The major manufacturers of Li-ion cells are juggling the competing forces of demand and raw material supply as well as standardising on cell size and construction to get economies of scale. Many existing designs of the ‘prismatic’ style in welded aluminium or steel housings are being discontinued in favour of ‘pouch’ cells, often in lithium-polymer technology that allows a laminated construction, which is lighter and gives mechanical flexibility and slightly higher specific energy. Pouch cells do suffer from swelling with charge/discharge cycling though, with smaller sizes growing as much as 10% in volume over 500 cycles. The standard 18x65mm 18650 cylindrical cells and larger variants will certainly still be supported for some time to come, as the format suits applications like Tesla’s 100kWhr module where 8256 cells are stacked in staggered rows with pipes for liquid cooling. The cylindrical wound format is good for mechanical stress resilience and the small remaining gaps between cells allow for some air-cooling. The volume of cylindrical cells produced over the years has also brought their cost down considerably.
So, as a design engineer, you’ve decided on a Li-ion battery for your new device and need a few prototypes. The prospective production volume is, you hope, high but getting one of the ‘big four’ manufacturers to consider supporting a new custom design is a mountain to climb. A solution is to pick from the extensive range of standard parts from Avnet Abacus, which includes the 18650 size cylindrical cells from major suppliers Dubilier, Panasonic, RRC, Samsung and Varta, available in single 3.7V cells from 2250mAh to 3300mAh, to packs of up to 70 cells at 25.2V/29000mAh. A range of ‘prismatic’ types are supported in single and 3-cell formats along with a more extensive range of ‘pouch’ lithium polymer cells in varying mechanical sizes and ratings from 130mAh to 3000mAhr. Many of the prismatic ‘hard pack’ variants are supported by relevant chargers. The standard range also features the Coin Power Li-ion button cells from Varta.