Sizing Solar Controllers

rreynolds51

I'm looking at 6ea 200 watt panels and I'm trying to decide whether to break it into two groups or keep it as one large one. With two groups I could use two smaller controllers. maybe a 100/50 or 60 amp. If I use it as one string I will probably need at least a 70 or 80 amp converter. If I got the calculations right. What does experience suggest? Which works better and how do I get a better idea on sizing the controller. Planning on running the panels in parallel rather than series. 12 system. Thanks 

BB.

What voltage battery bank are you looking at (seems like 24 volt)?

How far is your cabling run from the Array to the solar charge controller?

What Vmp/Imp are your panels?

Near what major city will the installation be?

Any particular solar charge controller brands/models you are interested in using?

-Bill

mike95490

Make it a 24V system and use 1,  60A charge controller.

Not sure why all the reluctance to move from 12V for systems needing larger voltage

Much easier to build up a high voltage (24 or 48V ) battery, then 17 , 12v batteries in parallel !!

mountainman

You stated 12 volts Are you in a rv? 

rreynolds51

RV roof top solar panels Max Operating Voltage (Vmpp): 21.01Volts, Max Operating Current (Imp): 9.52Amps, Battery bank is 12vdc 400 AH Lithium batteries. We travel the southwest primarily but are based in El Paso, Tx. I like Victron CC mainly but we use to have a Tristar. Panels are on the roof so no more than 15ft from controller max.

Estragon

IMHO, using 2 x 50-60a controllers would be better than 1 x 70-80a for two reasons; some redundancy so it isn't lights out if there's a problem with a controller, and this provides some capacity overhead.

Regularly running a controller at/near capacity can make it run hotter, reducing life expectancy, and it may derate output.  In an RV, I'd probably look for one with a large heatsink in lieu of internal ventilation fan.

mountainman

Mppt has it's advantages. Like long runs from the charge controller to the panels. Or using higher voltage  panels with low voltage batteries. But In your case with 12 volts  21 volt panels and a 15 foot run. I'd use 
A (Or 2) quality adjustable pwm controller. 

mountainman

my system is pole mounted and adjustable. I run 2 controllers 1 pwm 1 mppt With panels pointed directly at midday sun and battery low ~60℅ soc.
80f day at 3500 foot alt.  with 400 watts on each system.  Mppt or pwm I'll get 6 max amps per 100 watts. 1200 watts 72 amps. 
 mounted on top  your  amps will be less. when panels get very hot  in extremely high temperatures such as yours.
They drop power.  Mount them so air can circulate.