A while ago, I did some research about battery desulfators, and I have since then built this breadboard prototype out of junk box components. It’s essentially the same design on the power side of things, although the coil is unknown, but seemingly capable of delivering a similar current pulse as the one Carpenter used in his design.
There’s a key difference on the logic side, though, and that is the use of a PIC12F629 for delivering the MOSFET gate drive, rather than a 555 timer and a dedicated MOSFET driver. The use of a rather easily driven, logic-level FET and a µc capable of delivering a reasonable amount of current allows for this configuration without excessive time spent in the linear region of the FET.
I forgot to take any pictures of the gate of the FET, though, but I assure you that they’re more than acceptable; There’s hardly any heat generated in the FET at all.
I’ve measured a peak current pulse of about 5.5A across the 0.11Ohm sense resistor, and an RMS current consumption of about 40mA during operation.
Scope shots taken with a 3Ah flooded moped battery:
Across the battery terminals: