Battery Desulphators/ Desulfators - What are they?

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We are now trialling a potted basic desulphator/ pulser in response to some customer enquiries as per the adjacent photo. Production models won't have the capacitor poking out like this!!! Furthermore, unlike one of our competitors, we won't be charging you £125 for 'the only waterproof desulfator on the market'!!Potted Basic Desulphator

Our low voltage cut-off devcies are now on sale as kits and built units. The devices have been designed to stop operating at around 12.2V. There are more details below.

A Google (or other internet search engine) search will bring up a whole host of references if you type in desulphator/ desulfator or pulser (although in truth these devices should be called battery desulfators to segregate them from pulsing type battery chargers which are a different animal).

Which route to go then you may well ask, we would recommend looking at or as a start as this is what we did?

So you're probably wondering do these devices really work because we wondered exactly the same thing? The presence of the former ezboard BB now found at and people who clearly believed it did led us to 'give it a try'.

Reading through the whole of the BB's above took some time and is something that not everybody will have the time or inclination to do (unfortunately quite a bit of the historical stuff on the former ezboard desulfator forum has been lost). We certainly don't profess to understand all the technical parts of what they contain but it does allow you to see how some 'improvements' to the original AC design have been arrived at.

We make no claims to having 'designed' outright the Basic and High Power devices we offer for sale but have done some 'matching' with regards to the replacment parts we've used.

The 'High Power' desulphator/ desulfator version is a development of the original and is an amalgamation of several threads on the BB.

For those less confident in their electronic skills we offer the kits built up in two stages. One is simply the device built on its PCB and tested ready to be fitted with leads and boxed by the customer. A look at our 'new' eBay shop site Shop will show we have placed kits, built up PCB's and fully built devices in to seperate sections. Hopefully customers will find this format more obvious than our old Shop page.

The fully built version is just that, it is supplied in a box c/w output leads and a pair of battery terminals ready to go (as noted elsewhere crocodile clips and the plain 8mm soldered ring terminal are other options).

At this point we must comment on some of our competitors products. The photo below shows a device which is sold as a 48V desulphator. I have included a ruler for scale and one of our standard 'High Power' inductors. Note the very small crocodile clips (no chance of fitting a large battery terminal), the wires are hopelessly undersized and will lose too much energy and you can just see the inductor they use. We may not be the cheapest but we still believe we offer a very good product which is well engineered and does 'what it says on the tin' to paraphrase a well known British TV advert.Australian Desulphator

Basic Pulser Kit

This kit is the circuit in its simplest form with some substitute components that have been tested to ensure they work. The cheapest way to start.

The only modifications are the addition of a Zener diode to protect the 555 from voltage spikes, an LED to show it is 'working' and both electrolytic capacitors are larger values.

All the necessary components and a PCB are supplied along with some brass nuts/ bolts and washers to make mounting posts to connect the leads to the battery. It consumes about 50mA.

High Power Pulser Kit

This version is a development of the basic version for which we take no credit that belongs to the contributors at the Desulfator BB.

In addition to the above basic modifications this kit has a superior MOSFET, a larger still output capacitor, larger capacity inductors and R2 (the 22k resistor) is replaced with a pair of 47k NTC thermistors in parallel. These will be supplied 'glued' directly to the components themselves.

All the necessary components and a PCB are supplied along with some brass nuts/ bolts and washers to make mounting posts to connect the leads to the battery.

This version is a more powerful pulser than the Basic device and consumes more current - circa 65-110mA.

Low Voltage Cut-Off Versions of the 12V Devices

Since we started selling our desulphators we have had various suggestions/ shortcomings with such devices brought to our attention. The first was the issue with blowing the devices up when connected wrongly, we addressed this initially with a diode and conventional fuse and more recently with a diode and a resettable fuse. The 'High Power' and PIC devices have a measure of overheat protection incorporated in to their design.

One issue we have tried to resolve but not found a satisfactory solution to previously was how to stop these devices from dragging a battery down to very low (damaging) voltage levels when the end user/ customer forgets to disconnect the device! We've done it ourselves. Courtesy of Bill Roth we do now have a working device.

As an experienced EE he has taken a look at the standard circuit and added an op-amp as a comparator. Additionally the location of the protection zener has been moved as it's previous location didn't provide the measure of protection it should. It should also mean that the new PCB will be both 12 and 24V capable without the addition of a -12V regulator as has been necessary in the past. We have yet to test the new circuit at 24V.

As of 10/09/11 we are supplying the 10k resistor in the comparator as a 1% device in addition to the other 1% resistors already supplied. This is to ensure a correct cut-off voltage.

PIC Pulser Kit

This device is based around a PIC (Programmable Interface Controller) and was designed by my Canadian colleague Rick who should take all credit for the design and development. Basically Rick had looked at the Alastair Couper original designs and concluded they had certain shortcomings being based around a simple 555 timer and set about developing his own device.

PIC Prototype

This is a close up of a prototype device which didn't go through to production due to complexity.

The current version is our most 'powerful' desulphator/ desulfator and consumes some 300 mA of current and is ideally suited to larger batteries. Additionally, as of 10/04/09, it has been revised to incorporate a TC4428 MOSFET driver chip in place of the previous 2N3904/ 3906 driver (totem pole) set-up. As a kit the PCB is now double sided eliminating the two wire links previously required making it a more 'user friendly' kit.

Ready built kits/ PCB's

These are ready built and tested PCB's for those without the necessary skill/ or confidence to build their own and which are supplied without output leads or a case saving the end user some money.

Output Leads

We only use multi-strand 10AWG cable for our output leads terminated in soldered ring 8.4mm (5/16") connectors. Please note our standard lead length is 250mm (10"). These are more substantial than any of our competitors

Battery Terminals

Self-explanatory really. Two off, one for each terminal, with a 8mm post for attaching the output leads.

Complete Pulsers

These units come complete in that they are in an ventilated ABS box with output leads connected to battery terminals and 'ready to roll'; as soon as they are unpacked. The LED is inserted in the lid.

How do I know its working?

All battery charging operations should be carried out in a well-ventilated environment, this is doubly so when connecting or disconnecting a pulser.

Basically you can consider it is working if:-

  1. The LED is lit
  2. None of the components get hot or go pop. The recommended way of doing things is to connect the negative lead first and then touch the positive lead to the battery terminal briefly. This should be accompanied by some low level sparking (the need for the ventilation now clear perhaps?).

    If it sparks then leave it connected for a couple of seconds and then disconnect and check component temperatures.

    Re-connect for a slightly longer period and then disconnect again and check temperatures.

    It will be self-evident if all is well.

  3. The unit emits a 'buzzing' near 1kHz tone, if you're hard of hearing then grab an AM radio and turn the volume up and stick it close by.


We're still looking at a 'potted' or encapsulated version. We have tried a silicone type encapsulation and it simply wasn't durable enough so it looks like we'll have to stick with the hard expoxy option.

As you'll see on our Home page we are now selling a range of 'Tesla Switch' based charger/ desulphators. This title is probably a bit misleading but it alludes to the concept of charging a capacitor from a source of power and then physically disconnecting it from this source prior to releasing its energy in to the battery. The circuit is actually quite simple but surprisingly effective.

If you go the TSW page TSW Charger you'll find more details. This device again answers requests we've had from customers about whether we market a device that will both charge and desulphate. It is a device primarly aimed at users of larger capacity batteries and the ideal source of power for it is a solar panel.


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