System Recommendations, Improvements?

BB. wrote: »

Welcome to the forum... First lets start with the solar array... What are the panels and how many do you have (watt/Vmp/Imp ratings).

You show the panels wired in series--But I would guess they are wired in parallel (Vmp-array should be in the 17.5 to 18.6 volt range for optimum power transfer when using a PWM controller).

Next, tell us more about your batteries... a pair of 6 volt @ ~220 AH wired in series for a 12 volt battery bank?

It would also be helpful to understand your AC loads (watts * hours per day at the very least).

-Bill

BB. wrote: »

Ok... That is a good start. First, the panels should be wired in parallel (+ to +, - to -, for all panels). That will give you an array with Vmp~18.7 volts and Imp~38.75 amps for the array.

If the panels are connected in series (+ from one panel to - to the next, and so on for the rest of the panels) that would give you a Vmp-array ~ 93.5 Volts and Imp-array~7.75 amps.

If these panels are series connected (like stacking D Cell batteries in a flash light), that is not going to make either your PWM controller or you very happy. PWM controllers (pulse width modulation) are just "fancy" On/Off switches. When current is needed, the controller turns on, and when less/zero current is needed, the switch (PWM controller) just turns off (do this 10's to 1,000's of times a second, more "on time" is higher average current, less "on time" is less average current--or Pulse Width Modulation).

Depending on the PWM controller, the maximum Voc-array votlage (open circuit voltage) will be >130 VDC pretty easily. Not many small/less expensive PWM controllers can manage that sort of voltage level (most can manage ~30 to 40 volts for a 12 volt controller).

And you won't be happy, because the most current you can get out of that array is ~7.75 amps--Or the current of one solar panel.

So--Your first step is to check if your panels are parallel or series connected.

And, you will need to decide if you want to rewire to parallel connected solar panels (you should have a fused/breaker equipped combiner box to protect solar panels against internal shorts) and a new PWM controller (same brand or different). You would need to check the specifications and ensure that it can manage near 40 amp Imp solar array (many controllers have safety margins built in, others need to be derated--depends on the controller mfg.).

Or, you can get an MPPT type charge controller. These are very nice devices, can have a lot more options (logging, remote battery temperature sensing, some have Internet web servers built in, etc.). But, you are looking at $500 to $600+ for such a controller. The MPPT controller can take the high voltage / low current from the solar array and efficiently "down convert" to low voltage / high current to charge the battery bank. A useful reason to use "higher Vmp-array" setups is you can put the solar array much farther away from the Battery bank+charge controller and use smaller gauge copper wire (save money on copper).

In general, if this were a smaller system with a closely mounted solar array, less than 400 watts, a PWM controller may work just fine. And for over 800 watt array and/or a more than a few 10's of feet of distance from array to battery bank, you probably should look closely at a MPPT type charge controller.

We have more to discuss--But lets get the "front end" right first. You need to get those batteries on charge so they do not get damaged (do you have a hydrometer to check that they are getting >90% charged a couple times a week and don't sit below ~75% state of charge for more than a few hours/days at a time?).

-Bill