from chemistry to pack
The anti-shunt tab design is there to enable a better resistance micro spot weld. The busbar for a cylindrical or prismatic cell has to be welded blind. Meaning you can only weld from the topside of the busbar as the cell itself is a sealed system. The anti-shunt tab design shown on the left welded … Read more
Isolation Tests on Assembled Cells come in a number of forms, but the intention is to check for: Although very rare, cell internal short circuits are a leading cause of battery thermal runaway. They are a major safety issue for any application of a battery pack. Hence there is a requirement to prevent them and … Read more
As you charge a cell it expands, when you discharge a cell it contracts and as the cell ages over its lifetime we see a continuing cell expansion. Thus the cell expansion can be divided into: The reversible cell expansion comes from changes in graphite layer spacing associated with different graphite-lithium intercalation compounds induce reversible … Read more
What do we need to see on a cell specifications sheet? Of course we need high level data, but I think we need quite a bit more. This is my starter, but I would like to develop this list into a more concise draft for a datasheet. Some of the better datasheets are from Saft … Read more
A 4680 cell concept The battery industry is targeting larger cell formats, which enable simplified module design and cell-to-pack or even cell-to-chassis solutions. In this regard, hard case battery cells and in particular cylindrical cells will play an important role in enabling the named developments. Tesla’s announcement of a tabless 4680 cylindrical LIB has triggered … Read more
When we say cell energy density we need to consider if this is gravimetric (Wh/kg) or volumetric (Wh/litre). The energy content of the cell will be determined by the discharge rate, temperature and other parameters. Discharge rate capability of a new SAFT MP 176065 xtd battery. As you can see, at a C/8 discharge rate … Read more
Cylindrical Cell Electrode Estimation: An alternative geometric approach. Here we present a simple method for estimating electrode length in a cylindrical cell. The method is equally applicable to other formats since we make an estimation of the total active electrode area. Results require knowledge of one electrode Active Material (AM) chemistry, electrode porosity and thickness … Read more
Using some simple mathematics and dimensions we can do some cylindrical cell electrode estimation. Knowing the outer and inner diameter of the spiral along with it’s thickness we can calculate the length of the material to create it. D is the inner diameter of the cylindrical can. The inner diameter is that of the mandrel … Read more
The cell electrode pressure is required to keep the cell operating at it’s peak performance over it’s lifetime. However, is there an optimum pressure and why exactly does the cell need it? As the cell is charged lithium ions move into the graphite anode and the cell will increase in thickness. Silicon in the anode … Read more
The Tesla 4680 cell has intrigued ever since it was announced. A cylindrical cell that is 46mm in diameter and 80mm high. Estimated Specifications: Capacity tests [6]: Capacity: 23.35Ah at 2.5A discharge ~C/10 Capacity: 20Ah at 25A discharge ~1C 26.5Ah (estimate based on 21700 5Ah volumetric energy density) and this fits with capacity of the … Read more