about Battery packs

Battery packs



The cells in a battery can be connected in parallel, series or in both. A parallel combination of cells has the same voltage as a single cell, but can supply a higher current (the sum of the currents from all the cells). A series combination has the same current rating as a single cell but its voltage is the sum of the voltages of all the cells. Most practical electrochemical batteries, such as 9-volt flashlight batteries and 12-volt automobile batteries, have several cells connected in series inside the casing.[46] Parallel arrangements suffer from the problem that, if one cell discharges faster than its neighbour, current will flow from the full cell to the empty cell, wasting power and possibly causing overheating. Even worse, if one cell becomes short-circuited due to an internal fault, its neighbour will be forced to discharge its maximum current into the faulty cell, leading to overheating and possibly explosion.[47] Cells in parallel are therefore usually fitted with an electronic circuit to protect them against these problems. In both series and parallel types, the energy stored in the battery is equal to the sum of the energies stored in all the cells.

Traction battery
AGM Battery Cutaway Drawing of Braille Carbon Battery. Click to Enlarge Detail
AGM Battery Cutaway Drawing of Braille Carbon Battery. Click to Enlarge Detail

A traction battery is a high-power battery designed to provide propulsion to move a vehicle, such as an electric car or tow motor. A major design consideration is power to weight ratio since the vehicle must carry the battery.[48] While conventional lead acid batteries[49] with liquid electrolyte have been used, gelled electrolyte[50] and AGM-type[51] can also be used, especially in smaller sizes.

The largest installations of batteries for propulsion of vehicles are found in submarines, although the toxic gas produced by seawater contact with acid electrolyte is a considerable hazard.

Battery types commercially used in electric vehicles include

* lead-acid battery, which uses lead(IV) oxide (PbO2) and sulfuric acid (H2SO4)[22]
o flooded type with liquid electrolyte
o gel
o AGM-type (Absorbed Glass Mat)
* Nickel-metal hydride and Nickel-Cadmium batteries
* Lithium-Ion and Lithium-Polymer batteries
* Zebra Na/NiCl2 battery operating at 270 °C requiring cooling in case of temperature excursions
* NiZn battery (higher cell voltage 1.6 V and thus 25% increased specific energy, very short lifespan)

See also: battery electric vehicles and hydrogen vehicle.