More amperage than rated, but within VOC? Fuse? Damage? Reset trip?

[MikeGoodman59]

As a "recovering engineer" with an off-grid system at home, I understand that VOC limits are non-negotiable, but what happens if AMPERAGE is beyond tolerance? I am considering the DELTA Pro? DELTA Pro Ultra, Hysolis Apollo?

Is it something you fuse or install a breaker. Can you reset the unit? Does it simply get wasted?

Is it something that the Apollo can handle because the power in the morning is low?

I have 12X RAC PANELS, 235W, 37.4 VOC, 7.9A Immp (8.3A Isc).

A 4S2P is within the VOC of, say, a DELTA Pro (11-150 Vmax) but 4S2P 235W above is 15.8A ... Or as much as 16.6A.

Is this a negligible overcurrent that I will likely never see? My 2820W (design) system has never produced more than about ~2450W on the 6/12 pitch of my house in Central NC.

Obviously a 15 amp fuse or resettable breaker seems to be in order. ... Unless I'm missing something and the overage is negligible.

My consideration for the 2x DELTA Pro, or 2x Apollo is that the systems are "seperable," meaning one unit can be at my home as a backup, the other unit as it at remote location.

 

[sunshine_eggo]

Most equipment has no issues with reasonable PV input over current potential. They just ignore anything they can't use.

Panels do not push current/power.
Loads draw current/power.

The charger is a load to the panels, so it's going to see the array voltage and start pulling current to charge/power loads until it maxes out at 15.8A. The fact that the panels have more to give won't matter except you'll get the 15.8A for as long as the panels can deliver that or more.

Also, panels almost never put out rated current because conditions are almost always worse that STC. Look for your panel's NOCT or NMOT rating for a more "real-world" performance rating (mostly in reduced insolation and warm cell temps).

Some of the lower end MPPT controllers limite over-paneling to 150% of rated.

 

[MikeGoodman59]

Googled:
ecoflow Delta Pro voltage amperage limits

Got:
The product supports 11-150V DC input, 15A max current, and 1600W max charging power.

Would that be true of every battery backup system? "Solar generator?" Every MPPT?

Please accept a marine engineer's "water" analogy, but we just want to make sure electrical stuff won't blow up. Since "potential is pressure" ... as long as you stay below the 150V above, you can't "blow the penstock?"

You're just saying that my 15.8 Immp (on a 15A limit) will simply skip the penstock to the turbine and go through the diversion channel? Back to the pool at the bottom of the spillway?

I can run the panels as described above, 4S/2P? ... Could I run 4S/3P? ... And simply over panel?

 

[zanydroid]

The extra current, if actually available (function of how much sun you have) will be burned within the solar panels if they don’t have a place to go. This is no big deal, because it would have turned to thermal anyway to the exact same extent if the solar panels were sitting on the roof unconnected.

Use it or lose it.

Note: the current is available during faults to cause fires, so you do need to follow the fusing etc rules. Unconnected solar panels can’t accidentally send the power into a short.

 

[MikeGoodman59]

The extra current, if actually available (function of how much sun you have) will be burned within the solar panels if they don’t have a place to go. This is no big deal, because it would have turned to thermal anyway to the exact same extent if the solar panels were sitting on the roof unconnected.

Use it or lose it.

Note: the current is available during faults to cause fires, so you do need to follow the fusing etc rules. Unconnected solar panels can’t accidentally send the power into a short.

Can you elaborate on conditions that might cause a fault, result in a fire?.

Is there an outline, some source for etc rules

 

[zanydroid]

Can you elaborate on conditions that might cause a fault, result in a fire?.

Is there an outline, some source for etc rules

Sure, basically ground faults, arc faults, from frayed wires and splices. Shorts inside equipment.

NEC has rules for fusing and sizing wires.

The nefarious thing about solar panels is that you can’t easily stop them from pushing power if there is something pulling it. Nobody fuses individual solar panels. And in general even if you do that, you can’t interrupt all faults (suppose you pick a 10A fuse but there’s a ground fault on a cloudy day where the panel can only push 1A. That fuse won’t open. Very different from AC, where that ground fault will always open the breaker).

In some cases having big enough wire is enough (1p or 2P config). For 3P and up each substring needs a fuse.

 

[sunshine_eggo]

Googled:
ecoflow Delta Pro voltage amperage limits

Got:
The product supports 11-150V DC input, 15A max current, and 1600W max charging power.

Would that be true of every battery backup system? "Solar generator?" Every MPPT?

Please accept a marine engineer's "water" analogy, but we just want to make sure electrical stuff won't blow up. Since "potential is pressure" ... as long as you stay below the 150V above, you can't "blow the penstock?"

Close enough.

You're just saying that my 15.8 Immp (on a 15A limit) will simply skip the penstock to the turbine and go through the diversion channel? Back to the pool at the bottom of the spillway?

Sorta.

It doesn't actually go anywhere. 80% of the sun to the panel goes to heat with 20% going to current/power. If only 10% goes to current/power, now 90% of the energy from the sun is converted to heat. Additionally, Vmp and Imp are related. If you draw less current, the voltage will naturally rise to whatever value is needed to make the power equation work, i.e., V_out * I_out = V_in * I_in (ignoring inefficiencies).

Not sure how to describe that in your analogy.

I can run the panels as described above, 4S/2P? ... Could I run 4S/3P? ... And simply over panel?

So about 24A on a 15A MPPT? I would probably try it.

 

[timselectric]

Think of the solar array as a receptacle in your house.
It may have 15 amps available. But you don't have to use it all. You can plug in a microwave or a phone charger. It will only give you what you draw from it.

 

[Hedges]

Some equipment, such as SMA inverters, list a max current they will use in operation, also a max PV Isc. Reason for that is if you connect panels backwards, they have a diode to clamp the voltage and prevent damage.

In that case, if using multiple PV strings in parallel that would exceed max short circuit current, I'd suggest commissioning the system with a single string. Once operational, you know polarity is correct, then add more strings in parallel.

An SCC performs sweeps to determine max power point. You would hope it would stop at a current that didn't hurt itself, not pull all the way to zero volts.

Clouds moving away would suddenly allow more current, but Vmp doesn't change that much. If in the middle of an MPPT sweep, could be at an operating point where current could be excessive. But MPPT circuit is a switching power supply, think it takes time for current through inductor to ramp up. Quality product should see rising current and back off. Tier-? might not.

I would want to over-panel with parallel strings of different orientation. Lower peak current, more hours production.