First this is a scrap magnet on an excavator so AC is unavailable.

I have a single 24volt charging source of 70 amps linked to four batteries (8D's) as buffers. I need to feed both 12 and 24 VDC into a control panel to run a magnet at either 12 or 24 volt.

It draws 100 amps on 24v and 60 amps on 12v. The 24v operation is at 75% duty cycle but the force is much higher and the 12 v is 100 % duty cycle. I need to be able to use both and I can't switch off the 24V since it is the control voltage.

I tried isolating with diodes but - no go. It would be simple to switch from parallel to series with SCRS or relays but I lose the 24V feed and the charging voltage when I do.

I considered using an SCR and pulsing it (PWM) to get a 12v output while still able to use the 24v for the control circuit and charging. The quality is not critical nor is the exact voltage as this is just feeding an electromagnet.

What other options are there ? I know i'm probably overlooking something.

Guy