130 volt PV array?

benthere

Hi. I'm the new guy. I've been lurking a bit and reading elsewhere for a while, but haven't seen this subject addressed.

I visited a local solar equipment store yesterday and was told that they now do most of their PV arrays in series, up to 130v. I understand the wiring and resistance losses are less this way, but I have to question the efficiency of making such a large adjustment at the charge controller. Is this common practice? Is it the efficient way to wire an array?

Thanks!

mike95490

Re: 130 volt PV array?

This is for use with whats called a MPPT (Multi point power tracking) charge controller.
They are "smart" and can adjust themselves to provide the best transmission of power from the panels to battery charging.
Their advantage, is that you can run 20AMP wiring from the PV array, to the charge controller, and then run the 60A wires just a few feet from the controller, to the battery bank.
The expense of the 60A rated wire is pretty high, and it's stiff and difficult to work with. This way, you get reduced losses in the wires, and save $.
The MPPT charge controllers are very efficient, and you don't loose much power with them (just a couple of percent)

Grid-tie installations use 200 - 600V solar arrays, and convert it to 120V, and with only about 5% loss

benthere

Re: 130 volt PV array?

Thanks for the reply.

I figured that might be the case but couldn't imagine it being efficient at the controller.

Interesting.

BB.

Re: 130 volt PV array?

The MPPT DC Charge Controller is basically a switch buck mode power supply that can efficiently convert high(er) voltage / low(er) current into lower voltage / higher current.

Vin*Iin=Power=Vout*Pout - 5-7% losses

If Vin is 2x Vout, then Iout will be ~2x Iout

For a system where the Vmp of the solar panels is ~2 volts over the battery voltage, the MPPT controllers do no help much at all (except on very cold days).

If you can put a bunch of panels in series (or series+parallel), then you can reduce the input current (smaller wires and/or longer runs from panels to controller) and have the short, large awg wire from the controller to the batteries.

-Bill

crewzer

Re: 130 volt PV array?

I visited a local solar equipment store yesterday and was told that they now do most of their PV arrays in series, up to 130v. I understand the wiring and resistance losses are less this way, but I have to question the efficiency of making such a large adjustment at the charge controller. Is this common practice? Is it the efficient way to wire an array?

Benthere,

I’d suggest having the “solar equipment store” define “up to 130 V” as well as the system configuration.

Is the 130 V based on the module series spec for maximum power voltage at Standard Test Conditions (STC Vmp), or open circuit voltage at STC (STC Voc), and is the value temperature-adjusted per the National Electrical Code (NEC) Article 690.7?

Is the configuration intended for grid-interactive systems without batteries? If so, 130 V sounds rather low.

Is the configuration intended for grid-interactive systems with battery backup, or for off-grid systems? If so, depending on the “130 V” definition, that value could be too high for most solar charge controllers.

Due to input voltage specification limits for solar charge controllers used in battery-based systems, as well as voltage limits for DC-rated circuit breakers, and factoring in NEC 690.7, understanding the definition of "130 V" for your intended off-grid application is critical.

HTH,
Jim / crewzer