150 amps is not a lot of storage, at that rate you would need5 of those batteries to compete with the one battery u have under the hood of most new 8 cylinder pick up trucks on the road today.
Really? Name one vehicle that has a 750Ah starting battery.
running a converter 12 / 120 is usually about 50% efficient at best.
Most any contemporary AC inverter is closer to 90% or better.
the Super Battery Boost is only about 75% efficient,
The MFJ in question specs out at 90%-94%.
I would expect one automobile battery to make enough power to supply enough power to run your medical equipment for one 8 hour period of time, but not a couple of boat batteries.
A typical car battery is a group 24 size with a reserve capacity of 75 minutes (31.25Ah). A group 31 marine battery is nominally 100 Ah. Even factoring Peukert effects the marine battery will be more than twice the capacity of a typical car battery. Put two marine batteries in parallel, and the battery efficiency is even greater.
The purpose of the Super Battery Booster is to throw away battery life in exchange for a little more radio time.
Correct, but consider the cycle life of a deep cycle battery and its intended application. A quality battery can deliver somewhere between 500 to 750 cycles down to 20% SOC (10.5V under load). You can also figure, properly cared for, a deep cycle battery will last 5 years. Simple math tells us you can completely discharge this battery twice a week for 5 years straight. Since in this application that's not anywhere near likely to happen, the battery would expire from age before deep cycling, making the deep discharge argument moot. Ideally you'd spec a battery size that would expire from cycling at the same time it would expire from age. But it often turns out the more economically priced batteries tend to be larger, so you buy the cheapest Ah and throw some away at the end of life. So the "rule of thumb" of never discharging below 50% is misplaced. In my opinion, it would be better to use up a battery through cycling than taking it to the recycler after 5 years with cycles still left in it. Unless you're discharging your battery at least once a week, you will never wear that battery out before it expires from age.