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I window-shopped for a car air compressor and there's a variety of them with different performance levels.

Low performance compressors (like 30 liters per minute) have a cigarette lighter connector, but high performance compressors (like 160 liters per minute) seem to draw something like 50 amperes current and only have clamps for connecting to the battery terminals. The latter implies opening the hood which is not very convenient.

What other ways are there to power a short-term load like an air compressor that drains current about 50 amperes off the car electrical circuit?

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I would recommend that you investigate the power connections used by the off-roaders for the winch systems. As you can see (third post into the cited thread), common winches draw much more power than you are looking for. Those guys make it clear that you can directly connect the winch to the battery. The battery is then charged by the alternator while also expecting the engine to be running to avoid draining it flat.

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To run a current of that size requires fairly hefty cabling, hence why they are provided with battery clamps. You could run heftier cables into the cabin, but you would have to make sure it was done properly - using cables capable of taking the load, properly insulated and protected where they pass through the bulkhead, and using a suitable fuse (fitted as close to the battery as possible).

Bear in mind that 50 amps is a very large current for an automotive circuit - 600W, or nearly 6 times the power of a normal pair of headlamps, and around 2/3 of the total rated output of most alternators...

What are you intending to use it for? If it is just for topping up tyres, the lower rated compressor will be all you would need - The only advantage of a higher rated one in that situation is that it'll do the job a bit quicker. Obviously if you're intending to run a spray gun or something off it, or reinflate tyres from flat, that becomes a bit different.

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