LiFepo4 RV battery bank, charge from beefy alternator setup
Q3- So you need just a little more complex system: Alternator -&gt; Boost convertor -&gt; bulk capacitor -&gt; Charging circuit -&gt; battery.
The battery charging current must be controlled- otherwise, you risk damaging the battery, and basically, there is no reason not to do it. Also, this will allow adjusting the charger to various battery setups.
The boost converter will take whatever the alternator provides up to a certain voltage, allowing a stable input voltage for the charger. The reason not to try combining booster and charger is this- if you do, the input of the charger may not be stable enough to sustain the normal operation. This is why some bulk capacitor is required in between.
So yes, the currents are going to be pretty wild, and controls require some minimal EE experience, but all of it is totally doable. Actually, I am now working on a system capable of performing in this range.
Q1- no, not exactly. It greatly depends on what is allowed on the batteries and what does the charger support. Whent he battery is empty (voltage significantly lower than the charger input voltage) you may be able to push more current- it's a thing about energy conservation, you take I1 from the voltage V1, put it into V2 with the current I2, I1 * V1 = I2 * V2 (neglecting losses), but since V2 &lt; V1, I2 &gt; I1. But as a rule of thumb what you write is fine.
Q2- i wouldn't count on it, as you say, it's probably all about balancing and shut off on overcurrent/overvoltage, but charging current should be controlled externally.