...knew of a shop that could rebuild a [stock] alternator to put out more power.
The drawback to rewinding a stock alternator is that it cannot put out as much voltage at idle, so the battery may not get charged at idle but the alternator can put out more current than stock once at rpms higher than idle. I do not know exactly what the output is for stock, nor the exact output for the rebuilt (at differing rpms) so I won't say that a rebuilt for higher current won't charge at idle. But the physical trade-offs require fewer turns of a larger wire - the larger wire gives more current output, but the reduction in turns means that more revs are needed for the same voltage. Both are needed to charge the batteries, especially at idle.
On the other hand, the stock Pinz alternator can only be the size it is to fit within the housing resulting in the trade-offs above. Once you go to an external, secondary alternator then you can go as physically large as desired and get both higher currents and enough current/voltage at idle, too.
At one time I had 75W headlights, 70W driving lights, 70W fog lights (all 24V halogens, and two lights each), plus six (6) 50W floodlights (two on each side, plus two at the rear). These totaled 730 watts, plus ignition current and running lights (not much for either). Even though just the lights add up to 87% of the 30A specified alternator, it STILL had enough "omph" to keep the batteries up to proper voltage, at idle, with every one turned on. I didn't do this but for testing purposes as I had no need to run them all, especially continuously.
Your REDARC 24 to 12V charger won't draw 20A continuously. Honestly I would expect that all your equipment you listed probably won't draw more than 10A at 12V (equivalent to 5A at 24V) on
average. Peak power doesn't count; average power (average current) is what is important. For example, NO alternator can be expected to keep up with the current draw from a winch, but the winch's average current draw during the course of even a day is likely be be only a few amps (a minute's worth of hard pull every hour?) average.
On the other hand, I have two 100AHr batteries to run the box of my truck (similar to your Yellow Tops, perhaps not as big in capacity but somewhat close) and I ran them down deeply camping one week. I plugged them into the Pinz charging circuit and it took over 3 hours of driving to bring all the batteries back up to 28V! Yes, a larger rated alternator would have done this faster.
So that's why I have not ever seen the stock alternator as insufficient. I'm not saying that you should not change it; I, too, would be interested in what you come up with and how it works. My point was just that my wildest imagination never thought that the stock alternator would be undersized (assuming it is working as it
should!). But if yours is not working well then it does make sense to me to "improve" upon it, since it needs fixing anyway.
Jim M.
712W and 710M