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Simultaneous Thermal Monitoring of Multiple Cells While Charging Using a Single Thermal Sense Device.

IP.com Disclosure Number: IPCOM000033268D
Original Publication Date: 2004-Dec-02
Included in the Prior Art Database: 2004-Dec-02
Document File: 2 page(s) / 40K

Publishing Venue

IBM

Abstract

Disclosed is a method of measuring a representative temperature of a multi-cell battery string using a single temperature sensor. The method disclosed provides the capability to view a representative temperature of the battery string as opposed to measuring a single point and relying on that point to be representative of the entire strings temperature profile.

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Simultaneous Thermal Monitoring of Multiple Cells While Charging Using a Single Thermal Sense Device.

For most rechargeable battery technologies, e.g. NiMH. NiCad, LiIon, Lead Acid, the process of charging is exothermic. The charging process is not 100% efficient so some of the energy fed to the cells is lost as heat. This heat causes the temperature of the battery cell to rise. If the rate at which energy is added is small as it is in trickle charging, the battery is able to shed the excess heat via radiation, convection and/or conduction so that temperature rise above ambient is small. If the rate at which energy is added is large the temperature difference will be larger. It is important that the battery cell temperature not exceed some maximum temperature (the value of which will vary with battery chemistry and cell construction) or irreparable and potentially catastrophic may occur. For many cell chemistry, the amount of energy lost as heat increases substantially as the cell approaches and passes its fully charged state. Overcharging a battery can also damage it. Also, a defective battery cell will heat up faster than a normal cell while charging, so the temperature rise can be used as a method to detect a faulty cell. For these and other related reasons, it is common practice to measure the temperature of a battery during rapid or high current charging.

Batteries are often composed of multiple battery cells in series. These cells in series are often referred to as a battery pack. When charging these multiple cell batteries it common practice to place a single thermal sensing device, e.g. a thermistor as near as possible to the center of the thermal mass of the battery pack. A single sensor is used rather than one or more per cell primar...