Connecting series PV panels

Arkansasoffgrid

When making the series connections of 3 panels, should the panels be "covered" so no power is being generated during the string connecting?

Cariboocoot

Re: Connecting series PV panels

Panels are a current source: without a circuit they produce no power. You can plug them together without worry of arc or spark so long as there is no load connected to the output.

BB.

Re: Connecting series PV panels

Two issues...

1) you don't want to get shocked. Three panels in series is pretty close to 120 VAC shock--And DC shocks can be worse. If you are comfortable working on "hot 120 VAC connections", you can make these up too (use insulated tools, don't work with two hands--one on wire, second grounded to metal framework, etc.). Make sure that any electrical boxes/equipment are properly grounded before making up hot connections.

2) current flow... Making up the MC 4 connectors, you do not want current flow. Making sure the DC disconnect/breaker is off (if you have one) and or making up a non-MC4 connection last will reduce arcing and prevent damage to the MC4 connectors.

Many years ago, folks who worked with electrical circuits were pretty cavalier working with low(er) voltages.

Today, there have been enough people that have been injured or even died hours/day or so later after getting hit with 120/240 VAC--That the doctors and regulatory agencies are much more careful and preventing any shocks in the first place and even mandating trips to the ER after "minor" shocks.

-Bill

zoneblue

Re: Connecting series PV panels

What i did was tape all the mc4s male and female pairs together but not connected. Route the pv cables tie them down neatly and terminate at the combiner. PV breaker off as said above. When ready to make live, clip the mc4s, one string at a time. Then check voltage and polarity at combiner. Finally, when your happy flip the breaker on (makign sure that the controller is also first on). Done slowly and mindfully, its a safe enough procedure, but best have someone nearby just in case. Same as working with batterys, or chainsaws...

And for those that try and get away without a combiner (like i did inittally), you have a related problem. How to service the disconnect, with no way to depower the array outside? Combiners are good for that...among other things.

Cariboocoot

Re: Connecting series PV panels

You can power down an array by covering it.

Arkansasoffgrid

Re: Connecting series PV panels

Thanks, that seems like the safest way for me.

BB.

Re: Connecting series PV panels

Remember that even a little amount of light leaking through a "less than black" blanket/tarp can still energize a panel with enough current to shock (0.001 amps) or kill (0.015 to 0.100+ amps).

-Bill

jcheil

Re: Connecting series PV panels

BB. wrote: »

Remember that even a little amount of light leaking through a "less than black" blanket/tarp can still energize a panel with enough current to shock (0.001 amps) or kill (0.015 to 0.100+ amps).

-Bill

Funny, at night down here in FL when it is a clear sky and a full moon, my PV voltage sometimes shows around 13-14v (my pv runs at 101 voc). Not enough amps (if any) to bring the controller out of silent/sleep mode but just interesting that even reflected sunlight off of the moon could produce a tiny bit of voltage.

Cariboocoot

Re: Connecting series PV panels

jcheil wrote: »

Funny, at night down here in FL when it is a clear sky and a full moon, my PV voltage sometimes shows around 13-14v (my pv runs at 101 voc). Not enough amps (if any) to bring the controller out of silent/sleep mode but just interesting that even reflected sunlight off of the moon could produce a tiny bit of voltage.

When I had three in series on the 12 Volt system the MX60 would wake up under a full moon and try to start, but of course there was never enough current for it to stay active. This is the difference between the relative ease of achieving Voc (and thus > last V triggering a start attempt) and actually producing power.

inetdog

Re: Connecting series PV panels

jcheil wrote: »

... just interesting that even reflected sunlight off of the moon could produce a tiny bit of voltage.

Of course what is really happening is that the light is producing full voltage but at low current and the internal leakage resistance of the cells is dropping the output voltage down below what we are used to seeing as Voc.