GB2501251A - Battery Recharging Method - Google Patents

Abstract

A method of maintaining a rechargeable lead acid battery and charge controller therefore in which the battery is subjected to:- a) A refresh charge cycle to increase the battery voltage output b) A conditioning charge cycle to desulphate the battery Wherein step (a) is of shorter duration than step (b) and steps (a) and (b) are performed sequentially but non contiguously with partial battery depletion between stapes (a) and (b) The battery may be included in a security mast module for CCTV , infra red cameras etc which module incorporates a generator.

Description

Security Modules and Recharging Method This invention relates to a method of maintaining a rechargeable lead-acid battery forming a power source in an uninterruptible power supply application, a charge controller, a security mast module and a security module.

Security modules are known which provide security functions for a variety of applications. These modules must be secure in that there must be able to withstand tampering and / or vandalism. For example, security mast modules are known which include a mast for holding security equipment such as CCTV cameras, infra-red cameras and the like at an elevated position for extended line of sight. Such security equipment requires an electrical power source for operation, with this power source being uninterruptible. For many applications, particularly where the module is located in a remote area, a dedicated power source may need to be provided. The typical set up is to provide an array of rechargeable batteries, such as lead-acid batteries, with an electrical generator, such as a liquid petroleum gas (LPG) generator, to provide recharging power as required. A standard set-up is to provide a generator separately to the module.

There are various problems associated with such arrangements: Lead-acid batteries are commonly used rechargeable batteries, which generate electricity through a double sulphate chemical reaction, where both the lead battery plates and lead dioxide react with sulphuric acid in the electrolyte to form lead sulphate. When the battery is recharged, the lead sulphate reverts to lead, lead oxide and sulphuric acid.

However, over time and use, lead-acid batteries tend to suffer from sulphation, where some lead sulphate is not recombined into electrolyte and instead is converted into a stable crystalline form. This means that lead is gradually lost from the plates, which adversely affects the energy generation, and can even lead to destruction of the battery.

In order to prevent problems associated with sulphation, batteries are typically subjected to a "conditioning" ordesuiphation process, also known as "float charging".

A common technique, known as pulse conditioning, subjects the battery to a cycle of relatively short and powerful current surges. This can cause the sulphate crystals to dissolve, which improves the performance of the battery.

Conditioning can take a relatively long time, and in an uninterruptible power supply application such as powering a security mast, typically a ten to twelve hour charging cycle -including conditioning -will be performed every twenty-four hours.

This schedule requires the generator to run often and for a long time, in turn requiring large amounts of fuel for the generator, e.g. oil or LFG, which is expensive, environmentally damaging and may be time-intensive.

Furthermore, the provision of a separate generator creates a weakness to the module, in that it may be comparatively easy to tamper with or vandalise the connection between the generator and module.

It is an aim of the present invention to overcome these problems. This aim is achieved by a number of innovations, including a new battery maintenance regime, an integrated yet highly portable security module and a mechanism for enhancing the security of such a module. It is to be noted however that certain aspects of the invention have application outside the field of security equipment.

In accordance with a first aspect of the present invention there is provided a method of maintaining a rechargeable lead-acid battery forming a power source in an uninterruptible power supply application, comprising the steps of: a) applying a refresh charge cycle to an at least partially depleted lead-acid battery to increase the voltage output of the battery, and b) applying a conditioning charge cycle to the battery to desulphate the battery; the duration of step a) being shorter than the duration of step b), wherein steps a) and b) are performed sequentially but noncontiguously, such that the battery at least partially depletes between the conclusion of step a) and the start of step b).

In accordance with a second aspect of the present invention there is provided a charge controller for maintaining a rechargeable lead-acid battery forming a power source in an uninterruptible power supply application, comprising means for: a) causing a refresh charge cycle to be applied to an at least partially depleted lead-acid battery to increase the voltage output of the battery, and b) causing a conditioning charge cycle to be applied to the battery to desulphate the battery; the duration of the refresh charge cycle being shorter than the duration of the conditioning charge cycle, wherein the charge controller is operable to cause the refresh charge cycle and the conditioning charge cycle to be performed sequentially but noncontiguously, such that the battery at least partially depletes between the conclusion of the refresh charge cycle and the start of the conditioning charge cycle.

In accordance with a third aspect of the present invention there is provided a security mast module comprising a charge controller in accordance with the second aspect.

In accordance with a fourth aspect of the present invention there is provided a security mast module comprising: a security mast carrying an electrically operable security device, a rechargeable battery, an electrical power generator, charging transmission means for conveying electrical energy from the generator to the battery, operation transmission means for conveying electrical energy from the battery to the security device, and a housing; wherein the rechargeable battery and the electrical power generator are located within the housing.

In accordance with a fifth aspect of the present invention there is provided a security module adapted for mounting location on a surface in use, comprising: a housing comprising a sidewall having a plane which is approximately vertical in use; and a plurality of surface engagement means for engagement with the surface, which are independently relatively moveable with respect to the housing, such that the housing may be positioned at a desired orientation with respect to the surface, wherein the module further comprises a skirt element located adjacent and substantially parallel to the sidewall, the skirt element being fastened to at least one of the plurality of surface engagement means for movement therewith relative to the housing, the lower edge of the skirt element in use being dimensioned to lie proximate the surface, to prevent physical access to the underside of the housing in use.

The invention will now be described with reference to the accompanying drawings, in which: Fig. 1 schematically shows an oblique perspective view of a security mast module in accordance with the present invention; Fig. 2 schematically shows an oblique perspective view of the underside of the module of Fig. 1; Fig. 3 schematically shows an oblique perspective view of the interior of a sidewall of the module; Fig. 4 schematically shows a plan view of the interior of the sidewall of Fig. 3; Fig. 5 schematically shows a perspective view of the interior of the module of Fig. 1; Fig. 6 schematically shows a perspective cut-away view of the module of Fig. 1; and Fig. 7 schematically shows a charging I maintenance arrangement for the module of Fig. 1.

An embodiment of the invention, being a security mast module 1, is schematically shown in Fig. 1. There are two main components to the module, a housing 2, here of generally square plan, which houses the control and power components as will be described below, and a mast section 3 which carries security equipment such as CCTV or infra-red cameras as is known in the art. The module 1 is shown in a transportable state, suitable for towing behind a vehicle. As such, the mast section 3 is folded close to the horizontal about a pivot point 4 located at the top of the housing 2. The mast section 3 is supported in this inclination by an arm 5 with a supporting cup 6 in which the mast section 3 is loosely retained. The lower end of arm 5 is carried by a tow-arm 7 which contains an attachment (not shown) at its end enabling attachment to a vehicle. Wheels 8 are provided at the base of the module 1 for transportation. The housing 2 is defined by a plurality of sidewalls 9a-d (9a and 9b only being visible in Fig. 1), and a cover 10 which overlies the sidewalls 9a-d. Each sidewall 9a-d is stepped such that a lower portion 11 a-d of each sidewall is parallel to, but displaced outwardly, with respect to the housing 2, from an upper portion of the respective sidewall, as will be described in more detail below. Also shown in Fig. 1 are a ventilation exhaust opening 12 covered by a protective grille, and worm gear actuation means 13, which again will be described in mare detail below.

When the module 1 is deployed, mast section 3 is lifted to the vertical by hydraulics and a winch mechanism located within housing 2 as is known in the art, and arm 5, cup 6 and tow-arm 7 are removed from the structure.

Fig. 2 schematically shows an oblique perspective view of the underside of the module 1 of Fig. 1. It can be sidewall 9d is provided with an additional ventilation exhaust opening 12, and worm gear actuation means 13. Tow-arm 7 is shown as being telescopically and lockably received within a spine 14. When the module 1 is deployed, the two-arm 7 is simply unlocked and slid out from the spine 14. A surface engagement means in the form of a leg 15 carrying a surface engaging foot 16 is provided at each corner of the housing base, defined by two adjacent sidewalls 9a-d.

Each leg 15, and hence foot 16, is independently relatively moveable with respect to the housing 2, telescopically into and out of the housing 2. This enables the housing 2 to be positioned at a desired orientation with respect to the surface on which the module 1 is deployed. Located on the base of the housing 2 is a ventilation intake opening 17 which faces the surface during deployment.

Figs. 3 and 4 respectively show oblique and plan views of the interior of a sidewall 9c, which is positioned diametrically opposite to the sidewall 9a shown in Fig. 1, to more clearly show the orientation control for the module 1. The relative position of each leg 15 and the housing 2 is controlled by actuation of a respective worm gear actuation means 13, which drives a worm gear connection 18 between housing 2 and leg 15. This enables the projection amount of each leg from the base of the housing to be accurately controlled and held in place. A trapezoidal skirt element 19a-d is located adjacent to the inner side and substantially parallel to the lower portion lla-d of each respective sidewall 9a-d. The longest length of the trapezoid is at the lower edge of the skirt element 19a-d, dimensioned to lie proximate the surface during deployment. Each skirt element 19a-d is fastened, for example by bolting, to a leg 15 at each end of the lower edge, but is not directly connected to the housing 2. This arrangement means that each skirt element 19a-d will move with the legs relative to the housing 2 when the respective legs are positioned. It will be noted that if the two legs connected to a skirt element are moved into different vertical positions, the skirt element will pivot. The use of a trapezoidal shape for the skirt elements is advantageous since it prevents adjacent skirt elements from contacting when pivoted. Such contact is also avoided by setting the legs 15 slightly spaced from the sidewalls 9a-d, as most clearly shown in Fig. 4. Since when deployed the skirt elements 19a-d physically block the gap between the surface and the housing 2, they act to prevent physical access to the underside of the housing 2.

A planar sheet 20a-d depends from the upper portion of each sidewall 9a-d, so that each skirt element 1 9a-d is "sandwiched" between a lower portion 11 a-d and sheet 20a-d, which provides guidance for the skirt elements and helps to prevent lateral movement of the skirt elements. It can be seen from Fig. 1 that sidewall 9a, and hence also skirt element 19a, are required to have an aperture provided in order to accommodate tow-arm 7. When the module 1 is deployed, and tow-arm 7 is removed, it is advantageous to block this aperture to prevent tampering I vandalism.

This is achieved simply by affixing a separate plate member (not shown) to the skirt element 19a to block the aperture. This may be achieved for example by providing guide channels around the aperture in the skirt element, and slotting side wings of the plate into the guide channels to prevent lateral movement of the plate relative to the skirt element. Vertical relative movement may be prevented by further providing connection means, such as a hook, at the top of the plate to connect to a complementary connection on the skirt element.

Figs. 3 and 4 also show part of an LPG generator 21 used for recharging a battery array, as described below.

Fig. 5 schematically shows a perspective view of the interior of the housing 2. The housing interior is divided into chambers by internal partition walls. A relatively large chamber 22 extending across the width of the housing accommodates generator 21.

Ventilation ducting 23 runs along the top of the chamber 22, providing fluid communication between exhaust openings 12 on sidewalls 9b and 9d, and communicating with generator 21 at an intermediate point. In this way, exhaust gases from generator 21 enter ducting 23, and exit through either of exhaust openings 12. The ducting 23 comprises barrier means (not shown) within the ducting which permits gas flow past the barrier, but prevents the flow of liquid past the barrier in a direction toward the generator, and such a barrier means is located between each exhaust opening 12 and the generator 21, set back from the openings 12 to prevent unwanted access thereto. It is advantageous to prevent such liquid flow, since it has been known for vandals to pass flammable liquid into ducting to damage generators. Although not visible in Fig. 5, generator 21 draws in air through intake 17. A powered fan (not shown) may be provided to aid this air flow, the fan being powered by the batteries of the module. Spare battery racks 26 may be provided within chamber 22. Two additional chambers, 24 and 25, are provided within the housing, proximate sidewall 9a. Chamber 24 accommodates a gas store (not shown) for providing the fuel for the generator 21. Chamber 25 accommodates an array of lead-acid batteries 27 (see Fig. 6) and electronics for controlling the functions of the module, including for example camera operation, battery recharging logic. Chambers 24 and 25 are physically separated by a partition wall to prevent gas from the store leaking to the electrical components. Charging transmission means such as wires are provided for conveying electrical energy from the generator to the battery, while operation transmission means such as wires are provided for conveying electrical energy from the battery to the security devices on the mast 3, these transmission means not being shown.

Fig. 6 schematically shows a perspective cut-away view of the housing 2, showing the internal chambers in more detail. Here it can be seen that chamber 22 also contains hydraulics 28 and a winch 29 (not clearly shown) for lifting the mast into a vertical configuration for deployment. Chamber 24 includes a spare wheel 30.

Since with this arrangement the generator and batteries are accommodated within the same housing 2, the module is made more secure than existing designs, as well as being easily transportable.

Fig. 7 schematically shows a charging / maintenance arrangement for the module 1.

Battery array 27 is connected to the output of generator 21 via a single pole normally open (SPNO) relay 31 and a charge controller 32. Charge controller 32 includes a voltage sensor (not shown) for monitoring the output voltage of battery array 27, as well as a latch counter for monitoring charging cycles, as will be described below.

By way of example, the following description will describe a typical embodiment, in which an array 27 of eight absorbed glass mat (AGM) gel lead-acid batteries is used, each battery having a maximum output 1 2V and 105 Amp-hours. Such batteries are manufactured by the company Lifeline Batteries Inc. for example. The voltages, currents, charging times and voltage drop times quoted below are specific to that type of battery, and it will be understood that these parameters will change for other batteries / battery set-ups.

The charge controller 32 is designed to control a power supply used for charging large arrays of lead-acid batteries such as array 27. It is optimised for use with chargers that are powered directly from an internal combustion engine-powered generator, such as [PG generator 21. The charge controller 32 uses a special charging algorithm which allows it to keep fuel overheads to a minimum, while prolonging the life of batteries that it is recharging.

When the charge controller 32 is connected and switched on, it will monitor the voltage of the batteries and start I stop the generator 21 as required.

A suitable charging sequence is as follows: The charge controller's initial latch count = 0.

A) Ready -power is on and voltage monitoring is active. If battery array voltage is below 12.20V (approximately 50% of maximum output voltage of the battery array), the generator is powered on by the charge controller and charging will commence. If the latch count = 0, 1, 2 or 3, the charge controller proceeds to a refresh cycle (stage B). If the latch count = 4, the charge controller proceeds to the conditioning cycle (stage C).

B) Refresh cycle: i) Bulk phase -constant current applied to batteries for a duration of approximately two hours; followed by H) Absorption phase -constant voltage applied to batteries for a duration of approximately two hours; followed by Hi) Latching -at the end of the refresh cycle, the charge controller latches to increase the latch count by 1, to register that a refresh cycle has completed.

iv) Revert to ready state (stage A).

Following a refresh cycle, the battery output voltage will be at approximately 90% of its maximum output.

C) Conditioning cycle: i) Bulk conditioning phase -constant current applied to batteries for a duration of approximately two hours; followed by H) Absorption conditioning phase -constant voltage applied to batteries for a duration of approximately eight hours; followed by Hi) Latching -at the end of the conditioning cycle, the charge controller clears the latch count to 0.

iv) Revert to ready state (stage A).

It can be seen that following this sequence, at least one refresh charge cycle is applied to an at least partially depleted lead-acid battery to increase the voltage output of the battery, with the duration of each refresh cycle being shorter than the subsequent conditioning charge cycle applied to the battery. Furthermore, the refresh cycles and conditioning cycle are performed sequentially but noncontiguously, such that the battery at least partially depletes between the conclusion of the first refresh cycle and the start of the conditioning cycle.

The use of bulk and absorption phases for charging is known per se, the "bulk" phase also being known as an "I-phase", while the absorption phase is also known as a "Uo-phase". The conditioning cycle may comprise pulse conditioning as is known in the art.

The charge controller 32 may also include an "ADVANCE" control button, which when pressed increases the latch count by 1, up to a maximum value of 4, at which point the latch count clears to 0.

It can be seen that each refresh cycle (Stage B) lasts approximately four hours, i.e. two hours in bulk mode and two hours in absorption mode. The conditioning cycle lasts for approximately ten hours, having a two hour bulk mode and an eight hour absorption mode. The voltage output from the battery array will drop to about 50% of its maximum, thus triggering recharging, in about fifty hours. It can therefore be seen that the total charging time over a two hundred and fifty hour period is about twenty-six hours. This compares favourably with known systems, which as previously described may require about ten to twelve hours of charging in every twenty-four hour period, or even to systems where conditioning is only carried out once in every forty-eight hours.

The recharging cycle of the present invention does produce a reduction in the working life of the batteries of about 20%. However, it is considered that this drawback is more than compensated for by the achieved reduction in charging time and hence generator fuel consumption.

The above-described embodiments are exemplary only, and other possibilities and alternatives within the scope of the invention will be apparent to those skilled in the art. For example, the internal arrangement of components within the housing is relatively flexible, and may be set out as the particular application demands or allows. Specific applications may require the use of different sized batteries! battery arrays, and the optimum charging cycle will alter accordingly.

There are other ways of making sure only four consecutive refresh cycles (Stage B) are performed between consecutive conditioning cycles (Stage C), rather than using the latch mechanism described above.

Various aspects of the invention, such as the battery maintenance method described, have wider applicability than security modules alone, and may be used for many different applications of lead-acid batteries.

Claims (27)

1. Claims 1. A method of maintaining a rechargeable lead-acid battery forming a power source in an uninterruptible power supply application, comprising the steps of: a) applying a refresh charge cycle to an at least partially depleted lead-acid battery to increase the voltage output of the battery, and b) applying a conditioning charge cycle to the battery to desulphate the battery; the duration of step a) being shorter than the duration of step b), wherein steps a) and b) are performed sequentially but noncontiguously, such that the battery at least partially depletes between the conclusion of step a) and the start of step b).
2. 2. A method according to claim 1, wherein step a) is repeated at least once before performing step b), each performance of step a) being carried out sequentially but noncontiguously, such that the battery at least partially depletes between the repetitions.
3. 3. A method according to either of claims 1 and 2, comprising the step of monitoring the voltage output of the battery during use.
4. 4. A method according to claim 3, wherein the or each performance of step a) is carried out when the voltage output of the battery is determined to be around 50% of the battery's output voltage when fully charged.
5. 5. A method according to any preceding claim, wherein the refresh charge cycle comprise a bulk phase followed by an absorption phase.
6. 6. A method according to any preceding claim, wherein the conditioning charge cycle comprises a bulk phase followed by an absorption phase.
7. 7. A method according to any preceding claim, the uninterruptible power supply application being powering a security mast.
8. 8. A charge controller for maintaining a rechargeable lead-acid battery forming a power source in an uninterruptible power supply application, comprising means for: a) causing a refresh charge cycle to be applied to an at least partially depleted lead-acid battery to increase the voltage output of the battery, and b) causing a conditioning charge cycle to be applied to the battery to desulphate the battery; the duration of the refresh charge cycle being shorter than the duration of the conditioning charge cycle, wherein the charge controller is operable to cause the refresh charge cycle and the conditioning charge cycle to be performed sequentially but noncontiguously, such that the battery at least partially depletes between the conclusion of the refresh charge cycle and the start of the conditioning charge cycle.
9. 9. A security mast module comprising a charge controller in accordance with claim 8, and an a rechargeable lead-acid battery.
10. 10. A security mast module comprising: a security mast carrying an electrically operable security device, a rechargeable battery, an electrical power generator, charging transmission means for conveying electrical energy from the generator to the battery, operation transmission means for conveying electrical energy from the battery to the security device, and a housing; wherein the rechargeable battery and the electrical power generator are located within the housing.
11. 11. A module according to claim 10, comprising ventilation ducting to enable ventilation of the generator, the housing including a ventilation intake opening and a ventilation exhaust opening in fluid communication with the ducting.
12. 12. A module according to claim 11, wherein the ventilation intake opening is located on the base of the housing, such that the intake opening faces the surface in use.
13. 13. A module according to either of claims 11 and 12, wherein the ducting comprises barrier means within the ducting which permits gas flow past the barrier, but prevents the flow of liquid past the barrier in a direction toward the generator.
14. 14. A module according to any of claims 10 to 13, wherein the generator comprises a gas-fired generator, and a store of gas for fuelling the generator is located within the housing.
15. 15. A module according to claim 14, wherein the gas store is physically separated from electrical components of the module.
16. 16. A security module adapted for mounting location on a surface in use, comprising: a housing comprising a sidewall having a plane which is approximately vertical in use; and a plurality of surface engagement means for engagement with the surface, which are independently relatively moveable with respect to the housing, such that the housing may be positioned at a desired orientation with respect to the surface, wherein the module further comprises a skirt element located adjacent and substantially parallel to the sidewall, the skirt element being fastened to at least one of the plurality of surface engagement means for movement therewith relative to the housing, the lower edge of the skirt element in use being dimensioned to lie proximate the surface, to prevent physical access to the underside of the housing in use.
17. 17. A module according to claim 16, wherein the skirt element is located adjacent an inner side of the sidewall.
18. 18. A module according to claim 17, wherein the sidewall is stepped, such that a lower portion of the sidewall is parallel to, but displaced outwardly, with respect to the housing, from an upper portion of the sidewall, and the skirt element is located proximate the lower portion.
19. 19. A module according to any of claims 16 to 18, comprising a plurality of sidewalls defining the external footprint of the housing, and a respective plurality of associated skirt elements located parallel to respective sidewalls.
20. 20. A module according to claim 19, wherein each surface engagement means comprises a leg, and each leg is being positioned proximate a corner of the housing defined by two adjacent sidewalls.
21. 21. A module according to any of claims 16 to 20, wherein the or each skirt element is substantially trapezoidal, with the longest length of the trapezoid lying proximate the surface in use.
22. 22. A module according to either of claims 20 and 21, wherein each leg is operatively linked to the housing via a worm gear, such that actuation of the worm gear causes relative movement of the leg and housing.
23. 23. A module according to any of claims 16 to 22, being a security mast module.
24. 24. A method as herein described with reference to the accompanying figures.
25. 25. A charge controller as herein described with reference to the accompanying figures.
26. 26. A security mast module as herein described with reference to the accompanying figures.
27. 27. A security module as herein described with reference to the accompanying figures.