What can we learn from Battery Benchmarking? was presented at the Battery Tech Show 2024 and has been abrieviated and turned into a post.
We don’t have the resources to take batteries apart, but there are lots out there who do and they share lots of data. On top of that there are certification reports, technical presentations and cell specification sheets.
We gather that data into cell and pack spreadsheets, we also build simple spreadsheet models of the packs to check the numbers. All of these tools are available in Downloads.
Tesla 2022 Model Y 4680
A great example of this is the Tesla 4680 cell introduction, we had a mass for the battery pack and the interior floor trim, seats etc. We built a simple table of what was included and started estimating part weights with our knowledge of automotive engineering.
That gave an estimated pack mass that we could then use to see the advantage of the 4680 cell and structural pack design. Very soon we started seeing papers with cell capacity numbers and a great teardown by The Limiting Factor.
The configuration of the pack, metrics for the pack and cell all started coming together.
Tesla 4680 Cell
This allowed us to look at the 4680 cell in detail and position it against the Tesla 21700 cell it was replacing.
At a cell level this first version of the 4680 was not as good in terms of energy density, but we know this is all about reducing costs.
What can we actually learn from Battery Benchmarking?
One simple aspect is we can look at the arrangement of parts.
This Audi etron pack has the cooling system outside of the battery main enclosure. Any leaks with not result in HV isolation issues or more catastrophic failure.
This post has been built based on the support and sponsorship from: MAHLE Powertrain Ltd, Thermo Fisher Scientific, Eatron Technologies, About:Energy and Quarto Technical Services.
Battery Pack Weight
The battery pack database is continually growing and that gives us the ability to look at relationships.
Everything but the Cells
If we know what cell is being used we can remove the mass of the cells and create a bit more information. It is interesting that the constant part of the straightline best fit is 31.2kg as that represents the parts that are more or less fixed in every pack (BMS, BDU, Connectors).
We use this in our online pack mass estimation tool.
Alternative Pack Mass Estimation
If we have an energy density for a new cell we can estimate the pack mass.
This is only a first rough estimate, but this is a good way of checking if you are in the right ballpark.
Examples
In the presentation we gave two examples of using this data and as these are already covered elsewhere within BatteryDesign.net I will give an overview and let you read further.
Copper Busbar Sizing
Benchmarking data shows that the 6A/mm2 rule of thumb is a good starting point for sizing copper busbars.
Cooling Pouch Cells
The development of the pouch cell and edge cooling is a great example of how designs mature. This maturing of designs we see in benchmarking over time.
What can we learn from Battery Benchmarking? was presented at the Battery Tech Show 2024.
