A battery pack is a set of any number of (preferably) identical batteries or individual battery cells. They may be configured in a series, parallel or a mixture of both to deliver the desired voltage, capacity, or power density. The term battery pack is often used in reference to RC hobby toys and electric vehicles. Four double-A (AA) batteries In science and technology, a battery is a device that stores energy and makes it available in an electrical form. ... An electric vehicle is a vehicle whose motion is provided by electric motors. ...

Components of battery packs include the individual batteries or cells, and the interconnects which provide electrical conductivity between them. Interconnects are also found in batteries as they are the part which connects each cell, though batteries are most often only arranged in series connections. When wiring a pack in parallel there are various methods and one should take into consideration the balance of the electrical circuit. Battery regulators are sometimes used to keep the peak voltage of each individual battery or cell below its maximum value so to allow weaker batteries to be fully charged, bringing the whole pack back into balance. Active balancing can also be preformed by battery balancer devices which can shuttle energy from strong batteries to weaker ones in real time for even better balance. A well-balanced pack lasts longer and delivers better performance so it is a rather beneficial component of high capacity or expensive packs. A battery regulator is a device in a battery pack which bleeds of excess charge current to allow all cells or batteries in a string to be fully charged without overcharging other cells. ... A battery balancer is a device in a battery pack which can actively shuttle energy into a weak cell from other more healthy cells in the pack, they may also include the function of a battery regulator to prevent overcharging. ...

Calculating State Of Charge

SOC or State of charge is the equivalent of a fuel gauge for a battery. SOC is sometimes difficult to determine as it can not usually be determined by simple voltage measurements. Electrolite PH levels are a good SOC indication, but many modern chemistries don't offer easy access to that part of the battery. Most SOC methods take into account voltage and current as well as temperature and other aspects of the discharge and charge process to in essence count up or down within a pre-defined capacity of a pack. E-Meters take into account Puckert effect which is a function of charge/discharge rate or amps.

• Good information to be integrated...
• http://autos.groups.yahoo.com/group/ev-list-archive/message/42128 - Calculating State Of Charge (SOC)
• http://autos.groups.yahoo.com/group/ev-list-archive/message/42428 - Calculating State Of Charge (SOC) deeper

Advantages

An advantage of a battery pack is the ease with which it can be swapped into or out of a device. This allows multiple packs to deliver extended runtimes, freeing up the device for continued use while charging the removed pack separately.

Another advantage is the flexibility of their design and implementation, allowing for the use of cheaper high production cells or batteries to be combined into a pack for nearly any application.

Disadvantages

Packs are often simpler for end users to repair or tamper with than a sealed non-serviceable battery or cell. Though some might consider this an advantage it is important to take safety precautions when servicing a battery pack as they pose a danger as potential chemical, electrical, and fire risks.