Battery Desulphator Experience

[Maine Sail]

The principle of desulphation is that you pulse very large currents through the battery to knock the sulphation off the plates, If you only have croc clips attaching it to the battery, its likely that you have reduced the output of your desulphator by more than 50% because of the resistance the croc clips have introduced and rendered it worse than useless, they need to be bolted to the battery terminals with large surface area connections and thick short length cable.

Actually desulfators work on quite low current but high voltage pulses at specified duration of pulse.

which is why a decent equalisation charge appears to rejuvenate an apparently tired and ageing battery,

They don't just appear to improve performance it can actually be measurable but in the long run the battery is still aged if you've not kept up with the care..

and its the good quality chargers that do this, not because of the quality of the charge they provide, but because of the higher current outputs that they are capable of

An equalization charge is the opposite of high current and is actually low current with high voltage. This is why good chargers with an equalization stage will not equalize the batteries until they have been fully charged. High voltage and high current can damage the battery. Once the batteries are full then you can push the voltage and the current accepted will be quite low making an equalization a safer process. It can also important to use temp compensation when doing an equalization when out of the standard temp rating range for the battery..

 

[TopDonkey]

Actually desulfators work on quite low current but high voltage pulses at specified duration of pulse.



They don't just appear to improve performance it can actually be measurable but in the long run the battery is still aged if you've not kept up with the care..




An equalization charge is the opposite of high current and is actually low current with high voltage. This is why good chargers with an equalization stage will not equalize the batteries until they have been fully charged. High voltage and high current can damage the battery. Once the batteries are full then you can push the voltage and the current accepted will be quite low making an equalization a safer process. It can also important to use temp compensation when doing an equalization when out of the standard temp rating range for the battery..

I dont know how to do the multi quotes you did above, but i'll reply to your responses to my post

1, your very wrong about it being a high voltage pulse, its a high current pulse that does the work (up to 50amp pulses), it can be up to 50volts to start with on a heavily sulphated battery with high resistance, but this will drop fairly quickly, its pulsed using the collapsing field current from an induction coil, and the only reason the duration of the pulse is so short, is that the induction coil quickly saturates, and if you try and put more in, all you do is overheat the coils. The important part is the frequency of the timings that the current is pulsed at, this is done at the resonant frequency of the battery, this is why croc clips are useless on desulphators, the resistance they introduce stops the current in its tracks and the end result is that you think that desulphators dont do what they claim

2, you have misinterpreted what i had written, I didnt mean that an equalisation charge doesnt work, I mean that it does work, but many people think that its this 'miracle' equalisation that has rejuvenated their battery, when i practise, all it did was to apply about 15.4 volts for a short time to make the battery bubble so that the electrolyte got mixed, you can get exactly the same effect by other methods, like refilling the electrolyte (bit extreme, but reverses stratification) or shaking the battery or gently bubbling air through the battery with an airline

3, you simply cant do an equalisation charge on a flat battery, it has to be charged before you start as the internal resistance of the battery governs the current drawn at a specified voltage, and if you tried to put in 15.4 volts on a flat battery, the current draw would be huge and the battery would overheat and be destroyed, at the end of the day, you cant beat ohms law when charging a battery

 

[Plevier]

Actually desulfators work on quite low current but high voltage pulses at specified duration of pulse.



They don't just appear to improve performance it can actually be measurable but in the long run the battery is still aged if you've not kept up with the care..




An equalization charge is the opposite of high current and is actually low current with high voltage. This is why good chargers with an equalization stage will not equalize the batteries until they have been fully charged. High voltage and high current can damage the battery. Once the batteries are full then you can push the voltage and the current accepted will be quite low making an equalization a safer process. It can also important to use temp compensation when doing an equalization when out of the standard temp rating range for the battery..

Maine Sail is spot on with all his comments. I would summarise it as follows.
These gadgets will not have beneficial effects on batteries that are properly looked after with a good charging regime. They may in fact be harmful.
If you have a battery in poor condition from abuse, you may see some improvement but you will be shortening the life of the battery compared with what it would have given if properly treated to start with. Sulphation is not a problem in correctly treated batteries, it results from maltreatment.
The desulphator gadget is applying something not dissimilar to ripple current. Ripple current is very bad for lead acid batteries. It promotes surface erosion and shedding of active material and corrosion between the paste and the grid. If what it's getting rid of is a sulphate layer (resulting from a poor regime) that will give you the temporary improvement. Desulphators may help to convert some of the sulphate back to active material but they also cause shedding of it.
Also the recovery effect of some vigorous charge and discharge cycles is similar, and similarly damaging.
So it's a bit like an "Italian Tune Up" for your car; it may help conceal short term problems while doing long term damage.

On another point, in my experience acid stratification is rarely a problem in batteries of the size we are talking here. (Some of our industrial cells were about a metre tall and then it can be serious.) It is important to mix the electrolyte after topping up with water though. An equalising charge will do it, or going to sea.

 

[VicS]

Its mainly due to not fully charging a battery frequently, or long periods of no use, the specific gravity of the acid in the electrolyte varies as you charge and discharge a battery, and this can cause it to separate out and a decent fast balance charge that gets your battery gently bubbling remixes it, which is why a decent equalisation charge appears to rejuvenate an apparently tired and ageing battery, and its the good quality chargers that do this, not because of the quality of the charge they provide, but because of the higher current outputs that they are capable of

I dont understand why it separates out. If you stood a bottle of battery acid on the shelf it would not separate out. The acid concentration would surely remain equal throughout, even years later.

 

[Maine Sail]

1, your very wrong about it being a high voltage pulse, its a high current pulse that does the work (up to 50amp pulses), it can be up to 50volts to start with on a heavily sulphated battery with high resistance, but this will drop fairly quickly, its pulsed using the collapsing field current from an induction coil, and the only reason the duration of the pulse is so short, is that the induction coil quickly saturates, and if you try and put more in, all you do is overheat the coils.

Actually one of the desulfators I used has the specs below. It is not high current at all. I did also use ring terminals.


Output Current = 2.5 A dc Maximum
Output Voltage, Bulk Charge = 14.8 V dc
Desulfating Pulse Peak Amplitude = 250 mA Typical
Desulfating Pulse Frequency = 22 kHz to 28 kHz
Pulse Rise Time = < 1 microsecond

The important part is the frequency of the timings that the current is pulsed at, this is done at the resonant frequency of the battery, this is why croc clips are useless on desulphators, the resistance they introduce stops the current in its tracks and the end result is that you think that desulphators dont do what they claim

Funny that I have a 500A carbon pile load tester that has no trouble at all pulling 450-500A for 15 seconds through "croc clips". I also have a 20A bench charger that can pump 20A out through "croc clips" for hours on end.. But, to answer your question, both of the desulfators I used had ring terminals and both were low current and sold as "desulfators".

 

[TopDonkey]

Actually one of the desulfators I used has the specs below. It is not high current at all. I did also use ring terminals.


Output Current = 2.5 A dc Maximum
Output Voltage, Bulk Charge = 14.8 V dc
Desulfating Pulse Peak Amplitude = 250 mA Typical
Desulfating Pulse Frequency = 22 kHz to 28 kHz
Pulse Rise Time = < 1 microsecond

Are you sure that was designed for big lead acid batteries ?, i would have thought with specs like that, it is more suitable for pulse charging d size batteries !

Funny that I have a 500A carbon pile load tester that has no trouble at all pulling 450-500A for 15 seconds through "croc clips". I also have a 20A bench charger that can pump 20A out through "croc clips" for hours on end.. But, to answer your question, both of the desulfators I used had ring terminals and both were low current and sold as "desulfators".

Thats because a carbon pile load tester is a straight dc load, you try pulling that sort of current at 22Khz. At these sort of frequencies the current will travel only in the surface few microns of the conductor (skin effect), and the resistance of the connection between the battery and the desulphator circuit becomes critical to the correct functioning of the circuit, and the impedance increases at an astronomical rate, thats why you need ring terminals on a desulphater and dont need them on a load tester

For my sins, many years ago, i used to work as a circuit designer for Harris semiconductors and this was one of my specialist areas, so i generally (hopefully!) know what i'm talking about on this subject

 

[nigelmercier]

at 22Khz. At these sort of frequencies the current will travel only in the surface few microns of the conductor (skin effect)...

Skin depth for copper at 20kHz is about 1mm, not a few microns. But I agree that crocodile clips are not the right way to connect such a device.

 

[TopDonkey]

Skin depth for copper at 20kHz is about 1mm, not a few microns. But I agree that crocodile clips are not the right way to connect such a device.

Its actually 0.471mm !!, but thats just being picky , but your right, its more than microns, I should have been more precise in my response

 

[cimo]

That's pretty interesting. I never came across pulse conditioning before now.

I forget who it is who said that polarized opinion was a catalyst for developing understanding.

A high voltage/low current equalization charge can restore lost capacity, using the resistive battery model.

A high current pulse (at the resonant frequency of lead sulphate crystals from my research) is claimed to also restore lost capacity, (using a capacitive model I presume?)

Anyone got any published data for the latter?