I have to install an inverter in a work truck that will power work lights, some power tools, and other equipment too be used while the truck is parked. I've calculated the load to be at max 750 watts, which takes into account inefficiency of the inverter. So to run the load the vehicle should supply about 62 amps to the inverter while it's running. The vehicle battery is 72 amp-hours, so I don't count on it powering the system, but since the alternator is rated at 175 amps I considered just adding a high idle controller, that will speed up the engine, hence make the alternator produce its nominal output. I've read that this still requires a secondary, isolated battery for which to power the the inverter, but I'm not sure why. It would seem that with the engine idling high, 175 amps would cover the inverter load, and charge the vehicle battery, if necessary. So is the secondary battery really necessary?
At high idle would an alternator be sufficiant to cover a large load like 62 amps without it affecting the battery? ( I'm not sure how much of the current I should expect to got back to the battery and also keep the vehicle running, so I'm not sure how much is left over to power the load. )
Also, is there any drawback to running in high idle for extended periods of time, say between 2 - 12 hours?