Electricity: measuring and testing – Electrolyte properties – Using a battery testing device
Reexamination Certificate
2002-03-20
2003-03-25
Tso, Edward H. (Department: 2838)
Electricity: measuring and testing
Electrolyte properties
Using a battery testing device
C324S430000
Reexamination Certificate
active
06538449
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to the estimation of extant battery life for battery powered apparatus.
BACKGROUND TO THE INVENTION
Mobile telephones are an example of a battery-powered device familiar to most people. The extant battery life of battery-power devices, including mobile telephones, is of considerable importance to their users. Consequently, the provision of extant battery life indicators on mobile telephones is universal.
One method of determining the extant battery life of an apparatus, such as a mobile telephone, is to measure the battery voltage and then read an extant battery life value from a pre-programmed lookup table. This has the advantage of being relatively simple to implement but suffers from a lack of accuracy.
This problem is addressed in GB-A-2312517 which describes taking three voltage readings, fitting a discharge curve to the readings and then determining the extant battery life from the curve fitted to the readings. This approach is more accurate that the earlier lookup table technique. However, it is computationally intensive since the parameters of a formula for determining the battery discharge time to a specified voltage must be repeatedly calculated. It should be noted that these calculations are not trivial.
Some saving in computation can be made by storing pre-calculated values for the parameters of a battery discharge model formula. However, the calculation of these parameters requires lengthy discharge tests of many batteries having different chemistries and capacities for each of the characteristic operating currents of the device, e.g. idle and active modes of a mobile phone. The fact that it takes 18 days for a 900 mAh battery to discharge at a constant current of 2 mA gives some idea of the problem when one considers that the characteristic current may be constantly changing during the development of a product.
SUMMARY OF THE INVENTION
According to the present invention, there is provided a battery powered apparatus comprising a battery, a memory storing a set of parameter values appropriate for calculating a total life estimate of a reference battery according to an algorithm and processing means programmed to estimate the extant life of said battery of the apparatus by scaling at least one of said parameter values in dependence on the capacity of said battery of the apparatus and calculating a total life estimate for said battery of the apparatus using the or each scaled parameter value and said algorithm.
Thus, the apparatus does not need to be programmed with so many parameter values.
Preferably, said battery of the apparatus includes means identifying its capacity and the processing means comprises means for determining the capacity of said battery from said capacity identifying means. This means that a new battery can be introduced for the device after the end of its development.
Preferably, the processing means is programmed to implement said algorithm by calculating said total life estimate for the battery of the apparatus using the formula:
ln
(
ϕ
-
V
low
ζ
)
ln
α
where &phgr;, &zgr; and &agr; constitute parameters for which said default values are stored in the memory and V
low
is a battery voltage indicative of the battery of the apparatus approaching an empty state. More preferably, the processing means is programmed to scale the parameter &agr; according the capacity of the battery by implementing the formula:
α
=
[
(
α
default
-
1
)
·
C
default
C
new
]
+
1
where C
default
is the capacity of the reference battery and C
new
and the value of &agr;
default
being one of said default parameter values stored in the memory.
The reduction in the amount of battery testing that may be achieved is primarily a benefit for the manufacturing process.
According to the present invention, there is provided a method of manufacturing a battery powered apparatus having processing means, the method comprising:
discharging a battery at a constant current and recording the voltage across the battery as it discharges;
determining default parameter values for a battery discharge model for estimating total battery life from the recorded voltages; and
programming said processing means with a program implementing said model and the values of said parameter values,
wherein the programming means is programmed to scale the product of the application of said model in dependence on a current demand value dependent on said apparatus.
Preferably, a manufacturing method according to the present invention comprises:
discharging a battery, of the same type, at a further constant current and recording the voltage across the battery as it discharges;
determining further default parameter values for the battery discharge model for estimating total battery life from the recorded voltages for said further constant current discharge,
wherein the model parameter values programmed into the processing means are selected from said determined default parameter values in dependence on said apparatus dependant current value.
According to the present invention, there is provided a method of manufacturing a plurality of different battery powered apparatuses having respective processing means and different current demands, the method comprising:
discharging a battery or a plurality of batteries of the same type at a plurality of different constant currents and recording the voltage across the or each battery as it discharges;
for each discharge current, determining default parameter values for a battery discharge model for estimating total battery life from the recorded voltages; and
for each apparatus, programming its processing means with a program implementing said model and the default parameter values for the discharge current nearest to a respective apparatus dependent current demand value,
wherein each programming means is programmed to scale the product of the application of said model in dependence on the relevant current demand value.
Preferably, in a manufacturing method according to the present invention, the parameters are for a model of the form:
ln
(
ϕ
-
V
low
ζ
)
ln
α
where &phgr;, &zgr; and &agr; constitute parameters for which said default values are stored in the memory and V
low
is a battery voltage indicative of the battery of the apparatus approaching an empty state. More preferably, said scaling comprises scaling the default value of the parameter &agr;, stored in the memory.
If the or each battery is a Li-ion battery, the or each processing means is preferably programmed to scale the default value of &agr; according to the formula:
α
=
[
(
α
default
-
1
)
·
I
exp
I
default
]
+
1
where I
exp
is said apparatus dependent current value and I
default
is the respective discharge current for which the parameter values, programmed into the or each apparatus, were determined.
If the or each battery is a NiMH battery, the or each processing means is preferably programmed to scale the default value of &agr; according to the formula:
α
=
[
(
α
default
-
1
)
·
I
exp
I
default
·
(
1
-
X
)
]
+
1
if the apparatus dependent current is greater than that relating to the programmed parameter value and according to the formula:
α
=
[
(
α
default
-
1
)
·
I
exp
I
default
·
(
1
+
X
)
]
+
1
if the apparatus dependent current is less than that relating to the programmed parameter value,
where I
exp
is said apparatus dependent current value and I
default
is the respective discharge current for which the parameter values, programmed into the or each apparatus, were determined. Preferably, is about 0.05.
According to the present invention, there is also provided a battery powered apparatus comprising a battery and processing means configured for calculating an extant battery life estimate for the battery using a battery discharge model, wherein the product of the use of said model is scaled by the processing means in dependence on a current demand value fo
Christensen Frank Knudsen
Juncker Carsten
Luk Lawrence
Nokia Corporation
Tso Edward H.
LandOfFree
Battery life estimation does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Battery life estimation, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Battery life estimation will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3021119