Too many Panels, so little Time...

[Sundog33]

I purchased the

Hyundai 305W Half-Cell Monofacial Solar Panel (Black) | HiA-S305HG​

in a 10 pack on Signature Solar. Was a great deal! $105 bucks, now they are $88 bucks a piece! Unbelievable!

I'm using 4 right now for my Mini Split, 2 for my Pecron with 4 left over.

I don't think I can add one to my other small Victron 100/20 - Overkill 4s - 200ah lifepo4 System
to replace my 2 - 100 watt panels on that one? Im not sure...
The Hyundia's run at:
Wattage: 305W VOC: 39.42V ISC: 9.86A

So if I was running it to a 12v battery bank that would change the Amps to 25Amps if I am correct?
I'm thinking I have to pony up to a 100/30 Victron to use this.
Any thoughts...

 

[Quattrohead]

2s2p would work

 

[Sundog33]

2s2p would work

Ya. Just wondering if that extra 5 amps would blow it up.

 

[Daniel644]

Ya. Just wondering if that extra 5 amps would blow it up.

No, amps don't work that way. the device (charge controller or inverter won't (or shouldn't) "pull" more amps then it is rated for, the device taking the power decides the amps, not the panels. amps are the flow, volts are the pushing force, thats why over volting damages but over amping doesn't.

 

[Sundog33]

No, amps don't work that way. the device (charge controller or inverter won't (or shouldn't) "pull" more amps then it is rated for, the device taking the power decides the amps, not the panels. amps are the flow, volts are the pushing force, thats why over volting damages but over amping doesn't.

That makes sense on paper, but I'm not sure that's 100% correct.

Say in the case of my hybrid AC/DC mini split:
Rated Voltage 115VAC | 90VDC-380VDC
Rated Current AC: 8.3A | DC: 9.1A-2.4A
VOC of PV <380V
ISC of PV <12A
Frequency 60Hz
Minimum Circuit Ampacity 19.05A
Maximum Fuse Size 20A
Maximum Starting Current 4A

These Panels have a ISC: of 9.86A
If I were to put just 2 of theses panels in parallel I would exceed the Max Amp input of 12Amps with only a measly 600watts of PV.

So Amps are being pushed to the mini split from the Panels I would presume...

 

[ksmithaz1]

That makes sense on paper, but I'm not sure that's 100% correct.

Say in the case of my hybrid AC/DC mini split:
Rated Voltage 115VAC | 90VDC-380VDC
Rated Current AC: 8.3A | DC: 9.1A-2.4A
VOC of PV <380V
ISC of PV <12A
Frequency 60Hz
Minimum Circuit Ampacity 19.05A
Maximum Fuse Size 20A
Maximum Starting Current 4A

These Panels have a ISC: of 9.86A
If I were to put just 2 of theses panels in parallel I would exceed the Max Amp input of 12Amps with only a measly 600watts of PV.

So Amps are being pushed to the mini split from the Panels I would presume...

Nope, push volts from the source pull amps from the load. <12A would indicate the load will never draw more than 12A. It isn't paper, it's physics and Ohms Law.

 

[Sparks-n-Splinters]

No, amps don't work that way. the device (charge controller or inverter won't (or shouldn't) "pull" more amps then it is rated for, the device taking the power decides the amps, not the panels. amps are the flow, volts are the pushing force, thats why over volting damages but over amping doesn't.

I've been struggling to get this very concept myself. I thought both the 100v and the 20a were hard limits of the controller input. So what is the 20a rating Sundog33's controller really mean?

 

[Sparks-n-Splinters]

Nope, push volts from the source pull amps from the load. <12A would indicate the load will never draw more than 12A. It isn't paper, it's physics and Ohms Law.

So the 20a would be the highest amp available to supply the load or battery charging.

 

[Quattrohead]

Voltage is hard, amps are not within reason.
But then there are exceptions, so read the documentation.

 

[ksmithaz1]

So the 20a would be the highest amp available to supply the load or battery charging.

Think of it like water pressure (volts) and size of the pipe (amps). I can take a 1/2" pipe run it up to my shower straight at 60psi turn it on and it will dump a buttload of water. Now I thread a shower head on the pipe, it has a restrictor that reduces the opening the water goes thru to 3/16". It's still 60psi but the total volume of water reduces dramatically, then it fills a chamber and lets the water out a bunch of pin-holes the area of which exceeds the 3/16" opening thus lowering the pressure so your shower head produces just enough pressure for you to wash your hair, but hey! your saving water! The shower head is your hvac unit. Making the feed pipe 1" or 4" (amps) will not change the 3/16" restrictor thus it will not improve your bathing experience. That will require you getting a shower head with a larger restrictor opening or fewer pin-holes. Raising the water pressure (voltage) could increase flow but might blow up the fixture. Lowering the water pressure (voltage) won't blow anything up, but may make the bathing experience increasingly abysmal.

 

[Sparks-n-Splinters]

@ksmithaz1 thank you very much that makes perfect sense.

 

[Daniel644]

That makes sense on paper, but I'm not sure that's 100% correct.

Say in the case of my hybrid AC/DC mini split:
Rated Voltage 115VAC | 90VDC-380VDC
Rated Current AC: 8.3A | DC: 9.1A-2.4A
VOC of PV <380V
ISC of PV <12A
Frequency 60Hz
Minimum Circuit Ampacity 19.05A
Maximum Fuse Size 20A
Maximum Starting Current 4A

These Panels have a ISC: of 9.86A
If I were to put just 2 of theses panels in parallel I would exceed the Max Amp input of 12Amps with only a measly 600watts of PV.

So Amps are being pushed to the mini split from the Panels I would presume...

I've been struggling to get this very concept myself. I thought both the 100v and the 20a were hard limits of the controller input. So what is the 20a rating Sundog33's controller really mean?

Ok, lets try to simplify this, there are 3 aspects to Electricity: Voltage, Amps and Ohms (resistance), the relationship is defined with Ohm's Law.

a battery or solar panel (when the sun is shining on it) has a Voltage but NO CURRENT (when they aren't connected to anything), this can be measured using a multi-meter and an ammeter will confirm no current.

your resistance (ohms) is your device you are connecting to the circuit, whether that be a light bulb, solar charge controller or a central air unit, these two things (volts and resistance) can be measured using a multi meter without completing a circuit but you can't measure current until you complete a circuit because the resistance of the device at a specific voltage determines the amps flowing in the circuit. So given a fixed Voltage the Load (resistance) determines what the amperage is, these 3 things are intrinsically linked to each other via Ohm's Law, its why a 12v battery requires 4 times the current a 48v battery requires to get the same watts of output.

The only question is whether the device is constructed properly so that it can't put a bigger load (resistance) then it was designed for on the circuit that would then be measured as more current flow, current is the by product of a resistance being inserted into the circuit.

Thinks of Volts like water pressure in a pipe, to much pressure and the pipe will burst, this is what happens when you put too many volts into something (did this in my highschool electronics class 20+ years ago, we hooked a resistor to a power supply and kept increasing the volts till the resistor couldn't handle it and it burned out), this is why volts are a hard limit. Now think of resistance like a Valve on that water pipe, the amount of resistance (how far open the valve is) as what controls the flow rate (in conjunction with the pressure, volts) of the water coming out.

 

[Sundog33]

Interesting...

So you are telling me the amps specified in the Mini Split documents
Minimum Circuit Ampacity 19.05A
Maximum Fuse Size 20A
Maximum Starting Current 4A

Are actually stating how much power or "Pipe Diameter" the Unit will demand at maximum.
If so, it seems like my Pipe is a tad skinny if I have 4 - 300watt panels in Series giving me 1200watts but only a ISC: of 9.86A, but pretty close.
The instructions said not to parallel panels? What if I did?
Would that mean I'm leaving power on the table as my mini split can only draw 12amps?

What would this number mean in the specs ISC of PV <12A. ?

Or basically just have a limp shower. : )

 

[ksmithaz1]

That simply means you should be using #12 or fatter wire. with a 20A fuse when you hook up the AC. Don't over-think this.

 

[Sundog33]

ok, anyway got a bit off topic...

Back to the Victron Charge Controller that my question is about.

The Hyundia's run at:
Wattage: 305W VOC: 39.42V ISC: 9.86A
So if I was running it to a 12v battery bank that would change the Amps to 25Amps if I am correct?

So, can I hook up a Hyundia Panel to a 100/20 Victron without damaging it?

 

[Brucey]

It wouldn't change the amps. The critical number is the Voc, has to be less than 100V and you need to take into account that V will increase as temperature drops.

One 305W Hyundai panels will be fine (as would two in series). The maximum output of the SCC will be 20A into your battery bank.

 

[Sundog33]

I still don't really get the whole amp thing.
When I played with Panels on this thing a while back, I tried 3 -100watt panels and kept blowing my 20 amp fuse.
So what it that about>. Is the battery pulling amps just to charge it with no load?
Very confusing.

I was thinking of putting a 30amp fuse in and swaping to the Hyundia Panel
Wattage: 305W VOC: 39.42V ISC: 9.86A

The Victron is only rated for 280watt but that wasn't my issue/

 

[Sundog33]

It wouldn't change the amps. The critical number is the Voc, has to be less than 100V and you need to take into account that V will increase as temperature drops.

One 305W Hyundai panels will be fine (as would two in series). The maximum output of the SCC will be 20A into your battery bank.

Thats 9.86amps @ 39volts. im dropping it down to 12volts. Would that not change the amps?

Just like when I used my chainsaw thru my 12v inverter it changed the amp draw by 10x because 12v to 120volts. I was tripping an 80amp fuse/

 

[Sundog33]

I suppose I'll just pony up for the Victron 100/30 and quit trying to reinvent the wheel.

The 100/20 is only rated for 280watts @ 12v
The 100/30 is rated for 440watts @ 12v

Bottom line.

 

[ksmithaz1]

Thats 9.86amps @ 39volts. im dropping it down to 12volts. Would that not change the amps?

Just like when I used my chainsaw thru my 12v inverter it changed the amp draw by 10x because 12v to 120volts. I was tripping an 80amp fuse/

Kinda of a non-sequitur, but sort of: E=I*R or VOLTS=AMPS*RESISTANCE. P = E*I or WATTS = VOLTS * AMPS

AMPS determines the wire size and heat dissipation of the components. Volts is a measure of electrical pressure. Draw is based on the resistance of the load. You can't just mix and match the numbers you like, but you can plug in the numbers you have.

A mythical panel 50v/10a = 500watts (E*I = P) to charge a 12.5v battery. Theoretically we want to keep the WATTS (P) constant, a perfect 500W SCC/MPPT is going to provide 12.5v/40a = 500Watts, by storing the energy then releasing it at a lower electrical pressure. It will limit the current to 40a by creating a variable load (R) inline with the load the batteries create. E=I*R 12.5=40*R 12.5/40=R , R = ~0.31Ohms. A thirsty battery will be near zero ohms, that resistance will increase as the battery is charged up, likely to a point higher than 0.31. A Trickle charger would then increase it's resistance to meet whatever you want for the trickle charge rate, say .5A bumping the resistance up to ~25 Ohms. In the old days this was done with actual ceramic resistors and relays.

Heat generation is going to be from amps not volts, so the 50v/10a wires are not going to dissipate as much heat. The 12.5v/40a wires on the other hand are going to create 4 times the heat, thus need a larger conductor. Over-simplified, but that's the idea.

You want to go the other way it's the same, so if your chainsaw is the load and you need say 120v@10a that's 1200W P = E * I. So if your inverter is being fed from 12V batteries it will requiore P = E * I , 1200 = 12 * I, I = 100A, which is why a "1200W" inverter that plugs into your cigarette lighter on a 20A fuse is completely ludicrous, but I digress. So yes, your inverter or SCC/MPPT is converting the power by stepping up/down both voltage and current. An MPPT/SCC will control total current to the batteries by adjusting the resistance of the load. An inverter will simply trip a breaker if you try and draw too much current (or overheat and burn up if not properly protected).