Peukert's law

Encyclopedia : P : PE : PEU : Peukert's law

Peukert's Law expresses the capacity of a battery in terms of the rate at which it is discharged. As the rate increases, the battery's capacity decreases, although its actual capacity tends to remain fairly constant.

Peukert's law is as follows:

[C_p = I^k t \,]

where:

[C_p \,] is the capacity according to Peukert, expressed in Ah.
[I \,] is the discharge current, expressed in A.
[k \,] is the Peukert constant, dimensionless.
[t \,] is the time of discharge, expressed in h.

For an ideal battery, the constant k would equal one, in this case the actual capacity would be independent of the current. For a lead-acid battery, the value of k is typically between 1.1 and 1.2 however.

The Peukert law becomes a key issue in a battery electric vehicle where batteries rated at 20 hour discharges are used at much greater rates of about 1 hour.

There is a particular Watt-Hour counter called an E-Meter produced by Xantrex which can be programmed with battery capacity, Peukerts exponent, and other particular batteries characteristics. It then counts watthours and can display various information relating to the SOC (State Of Charge) of the battery pack, including remaining energy and thus range. Similar products are offered by other manufacturers.

External links

From Wikipedia, the Free Encyclopedia. Original article here. Support Wikipedia by contributing or donating.
All text is available under the terms of the GNU Free Documentation License See Wikipedia Copyrights for details.