I think your assumptions are based on high voltage and high power systems.
A 12V system with a handful of amps is a different animal.
If you want the battery maintained at a fairly stable voltage, even within say 0.25V, then the relays will be switching pretty fast... and wear out.
High voltage, high amps, and high frequency make mosfet switching tricky.
It is pretty simple to switch in a 12VDC system.
Not sure what the contact rating (voltage drop or resistance) of your relay is,
but a common IRFZ44N is rated at 0.0175 ohms Max, typically under 0.014 ohms.
If that's not low enough for you, the $2 fet on my website, FDP7045L, is rated 0.0039 ohms typical, and that's with 50A going through it.
And it is even logic level so it is compatible with logic level ICs.
Sadly, that one is not suitable for anything but 12V systems.
The IRFZ44N is pretty much bullet proof in a 12V system, as long as
- Schottky flyback/freewheel diodes are included on inductive loads
- The Gate is driven to at least about ~12V
- The Gate is not allowed to float
- The (simplified) power dissipation is reasonable
(max ohms x I x I = ? Watts, which I like to keep it under about 1W, so a $1 IRFZ44N with a small heat sink should deal with as much as 8.5A without any problems)
I go overboard on keeping the heat in anything far below what most people do, but it works for me.
I learned if something is hot, it Will fail. Eventually.
I also learned that relays Will fail. Eventually.
In a (non-MPPT) reasonable controller design, the only time the fets are wasting heat is when the battery is at full voltage, and the controller is trying to stop the battery voltage from climbing by using or stopping the extra power anyway. So the 1W of loss or heat is no issue.
"Do you know of any resource that I could use to educate myself."
Some general stuff about driving fets? Maybe my original post about the ghurd controller.
It shows and explains how a 0 or 5V signal switches a logic level N-fet.
That N-fet switches a P-fet, which switches off-board power N-fets.
And it explains why it starts and ends with N-fet(s).http://fieldlines.com/board/index.php/topic,129060.0.html
If you mean about MPPT, then probably a Masters degree in EE.
Things that seem totally unrelated can have a major effect on the circuit. Which direction a cap sits on the circuit board, how close it is to other components, even the length and layout of the traces on the circuit board, can create all kinds of confusing issues.
There were a couple postings here on FL about modifying computer PSUs to MPPT or switching supplies.
MPPT falls in a dead zone of what I play with, and is something I would rather pay a couple $hundred for a factory made unit that works properly instead of several $hundred and countless hours making one that does not work as well.
BTW- I expect the series panels, in decent sun, will put out about 10% more than a single panel. 45% loss compared to standard parallel connection.
In poor sun, series may make a couple dozen ma in conditions where the parallel panels would have just stopped making any ma, but those conditions will not last long (measured in minutes?).
I expect the control and monitoring circuit will use more power than switching the configuration gains per day.