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ad Acid Battery Desulphator 

s is based on a modified version of Jaycar kit KC5414, also published in Silicon Chip magazine July 2005. It is designed to desulphate

desulfate if you are American) 12 Volt lead-acid batteries. There is still dispute over just how well it works, and it may not be effective in

toring every lead-acid battery problem. The principle is pretty s imple - short high-energy electric pulses are fed into the battery at a

quency which resonates with and breaks up the sulphate crystals that build up inside the battery shortening its life. The optimum

quency seems to be a few MegaHertz. Jaycar is also selling bottles of battery desulphation fluid (cat no NA1420) which would also be

ective - battery manufacturers will extend the warranty if such a fluid is used with a newly purchased battery.

e complete circuit is shown below. This consists of the Jaycar kit plus:

1 mH air-cored inductor to isolate the battery charger (as recommended in the Silicon Chip article)

200 mV panel meter with isolating inverter, and peak detector 

e㜭瀵xiconChip circuit delivers a 50 us pulse every 950 us to the power MOSFET, which causes a discharge of energy from the 100 uF

pacitor and 220 uH inductor through the BY229-200 fast recovery rectifier back to the battery. The picture below shows the pulse on my

il loscope - I measured the ringing f requency to be about 5 MHz. The panel meter picks up the peak voltage pulse to give some

cation of the state of the battery and how well the desulphation process is going. The rule here is lower is better . The good batteries I

asured had readings between 17 Volts and 25 Volts. The web page reference below reports batteries in poor condition to start around

Volts, and gradually decrease as desulphation proceeds - a process that can take weeks.

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The unit uses just over an Amp-Hr of power from the battery per day (about 60 mA), so for long periods a battery charger should be

attached. The 1 mH inductor attenuates the high-voltage pulse from affecting the battery charger, and attaching the charger had no

measurable affect on the effectiveness the pulse being delivered to the battery. Always disconnect the battery from the car or other 

appliance before attaching the desulphator as the high voltage pulse could do damage to other electronics inside the car. It is important to

keep the leads between the desulphator and battery short - as short as possible. The inductance of long leads results in much higher 

voltages being seen by the meter which can erronously lead you to believe that a battery is in poor condition.

The㜭瀵 x sabove shows the desulphator mounted in a small box, with meter at the front. The PCB with two inductors is f rom the Jaycar 

kit, the upper PCB has the additional circuitry for the panel meter, and the additional 1 mH inductor. If you purchase a panel meter that does

not require an isolated power supply you can dispense with the 9 V inverter.

In use the circuit emits a very faint whine, otherwise the panel meter is the only indication that it is operating. I have yet to give it an

extensive test restoring a dying lead-acid battery. I have experienced a number of car batteries dying after only about 2 years use, so my

aim is to use the desulphator to prolong the life of my car battery.

Update - I've been using this now for over a year on my car battery. The battery is still in good condition, but I can't say for sure whether thedesulphator has had a positive effect.

 

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