Apparatus and method for maintaining the charge of a battery

• US 5,493,198 A
• Filed: 05/13/1994
• Issued: 02/20/1996
• Est. Priority Date: 05/13/1994
• Status: Expired due to Term

• Current Assignee: Google Technology Holdings LLC (Alphabet Inc.)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Kamke, James E.
• Primary Examiner(s): Wong, Peter S.
• Assistant Examiner(s): TSO, EDWARD H
• Application Number:
  US08/242,754
• Time in Patent Office: 648 Days
• Field of Search: 320/22, 320/23, 320/24, 320/31, 320/32, 320/35, 320/36, 320/37, 320/38, 320/20
• US Class Current: 320/150
• CPC Class Codes: H01M 10/345 Gastight metal hydride accumulators
• CPC Class Codes: H01M 10/443 in response to temperature
• CPC Class Codes: H02J 7/007194 of the battery
• CPC Class Codes: Y02E 60/10 Energy storage using batteries

Abstract

A battery charger (10) and associated method for maintaining the charge of a battery (12). The battery charger (10) has a processor (16), power supply (14) and power regulator (15). The battery charger (10) first applies a high current charge to the battery (12), which is terminated when the battery voltage or temperature reaches a defined limit. Then the battery charger (10) applies a low current charge (102) for a set period of time. Next, no charge is applied until the battery (12) cools to an ambient temperature. The ambient temperature is then measured using a thermistor (18) in the battery (12). If the ambient temperature is above a certain threshold no charge is applied for a wait period. If the ambient temperature is below the threshold the low current charge is applied for a the set period of time.

Claims

1. An apparatus for maintaining the charge of a battery comprising:

a power supply;

a regulator means coupled to the power supply for regulating the current to the battery; and

a processor means coupled to said regulator means for controlling the regulator means, the processor means having two modes, a first mode for charging the battery and a second mode for maintaining the charge of the battery by applying a maintenance charge from the regulator means to the battery based upon an ambient temperature, wherein the battery contains a thermistor and the maintenance charge is turned off for a predetermined period of time before the thermistor temperature is sampled, whereby the thermistor'"'"'s temperature is at ambient temperature.

2. The apparatus of claim 1 wherein the maintenance charge is only applied to the battery if the ambient temperature is below a predetermined temperature.

3. The apparatus of claim 1 wherein the battery to be charged is a NiMH battery.