from chemistry to pack
How can we go about maximising pack energy density? What can we look at to reduce the mass and volume? Where are the opportunities given a defined cell? A great example of shrinking the size of a battery pack is the Mercedes Vision EQXX research car. The advantage they had was a much more energy … Read more
When we look at the battery versus system voltage we have to remember that these are working together. In fact we have to look at the complete system and all components to ensure they can work together over the maximum and minimum voltage range. This will normally be the maximum charge voltage and the minimum … Read more
Why are we moving to higher voltage packs? We know that the battery cell is not a perfect current source as it also has an internal resistance. Symbolically we can show a cell with the internal resistance as a resistor in series. Rint is the DC internal resistance, sometimes abbreviated as DCIR. The DCIR is not … Read more
Often it is difficult to estimate the battery pack volume, hence here is an approximation based on data fitting. Hence a first approximation is that the battery pack volume will be 5x the total energy in kWh. A 100kWh battery would have a volume of 500 litres. If this was a design optimised for volume … Read more
It is possible to use the battery pack database to estimate the pack mass from cell density. The key relationship we have is between cell and pack gravimetric energy density. This graph has been pulled together by scouring the internet for cell and battery data. The ratio of cell density to pack density is 0.6235 … Read more
Cold climate EV range is determined by a number of factors. First of all though, let’s look at the range results as conducted by Motor.no in their winter range tests. An impressive test with 29 different electric vehicles. Read the full description of the tests on the Motor page and there you can see some … Read more
Obviously Cell Capacity and Pack Size are linked. The total energy content in a battery pack in it’s simplest terms is: Energy (Wh) = S x P x Ah x Vnom Hence the simple diagram showing cells connected together in series and parallel. What about flexibility in pack size? There are very good reasons for … Read more
Battery pack size versus application is an interesting comparison. The plot is based on real data from real products in the market and shows total battery pack size. The Y-axis is a logarithmic scale and hence the eLorry battery is nearly 6 orders of magnitude, or 1 million times, bigger than the smart watch battery.
In the simplest terms the usable energy of a battery is the Total Energy multiplied by the Usable SoC Window. The total energy is the nominal voltage multiplied by the nominal rated capacity. However, if you have been through the Battery Basics you will have realised that the battery cell and pack do not have … Read more
A look at the electrified aircraft propulsion targets. NASA state in their November 2021 presentation that they have the following requirements for the battery pack: The targets at pack level are rather tough: The gravimetric energy density plotted versus total pack energy shows that the automotive packs are currently plateauing around 180Wh/kg. The roadmap to … Read more