from chemistry to pack
Cell Gravimetric Energy Density with the units Wh/kg is a key cell metric. The optimum metric is a high Wh/kg. Hence: High nominal voltage High Ah capacity Low mass Perhaps the simplest of the battery metrics as the capacity of the cell is fairly easy to measure and the mass is just a set of … Read more
Comparing power versus energy cells we see there are some fundamental differences. A high energy cell will have better volumetric and gravimetric energy density at the expense of the ability to deliver a high current. The power cell will have a low internal resistance and will be optimised to deliver current over energy density. Teardown … 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
Cell balancing is all about the dissipation or movement of energy between cells. The aim being to align them all with respect to state of charge. Aligning the state of charge of all of the cells in a pack will allow the pack to deliver the most energy and power. A set of cells connected … Read more
When connecting cells in series the negative terminal of the first cell is connected to the positive terminal of the second cell. The negative terminal of the second cell is connected to the positive terminal of the third cell. This continues until we reach the total number of cells required in series. The nominal voltage … Read more
The amount of energy available from a battery. Chemical Capacity – full storage capacity of the chemistry when measured from full to empty or empty to full. This is normally defined at a given C-rate and maximum and minimum voltages. Designed Capacity – the storage capacity allowed to be used by the application. Often called … Read more