Even after well over 100 years of development and much promising research into other techniques of energy storage, the lead-acid battery is still the best choice for motor vehicle use. This is particularly so when cost and energy density are taken into account.Incremental changes over the years have made the sealed and maintenance-free battery now in com- mon use very reliable and long lasting. This may not always appear to be the case to some end-users, but note that quality is often related to the price the customer pays. Many bottom-of-the-range cheap batteries, with a 12 month guarantee, will last for13 months!The basic construction of a nominal 12 V lead- acid battery consists of six cells connected in series. Each cell, producing about 2 V, is housed in an individual compartment within a polypropylene,or similar, case. Figure 5.2 shows a cut-away battery showing the main component parts. The active mater- ial is held in grids or baskets to form the positive and negative plates. Separators made from a micro- porous plastic insulate these plates from each other.The grids, connecting strips and the battery posts are made from a lead alloy. For many years this was lead antimony (PbSb) but this has now been largely replaced by lead calcium (PbCa). The newer mater- ials cause less gassing of the electrolyte when the battery is fully charged. This has been one of the main reasons why sealed batteries became feasible, as water loss is considerably reduced.However, even modern batteries described as sealed do still have a small vent to stop the pressure build-up due to the very small amount of gassing. A further requirement of sealed batteries is accurate control of charging voltage.
đang được dịch, vui lòng đợi..
