GB2395376A

GB2395376A - Energy management

Info

Publication number: GB2395376A
Application number: GB0322029A
Authority: GB
Inventors: Barry Chuter; Robert Knight; Adam Osborn
Original assignee: Kigass Electronics Ltd
Current assignee: Kigass Electronics Ltd
Priority date: 2002-09-20
Filing date: 2003-09-19
Publication date: 2004-05-19
Also published as: GB0322029D0; GB0221912D0

Abstract

An energy management system has a plurality of power supply inputs 1,2 for receiving electrical energy from respective ones of a plurality of sources and a power supply output 11. A switching means selectively connects the power supply inputs 1,2 to the output 11. A power detector 9 detects the power supplied to the output. The switching means comprises at least one high power switch 3,4 for selectively connecting the sources to the output and at least one low power switch 5,6,7,8 for selectively connecting the sources 1,2 to the output 11. The high power switch 3,4 requires a control signal of higher current than the low power switch 5,6,7,8. Control means 10 select the high power switch 3,4 in the presence of a high output load and select the lower power switch 5,6,7,8 in the presence of a low output load. Also claimed is an energy control system which monitors the sources.

Description

r Energy Management The present invention relates to managing power

supplies.

Illustrative embodiments of the invention relate to managing power supplies on vehicles for example caravans, motor caravans and boats. In those examples, the 5 power supplies are batteries, typically 19 volt batteries.

Batteries in vehicles may be required to supply up to 100 amps or more. In addition, vehicles often use two or more batteries and a switching circuit is provided to switch between batteries. This allows a first battery to be a back up to be used in place of a second battery when the other second battery runs down.

to Because of the high current loading (100 amps) which a battery may be required to provide, it is known to use high power relays for the switching. However, high power relays require a control coil current open in excess of O.S amps. Whilst such a coil current may be acceptable when controlling heavy loads, such a control current would prematurely flatten a battery if used all the time. For example when a 15 battery powers a low current devices for example a digital clock which requires for example 100 micro amps, the control current would be O.S amps.

The present invention seeks to provide management of energy sources in a way appropriate to the load supplied by the sources.

According to one aspect of the invention there is provided an energy 20 management system having: a plurality of power supply inputs for receiving electrical energy from respective ones of a plurality of sources, a power supply output; switching means for selectively connecting the power supply inputs to the output; means for detecting the power supplied to the output; the switching means comprising at least one high power switch for selectively connecting the sources to the output and a low 25 power switch for selectively connecting the sources to the output; and control means for selecting the high power switch in the presence of a high output load and for selecting the lower power switch in the presence of a low output load. Another aspect of the invention provides an energy control system having: a 30 plurality of inputs for connection to a plurality electrical energy sources; switching means for selectively connecting the inputs to an output; means for monitoring the

voltage of the sources, and a controller for selectively connecting the sources to the output in dependence upon the monitored source voltages.

Yet another aspect of the invention provides an energy management system comprising: a plurality of inputs for connection to a plurality of electrical energy 5 sources, switching means for connecting the inputs to an output; means for monitoring the load required by the output; and control means for selectively connecting the inputs to the output in accordance with the load.

In embodiments of the invention the sources are batteries, for example 12 volt bakeries. 10 For a better understanding of the present invention, reference will now be made by way of example to Figure 1, which illustrates a battery management system for use in vehicles, for example caravans, motor caravans and boats.

The system of Figure 1 has two 12 volt batteries I and 2 connected in parallel to respective inputs.

15 The batteries are connected by a switching arrangement to an output 11.

Battery I is connected to the output l l via a high power relay 3 and also via a series arrangement of two MOSFETs 5 and 6 which form a low power switch parallel to relay 3. Likewise battery 2 is connected to the output 11 via a high power relay 4 which is in parallel with MOSFETs 7 and 8 forming another low power switch. The 20 relays 3 and 4 are controlled by control coils RLY 3 and RLY 4. A control means comprising a microprocessor 12 and control logic 10 controls the relays 3 and 4 via the coils and controls the MOSFETs 5, 6, 7 and 8.

A load sensor 9 senses the load supplied to the output 11. If a high load is required then one (or both) batteries are connected to the output via one or both of the 25 relays 3 and 4. If the load required by the output is small, then one, or both, of the batteries is connected to the output I I via the MOSFETs 5 and 6 and/or 7 and 8.

In the example of Figure I, the load sensor is a comparator which senses the load current. At a predetermined current, em 1 5A set by a resistor Rl on one input to the comparator, control logic 10 activates the relay 3 or 4. If the current falls below 30 the predetermined level, the relay is de-activated and MOSFETs 5 and 6 or 7 and 8 are activated.

The relays 3 and 4 require high currents through control coils to operate and thus consume a relatively high power. Thus using the relays is acceptable when the load required by the output is high but is wasteful when the load required by the output is low, for example when only a low power item such as a digital clock is being 5 powered. When the load is small the MOSFETS 5 and 6 and/or 7 and 8 are used because they require extremely small control signals applied to their gates and thus consume a relatively low power.

The system of Figure 1 includes a charger 16 which may be connected to AC mains and/or be an alternator of the vehicle. When the charger is operational, a signal 10 "charge?" is supplied to the microprocessor which causes the switching arrangement 3 to 8 to connect both batteries in parallel to the charger.

A battery voltage sensor 14 is provided for sensing the voltages of the batteries 1 and 2. When battery voltage is at a critical level for example at or below about 10.7 volts, continuous use of the battery can result in permanent damage. The battery 15 voltage sensor 14 senses when the battery voltage is approximately 10.7 volts and signals that to the microprocessor 12 which causes the control logic 10 to disconnect that battery from the load and connect the other battery to the load.

Should the alternative battery fall to approximately 10.7 volts within a pre-set time, say one minute, the system warns the user and initiates a shutdown sequence of 20 the system one minute later. This protects the batteries from damage.

Under nommal circumstances batteries would not discharge to approximately 10.7 volts. The battery voltage sensor 14 and the microprocessor 12 monitor the battery voltage and at a predetermined level, for example approximately 11.7 volts, switches to an alternative battery. This allows the first battery time to recover. The 25 battery voltage sensor 14 monitors the battery voltages and at the point that the second battery is discharged to approximately 11.7 volts, the first battery can then be used again having recovered. If both batteries fall to approximately 11.7 volts within a predetermined time of being loaded, for example one minute, then both batteries are connected in parallel to maximise the service period. It has been found in experiments 30 that this can provide up to the three hours additional operation from the batteries.

The load sensor 9 monitors the load required by the output 11. In normal operation of the system of Figure 1, only one battery is connected to the output 11 via

one of the relays 3 and 4 under heavy load conditions. If an exceptional load is applied to the battery, the load sensor 9 senses that condition. The control logic responds to that by connecting both batteries via both relays to the output 11 reducing the overall load on the individual batteries and individual relays.

5 The loading at which that occurs is, for example a load approaching the maximum relay rating or the maximum rating of a single battery.

Although the invention has been illustrated with reference to high power relays 3 and 4, they may be replaced by other power switching devices. The MOSFETS 5, 6, 7 and 8 may be replaced by other LOW power devices which require small control 10 signals. They may be replaced by, for example, sensitive relays.

The following features of the system of Figure 1 are believed to be novel; 1) The switching arrangement 3, 4, 5, 6, 7 and 8 does not consume significant energy except when the current demand is high.

2) The system incorporates an automatic shutdown procedure to protect 15 batteries from permanent damage.

3) The system automatically charges all batteries regardless of which may be connected to the output at any one time.

4) The controller 10,]2 automatically switches between the batteries allowing the battery approaching discharge to recover and maximising battery 20 life. 5) Under conditions of heavy load, plural batteries are connected to the output via respective switches to reduce the load on individual batteries and switches.

Claims

1. An energy management system having: a plurality of power supply inputs for receiving electrical energy from respective ones of a plurality of sources; a power supply output; switching means for selectively connecting the power supply inputs to 5 the output; means for detecting the power supplied to the output; the switching means comprising at least one high power switch for selectively connecting the power supply inputs to the output and at least one low power switch for selectively connecting the power supply inputs to the output; and control means for selecting the high power switch in the presence of a high 10 output load and for selecting the low power switch in the presence of a low output load.

2. A system according to claim 1, wherein the or each high power switch requires a control signal of higher current than the low power switch.

3. A system according to claim 2, wherein the or each high power switch comprises a relay.

4. A system according to claim 1, 2 or 3, wherein the or each low power switch 20 comprises a MOSFET.

5. A system according to claim 1, 2, 3 or 4, further comprising the plurality of sources. 25

6. A system according to claim 5, wherein the sources comprise batteries.

7. A system according to claim 6, further comprising means for monitoring the voltage of the sources, the control means being operable to cause the switching means to selectively connect sources to the output in dependence on the monitored voltages.

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8. A system according to claim 7, wherein if the voltages of all the sources 11 to a preset limit, then the said control means causes the switching means to disconnect all the sources from the output.

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9. A system according to claim 8, wherein the sources are disconnected from the output at a preset time after the said preset limit is reached.

10. A system according to claim 7, wherein if one source is connected to the output and its voltage falls to a threshold level, said control means causes the switching 10 means to disconnect that one source from the output and connect another source to the output.

11. A system according to claim 10, wherein if the voltage of both the one and the other source fall to the threshold level in a preset time, then said control means causes 15 the switching means to connect both sources in parallel to the output.

12. A system according to any preceding claim, wherein the control means is operable, in response to detection of a high output load by the detects means, to connect a plurality of the sources to the output.

13. A system according to any preceding claim, wherein the control means further comprises an input for receiving a signal indicating that a battery charger is operational, the control means being operable to cause the switching means to connect the sources to the charger.

14. An energy management system comprising: a plurality of inputs for connection to a plurality electrical energy sources; switching means for connecting the inputs to an output; means for monitoring the load required by the output; and control means for selectively connecting the inputs to the output in accordance with the load.

15. An energy control system having; a plurality of inputs for connection to a plurality electrical sources; switching means for selectively connecting the inputs to an

J output; means for monitoring the voltages of the sources; and a controller for selectively connecting the sources to the out put in dependence upon the monitored source voltages.

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16. A system substantially as hereinbefore described with reference to the accompanying drawings.

17. A vehicle in which a system according to any preceding claim is installed.

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18. A vehicle according to claim 17, which is a caravan, motor caravan or boat.