In the first part of this topic, we showed the process that lead us to the sizing and configuration of our battery pack. In this post, we are going to go through the process of adapting that batterypack to the motorcycle, how the first version of battery containers were designed and produced.
The changes made in the design of the accumulator container and consequent changes in other parts of the electric system such as the BMS were made with the objective of simplifying integration of the various parts of the electric system increasing the overall safety of the accumulator container and also to make the harnessing simpler and easier.
With this in mind, the suggested layout for the accumulator container can be seen below (side view).
The changes to be made include: converting the 3 BMS independent units into one centralized BMS board, enclosing the batteries inside two boxes connected to each other in series, place all the electronics, including the DC/DC converter and excluding the dashboard, in front of these packs and place the line contactor on top of the packs, among others.
Starting with the battery packs containers, the idea was to make the cell parallel and series connections as simple and protected as possible. Regarding the cells parallel connections, one of the first ideas was to embed copper conductors into some sort of composite like kevlar leaving only the connectors for the cells exposed, but this idea was quickly abandoned and we opted for a variation of the test bench connections, where all the wires, each corresponding to one voltage level all join in a MX150 connector, which would be placed on the surface of the container so it can be connected to the BMS harness.
The series connections were maintained as they were, for the exception of the battery terminals, wich were done using an electrolytic copper busbar with screws to the front and back of the container. The front screws are supposed to serve for the DC/DC (buck, for low voltage electronic supply ) converter supply and both IMD (Insulation Monitoring Device) and ECU (Electronic Control Unit, which controls an SSRelay that opens and closes the motor controller supply). The back screws of the busbar are used for power connections. There is also one other connector on the container surface for thermistor connection, as each container features 6 thermistors for temperature monitoring.
There is one screw that goes through each busbar and another dummy screw to connect a 500 amp fuse. A CAD design for each container can be seen below, please note some things are not shown here, such as the dummy screw.
In order to hold the the containers and electronics, and fix them to the motorcycle frame, a steel structure was designed. The idea was attach the battery containers and the electronics to the structure and perform most connections before enclosing everything in an outer protective container. Please note that some of these designs suffered further modifications during design itself or during production. This structure can be seen below.
Finally, small boxes were designed to protect the PCBs. The final assembly can be seen below.
With all the designs ready, it was time for the production.
The boxes for the electronics were made in PLA and the battery containers were printed in frieproof ABS. The problem was, it is very hard to print such large pieces in that material so some parts of the containers were made in that material, others were made in ABS Pro, from one of our sponsors.
The structure was water cut and welded afterwards.
The soldering of the new cell connectors can be seen in the image below.
The images below show de construction and assembly of the containers.
After placing all the cells, along with some protective foam, the packs look like this:
The first lids, which hold the terminals and the busbar are shown below:
After the assembly, the open containers look like this:
Which when connected, including the thermistors, look like the following:
The image below identifies the main parts that compose the containers.
Finally, in the following image, we can see both packs placed on the structure.
Some features had to be added such as protective ruber and foam, the structure was painted and some handmade L shaped bars were added to hold the electronics in place.
These changes can be seen below, after reassembly.
We hope you enjoyed this post and want to let you know that the battery pack odissey is not over! There are still changes to be made and the final version will be shown in another blog post. Thank you for following and, once again thank you Farnell Element14 for giving us the chance to participate in this comunity