GB2338074A

GB2338074A - A method and means of identifying an electrical cell type

Info

Publication number: GB2338074A
Application number: GB9812232A
Authority: GB
Inventors: Stephen David Harris; Adrian Bruce Nickerson
Original assignee: Motorola Ltd
Current assignee: Motorola Solutions UK Ltd
Priority date: 1998-06-05
Filing date: 1998-06-05
Publication date: 1999-12-08
Also published as: GB9812232D0

Abstract

A method and means of identifying an electrical cell type of a battery 8 comprises measuring a battery's low-load voltage and low-load to high-load voltage drop. Determining a threshold value related to one of the said measurements, then comparing the other of the said measurements with the threshold value to identify the cell type of the battery. The threshold value may be derived from a predetermined look-up table stored in a memory. The method and means may be used in a radio device in which the low-load condition relates to a standby condition and the high-load condition relates to a transmitting condition. The identification of a battery's cell type allows effective battery monitoring to be provided in devices which may use different types of battery.

Description

2338074 Method And Apparatus For Determining Battery Type

Field Of The Invention

This invention relates to a method and apparatus for determining a type of battery. It is particularly applicable to radio transmitting apparatus which is powered by the battery but will also have application in other battery powered equipment.

BackL-round To The Invention Battery checking is now a common feature on battery powered equipment, particularly, where a user of such equipment must receive a timely warning to renew a battery to prevent loss of data or otherwise where it is essential for the equipment to remain available for use. Such an application is two way radio equipment.

In two way radio equipment, the length of warning period before the battery reaches such a low power level that the equipment has to stop functioning is considered to be adequate by most users if about thirty minutes. A user of the equipment will then have sufficient time, under most circumstances, to replace the battery pack with a fresh one or to complete a communication before the battery pack is exhausted.

Battery performance varies with the type of battery being used. Rechargeable nickel cadmiun batteries will have different discharge characteristics to those of alkaline cells. Thus, battery monitoring circuits optimised for a particular type of battery will not work satisfactorily with other types of battery. For example, if a hand portable radio has a low battery warning threshold set for NiCad cells, then when alkaline cells are used the low battery level warning thresholds will not be appropriate. In a high current drain operation, such as when the radio is transmitting, even a fresh alkaline battery will be below the low battery threshold for a Nicad battery. The radio will then provide a warning that the battery level is low which is inappropriate.

2 CM00524P In the same circumstances, when the radio is in standby mode, by the time that the alkaline battery drops below the low battery threshold for a NiCad the alkaline battery has insufficient life left to receive or transmit. Thus no useful warning is given that the battery is exhausted.

Summary

According to the invention there is provided a method of identifying an electrical cell type comprising the steps of; determining one of a standby voltage and a standby to high-load voltage drop; providing a threshold appropriate to the determined one of the standby voltage and standby to high-load voltage drop, comparing the other of the standby voltage and high-load voltage drop to the threshold, to identify the cell type.

The invention also provides apparatus for identifying an electrical cell type.

Brief Descri-otion Of The Drawines A specific embodiment of the invention will now be described, by way of example only, with reference to and as illustrated by the drawings in which:

Figure 1 is a schematic block diagram of a radio transceiver with a battery, checking function operating in accordance with the invention; and Figure 2 and 3 are explanatory diagrams.

Detailed Descriv)tion Of A Si)ecific Embodiment As is shown in figure 1, a hand-held portable radio 1 in accordance with an embodiment of the invention includes a microprocessor 2, a memory 3, a transmitter section 4, a receiver section 5, an antenna switch 6, an 3 CM00524P antenna 7, a battery 8, a liquid crystal display 9 and resistor network 10 comprising resistors R1, R2.

The microprocessor 2 is connected to the memory 3, the transmitter and receiver sections, the antenna switch 6 and to the junction between R1 and R2. The microprocessor 2 provides the intelligence for the radio 1 and controls its operation.

The memory 3 holds the program which governs the operation of the microprocessor 2 and it may be read and written to by the microprocessor 2 by means of a databus.

The battery 8 may be an alkaline, nickel cadmium or other type and is of conventional form. The type of battery used can vary at the option of the user.

The receiver section 5, transmitter section 4, antenna 7 and antenna switch 6 are of conventional form. The antenna switch 6 operates under the control of the microprocessor 2 to selectively couple the transmitter section 6 and the receiver section 5 to the antenna 7.

The liquid crystal display is also of conventional form and it is used for the display of information to a user of the radio.

The resistor network is connected to a battery monitor input of the microprocessor 2, to the positive terminal of the battery 8 and to ground. The network provides a potential divider thus presenting at the input of the microprocessor 2 a voltage to be monitored. The microprocessor 2 is programmed to provide an analogue to digital conversion function to convert the voltage level into a digital form.

The memory 3 includes a table data structure in which a number of battery voltage in standby values and voltage drop threshold values are 4 CM00524P stored. The table is shown in figure 2 and it comprises in the left hand column a set of battery voltage in standby(receive mode) values ranging from 6.4 to 9 volts in steps of 0.2 volts and a set of corresponding appropriate threshold values ranging from 1.6 to 1.3. The values are shown in decimal form rather than as stored hexadecimal for the convenience of the reader.

The table structure works in the following way. When a voltage value is measured by the microprocessor 2 it is passed to the table in memory 3.

The table then returns the appropriate voltage drop threshold to be used by the microprocessor 2 to identify the battery 8 and this is held at a further memory location.

When the user places the radio in transmit mode, (by depressing a pushto-talk switch not shown) the microprocessor 2 will via the resistor network determine the voltage drop in this high current drain mode as well as carrying out the conventional functions when a radio is operating in transmit mode.

The microprocessor then compares the detected voltage drop with the threshold held in the further memory location. If the drop exceeds the threshold the battery type is identified by the microprocessor 2 as being an alkaline type. If the drop is less than or equal to the threshold the battery type is identified as being a nickel cadmium.

The type of battery determined may then, or at a later stage, be used to determine whether or not to issue a low battery warning to the user via the liquid crystal display 9.

The steps carried out to identify the battery are shown in Fig. 3. In a first step 30 the standby voltage is measured and the measured voltage used to select the appropriate threshold step 31. When the radio is used in a high current drain mode, that is to say, in transmit the voltage drop is again CM00524P measured, step 32. the voltage drop is then compared with the threshold in comparison step 33 and the result used to identify the battery step in step 33.

The battery voltage is then monitored for a low condition in step 35. If the battery is low then a warning to the user is given on the liquid crystal display in step 36. If the battery is not low then after a suitable pause the process returns to step 35.

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Claims

Claims

CM00524P 1. A method of identifying an electrical cell type comprising the steps of. determining one of a standby voltage and a standby to high-load voltage drop; providing a threshold appropriate to the determined one of the standby voltage and standby to high-load voltage drop; comparing the other of the standby voltage and standby to high-load voltage drop to the threshold to identify the cell type.
2. A method as claimed in claim 1 wherein the standby voltage is determined and the threshold is a standby to high-load voltage drop which is compared to a measured standby to high-load voltage drop to identify the cell type.
3. A method as claimed in claim 1 or claim 2 comprising the step of providing a plurality of standby and corresponding standby to high load voltage drops.
4. A method for identifying a cell type substantially as hereinbefore described with reference to and or as illustrated by the drawings.
5. Apparatus for identifying an electrical cell type comprising:

a voltage determinator for determining a voltage of the cell when in a standby condition and a high load condition; a processor responsive to the voltage deterniinator to determine one of a standby voltage drop and a standby to high load voltage drop; memory for, in use, storing threshold values; comparitor for comparing the determined one of a standby voltage drop and a standby to high load voltage drop to the threshold values to determine the battery type.
6. A radio including an apparatus as cl aimed in claim 5.
7. Apparatus for identifying cell type substantially as hereinbefore described with reference to and as illustrated by the drawings.

7 CM00524P 6. A radio including an apparatus as claimed in claim 5.