backchannel: Renogy DCC50S mppt is useless

from this discussion

Note:  the PV input max on the unit really is 25v;  that is not disputed.

ALSO... it only has a 25V MAXIMUM solar input... which means the MPPT is useless on this thing.

Bold claim.   Let’s see where this goes. 

You'd have to configure 3x 12V/100W panels, which maxes the system V and A wise,

The manual states max input wattage is 660W.  Inconvenient with 12v panels, yes, but doable.

and makes your system voltage the same as the array voltage.

Wut?

Let’s say Vabs == 14.4v.  The Renogy mono panels have a Vmp of 18.9v:

and Renogy gear typically runs the MPPT algo at >= (Vbatt +1v).  MPPT has plenty of headroom to play with until over 90deg F when Vmp drops to 15.4v.  It could hold Vfloat 13.8v + 1v until over 101deg F.

What are you paying for?? An extremely overpriced VSR and PWM combined... with multistage charging.

You are paying for a DC-DC smart charger and MPPT for nominal 12v panels.  Worth it?  That’s up to the customer.

This product is garbage to me... just for calling itself a 50A charger.

My general rule is to not take advice from people who refer to objects with emotional language like “junk”, “trash”, or “garbage”.   In this case, the person is also wrong;  it is indeed a 50A charger.   The 25A limit refers to each charging source when both solar and alternator are contributing: