From this article, we will learn how to make spot welding, assemble a battery from individual elements, install a wheel motor on a bicycle and connect a previously assembled battery to it. This electric bike is assembled on the basis of a mountain bike and has a speed of up to 65 km/h. Of course, this is not the cheapest assembly, but from the article you can glean a lot of useful information including links to materials for making spot welding, a battery pack and the electric bike itself.Tools and materials:
-Soldering iron;
-Screwdriver;
-Drills;
-Kerner;
-A tool for stripping wires; -Hexagonal keys; -Repair key for a bicycle chain; -Set for chain assembly;
Bicycle parts
-Motor wheel with the necessary accessories; -Ready battery (option); -Charger; -M6 screws with an internal hexagon; -Threaded bushings; -Waterproof cover (158x90x60 mm); – Lever; -Connecting rod; -Spider; -Brake calipers ; -Chain (7 speeds); – Connecting links on the chain; – Rack on the handlebar for attaching accessories; -Phone holder for installation on the handlebars of a bicycle; -Shift selector (7 speeds); – Gear shift lever (7 speeds); – Pedals ;
For battery pack
-Li-Ion rechargeable batteries – 84 pcs; -BMS board (module 14S 50A + BT); – Battery compartment for 91 cells; -Nickel strip (0.15×8 mmx5 m); -Kapton tape; -Insulating rings for the battery; -Soundproofing with an adhesive base; -Silicone wire (12AWG); – XLR connector;
Parts for spot welding
-SHF transformer; -Control board for spot welding 100A; -Cable 35 mm² – 4 meters; -Cable lugs M8 35 mm²; -Quick connector; -Holder with electrodes for spot welding; -Connector; – Power cable; -Heat shrink tubing;
Step one: design and selection of parts
To convert your bike to an e-bike like this, you will need a 1500W e-bike conversion kit. The kit uses a 7-speed gearbox, so if you are using 9 or more gears on your bike, you will need to “downgrade” to a 7-speed system. To do this, you will need a gear selector and a shift lever. All at 7 speeds (see the link in the materials).
You also need a good mountain bike. The craftsman purchased an old Cube AMS Pro CC with 26-inch wheels that was in great shape. It was driven mainly on the beach. This bike has plenty of space in the frame to accommodate a large battery pack.
Perhaps the most expensive part of this build is the battery. Since this is the powertrain for the entire bike, it must supply enough current for the powerful motor-wheel motor. The craftsman decided to assemble the battery himself and place it in a plastic case so that the battery could be removed from the bike if necessary.
To assemble his own battery, he had to upgrade his spot welder.
Step two: making spot welding
Samodelkin begins work with the manufacture of spot welding. The scheme is approximately the same as in the photo. Instead of a foot switch, the wire will be connected to a switch installed in the holder (handle with electrodes) for spot welding.
Further, the secondary winding must be removed from the transformer. The master saws it with a hacksaw for metal, and then knocks it out.
Instead, wind another winding with a 35 mm² cable. the master uses two meters of cable and before winding it must be removed from the insulation. The point is that the insulation is thick and not flexible. Instead, he insulated the wire with heat shrink tubing.
Then you need to wrap the metal parts of the transformer with Kapton tape and wind four coil of cable.
I cleaned the ends of the windings and soldered the terminals on them.
I installed the transformer in a plastic case. I drilled holes in the front panel and installed quick-release terminals. I connected the terminals of the secondary winding of the transformers to them. I assembled everything according to the scheme. I connected the holder to the wires. Quick-detachable terminals are installed at the second ends of the wires.
You can watch the process of spot welding assembly in the video.
< iframe width = "700" height = "394" src = "https://www.youtube.com/embed/UseccvORpk8?feature=oembed" frameborder = "0" allowfullscreen> Step Three: Battery
Safe assembly of the battery is the key to this step.
Case and holders for 91 batteries were purchased from the online store. Since the case still needs to place the BMS module, the assembly will have only 84 batteries, the wizard removed 7 holder cells.
Original Samsung INR18650-35E cells were selected as lithium-ion batteries. They have a capacity of 3450mAh and a discharge current of 8A, which is ideal for powering a 1500W kit.
Before proceeding with the assembly of the battery pack, you need to glue the ring insulators to the cell body on the plus side. The insulators have a sticky base on one side. Insulators are needed for short circuit protection.
The wizard recommends using a smart BMS like the one listed in the list of materials. Make sure a Bluetooth adapter is included. This will make it easier to monitor battery parameters, including output/input power (while charging), accurate temperature, speed, current and voltage parameters.
After placing the first 6 battery cells, using Kapton tape and thermal paste, it attaches one temperature probe to one end of the battery pack (negative side) and one probe to the other side of the battery (positive side).
Sets the second half of the holder on top.
Now you can start welding. After a lot of test welds on a faulty battery, he found that the best welds were obtained with the time set to 03 and the power to 56.
It first connects the batteries in parallel. It is imperative to weld the nickel plate in the center of the contact pad of battery cells.
Then it makes a serial connection.
Now you need to solder the wires to balance the battery. The negative black wire of the balancing connector is soldered to the negative side of the battery, and every other wire is soldered to the serial connection on the battery pack. By following the link, you can download the Xiaoxiang BMS application;
After installing each balancing wire, make sure that it is connected correctly. To do this, the master checks the voltage with a multimeter by connecting one probe to the negative, black wire of the connector, and the second to one of the positive connectors (to the first from the negative). The voltage should be 3.6-4.2V depending on the state of charge of the cells. As you move the positive lead to the next pin, it should read 7.2–8.4 V, and so on, until 50.4–58.8 V is displayed.
After making sure the balance wires are soldered correctly, secure the BMS module and solder the blue B- wire to the negative side of the battery. Once this is done, the balance connector can be connected. Now solder the red B + wire to the positive side.
Places the substrate on top and bottom and wraps it with Kapton tape. Connects connectors for temperature sensors and a Bluetooth module.
< a href = "https://usamodelkina.ru/uploads/posts/2020-12/1607869707_1-52.jpg" rel = "prettyPhoto">
Step four: battery compartment
He slightly modified the battery compartment that the master purchased. I installed a charging connector in the case, and moved the switch to another place. In principle, the switch does not need to be connected, since the battery can be disconnected through the application on the smartphone.
With the XLR charging port installed, he soldered some thinner wires to charge the battery. The number “1” on the connector indicates positive terminal, and “2” indicates negative. The wires from the charging socket are soldered to the battery connector on the case. The wires of the LED indicator and the main thicker wires from the battery pack are soldered to the same contacts. Then closes everything with a Kapton tape.
Installs the upper part of the case and screw it on.
Step five: bracket
To securely to fix the battery to the frame, the master designed and 3D printed a bracket.
Download the file for printing below.
hailongshock.stl
He marked and drilled holes to install the brackets on the frame.
I installed threaded rivets in the holes.
With the threaded nuts in place, I soldered the included power cord to the power connector on the case holder. I painted the brackets with black paint, attached a few pieces of adhesive foam and screwed the brackets on.
Step six: assembling the bike
Now you can start assembling the e-bike and installing the motor-wheel on it.
First, he installs a waterproof box on the controller. The box will contain all the connectors and connections.
The kit includes a Maxxis tire, but the master chose to fit wider CST tires. A brake disc is also included, but he used an old one from the bike and screwed it to the wheel motor. After the brake disc was screwed on, I installed the wheel on the frame.
Installs the pedaling sensor. This sensor is installed on the bicycle carriage. As soon as you start pedaling, the sensor sends a signal to the controller and the motor turns on. Thus, you can drive in automatic mode even without a throttle on the steering wheel.
Next installs LCD, throttle, brake levers, switches, etc. Detailed installation and configuration can be viewed by following this link.
Then he fixes and connects the cables.
Now the battery can be charged, inserted into the case, fixed with a key and tested.
Step seven: testing
It took the builder a long time to assemble this e-bike, but he is very pleased with the result. The distance an e-bike can travel 100 km (62 miles) when pedaling and about 50 km on the engine alone at a top speed of 65 km/h.
Pedals are great for saving battery power and helping your bike accelerate even faster. There are many programmable options on the LCD itself and the best part is the BMS Bluetooth connection. The battery can be turned on and off using the app It also shows temperature, range, current, cell group voltage and many variable parameters.
Below you can watch a video with the process e-bike assembly.
