mstar tri 45 mppt efficient wiring....

jimbob01

Hi again :-) have 2 x mstar tristar mppt 45s...
6x 235w sharp 38v
will it be more efficient wiring 2 strings @ 114v
0r wiring all in parallel@38v?
mstar is max 150v in ,
no panels get shaded individually.
jim

Cariboocoot

Re: mstar tri 45 mppt efficient wiring....

One question that will be asked: what is the nominal system Voltage? The only way you could get all six panels on one 45 Amp controller is @ 48 Volts where the output would be around 30 Amps max. (It would be just over 45 Amps with the typical derating on a 24 Volt system - a bit dicey.)

Otherwise, if that 38 Volts is Vmp then the Voc will be about 46, and that must be considered when planning an array. Three in series would give a Voc of 138 which with a bit of cold temperature could easily exceed the Morningstar's maximum input Voltage.

If you're dividing up the six panels between two charge controllers for a lower system Voltage then you'd want to go all in parallel to both avoid the high Voc issue and reduce the Voltage down-conversion to improve controller efficiency.

jimbob01

Re: mstar tri 45 mppt efficient wiring....

the voc is 38v....

jimbob01

Re: mstar tri 45 mppt efficient wiring....

the system is 24v

jimbob01

Re: mstar tri 45 mppt efficient wiring....

so keeping the voltage down conversion to a minimum on a mppt does increase the output from the system?

Cariboocoot

Re: mstar tri 45 mppt efficient wiring....

In that case three in series produces a Voc of 114 which would work in cold temps.
But that also means the Vmp is around 30 so you must have two panels in series to have sufficient Voltage for charging the 24 Volt batteries.

If you put three parallel strings of two in series on one 60 Amp controller that would be best. You could do it on one 45 Amp controller, but you may lose a bit of power potential under some conditions (mild 'clipping' of current above 45 Amps).

jimbob01

Re: mstar tri 45 mppt efficient wiring....

but does keeping the voltage down conversion to a minimum on a mppt increase the output from the system?
thanks.

NorthGuy

Re: mstar tri 45 mppt efficient wiring....

jimbob01 wrote: »

but does keeping the voltage down conversion to a minimum on a mppt increase the output from the system?
thanks.

It does increase efficiency a bit. However, you usually do not have much of a choice because of other factors.

jimbob01

Re: mstar tri 45 mppt efficient wiring....

thanks north guy..