garyc
New Member
Posts: 3 
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Post by garyc on Sept 3, 2016 23:33:26 GMT -8
I recently installed a Renogy Tracer 40 watt MPPT 12v/24v auto select charge controller on an older Renogy 200 watt (2 x 100 watt pv cell) 12 volt system with 6 ea 6 volt 220 AH golf cart batteries in series-parallel for 12 volt 660 AH capacity running a 3KW PSW inverter. Knowing the new controller is rated for 500 watts at 12 volts or 1000 watts at 24 volts , and wanting to increase my system capacity I set out to acquire more panels at 24 volts. Fortunately I was able to I acquire 4 ea 320w/24v total of 1280w/24v solar panels in a package deal. With the above info, is it possible to split the panels output between 2 MPPT controllers to charge a 24 volt battery system? While also using the old 100w12v in series along side my new panels for a total of 1480 watts.
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Post by spiderbob on Sept 8, 2016 19:23:17 GMT -8
There are some controllers that are stackable, but I don't believe Renogy has a stackable, yet. Perhaps they will chime in, in the morning. I have a MPPT 40, along with a PWM 30 (which is stackable) but with the same output and after using the later I'm beginning to believe the MPPT is overrated. But I don't want to go into that here. Lets get your question answered. I believe you are asking if it is possible to split your panels output. I'm not sure if you are saying both are 24v or one is 12 and the other is 24? The controller is going to recongnize either but not two at the same time, voltage differences that is.
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garyc
New Member
Posts: 3
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Post by garyc on Sept 9, 2016 23:05:37 GMT -8
Spiderbob., thank you for your reply. I may have been a bit confusing in my initial rambling. My intention is to completely convert to a 24volt system by placing the original Renogy100/12 panels in series for 24v in parallel to the 4 new 320w/24volt panels. I mentioned I had 6 - 6 volt golf cart batteries in series parallel for 12 volt / 660 ah capacity. This battery bank will be changed with the addition of 2 additional batteries to be wired series / parallel for 24 volt / 440 ah capacity. 8 batteries total.
Based on your input I will contact Renogy directly and report back to this forum.
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Post by rabird on Sept 10, 2016 3:19:35 GMT -8
2 chargers on one battery ok
so one charger has 2 x 320w x 24v
the other will have 2x100 + 2 x 320
or whatever combination you decide in parallel.
the problems is that 2 x 100 is more than '24v'. Compare Voc, Vmp of the 12v x2 versus the 24v
The lower Vmp of the 24v will drag down the 2x100 somewhat.
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garyc
New Member
Posts: 3
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Post by garyc on Sept 10, 2016 8:42:07 GMT -8
rabird, thanks for the heads up regarding the panel performance differences. The 100w panel system is installed in Mexico so I will have to wait until my return to compare old with new. Are you saying that the total power of the 2x100 + 2x320 will be less than the "face value" power of 840 watts but still somewhere in between 840 to 640 watts due to the "averaging effect" of paralleling the 3 24 volt modules?
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Post by rabird on Sept 10, 2016 10:42:55 GMT -8
yes, 12v panel is 36 cell, Vmp 17-19 (x2 34-38)
24v 60 cell has Vmp of ~31v.
they do make 72 cell panels.
As I understand it, say the 2X100 have a Vmp of 36v combined, 5.55A. If the mppt controller finds a Vmp of 31 then the 2X100 watt panel will operate @ 31v*5.55A = 172 watts and the others @ 320 each (less the eff of the controller of course).
Don't forget the cost of a new 24v inverter and/or dc-dc 24v-12v transformer!
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