Confirmation needed from all the expert

DarkstormNH · November 2015

I called Magnum today to make sure I can wire 4X250 panels straight to the pv bus bar in the magnum mmp panel
I was told this can be done, also i will be using the magnum cc can handle the 120 volts .
any input please

BB. · November 2015

Do you have links to the exact controller and solar panels you want to use?

Series/parallel connections depends on the details of the controller, solar panels, and battery bank (voltage) you want to charge.

-Bill

DarkstormNH · November 2015

BB. said:

Do you have links to the exact controller and solar panels you want to use?

Series/parallel connections depends on the details of the controller, solar panels, and battery bank (voltage) you want to charge.

-Bill

Bill Thanks for the reply

the charge controller is from magnum please see link below
http://www.solar-electric.com/inverters-controllers-accessories/chco/magnum-energy-solar-charge-controllers.html
the panels are 36 volts 300 watts
spec bellow

Characteristics	Unit	SL6P72-300W
Maximum Power (Pmax)	W	300
Power Tolerance	W	(0,+5)
Maximum Power Voltage (Vmp)	V	36.5
Maximum Power Current (Imp)	A	8.21
Open Circuit Voltage (Voc)	V	45.10
Short Circuit Current (Isc)	A	8.67
Module Efficiency (ηm)	%	15.46
Dimension of module	mm	195699240mm(77.039.11.6inch)
Pmax Temperature Coefficient	%/C	-0.42
Voc Temperature Coefficient	%/C	-0.3
Isc Temperature Coefficient	%/C	0.05
Maximum System Voltage	VDC	1000(TUV);600(UL)
Maximum Series Fuse Rating	A	15
Operating Temperature	C	-40~ +85
NOCT	C	45±2
STC:1000W/m2.AM1.5 and 25C cell temperature, NOCT : Nominal Operating Cell Temperature I know by your calculation I would not have enough panels to charge a 8 t105 24 volts bank what I was hoping to do is connect the 4 panel directly to the magnum mmp (pv bus bar) and later I would add 2 more panels I'm open to your expert guidance thanks

vtmaps · November 2015

DarkstormNH said:

I called Magnum today to make sure I can wire 4X250 panels straight to the pv bus bar in the magnum mmp panel
I was told this can be done, also i will be using the magnum cc can handle the 120 volts .
any input please

DarkstormNH said:

the panels are 36 volts 300 watts
<snip>
what I was hoping to do is connect the 4 panel directly to the magnum mmp (pv bus bar)
and later I would add 2 more panels

From the above quotes, I have no idea what you are trying to do. Will the CC be seeing 120 volts on its input? How are you configuring the panels? (series, parallel, or series/parallel). How will they be configured when you add two more panels?

If you are putting the 4 panels in parallel, you may barely have enough voltage to charge a 24 volt battery... it might work, the Magnum CC is too new to know for sure. The problem is that MPPT controllers need more voltage headroom than PWM controllers, and when the panels are hot their Vmp drops. I would prefer to see you put the 4 panels in a series/parallel configuration with a string length of 2. When you add 2 more panels, they can be a third string.

Also, if you are putting the 4 panels in parallel, you must have a combiner box and a circuit breakers for each panel. If you have 6 panels in three strings as described above, you will need a combiner box and a circuit breakers for each string.

The requirement for these breakers (or fuses) is an important safety issue. I suggest that you get a Midnite MNPV3 combiner box with three breakers. Wire up your 4 panels in two strings, using 2 of the 3 breakers. When you get 2 more panels, the third breaker is waiting there for them.

--vtMaps

DarkstormNH · November 2015

vtmaps said:

From the above quotes, I have no idea what you are trying to do. Will the CC be seeing 120 volts on its input? How are you configuring the panels? (series, parallel, or series/parallel). How will they be configured when you add two more panels?

Vtmaps

Thank you for the post, what I said was I called magnum and asked them if I can wire all four of the panels directly to their
mmp box using the so called pv bus bar, I was told I could and it would work.
i wanted to make sure from you guys, yes you are right on the midnight combiner box, i just wanted to avoid that if I could
i cant so be it I will get it, and wire as you said 2 X2 saving the 3 breaker for later

BB. · November 2015

Ok--First I have looked at the Magnum MPPT charge controller specifications:

Specifications:

Max PV input voltage: 200 VDC + battery voltage, or 240 VDC - whichever is lower
Max PV operating voltage: 190 VDC
Max PV array short circuit current: 100 ADC
Battery voltages: 12, 24, or 48 VDC
Max output power: 6,600 watts
Peak efficiency (at full power): >99% (98%)
Internal cooling: dual ball-bearing fans
Enclosure type: indoor rated, ventilated, with removable conduit box
Dimensions: 8.5" x 15.5" x 4.0"
Weight: 12.5 lbs (5.7 kg)
Max operating altitude: 15,000 feet
Mounting: mount on a vertical surface or install on a MP or MMP

Warranty: 5 years parts and labor

Looks to be a very nice/capable unit. And running Vmp-array~120 volts looks to be OK (Vpanel-max operating 190 VDC).

It does not appear that Magnum has a string sizing tool on the web yet.

-Bill

zoneblue · November 2015

For a 24V system, the 60 cell panels will not work in a 4P configuration. The other panel you refer to is a 72 cell panel, which will work with PWM controllers but not with MPPT controllers. If you go 4P of the 300W panels you NEED the combiner. IF you go 2S2P, as vt recomended, then you may skip the combiner as 2 strings is safe without one. However a combiner is useful for other reasons, youll end up adding one eventually.

Confirmation needed from all the expert

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