Battery desulfators

[nvisser]

I modified and build a Alistor Cooper desulfator with the help of Seamonkey.
I used a low side fet switch driven by a picaxe chip and a mosfet driver.
The rise and cutoff times (fall time) of the pulses are very sharp caused by the mosfet driver.
I drive it with a 3Khz signal with adjustable pulse widths. The pic draws 100mA.
Because of this fast rise and fall time the fet does not need a heat sink and with a relative long pulse of 120us , when this device draw 1A from the supply, the temp. on the fet rise to about 30 deg Celsius.
With a 50 us pulse the fet feels colder than ambient temp, drawing 200mA from the supply.
The output on a scope ,measured between 0V and the source, shows the perfect square waves with the up to 150V spike with the charge battery connected.
I set it up to give 120us pulses , drawing 1A from the supply to try and recover a very bad battery. In the last 3 hours the battery voltage went from 8V to 11.4V.
I will leave it 24 hours and report back.
Here are the diagram and some photos.

[Bit's-n-Bytes]

I modified and build a Alistor Cooper desulfator with the help of Seamonkey.
I used a low side fet switch driven by a picaxe chip and a mosfet driver.
The rise and cutoff times (fall time) of the pulses are very sharp caused by the mosfet driver.
I drive it with a 3Khz signal with adjustable pulse widths. The pic draws 100mA.
Because of this fast rise and fall time the fet does not need a heat sink and with a relative long pulse of 120us , when this device draw 1A from the supply, the temp. on the fet rise to about 30 deg Celsius.
With a 50 us pulse the fet feels colder than ambient temp, drawing 200mA from the supply.
The output on a scope ,measured between 0V and the source, shows the perfect square waves with the up to 150V spike with the charge battery connected.
I set it up to give 120us pulses , drawing 1A from the supply to try and recover a very bad battery. In the last 3 hours the battery voltage went from 8V to 11.4V.
I will leave it 24 hours and report back.
Here are the diagram and some photos.

Nicely done Vissie! There is some serious ringing in there.

Jeff

[nvisser]

Nicely done Vissie! There is some serious ringing in there.

Jeff

I'm not sure if it's good or bad. The ring frequency is about 500Khz. Not sure if it helps the charging.
Apparently you get ringing with very sharp cutoff times.
What I find the most interesting is that the mosfet runs cool without a heat sink while drawing 1A from the supply.

[smw1998a]

I'm not sure if it's good or bad. The ring frequency is about 500Khz. Not sure if it helps the charging.
Apparently you get ringing with very sharp cutoff times.

Hi nvisser,
Your 150v spike is actually a rapid oscillation centered around the sum of supply and charge battery voltages plus the 0.6v fly back diode. It is arguable that the positive component of this oscillation reaches the charge battery even though the potential is there, the negative component dose not have the potential to cross the diode. The second and most obvious damped wave oscillation is centered around the supply voltage, the positive component potential is less than the potential of the charge battery and is the result of the remaining energy of the collapsing field dissipating between the coils capacity and inductance.

Great pics and an interesting little circuit...

Regards Lee...

[linesrg]

PIC based desulphator

nvisser,

My former Canadian colleague Rick designed the PIC based unit I sell around the original Couper circuit some 4 years ago. It was upgraded from a totem pole to MOSFET driver chip output about 2 years ago.

It certainly improves the performance of the basic circuit by some degree.

Regards

Richard