Simple, Isolated, Switchable Power Supply Problem 360W-1000W

Please advise how I ought to proceed with this power delivery problem. I am currently driving a 12vdc brushed motor using an h-bridge (w/ relays), and an IRFP4368 N-channel MOSFET in enhancement mode with a current sensing circuit. A microcontroller is sending PWM to control the duty cycle. Duty cycle is typically 100% (5Vdc after ADC). I am doing current measurement with an op amp and using that current value to drive the control logic. If current is above a threshold, I initiate a task and change the control state. The challenge of this relatively high-power application is working around wire size (10AWG), relatively low voltage (12-14Vdc) and fuse constraints (30A). Duty cycle is about 10% over one hour period. The system typically operates using 20-30A at 12vdc–happily. The scope of work has expanded to include colder temperatures, which requires over 6X the torque than the nominal case due to the application in question. Since doubling, tripling or quadrupling the number of motors on the drivetrain is not economically feasible, I would like to have an alternative means of power delivery, up to 1000W for a short amount of time on larger diameter cable (2/0 AWG). Adding a separate power supply (SLA or AGM battery) engenders too much weight and is out of scope for what we want to achieve. Rewiring separate, larger diameter cables back to the main supply is out of scope (main supply could be disconnected half of the time when not in use). A portable, weatherproof jump pack may be a viable idea, but it is not a kosher solution. How would I wire this jump pack into a +12vdc system so that I do not trip the limiting 30A fuse or meld 10 AWG wire? Effectively switching from a 360W loop to a 1000W loop for the same load. I was thinking of using a non-specific relay but I am not sure how to implement this idea. Please advise! A circuit diagram would be very helpful to me. Better yet, are there any better solutions for this power delivery problem?


Understood that you’re trying to get more current to a load, but it’s not obvious from this side of the screen what the physical/practical constraints specific to your application are.

There’s no One Secret Trick that a person can use to pass a sustained 90A through a system with cabling, protection, and controls designed for 30. Whatever parts you want to pass the higher current through need to be designed to tolerate it. How exactly those parts are laid out, where the proposed introduction of an auxiliary source is, and so forth seem to be missing pieces of the puzzle here.

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