Data Required to Size a Pack

bmw-ix3 battery pack exploded view

When thinking about sizing a battery pack it is worth stopping and considering the data required to size a pack. These are the requirements. If you don’t have these then the design is likely to change considerably, these changes will cost time and can ultimately end in a poorly optimised design. The usable energy for … Read more

Higher Voltage Packs

Continuous charge / discharge power versus nominal voltage

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

Pack Mass from Cell Density

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

Summer vs Winter Electric Vehicle range

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

Cell Capacity and Pack Size

Size of battery packs vs cell capacity

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