Be aware that your controller(s) need to have sufficient amp capacity for total maximum amp output plus 10% additional headroom to allow for the lense effect…The AGM wire gauge should be of sufficient amp capacity too.
Another thing to consider when mixing-adding panels (using just one controller) is that the higher voltage panel will drop to (default to) the voltage of the lower voltage output panel, thus its best to find panels with specs as similar as possible…
If it is not possible to use just one controller, then avoid using a second (i.e. in parallel) ‘multi-stage’ type controller – Having previously had the problem you’re addressing, I found an acceptable alternative which has proved to work quite well by using a second less sophisticated single-stage type controller on the second set of panels. These are available in various amperes.
My set-up is 300w on a multi-stage MPPT controller, and separately (in parallel) 140w with the single-stage controller. In practice, one system shuts off a bit earlier than the other (near the final charging stage), but this is offset with the gain of the additional panel wattage which greatly compresses available harvest time ensuring that the batteries are restored.
BTW, Some controllers have adjustable output voltage settings which when used with a second controller can be adjusted to minimize any adverse effects..
Phil
