Battery backup installation for electric meter

A battery backup installation for a time of use register for an electric meter is mounted within a case of the electric meter. The case includes a hatch which permits removal and replacement of the battery without requiring removal of the case from the meter. In one embodiment, the battery is installed in a battery clip on the face plate of the meter where it is accessible through the hatch. An extra length of wires from the battery permits the battery, and its mating connectors, to be withdrawn through the hatch for replacement thereof. In a second embodiment of the invention, the battery is captured in a door of the hatch and is withdrawn from the meter by the action of opening the hatch. In this embodiment, the hatch may be hinged or not hinged. Battery replacement is facilitated while the electronic register module is separated from line-supplied power. An auxiliary battery provides an auxiliary source of backup power during batterychange.

BACKGROUND OF THE INVENTION 
The present invention relates to electric meters containing electronic 
registers and, more particularly, to apparatus for providing battery 
backup to an internal clock in an electronic register effective for 
maintaining at least a clock time during a power outage. 
Conventional electric meters employ an aluminum disk driven as a rotor of a 
small induction motor by an electric field at a speed proportional to the 
electric power being consumed by a load. Geared dials, or cyclometer 
discs, integrate the disk motion to indicate the total energy consumed, 
conventionally measured in kilowatt hours (one kilowatt hour equals one 
thousand watts of power consumption for one hour). 
It is well accepted that the cost of electricity entails two components (1) 
the out-of-pocket cost (fuel, labor, etc.) for generating the electricity, 
and (2) the capital cost for providing the generating equipment. The 
out-of-pocket cost is recovered by a charge per unit of electricity 
consumed. The capital cost is related to the maximum load which the 
utility must supply. That is, synchronized peak loads from a substantial 
part of a utility's users can produce an instantaneous maximum load that 
requires a total generating capacity, representing a capital expenditure, 
far exceeding an average load. In order to provide a financial incentive 
for energy consumers to shift their power consumption from times when peak 
loads are known to occur to times of lower consumption, many rate-setting 
bodies permit utilities to charge higher rates at such peak times. 
Thus, in addition to the above measurement of consumption, some electric 
meters contain means for separating the consumption into those parts 
occurring during predetermined peak and off-peak hours and for recording 
maximum demand during a predetermined period of time, in order to adjust 
billing according to such parameters. One type of electric meter is 
disclosed in U.S. Pat. No. 3,586,974, wherein a mechanical demand register 
records the power usage during a predetermined period of time and stores 
the value for later reading. The predetermined period of time may be, for 
example, the time between meter readings, or a period of time 
corresponding to the billing period of the utility providing the power. A 
clockwork mechanism restarts the mechanical demand register at the ends of 
regular demand intervals of, for example, a fraction of an hour, so that, 
at the end of the predetermined period, the stored value represents the 
highest value of power usage occurring during any one of the regular 
demand intervals in the predetermined period. 
Greater flexibility is obtained using electronic acquisition, integration 
and processing of power usage. An electronic processor such as, for 
example, a microprocessor, may be employed to manage the acquisition, 
storage, processing and display of the usage and demand data. U.S. Pat. 
Nos. 4,179,654; 4,197,582; 4,229,795; 4,283,772; 4,301,508; 4,361,872 and 
4,368,519, among others, illustrate the flexibility that electronic 
processing brings to power and energy usage measurement. Each of these 
electronic measurement devices includes means for producing an electronic 
signal having a characteristic such as, for example, a frequency or a 
pulse repetition rate, which is related to the rate of power usage. The 
electronic processor is substituted for at least part of the mechanical 
register of the prior art to keep track of the power usage during defined 
periods of time. 
Various aspects of an electronic register which may benefit from the 
techniques of the present invention are disclosed in U.S. patent 
applications Ser. Nos. 599,684; 599,685; 599,736; 599,744; 599,683; 
599,735; 599,743 and 599,742 all filed on Apr. 12, 1984; and Ser. Nos. 
550,407 and 550,142 both filed on Nov. 10, 1983, the disclosures of which 
are herein incorporated by reference. 
Electric meters which segregate usage and demand data according to time of 
use typically employ one mechanical or electronic register which 
accumulates the total energy usage, in addition to one or more additional 
registers which are active only between specific hours of the day or days 
of the week. More sophisticated time of use meters keep track of the day 
of the week, the season of the year and holidays. Such data is 
programmable for an extended period into the future such as, for example, 
20 years. One such system, disclosed in U.S. Pat. No. 4,050,020, employs 
first and second clockwork registers. One of the registers is continuously 
active to accumulate total energy usage, while the other is enabled only 
at preselected times by an electronic circuit containing a built-in, or 
real-time, clock. 
If such a real-time clock should stop for even a few relatively short 
periods of time, the relationship between data segregation and time of 
day, week, season and/or holiday would be damaged in a serious manner. As 
long as an electric meter receives line power, a real-time clock can be 
run from the line power. Line power occasionally fails, generally for 
relatively short periods of from a few minutes to an hour or two. It is 
conventional to provide a backup battery for maintaining operation of the 
real-time clock during such power failures. 
In the prior art, a real-time clock for an electronic register employs NMOS 
devices. Such devices, besides consuming substantial power, require a 
power source capable of supplying about 5 volts DC. Since 5 VDC exceeds 
the voltage output of a conventional single cell, a multi-cell battery is 
required. In addition, due to their high power requirements, NMOS circuits 
need large battery capacity. 
An electric meter generally has a design lifetime of at least 20 years. A 
battery, in contrast, reaches the end of its useful life in from about 2 
to about 10 years under normal service. Battery lifetimes can be 
significantly shortened under adverse conditions such as, for example, an 
extended power outage lasting many hours or days. Rechargeable batteries, 
which are recharged by a built-in charger when the line power is restored, 
partially solve the capacity problem, but the number of charge-discharge 
cycles and the total life of such rechargeable batteries remain limited to 
less than the life of the electric meter. A rechargeable battery system 
for a real-time clock is disclosed in U.S. Pat. No. 4,199,717. The finite 
lifetime of a rechargeable battery requires that means be provided for 
battery replacement. The referenced patent does not contain specific 
disclosure for battery replacement. 
Electric meters generally are built with a base mountable to a socket or 
terminals to sense the line voltage and current therethrough, a frame 
supporting and aligning the mechanical, electromechanical and electronic 
components, and a cover. The cover, which is generally transparent glass 
or plastic, provides a weather-tight and tamper-resistant enclosure for 
the frame and the apparatus mounted thereon. Security devices are 
generally used between the base and the socket, and between the cover and 
the base. A periodic requirement for removing the security devices, and 
then removing the cover for replacement of a battery, represents a 
significant labor burden on a utility. 
The prior art, as exemplified by U.S. Pat. Nos. 4,075,561 and 4,297,635, 
addresses the problem of battery replacement from outside the meter cover 
by providing an access hatch in the cover of an electric meter for 
installation and removal of a battery from a unitary battery clip. Besides 
retaining the battery, the battery clip also makes electrical connection 
thereto. The disclosed battery clips do not provide for continuing battery 
power to critical components in the electric meter while the battery is 
partially withdrawn from the electric meter, or for permitting the battery 
to remain electrically connected to an electronic register module when the 
electronic register module is separated from the remainder of the electric 
meter. 
More recent solid-state devices offer both lower power consumption and 
lower voltage requirements. A CMOS real-time clock circuit, for example, 
is capable of operation with a power consumption of about 200 microwatts 
at a voltage of about 2.5 volts. Thus, a 3-volt battery of modest total 
capacity is capable of powering a real-time clock for a period of, for 
example, 40 days. In addition, battery technology now offers long-life, 
non-rechargeable batteries such as, for example, lithium batteries, which 
have an improved power density and a lifetime of up to 10 years. This 
combination of low-power electronic circuits and long-life batteries of 
small size offers the ability to change the manner in which batteries are 
installed and replaced in electronic registers. 
A favored technique for field service on an electronic register includes 
substitution of a known-good electronic register module for one that is 
apparently in a failed condition. In order to avoid zeroing the real-time 
clock, its parameters, and other data when the register is removed from 
the meter, the battery installation preferably should permit the battery 
to remain connected to the electronic register module when the electronic 
register module is separated from the remainder of the electric meter. 
OBJECTS AND SUMMARY OF THE INVENTION 
Accordingly, it is an object of the invention to provide a mounting 
technique for a battery backup installation for an electronic register 
module of an electric meter which overcomes the drawbacks of the prior 
art. 
It is a further object of the invention to provide at least one mounting 
system for a battery backup installation which permits changing the 
battery from outside the meter cover without requiring removal of the 
meter cover. 
It is a still further object of the invention to provide a mounting device 
for a battery backup installation in an electric meter which permits 
continued battery supply to an electronic register module when the 
electronic register module is removed from the electric meter. 
It is a further object of the invention to provide means for permitting 
replacement of a battery connected to an electronic register module 
without permitting power to be cut off from the electronic register 
module. This objective is accomplished by providing an auxiliary battery 
connection which may be employed to continue battery power to the 
electronic register module while the main battery is being replaced. 
Briefly stated, the present invention provides a battery backup 
installation for a time of use register for an electric meter, wherein the 
battery is mounted within a case of the electric meter. The case includes 
a hatch which permits removal and replacement of the battery without 
requiring removal of the case from the meter. In one embodiment, the 
battery is installed in a battery clip on the face plate of the meter 
where it is accessible through the hatch. An extra length of wire from the 
battery permits the battery, and its mating connectors, to be withdrawn 
through the hatch for replacement thereof. In a second embodiment of the 
invention, the battery is captured in a door of the hatch and is withdrawn 
from the meter by the action of opening the hatch. In this embodiment, the 
hatch may be hinged or not hinged. Battery replacement is facilitated 
while the electronic register module is separated from linesupplied power. 
An auxiliary battery provides an auxiliary source of backup power during 
battery change. 
According to an embodiment of the invention, there is provided a battery 
installation for an electric meter, the electric meter being of a type 
including a cover, comprising a battery replacement hatch in the cover, 
means for retaining a battery within the cover in a location accessible 
through the battery replacement hatch, and means for permitting at least 
partly withdrawing the battery through the battery replacement hatch 
without disconnecting battery power from the electric meter. 
The above, and other objects, features and advantages of the present 
invention will become apparent from the following description read in 
conjunction with the accompanying drawings, in which like reference 
numerals designate the same elements.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
Although the present invention may be adapted to any suitable style of 
electric meter which employs an element rotating at a speed proportional 
to power consumption, including single phase meters with one or more 
current windings and polyphase meters, for concreteness, the detailed 
description which follows is directed toward an illustrative example of a 
2-wire single phase meter of the type having a single current coil and a 
single voltage coil. 
Referring now to FIG. 1, there is shown, generally at 10, an electric meter 
which includes a small induction motor 12 driving a register 14. Induction 
motor 12 includes a stator 16 made up of a voltage coil 18 and a current 
coil 20 disposed on opposite sides of a disk 22. Voltage coil 18 employs a 
core 24 upon which is wound a large number of turns of fine wire. Voltage 
coil 18 is connected across lines 26 and 28 which feed power to a load 
(not shown). Current coil 20 employs a core 30 upon which a small number 
of turns, typically one or two, of heavy conductor are wound. Current coil 
20 is connected in series with the power being fed to the load on line 26. 
Disk 22 is affixed to a shaft 32 which is supported on suitable bearings 
(not shown) to permit concerted rotation of disk 22 and shaft 32 under the 
influence of a rotating magnetic field produced by the combined influence 
of voltage coil 18 and current coil 20. A permanent magnet 34, having its 
poles disposed on opposite sides of disk 22, applies a retarding force 
proportional to the rotational speed of disk 22. The rotational torque 
produced by voltage coil 18 and current coil 20, combined with the 
retarding torque produced by permanent magnet 34, is effective to rotate 
disk 22 at a speed proportional to the product of the voltage and the 
current; that is, the power, consumed by the load. 
Register 14 includes a watthour register 36 which may include, for example, 
a plurality of dials 38 which are suitably geared and driven by a 
mechanical coupling 40 in proportion to the rotation of shaft 32. In the 
embodiment shown, mechanical coupling 40 includes a worm 42, which may be 
integrally formed in shaft 32, which engages and rotates a worm gear 44. 
Additional elements may be present in mechanical coupling 40 for coupling 
the rotation of worm gear 44 to watthour register 36 with or without 
change in speed and direction, according to the design of the particular 
electric meter 10. As is conventional, watthour register 36 totals the 
number of revolutions of shaft 32, suitably scaled by the gear ratios 
employed, for billing purposes. 
An electronic register module 46 in electric meter 10 receives pulses from 
a pulse generator 48 on a line 50 in response to the rotation of shaft 32. 
Electronic register module 46 is modular in the sense that it can be 
inserted into, and removed from, register 14 as a unit. Electronic 
register module 46 includes a display 52 of any convenient type such as, 
for example, a liquid crystal display, for presenting billing and 
troubleshooting data to a user. In addition, electronic register module 46 
includes a set of control switches 54 whose functions are described more 
fully in the referenced patent applications. 
A face plate 56, preferably of sheet metal and most preferably of aluminum, 
covers a face of register 14, and optionally provides a surface upon which 
necessary indicia may be printed or otherwise included. 
A DC power supply 58 is connected to line 26 and line 28 for generating DC 
power for electronic register module 46 as long as normal line power is 
available. DC power supply 58 provides power on a first line 60 to all 
circuits in electronic register module 46 which may be deprived of power 
during a power outage without adversely affecting either operation of 
electronic register module 46 or billing data. DC power supply 58 provides 
power to critical circuits on a line 62. Critical circuits are defined as 
those which permit the destruction of billing data, clock synchronization 
or calendar data during power outage. A diode 64 is connected from line 62 
to a junction 66. A battery 68 is connected between ground and a terminal 
of a diode 70. The other terminal of diode 70 is connected to junction 66. 
Junction 66 is connected to a line 72 which supplies power to all critical 
circuits. 
An optional auxiliary battery 74 and a diode 76, both shown in dashed line, 
may be provided for special purposes to be described. 
FIG. 2, and its description which follows, is included for an understanding 
of the environment in which the present invention operates. 
Energy usage pulses, each representing a predetermined quantum of energy 
usage, are applied on line 50 to an input of a total energy usage 
accumulator 78. Total energy usage accumulator 78, as its name implies, 
totals all energy usage pulses regardless of the time or conditions of 
usage. Total energy usage accumulator 78 essentially duplicates the 
function of mechanical watthour register 36, and its inclusion in 
electronic register module 46 is therefore optional. 
The energy usage pulses on line 50 are also connected to a switch 80 having 
a terminal 81 and first, second and third output terminals 82, 84 and 86, 
respectively. Terminal 81 is an isolated terminal without a destination. 
Switch 80 is connected to terminal 81 during times when specific 
accumulations are not required. Output terminal 82 connects energy usage 
pulses to a period A accumulator 88 whenever the movable element of switch 
80 is connected thereto. Similarly, output terminal 84 applies the energy 
usage pulses to a period B accumulator 90 when the movable element of 
switch 80 is connected thereto. As many period accumulators as desired up 
to period N accumulator 92 may be provided for accumulating usage data 
according to any desired schedule. Additional period accumulators require 
the addition of a corresponding number of terminals on switch 80. 
An accurate real-time clock 94 runs continuously as long as it receives 
sufficient power to actuate switch 80 at times predetermined by data 
stored in a clock parameter library 96. As the time maintained by 
real-time clock 94 reaches predetermined values, it actuates switch 80 to 
shift the usage pulses between its output terminals. For example, in 
accordance with data in clock parameter library 96, real-time clock 94 may 
actuate switch 80 to accumulate usage pulses in period A accumulator 88 
during normal operating periods of non-holidays which do not fall on 
weekends. Period B accumulator 90 may accumulate usage pulses at peak 
periods which may be, for example, morning startup time at industrial 
plants, early winter evenings coinciding with the heaviest domestic and 
business lighting load, and late summer afternoons coinciding with the 
heaviest air conditioning load. The utility may wish to encourage energy 
usage at times of minimum system load at which its marginal costs for 
generating power is lowest. At such times, real-time clock 94 may actuate 
switch 80 to accumulate usage pulses in period N accumulator 92. 
The accumulated usage data from total energy usage accumulator 78, period A 
accumulator 88, period B accumulator 90 and period N accumulator 92 is 
read out in a conventional manner using, for example, display of data on 
display 52 (FIG. 1) or by automatic data readout using electrical, 
optical, or other means (not shown). 
It would be clear to one skilled in the art that loss of data in total 
energy usage accumulator 78, period A accumulator 88, period B accumulator 
90, and period N accumulator 92 would have a serious effect on revenue. 
These elements are thus included within the definition of critical 
circuits requiring the availability of battery power or other means of 
permitting the data to survive a power outage. The data in clock parameter 
library 96 determines the times at which transition between the several 
accumulators takes place. Loss of this data effectively renders electronic 
register module 46 inoperative until it is reprogrammed. In addition, 
clock parameter library 96 may include a substantial amount of 
installation-specific items whose loss would entail a substantial effort 
to replace. For these reasons, clock parameter library 96 is included 
within the definition of critical circuits. If real-time clock 94 loses 
synchronism with real time, then transitions between accumulators cannot 
take place at the predetermined times. Thus, not only must power be 
maintained to real-time clock 94, but also it must continue to keep 
accurate time, unaffected by the occurrence of a power outage. 
Referring now to FIG. 3, electric meter 10 includes a base 98 to which a 
transparent cover 100 is affixed by a mounting ring 102. Mounting ring 102 
is frequently equipped with a security seal to discourage tampering with 
electric meter 10, and to give evidence of such activity when such 
tampering occurs. In addition, base 98 is conventionally affixed to a 
socket (not shown) which may also include a security seal. Frequently, the 
socket security seal also covers mounting ring 102. In such an 
installation, gaining access to the interior of transparent cover 100 
requires removal of two security seals before transparent cover 100 is 
removed from base 98. Replacement of a backup battery mounted in the 
interior of transparent cover 100 is complicated by such construction. 
An end face 104 of transparent cover 100 includes a battery replacement 
hatch 106 through which a backup battery may be removed and replaced. 
Battery replacement hatch 106 includes a hatch door 108 which may include 
means for attaching a security seal 110 of the wire or band type. 
Referring now to FIGS. 4 and 5, face plate 56 includes a battery clip 112 
affixed thereto. A battery 114, preferably of a type having an insulated 
casing, is clipped into battery clip 112. Power from battery 114 is 
connected through a pair of wires 116 to a polarized connector 118. A 
mating polarized connector 120 is connected to a pair of wires 122 which 
supply battery power to electronic register module 46 (FIG. 1). A split 
ring 124, disposed downstream of polarized connector 118 and mating 
polarized connector 120, helps support wires 122 and has an opening 
smaller than a cross-sectional dimension of mating polarized connector 
120, thereby preventing mating polarized connector 120 from being pulled 
so far that it disengages from polarized connector 118. Since it is split, 
however, wires 122 can be easily disengaged from split ring 124, when 
necessary. 
An opening 126 in end face 104 is aligned above battery 114 and includes an 
area sufficient for withdrawing and inserting battery 114 therethrough. A 
base member 128 of battery replacement hatch 106 is sealed to end face 104 
about the perimeter of opening 126. If end face 104 is made of a 
polycarbonate resin, then it is convenient to make base member 128 also of 
the same material, and to seal base member 128 to end face 104 by thermal 
means such as, for example, ultrasonic bonding. 
Base member 128 includes two hinge loops 130 and two latch halves 132 
integrally formed therewith. 
Hatch door 108 includes a compressible seal 134 in sealing abutment with 
base member 128 for sealing the interior of transparent cover 100 against 
entry of contaminants or moisture through opening 126. Hatch door 108 
includes a hinge pin 136 which is captured under hinge loops 130 when base 
member 128 is affixed to end face 104. In addition, hatch door 108 
includes a latch knife 138 fittable between first and second latch halves 
132. A seal hole 140 and a seal slot 142 pass through latch halves 132 and 
latch knife 138 for attachment of a conventional security seal (not 
shown). 
In operation, when it is desired to replace battery 114, hatch door 108 is 
opened and battery 114 is unclipped from battery clip 112. A substantial 
extra length of wires 122 is provided to serve as a service loop allowing 
battery 114, polarized connector 118 and mating polarized connector 120 to 
be withdrawn through base member 128. Once outside opening 126, polarized 
connector 118 and mating polarized connector 120 may be disconnected, and 
a polarized connector 118 of a replacement battery 114 may be mated with 
mating polarized connector 120. Then, the replacement battery 114 may be 
clipped into battery clip 112. As battery 114 is inserted through opening 
126 and placed in its final location, the extra length of wires 122 passes 
through split ring 124. When battery replacement is completed, hatch door 
108 is closed over opening 126 and may optionally be sealed in place using 
a seal threaded through seal hole 140 or seal slot 142. 
As long as battery replacement is performed while power continues to be 
supplied from lines 26 and 28, disconnection of polarized connector 118 
and mating polarized connector 120 does not interrupt the supply of power 
to electronic register module 46, and thus poses no problem of lost data. 
It is frequently desirable to permit battery 114 to remain connected to 
electronic register module 46 when electronic register module 46 is 
removed from register 14 for test or service. The embodiment of the 
invention shown permits removal of battery 114 from battery clip 112 and, 
when wires 122 are disengaged from split ring 124, electronic register 
module 46 can be separated from the remainder of register 14 while 
permitting battery 114 to remain attached thereto and continuing to 
provide backup power thereto. Among other desirable effects, the ability 
to permit battery 114 to remain attached to electronic register module 46 
while electronic register module is removed from register 14, permits 
replacing the remainder of register 14 without losing data from electronic 
register module 46. 
Referring again momentarily to FIG. 1, if it is desired to replace battery 
68 while electronic register module 46 is removed from register 14, that 
is, when the only source of power is battery 68, the resulting loss of 
power would cause data loss and lost synchronization in critical circuits. 
In order to prevent such loss of data and synchronization, auxiliary 
battery 74 may be connected in parallel with battery 68 through diode 76 
before battery 68 is disconnected. When a replacement battery 68 is 
installed, auxiliary battery 74 may be removed if desired. 
Since auxiliary battery 74 is primarily used as a temporary power source 
during the replacement of battery 68, it is not necessary to provide a 
permanent location for auxiliary battery 74 within electric meter 10. 
Should it be desirable to mount auxiliary battery 74 therein, however, the 
position where auxiliary battery 74 is mounted is immaterial to the 
invention. 
Referring now to FIG. 6, an embodiment of the invention is shown wherein 
battery 114 is relocated from the face of face plate 56 to a mounting 
location within hatch door 108. A battery retainer 144 clamps battery 114 
within hatch door 108 whereby, when hatch door 108 is opened, battery 114 
is moved through opening 126. This simplifies the task of grasping battery 
114 since it does not require removing it from a clip within transparent 
cover 100. Wires 122 requires an extra length to serve as a service loop 
permitting battery 114, polarized connector 118 and mating polarized 
connector 120 to be moved outside opening 126. 
Battery retainer 144 may be of any convenient type including a resilient 
mass, as shown, which is capable of retaining battery 114 by friction. 
Other types of devices may be substituted for the resilient mass in 
battery retainer 144 without departing from the spirit and scope of the 
invention. For example, a part-turn fastener may be formed cooperatively 
between an interior of hatch door 108 and an exterior of battery 114. The 
part-turn fastener is effective for securing battery 114 in the position 
shown and permits easy removal when battery 114 is moved outside opening 
126. 
An embodiment of hatch door 108 may be employed which does not swivel on a 
hinge pin. Instead, hatch door 108 may be removed by displacement whereby 
battery 114 is drawn straight through opening 126. This embodiment is used 
where the size and/or length of battery 114 is too great to permit it to 
pass through opening 126 on a swivelled hatch door 108. 
Having described preferred embodiments of the invention with reference to 
the accompanying drawings, it is to be understood that the invention is 
not limited to those precise embodiments, and that various changes and 
modifications may be effected therein by one skilled in the art without 
departing from the scope or spirit of the invention as defined in the 
appended claims.