The invention has been developed primarily with reference to lead-acid batteries and will be described hereinafter with reference to this field of use. However, it will be appreciated that the invention is not limited to this particular field of use.

BACKGROUND OF THE INVENTION Lead batteries are available for a wide variety of uses. The batteries are of different types and include sealed and unsealed lead acid batteries, leak-proof gel based lead batteries, and matt-type batteries. Most commonly, vehicle type unsealed lead-acid batteries are also used to store charge in solar systems, and uninterruptible power supplies amongst other uses.

Common sealed or unsealed lead-acid vehicle type batteries are typically rated at 12V EMF. In these batteries, a pair of lead electrodes are substantially immersed in a lead sulphuric acid electrolyte solution. In use and simply over time, especially long durations where no load is applied across the electrodes, a lead sulphate (PbSO4) film will grow on the electrodes. This film build-up also occurs during normal changes in ambient temperature or vibrations applied to the battery.

The growth of the lead sulphate film serves to increase the internal resistance of the battery. This result is disadvantageous as it not only reduces performance and life of the battery, but can also cause it to fail. Although efforts have been made to reduce the effect of ambient temperature changes, vibrations and other external effects on the batteries, use of such batteries in applications such as charge storage for solar power or in a vehicle, these factors cannot be practically eliminated.

Rather than stop the causes of lead sulphate film build up on the lead electrodes, it is known to apply pulses of charge between the lead electrode surface and the lead

sulphate film built up on the electrodes. The pulses strip away the lead sulphate film from the electrodes causing the removed lead sulphate to fall away into the sulphuric acid electrolyte solution. This provides only a temporary recovery in the performance of the lead-acid battery as the internal resistance is removed.

This is because as the lead sulphate is stripped away from the electrodes and generally falls to the base of the electrodes and the specific gravity of the electrolyte does not return to a normal level immediately. As a consequence, it is necessary to directly supplement the dilute sulphuric acid to restore the specific growth of the electrolyte.

However, after supplementing the dilute sulphuric acid, the lead sulphate film that is stripped and fallen to base of electrodes is gradually dissolved with the electrolyte solution causing a significant or undesirable rise in the specific gravity. The rise in specific gravity causes damage to the surface of the electrodes reducing the life of the battery. It is noted that this can also destroy the electrodes rather than just damage the surface.

In US Patent No. 5,592, 068 there is provided a battery rejuvenator (or conditioner) having a switching circuit for generating a pulse train of particular current and voltage characteristics. The pulse train must have a linearly rising current from a base current to a maximum current and a linear decay back to the base current where the rate of change of the linear rise is greater than the rate of change of the linear decay. Further, the pulse train voltage must have a first linear rate from a base voltage to a first voltage and then a linear voltage decay from the first voltage to a voltage greater than the base voltage. The voltage then further decays exponentially from the voltage to the base voltage.

Unfortunately, this battery rejuvenator is not efficient at removing lead sulphate built up from the electrodes. Furthermore, the lead sulphate that is removed is relatively large which is not readily absorbed into the electrolyte solution.

The patentees of the above US Patent improved their system as disclosed in US Patent No. 5,491, 399. In this patent, the pulse width provided necessarily must be 8. 33 KHz and the switching circuit must include a first DC power supply with a capacitor connected across it, and a transformer with a secondary winding connected across both the power supply and capacitor.

US Patent Application Publication No. 2001-0019257 discloses a battery charging controller in which pulses of a positive voltage are applied across the electrodes of a lead-acid battery.. The pulses employ a"fairly fast"rise time and a"slightly slower" decay time and is applied at fixed intervals of between 6 to 16KHz. However, the controller doesn't do more than remove relatively large pieces of lead sulphate build up from the electrodes which is not readily dissolved into the electrolyte solution.

It is further noted that known systems, methods and devices as above for use in charging or rejuvenating lead-acid batteries are mains powered. This results in the need for a motorist, in the case of a car battery, to remember to connect their battery to a mains powered device, which aside from not always being possible, is not always connected when desired.

OBJECT OF THE INVENTION It is an object of the invention to provide a lead battery conditioner that overcomes or substantially ameliorates at least some of the disadvantages of the prior art, or to provide a useful alternative.

SUMMARY OF THE INVENTION According to a first aspect of the invention there is provided a method of conditioning a lead battery, said method including the step of applying a negative voltage pulse across the terminals of said battery at a rate of between lkHz and 35kHz wherein said negative voltage pulse is characterised by having a negative amplitude of between two and ten times the amplitude of the EMF of said battery and having a pulse width of less than 10 microseconds.

Preferably, said method includes the step of providing power for said negative voltage pulses from said battery and said negative voltage pulse width is 1 microsecond or less and said pulse amplitude is four times said EMF.

According to a second aspect of the invention there is provided a lead battery conditioner including a negative voltage pulse generator configured for applying negative voltage pulses at a rate of between 1kHz and 35kHz across the terminals of a battery, said negative voltage pulses characterised by having a negative amplitude of between two and ten times the amplitude of the EMF of said battery and having a pulse width of less than 10 microseconds.

In preferred embodiments, said negative voltage pulses are powered from said battery.

According to a third aspect of the invention a method of conditioning a lead battery, said method including the step of applying a negative voltage pulse across the terminals of said battery at a rate of between lkHz and 35kHz wherein said negative voltage pulse is characterised by having a negative amplitude of between two and ten times the amplitude of the EMF of said battery and having a pulse width of less than 10 microseconds and wherein said negative voltage pulses are powered from said battery.

Preferably, negative voltage pulse is continually applied.

According to a fourth aspect of the invention there is provided lead battery conditioner configured for delivering a negative voltage pulse, said battery conditioner including: a reverse connection protection circuit having an output configured for electrical communication with a terminal of a battery; a voltage detector disposed electrically intermediate said reverse connection protection circuit and a voltage comparator; a differential voltage generator disposed electrically intermediate said reverse connection protection circuit output and said voltage comparator; an oscillator disposed electrically intermediate said voltage comparator and a peak voltage generator;

an amplifier disposed electrically intermediate said reverse connection protection circuit output and a waveform shape generator configured for electrical communication with an opposite polarity terminal of said battery.

Preferably, said negative voltage pulse has a negative amplitude of between two and ten times the amplitude of the EMF of said battery and having a pulse width of less than 10 microseconds, and said battery conditioner is configured for delivering said negative voltage pulses at a rate of between lkHz and 35kHz.

In preferred embodiments, there is included a conditioner running indicator tester and a corresponding display configured for displaying an indication of the operation of said conditioner. More preferably, there is also provided an operation switch disposed electrically intermediate said voltage comparator and said oscillator.

It can therefore been seen that the lead battery conditioner applies negative voltage pulses which efficiently remove lead sulphide to the electrodes of lead batteries.

Further, the conditioner employs the lead battery as the power source and in which the adhesion of lead sulphide to the electrodes is prevented by the continuous consumption of very small amounts of electric power.

BRIEF DESCRIPTION OF THE DRAWINGS Preferred embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings in which: FIG. 1 is a schematic diagram of a lead battery electrode conditioner according to the preferred embodiment; and FIG. 2 is a perspective view of a pulse generated conditioner of FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the drawings generally, FIG. 1 shows a lead-acid battery conditioner 1.

The battery conditioner 1 is configured for applying negative voltage pulses 2 across the terminals of a battery (not illustrated) at a rate of between lkHz and 35kHz. However, it is noted that any lead battery such as gel type or matt lead batteries can be used.

The negative voltage pulse is shown in FIG. 2 and includes a negative amplitude 3 of four times the EMF or voltage of the battery and is denoted E. However, the negative amplitude can be between two and ten times the battery EMF.

The pulses 2 have a width 4 of 1 microsecond, however, any pulse width less than 10 microseconds can be used.

The lead battery conditioner 1 includes a reverse connection protection circuit 5 having an output configured for electrical communication with the positive terminal 6 of the battery.

A voltage detector 7 is disposed electrically intermediate the reverse connection protection circuit 5 and a voltage comparator 8.

A differential voltage generator 9 is disposed electrically intermediate the reverse connection protection circuit 5 output and the voltage comparator 8. An oscillator 10 is disposed electrically intermediate the voltage comparator 8 and a peak voltage generator 11.

An amplifier 12 is disposed electrically intermediate the reverse connection protection circuit 5 output and a waveform shape generator 13. The waveform shape generator 13 is configured for electrical communication with the negative polarity terminal 14 of the battery.

The conditioner 1 includes a conditioner running indicator tester switch 15 and a corresponding display 16 configured for displaying an indication of the operation of the conditioner 1. That is, the switch 15 is actuated and an indication of the state of operation of the conditioner 1 and/or battery condition is provided on the display 16.

The conditioner 1 further includes an operation switch 17 disposed electrically intermediate the voltage comparator 8 and the oscillator 10. The switch 17 is movable between a closed position in which the conditioner 1 is operable and draws power from the battery to generate the negative voltage pulses applied across the terminals 6 and 14 of the battery, and an open position in which the conditioner 1 is inoperable.

When the operation switch 17 is moved to the closed position, pulses 2 are generated by the conditioner 1 and applied to the battery. This thereby results in the removal of lead sulphate build-up on the lead terminals.

The pulse with a voltage waveform width of not more than 10 microseconds that possesses a negative voltage of between two and ten times the battery EMF concentrates in and destroys a very shallow surface portion of the lead sulphide crystallization due to a shallow penetration depth and is preliminarily calculated to be 0.01 mm or less. This is determined by the surface effect and the surface depth accompanying the effect, and the crystals placed at the shortest distance between the crystals of the films of lead sulphate that adhere between the positive electrodes and the negative electrodes are progressively destroyed.

Hence, without damage to the electrodes, the crystals of lead sulphate float as extremely fine crystals of lead sulphate into the dilute sulphuric acid electrolyte solution. Through the next charging of the battery, the lead sulphate is separated in the dilute sulphuric acid electrolyte solution into Pb+ and S04-ions which return to the electrodes. This results in performance of the lead-acid battery being recovered and the initial specific gravity is relatively quickly restored. The variation in the frequency of the applied pulses from lkHz to 35 kHz affects the recovery time of the performance of the lead-acid battery.

When the pulses 2 are applied across the terminals 6 and 14, the load arising in the projecting portions of the surface of the lead sulphate crystallization is concentrated and surface of the lead sulphate crystallization that has grown extensively through the surface effect and to a surface depth determined by the effect is destroyed. This is progressively restored to sulphuric acid lead, lead oxide and water, and the performance of the lead-acid battery is recovered to that when the battery was first manufactured.

It can also be seen that damage to the electrodes 6 and 14 is avoided because direct current is not applied to the electrodes of the lead-acid battery, and the specific gravity

of the lead-acid battery is recovered in comparison with the time when the pulses were applied, and performance is recovered. It can therefore be seen that the lead battery conditioner 1 employs the lead-acid battery as the power source and, as such, the adhesion of lead sulphate to the electrodes is prevented by the continuous consumption of very small amounts of electric power.

The foregoing describes only a preferred embodiment of the present invention and modifications, obvious to those skilled in the art, can be made thereto without departing from the scope of the present invention.