I also wanted to clarify further with vtsoundman (or anyone with 2 cents on the matter), when we say not to hook up two MPPT's to the same solar array, does that mean that if you had two REDARCs/Kisaes wired in parallel you should avoid using the MPPT capability at all, or does that mean you just make sure that any panel its hooked up to is only wired through one of the two DC-DCs in parallel? I'm unclear on how independently the various parts of that system operate.
Ah...ok...sorry... solar controllers come in two forms - MPPT and non-mppt.
MPPT controllers (just Google the term) generate the most energy from the array by always operating at the max power point of the array (provided the load can accept it).
Non-mppt controllers are not worth the time or money to discuss...good for where money is primary concern and you have 1 very small panel (like battery tender style).
One solar controller per array ... period. One Kisae/Victron/Redarc...Doesn't matter if MPPT or not. (An array can be one panel or many panels).
A solar array has a I-V curve (current vs voltage) for a set of conditions - the I-V curve changes with temperature and irradiance (solar intensity).
The controller dictates where on the I-V curve the array operates, but not the I-V curve itself.
Multiple arrays, each controlled by a dedicated controller, can be connected to the same load (or battery).
More than one controller on an array, and the controllers get confused and up fighting the other (unless they are so designed).
Series vs parallel -
lots of misinfo out there, mostly I suspect due to folks only having one or two data points (their own systems) and an inability/time/money to test the various conditions ... hence the variety of opinions.
It's very simple: in a small array, if modules have different irradiance levels (shade, bird shoot, etc), put them in parallel. If you have a long way to go / have need to get the voltage up (to get the controllers to operate most efficiently or overcome I^2 * R losses) run them in series.
It is generally perfectly acceptable to run series-parallel panel configurations (ex: 2 in series then put those in parallel with other strings). It is not acceptable to run parallel/series...(2 in parallel then put those in series).
Large arrays are built with up to ~20 modules in series strings with many many of these strings in parallel.
Small arrays are usually built with them all in parallel or 2-3 in a series string that are then paralleled with other strings of the same length.
Happy to explain the engineering behind the above with specific questions, but there is plenty on the web to help understand why the above is true.
(I design all sorts of large solar and solar+storage systems for a living).
As an aside, Victron makes the best solar controllers for small arrays (RV, marine, off grid, etc) hands down. Getting above a few kW, things change...
The built MPPT function of the Kisae is a nice to have. And they really work well. There is little reason to run dedicated external controller UNLESS you want to support a load from the DCDC AnD the solar array at the same time (Kisae won't do that...not sure about Redarc. I don't use Redarc very much as they have very little ability to program/customize various operating parameters. Fine for 'stock' systems, not so much for engineered systems.).
I have seen about 1-5% variance in overall energy production between Kisae and Victron, with the Victron always generating more. Really too small to matter. I use the Kisae MPPT in combination with the Victrons when running multiple small arrays in different spots (i.e., one array on the roof, one portable)...or if on different sides of the van)...
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