simple desulfator circuit - question

[lynx]

What your Not Understanding is that 0.8 Volts is the Voltage under Load of the Battery.
On a Really Badly desulfated battery that Voltage might be 3 volt or more.
It Depends on the Battery's INTERNAL RESISTANCE.

The Lower this Internal Resistance is, the "CURRENT of this Spike" in a Desulfator must be Much Greater to create a Higher Voltage.
And a Battery that is Already BAD, Definately Can't deliver HIGH CURRENT to a Desulfator, to create a Higher Voltage Spike.

A NEW, Large 12 Volt Car Battery has a Very LOW Internal Resistance.
That is Why they can deliver Hundreds of Amps into a 12 Volt Starter.

Smaller, but good Batteries have Somewhat Higher Internal Resistance, so they Can't delive you expkained everything quite welll.. ty :r nearly as much current.

A Battery with a BAD CELL or a battery that is badly sulfated has even a Higher Internal Resistance.

If a Desulfator was made for Direct Mains Power, Than a VERY HIGH CURRENT SPIKE, with a Very High Voltage could be Created.
But That Spike would Probably do MUCH MORE DAMAGE than Good.

Everything has its LIMITATIONS.
Sorry I don't know How to explain this any better to you.

You explained everything quite well..it is me that i need more study on these matters... ty....

Btw.. first time i was so careless on a project and burned so many compononts. . once againburned the mosfet.. the metal case touched a battery pole... and for substitude im using irf4905, would it be any better in some aspect for the circuit?

 

[chemelec]

Basically Any P-Type Mosfet will work, as long as it can handle the Current and Peak Voltages..
Unlikely Any Difference in Performance.

And after doing the Tests I Did and seeing the waveform, I am NOT Impressed with that Circuit.

My BEST Advice is just: BUY A NEW BATTERY.

Take care, Have Fun....Gary