[el Jefe]

I don't think you mean it doesn't matter how big the DC-DC is. How would the two know how to divvy it up without potentially overtaxing the alternator? As far as I know, they are independent and completely selfish in their demands. But as long as their combined demand doesn't exceed alternator output, things are fine. I am fairly sure an 80A DC-DC can co-exist with the 220A alternator (depends on the DC-DC), but let's not unintentionally give folks the impression DC-DC size doesn't matter.

I don't think you mean it doesn't matter how big the DC-DC is. How would the two know how to divvy it up without potentially overtaxing the alternator? As far as I know, they are independent and completely selfish in their demands. But as long as their combined demand doesn't exceed alternator output, things are fine. I am fairly sure an 80A DC-DC can co-exist with the 220A alternator (depends on the DC-DC), but let's not unintentionally give folks the impression DC-DC size doesn't matter.

Totally correct. Heat is the issue. I once did a project with 4 V-smart 30a DCDC chargers. Client wanted redundancy and to see how far he could go before the alternator would overheat. We decided that we would stage the chargers automatically according to temperature. We used programmable relays and placed 4 ring terminal temperature sensors bolted to the alternator case to sense temperature. Each relay was programmed with cascading temperature ranges to stage the chargers. As the temperature of the alt chassis reached critical limit, the relays would "shed" 1 or 2 chargers until reaching an acceptable level and vice-versa. We used some wickedly expensive relays but it worked flawlessly. I think you could use some Inkbird's for a whole lot less but he wanted the relays to be programmable with an app and wanted them to show up in his Garmin system to monitor from the helm as well as at his nav desk.