 36V
• LM2596HV DC-DC Adjustable Step Down Buck Converter Power Module 4.5-50V to 3-35V
• Power Charger 42V/2A
• nickel tape: 0.15 mm/8 mm, 2.5-3 m
• Electrical wires and connectors
• PVC plug d = 50 mm (50PVC-U) x 1 pc
• Double-sided foam adhesive tape
• Heat-shrink tubing
• Paper tape or reinforced tape
• and other consumables: heat shrink, kapton tape, adhesive tape, plastic ties, etc.

⚡ Tools:

• Spot welding with the controller
• Drill
• Soldering iron and consumables
• Multimeter
• Charger: Liitokala Lii 600/500
• Device for checking the internal resistance of Li-ion batteries – YR1035
• Glue gun
• Mounting knife
• Wire stripping tool – stripper
• Hex key set
• Torx key set
• Wire cutters, screwdrivers, scissors, tape measures, markers, and other tools.

Step 1: E-bike Disassembly

Removing dead batteries from an e-bike is not an easy task. This bike is not standard; its batteries are in a tubular frame (Wanmoof S3). On the official website, in addition to the general scheme of the bicycle, I did not find any other instructions for disassembling it. It took me a little time before I figured out how to disassemble it.In order to get to the battery, you must first free the wires from the electronic components. First, you need to open the display cover and disconnect it from the controller connectors. After that, you need to remove the front headlight and rear red light from the horizontal tubular frame of the bicycle. Next, you need to unscrew the cover from the underside of the frame in order to release the conductors going to the motor and to the pedals. To be able to push the battery through the tubular frame, the bike's handlebar will need to be disassembled. But before you get to the battery, you first need to remove the lock from the back of the frame. When removing it, you need to be careful not to damage the wires that go to the rear light.

Step 2: Removing the Electronics & Battery From the E-Bike

After disassembling the mechanical parts of the electric bike, you can proceed to the electrician. Only after all conductors have been released can you push the controller along with the battery using a long iron or wooden rod. In the process of disassembling electronics, you need to be very careful with the conductors so as not to damage them! Connector connections that will be useful in the future are desirable to mark. I did the inscriptions on paper tape. At the same time, by wrapping tape around the electrical connectors, I protected them from damage during the disassembly of the bike.You also need to be especially careful when working with the wire that goes to the bicycle carriage. This wire connects to the pedal assist system (PAS). If it is accidentally broken, you will have to disassemble the entire carriage system of the bicycle pedals.

Step 3: Disassembly & Battery Check

After removing the battery from the electric bike, you can proceed to disassemble it and further check the batteries. The battery case is made of thin plastic, so you need to be very careful when handling it.The easiest way to understand and check the condition of a battery is to measure the voltage of the lithium-ion battery segments. For these measurements, you can use a simple voltmeter or multimeter. The battery of this e-bike consists of 10 segments of 4 cells (10S4P). If the battery voltage is higher than 3.3 V, this means that you can still try to recharge it up to 4.2 V. But if the voltage is below this value, they can no longer be charged and restored. In my case, some batteries have a voltage of approximately 1.7–3 V. You can also check the condition of individual battery cells using a special device that measures the internal resistance of lithium-ion batteries. But for this, you need to disassemble the battery into parts and check each one individually. Everything was obvious here; most of the batteries needed to be replaced. Therefore, I pulled out the failed batteries and handed them over to a special workshop for recycling.

🔋  Accumulators and batteries are very dangerous for the environment, so you can't just throw them away! Don't forget about it! Find a collection point in your area for further battery recycling. The state of the ecology of our planet is more important than we think!

Step 4: Batteries From Laptops

Being engaged in electronics, I saved many batteries from laptops. These gadgets are equipped with very high-quality batteries. And as often happens, out of the entire battery, some fail, and the rest are usually in good condition. Considering that high-current batteries are installed on electric vehicles, it is preferable to buy just such batteries for replacement. But they are very expensive, so for an electric bike with a low-power motor, as in my case (250 W), you can also use good-quality batteries from laptops and other electronics, for example, from wipes.To make a homemade product, you will need 40 cans of Li-Ion 18650. First, you need to remove them from the donor's plastic case. To do this, carefully cut the plastic around the perimeter at the junction line. I do this with an electric burner. It is much safer and easier to work with than a knife blade. In addition, this allows you not to accidentally pierce the thin case of the battery.

Step 5: Battery Preparation

After removing the jar from the plastic case, the contacts of the jar must be disconnected with wire cutters and cleaned of glue. At this stage, you can quickly check the presence of voltage in the batteries using a multimeter. Thus, those batteries that show below 3 volts or show nothing at all are eliminated. It is advisable to prepare the cans before further testing by removing the connecting plates from them. This operation can be done with wire cutters and pliers. For the final cleaning of the contact surface, you can use a drill by installing an emery or stone tip on it. This processing method will prepare the contact surface of the battery for further connection. After processing the batteries, they need to be sorted into boxes.

Step 6: Testing Batteries

Before using them for oure-bike, you first need to test the batteries for internal resistance and capacity. For these purposes, Liitokala Lii 600 (500) is quite suitable. This is a universal charger with the ability to determine the battery capacity (in ampere-hours) as well as the approximate internal resistance. At this stage, you need to choose batteries with the lowest internal resistance. A new battery has an internal resistance of approximately 20–30 milliohms (1 ohm = 1000 milliohms). Based on these parameters, you can navigate to the next choice of working batteries. From my experience and observations, I can say that batteries showing an internal resistance of up to 60-80mΩ can still be reused. Banks with a resistance greater than 80-100mΩ can be immediately rejected.After the next segregation of battery cans, they need to be tested for discharge, determining the working capacity of the battery. This indicator is recorded on the body with a marker. To more accurately determine the internal resistance of a lithium battery, you need to use a more serious device. For these purposes, I used the YR1035 device. After checking the resistance of all batteries, I wrote down their indicator on the case.After careful selection of batteries, you can proceed to further assembly of the battery for the electric bike.

Step 7: BMS Board

For normal operation of the batteries, one more component is required. This is the Battery Management System battery cell management board (BMS). It allows you to regulate the level of charge and discharge of the battery, thus ensuring its normal performance.My e-bike motor is powered by a 36 V battery. And the old ebike battery BMS board cannot be used due to a malfunction. Therefore, I applied the board I bought in the online store – 10S 4P. If you have an electric bike with a different voltage, then you must find the appropriate BMS board suitable for your case. For example, at 48 volts, the BMS board – 13S is used. My board can withstand a discharge current of up to 15 A. This is enough for a 250 W motor. If you have a larger motor, then both the controller and the battery management board should match, and have a slight current advantage. That is, in order to avoid strong heating of electronic components, it is better to buy components with a power margin.But before proceeding with the assembly of the batteries, they must first be connected to the BMS board and checked for operability.As a load, I connected a powerful wire resistance. After making all the necessary current and voltage measurements, I also checked the operation of the BMS by connecting a 42-volt charger to it. Having tested all the elements by hanging mounting, you can proceed to the next stage of manufacturing.

Step 8: Battery Balancing

The battery pack will consist of 10 sections connected in series, each section connected in parallel with four 18650 (10S4P) cells. In order for the entire battery to have a normal charge/discharge in each section, the battery banks must have balanced current and voltage ratings. To do this, you need to select lithium-ion banks with the smallest total spread. Based on this, I calculated the most suitable combination of all cans using the online programme. Thus, I achieved the highest battery output (~8 A /300 W) based on the best placement of each battery. Such a selection is very important, so you need to try to eliminate a strong variation in the capacity indicators in the battery. Having numbered the lithium-ion banks, you need to stock up on boxes and distribute the batteries according to the measured indicators. Link to the site for calculating batteries: https://www.repackr.com/#/

Step 9: Connecting Batteries With Nickel Tape

Having finished with the theoretical part, you can begin to practice! To connect the batteries, we need a nickel tape 0.15 mm thick and 8–10 mm wide. The thickness depends on the current that will flow through the connection circuits of the battery cans. That is, the more current the batteries give, the thicker the connection of the electrical conductor between them should be. Suitable for these purposes and a copper conductor. Especially if you want to solder the batteries together. Now you need to cut the nickel tape into plates of a suitable size to connect the cans. Experimentally, I calculated and cut plates 50, 40, and 27 mm long. The plates must match the connection distance on the batteries; otherwise, a too-long conductor may create a short circuit between the battery poles. For the convenience of connecting four lithium-ion cans, I came up with a small life hack that allows you to speed up this process. For these purposes, a plug from a PVC pipe with a diameter of 50 mm is excellent. As you can see in the photos, its diameter is almost adequate to accommodate 4 cans of 18650. In order to slightly reduce the size of the plug, you need to cut a small piece of tape and stick it along the inner edge of the plug. Masking tape or reinforced tape is suitable for this. Thus, we have a seat for further work with batteries. With four banks of lithium-ion batteries in parallel, you can begin to attach the nickel plates.

Step 10: Spot Welding

The best result when joining lithium-ion batteries can be obtained using resistance welding. At the same time, in its absence, you can connect the batteries using a powerful soldering iron (100 W) in order not to overheat them. I made special contact welding for such work with a welding machine (transformer). When working with it, you must first adjust the welding power and pulse time. You need to get used to it a little in order to prevent burns from connecting the tape to the battery. You also need to keep in mind that the metal on the positive contact of the battery is thinner, although it has an air gap between the case and it! That is, even if it is burned, it will not reach the main capacity of the jar with electrolyte. One way or another, I set different parameters for the current and welding time based on the thickness of the metal, case, battery, and connecting plates. I did not understand this right away, so later I tried to connect first one part of the cells (+) and then the other (-).

Step 11: Battery Assembly

For ease of use, when creating such a long battery, I first welded two segments, consisting of four cans. For each cell of four batteries, it is important to separately bring out the contact plate, which will be connected by wire to the BMS board.

In order to fix them together, you can use double-sided foam adhesive tape, as you can see in the photo. Adhesive tape should be thicker and stickier to achieve the best glueing result. In the process of connecting the batteries, you need to check their voltage in order to make sure that they are assembled correctly!

Step 12: Soldering

After assembling all 10 segments of the battery, you can start soldering. To do this, you need a plug for the BMS connector on the board. You need to make sure that its wires match the size of the assembled battery. In which case, you can add additional conductors by soldering them with a soldering iron and closing the connections with heat shrink tubing. Before soldering, the wires must first be prepared by cleaning their insulation with wire cutters or using a stripper. After connecting the BMS cable to the board, you can start soldering the remaining wires. The positive and negative conductors coming from the battery must have a larger cross-section than the conductors of the loop from individual segments. The cross-section must be calculated in such a way that it corresponds to the power of the battery. Having soldered all the conductors, including the one going to the charger, you can begin to check the assembled battery. You need to make sure that all wire connections match the wiring diagram of the BMS board. If something is installed incorrectly, it can lead to the failure of individual battery cells.

Step 13: Charger

To charge a 36-volt battery pack, I used a charger that outputs 42 V with an output current of 2 A. Such a charger automatically turns off battery charging when the specified voltage is reached. In addition, there is protection on the BMS board to turn off the battery cells when the voltage drops below 3.3 V or more than 4.2 V. As you can see in the photo, measuring the output voltage of the charger does not exceed 42 V (41.7 V) and, accordingly, will not lead to battery failure. I also measured a discharged battery's power consumption when connected to a charger. At the beginning of the charge, it is approximately 60 W and decreases over time. It takes approximately 4 hours to fully charge an 8-10 Amp/h battery. Such a powerful home-made battery can be assembled for different voltages and currents, depending on the power of the bike motor or your electric vehicle. Such a battery can be used as a power bank with a lower or higher voltage as well as power. To do this, it will be necessary to select the appropriate components for the output parameters. By using more than 4 lithium-ion cans (6), you can increase the total capacity of the battery!

Step 14: Controller Replacement & Modification

The controller on this e-bike was beyond repair, so I had to replace it with a new one. I bought a new controller complete with a display in an online store. The old wiring and PAS sensor remain the same. I had to install an additional throttle because this bike only had a sensor on the pedals. In addition, the bike has a four-speed automatic transmission system on the rear wheel. In my experience, I can say that the throttle is much more convenient to use on electric vehicles. To install it, you only need to disassemble the bicycle handlebar grip or purchase a collapsible throttle grip. Before installing a new controller on the bike, I tested it. To do this, by surface mounting, I connected the controller, together with the display and the throttle stick, to a 36 V power source. You always need to check the health of the electronic components, because it happens that after doing a lot of installation work, it turns out that some element is faulty from the manufacturer's factory! The problem that arose when replacing the controller was that the overall dimensions of the new controller were slightly larger than the old one. Therefore, I decided to disassemble the controller and install only its board along with a small heat sink. I had to sharpen the controller board a little with a needle file so that it would fit into the tubular frame of the bike. I soldered all the conductors with connectors to the controller board directly. There is very little space in the bike frame, so if I left the connectors from the new controller, they simply would not fit. All conductors were additionally fixed with a glue gun. And I insulated the controller case. I used a special thermal insulator made of fiberglass for this. In this way, the controller is isolated from the aluminium body of the bicycle and, at the same time, comes into contact with it in order to give off part of the heating temperature during operation. To completely seal the controller, you can also fill it with silicone or epoxy. But, in this case, the electronic board will not be repairable!

Step 15: E-bike Lighting Conversion

After connecting a new controller, you need to think about how to connect the lighting for an electric bike to it. The display has a function to turn on the lighting, but the voltage that will be supplied is 36–42 V. That is, when the light is turned on, the voltage controller output is the same as from the battery. The rear and front lights on this bike have an input voltage of 6 V. Therefore, they need to be provided with the appropriate voltage to connect the lights. To convert high voltage to low voltage, I used a DC-DC Step-Down board on an LM2596 chip. By connecting this electronic board, you can get the desired regulated voltage at the output. A voltage of 50–60 V can be applied to the input of this microcircuit while obtaining an adjustable output voltage with a current of up to 3 A. There was a small problem that I brought out in the process of disassembling the lighting. On the front headlight, the supply voltage was 10 V, and on the rear - 6 V. Having disassembled the lights, I experimented with the voltage and found out that the lights can operate at about 9 V. After that, I connected and soldered the wires for lighting, and insulated them with heat shrink tube. Thus, the issue of illumination was solved. No one wants to be without lights on a bike at night. Using such a voltage converter, you can adjust the output voltage to 5 V under USB.

Step 16: Assembling the Electric Bike

So, having collected all the electronic components, you can proceed to the final assembly of the electric bike. Before you squeeze them into the tubular bike frame, it is advisable to reconnect all the electronics and make sure that they work. In case of any problems, it is very difficult to disassemble everything again! First, I fixed the controller in its original place. After that, I connected the wiring connectors to the controller. I also installed and connected the battery to the down tube of the bike frame. When inserting the lock into place, you need to run the tail light cable. Then I connected the headlight and tail light and fixed them to the bike frame. After all this, you can install the bicycle handlebar back and tighten the mounting bolt. Now you can install a throttle stick and a display on the steering wheel. The bezel of the old display will no longer be connected and is a decorative element. Of course, you can put an LED voltage indicator under it, but I did not do this due to the fact that there was very little space left in the bike body. After assembling the bike, you need to make sure that the wires are well insulated and that there will be no short circuit with the aluminium frame body! The battery and its wiring must be double insulated for a secure connection! Additionally, you can remove the switch in order to be able to turn off the battery.

Step 17: Test & Conclusion

When testing an electric bike, you need to check the operation of all electronic components. The S866 electronic display requires some settings after being turned on. For example, in the display functions, you can set the diameter of the wheel as well as the operating modes of the electric motor. That is, you can turn on the motor only from the pedals or the gas handle, or you can use it from both. You can set the voltage of the controller as well as the current limit. For example, another display can be connected to this controller: the SW 900. From my own experience, I know that when overloaded, the motor of an electric bike can rattle and fail. It is also possible for the motor to overheat. My advice is to programme the display to turn off the power when it reaches a certain current, for example, 15 A or 20 A. This setting will save the motor of the electric bike from overload and failure. I really like to ride an electric bike. If I don't need to carry any goods or passengers in my petrol car, I prefer to use more environmentally friendly transport. I think that by giving new life to things that can be repaired or recycled, we prolong our lives and the prosperity of our planet.

🔋 Thanks for your time and attention to this topic! 🚴🏻‍♀️