Traditional battery pack assembly
If you open a traditional e-bike battery, this is what you will see:
- lithium-ion cells ( the pink cylinders) are spot welded together
- the BMS (grey and green part on top) has a lot of wires that are soldered to the cells
- there often a lot of adhesives
This way of manufacturing batteries is suboptimal because as this video proves it, dismantle a battery is requires too many operation to be economically viable and is very dangerous:
Why should we want to dismantle a battery ?
To repair them !
We have diagnosed about 5000 batteries from different applications (e-bike, moped, power tools, consumer electronics etc) and what we found is that batteries are fragile and most of dead batteries often have only one failing element. The three main catégories are:
- mechanical problems: the casing or the connector of the battery is broken. It can also be an unsoldered wire.
- electronic problem: the BMS can have one 0,01€ resistor that is broken and the battery cannot work
- chemistry problem: cells are not perfect and a slight discrepancy between them can lead to having few cells failing in the battery
At the moment, batteries are never repaired because they cannot be repaired in a safe an economical manner. So we need to pay for the recycling and pay for another battery. So the earth.
Add a chart with the stat of failure per category
To give a second life to the cells !
On the 5000 batteries that have been diagnosed, we took out all the cells and tested them individually. The conclusion is that 70% of the cells that go to recycling are still completely usable.
Link to Knowledge Base: result on our cell testing
To recycle them properly !
Lithium-ion batteries are recycled when they are collected. In France, the collection rate is about 50%. But the recycling consist in crushing batteries into black mass that can then be subjected to heavy chemical treatment in order to separate the valuable materials.
Not only does this method destroys all the casing, connector and electronics that account for more than 1/3 of the battery cost but also it creates a less pure black mass.
Link to knowledge base on how batteries are recycled.
How to eco-design batteries ?
Gouach invented a weld-less technology that uses PCB (Printed Circuit Board) instead of nickel sheets to connect the lithium-ion cells together. This simple idea declines into a design framework as the PCB can integrate many functionalities into a single piece of easy to produce hardware.
In this approach, there are no more wires, no more spot welding, cells are more protected and the electronics or any component (including cells) can be replaced safely in matter of minutes.
Add a video of dismantling a new model of Gouach battery
Is this applicable to other fields than e-bikes ?
Sure, as we can see in the following section, our weld-less contact is not the limiting factor. As most big batteries are designed as a combination of smaller pack, this method can apply. For instance a Tesla model S battery is composed of 14 modules:
Each module containing a few hundreds cells:
Is this approach limited to honeycomb cell layout ?
Gouach approach can be generalised to staked layout. We made a model and tested all the vibrational aspects.
In the following pages, we give more details on how this works and has been tested.
Weld-less contactsAdditional benefits of the Gouach approachManufacturing contactsPack assembly [WIP]