stupid(?) question: what exactly does one *do* with these weird voltage panels?

[0xkruzr]

There is no shortage of all kinds of different panels available on Facebook Marketplace:

30.79V maximum? what are you supposed to do with that, practically speaking? everything you're going to store charge in is going to be running around 12V, 24V, 48V, etc. solar controllers, as far as I can tell, expect voltage at a particular level. these panels you can find used have max voltages at all kinds of weird values. do they all have their own proprietary controllers running at their own proprietary voltages that only they use?

 

[Nobodybusiness]

There is no shortage of all kinds of different panels available on Facebook Marketplace:

30.79V maximum? what are you supposed to do with that, practically speaking? everything you're going to store charge in is going to be running around 12V, 24V, 48V, etc. solar controllers, as far as I can tell, expect voltage at a particular level. these panels you can find used have max voltages at all kinds of weird values. do they all have their own proprietary controllers running at their own proprietary voltages that only they use?

You need to have all the panels in your string preferably the same manufacture and model with same specs.

Trying to string mismatched panels is a nightmare.

If you have a bunch of random panels you can try Microinveters that have MPPT controller per each channel that it accepts.

IE. 1,2,3,4 panel Microinverter.

The Charge controller handle the voltage conversion to battery voltage.

 

[SamDeleted]

There is no shortage of all kinds of different panels available on Facebook Marketplace:

30.79V maximum? what are you supposed to do with that, practically speaking? everything you're going to store charge in is going to be running around 12V, 24V, 48V, etc. solar controllers, as far as I can tell, expect voltage at a particular level. these panels you can find used have max voltages at all kinds of weird values. do they all have their own proprietary controllers running at their own proprietary voltages that only they use?

Mppt controller converter input voltage to useable voltage , that's why we use charge controllers

(eg. 2 of those panels in series= 61voc.... Converted down to 15v~ for charging 12v system)

 

[upnorthandpersonal]

30.79V maximum? what are you supposed to do with that, practically speaking? everything you're going to store charge in is going to be running around 12V, 24V, 48V, etc. solar controllers, as far as I can tell, expect voltage at a particular level.

You can have an MPPT that takes 250V on the input and charges a 48V bank, or 120V, or whatever, and still charge the 48V bank. That's what MPPT charge controllers are for: you don't need to match panel voltage to the battery voltage. Instead, you have a range of input voltages it accepts (e.g. 60V - 150V), configure its output (e.g. for a LiFePO4 battery up to 56V or so) and call it a day.

 

[Quattrohead]

Those are totally standard voltage and current ratings for a 60 cell solar panel. Their maximum output is at full current but a lower voltage, that high voltage is only at no load and full sun.
If you look at a graph for power output of an mppt charge controller you will see the voltage climbing as the sun comes up until it gets to a point where the charge controller can pull good power then the voltage will drop down by about 20% usually as the current rises towards maximums.

 

[Mithril]

There is no shortage of all kinds of different panels available on Facebook Marketplace:
30.79V maximum? what are you supposed to do with that, practically speaking? everything you're going to store charge in is going to be running around 12V, 24V, 48V, etc. solar controllers, as far as I can tell, expect voltage at a particular level. these panels you can find used have max voltages at all kinds of weird values. do they all have their own proprietary controllers running at their own proprietary voltages that only they use?

For anything beyond token use of solar, panel voltage is above (often significantly) system voltage, and a Solar Charge Controller (of PWM or MPPT type) is used between the solar panel(s) and the system. Often solar panels are in series, which reduces the Amps and therefor wiresize and power lost to heat. The solar charge controller will have an upper limit based on that "open circuit" voltage. Most of the time you should add another 10-20% on top of that for what happens in very cold weather. Some typical SCC limits are ~150V, 250V, 400V, 450V, 500V. I have not personally seen anything for residential/consumer use above 500V but it might exist.

As far as mismatches of panels, another option is optimizers. And if you are going that route might as well get ones with rapid shut down. I have seen a few optimizers with rapid shut down that can do 2 panels per module brining the per panel cost to around 30 bucks. Considering the changing regulations, the *actual* safety rapid/module shutdown adds, and as Will and others have pointed out how often bypass diodes DON'T do what they should (perhaps especially in used panels) I think they are a reasonable thing to consider adding. With optimizers *in theory* you can more or less add any used panels you want so long as they are within the limits of the optimizer, and within the limits of the string.

Edit: Opened this a bit back, replied without reloading. Some people have covered parts of what I have.

 

[0xkruzr]

this is really helpful, guys, thank you. in retrospect it makes sense that that's what the charge controllers are actually for -- dynamically matching very variable input power from panels to whatever is required to meet a particular load (a battery charger, in this case).

I should add that I'm not particularly "planning" to have mismatched panels in my array. I think I am only going to be able to fit about six, max, in my deployment (the roof of a boat), so if I buy them it will be all at once and that'll be it.