from chemistry to pack
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
Lets look at the inputs to pack sizing, what do we need to know in order to size a pack? At the early stage you don’t need to think about total energy, concentrate on the usable requirement and conditions at which that needs to be achieved. The minimum and maximum voltage is likely to be … Read more
Cell to Pack is all about reducing cost and increasing the volumetric density of battery packs. This is primarily aimed at road vehicle battery design. Conventional battery pack design has taken the form: Cell -> Module -> Pack This means we add material to make the module strong enough to be handled, it needs fixings … Read more
Pack Gravimetric Energy Density has the units Wh/kg and is a key pack metric. The optimum metric is a high Wh/kg. Hence: The best you can achieve will be less than or equal to the cell Wh/kg that the pack is made from. Perhaps the simplest of the battery metrics as the capacity of the cell … Read more
If we want a battery cell to last a lot of cycles, extend the life in a power application or to ensure the available power is consistent then we need to set a usable SoC window that is smaller than 100%. That is we will limit the top end charge to perhaps 95% SoC and … Read more