Combiner box questions

wiseacre

Solar Enthusiast
Parts of a Eco Worthy kit

6 String PV Combiner Box
Number of Max Connection PV Array: 6
Max Input Current of Single PV Array: 10A
Total Input Current of PV Array: 60A
Max Input Voltage of Single PV Array: 250V
Max Output Voltage: 250V

Solar Panels
Rated Power: 195W
Open Circuit Voltage (Voc): 21.6V
Short Circuit Current (Isc): 10.83A
Working Current (Iop): 9.02A

The kit is set up to put 2 panels in series (max 6 strings). That I assume is because the PWM CC that came with the kit is rated for 50v max input.

the question is: Can I put more panels in series to up the PV voltage?
The stats for the combiner box state: max input voltage of a single PV array is 250v - the way they word things I'm assuming array=string (Number of Max Connection PV Array: 6)

Upping string voltages would allow me to upgrade the PWM CC to MPPT.

additional:
I see I'm limited to 10a for any string I add and that leads to another question
Can a higher wattage panel rated at 10 amps be set up in series and added to the combiner box if the voltage is different that the other strings.

I've been pleased with my kit system, it got me up and running without any real knowledge. Originally the system was meant to provide power to my Maple Sugar shed for lights and an induction cook top for finishing off small batches of sap and occasional power tool use. What got me was I was making power or the potential and not using it on a regular basis. Solar panels sitting in the sun and not doing anything irked me.

So I tweaked the kit by adding a Moes ATS (compliments to Will for reviewing it). The system now runs my Aquariums but soon runs out of steam when the sun goes down (switches to grid when my Gel batteries (2s for 24v) drops to 24.4v. So now I've got a bug up my posterior to upgrade the system and battery bank to prolong the switch back to grid power and the extra capability would certainly help during a power outage.
 
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MichaelK

Photon Sorcerer
It looks like some of your numerical values might be off. Assuming your panels are 195W, then 195W/9.02Imp = 21.62Vmp. The open circuit voltage is not used in the power production calculation. So, I think that one of your parameters is mislabeled?

Yes, the first thing I'd advise anyone is to get rid of a PWM controller and replace it with MPPT. Beware though of "budget" MPPT controllers marketed at a low price on EBay. They're fakes.

As you are observing, randomly assembled components aren't performing as well as you would like, because of the mismatch of input to output. What you need to determine first is how many watts you are going to consume per day, then select the number of panels and size of batteries to match that. Get some more numbers, and we can help you more.
 

wiseacre

Solar Enthusiast
The Voltage may very well be mislabeled.
Someone else gave me 25vmp to compensate for the cold, -40
Right now the numbers are not as important as just understanding what happens in the combiner box.

the question is: Can I put more panels in series to up the PV voltage in the combiner box?

The stats for the combiner box state: max input voltage of a single PV array is 250v - the way they word things I'm assuming array = string. (Number of Max Connection PV Array: 6) But also it could mean the combination box accepts 250V PERIOD

Thanks to your observation, I doubt anything in the description.
You also said, 21.6Vmp, does that mean a 2s string is 43.2Vmp
(If it was a 250V input max (the PERIOD mislabeling scenario) the 43.2 X 6 = 259.2 would seem unrealistic)
So by unreliable deduction it appears I could up the voltage in each string.

This might all be moot. The reason I ask is two fold. First, I should learn this stuff. Secondly is I want to upgrade my CC to MPPT and this was one approach to also plan for future expansion of my panel array. If anything the CC upgrade is of primary concern. As is, I still have the capability of expanding my panel array to some extent.

An Outback CC would be my first choice.
The big question then is, do the better CCs have a minimum voltage and/or would higher voltages be more efficient?
 

rhino

Solar Addict
Each string of panels (which are all in series) must be below 250V Voc for that combiner box. I am assuming this rating is because the circuit breakers in the combiner are only rated for 250V. When creating a string of panels in series you simply multiply the Voc by number of panels in series. You also must factor in temperature since the colder it gets the higher the Voc can be. You should keep the Voc below the circuit breaker rating and the charge controller rating. Given that you should be able to add 9 in series to stay below 250V or even 10 if you never get below 0F. The Midnite Classic 250 would handle that. Midnite has a calculator here you can use to check this but appears your panel specs is missing some of the data.

If you are wanting to go over 250V you should look at Midnite combiner boxes. The Midnite ones are also all metal. For over 250V you'll need to get correct combiner and use fuse holders rated for the higher voltage instead of regular DC circuit breakers like the MNPV6 with touch safe fuser holders.
 

chrisski

Photon Sorcerer
Circuit breakers are supposed to be 1.56 times the amps to avoid nuisance tripping. So with my 100 watt panels, that could push 6 amps at 18 volts. I use a 10 amp circuit breaker. With 9 amps, there could be some nuisance tripping.

So yes you could put more in series, but the 195 watt panel may be to big for the 10 amp circuit breaker. May need to get a 15 amp circuit breaker or something between 10 and 15 if available.
 

wiseacre

Solar Enthusiast
Each string of panels (which are all in series) must be below 250V Voc for that combiner box. I am assuming this rating is because the circuit breakers in the combiner are only rated for 250V. When creating a string of panels in series you simply multiply the Voc by number of panels in series. You also must factor in temperature since the colder it gets the higher the Voc can be. You should keep the Voc below the circuit breaker rating and the charge controller rating. Given that you should be able to add 9 in series to stay below 250V or even 10 if you never get below 0F. The Midnite Classic 250 would handle that. Midnite has a calculator here you can use to check this but appears your panel specs is missing some of the data.

If you are wanting to go over 250V you should look at Midnite combiner boxes. The Midnite ones are also all metal. For over 250V you'll need to get correct combiner and use fuse holders rated for the higher voltage instead of regular DC circuit breakers like the MNPV6 with touch safe fuser holders.
I expect to see -40 in winter, the coldest days are usually bright and sunny.
I'm reassured, I don't plan on going over 100V (+or-) or basically 4s.
I just want to go from small to modest
Looking at a ~ OutBack Power FM60-150VDC FLEXMax 60 Charge Controller
 

wiseacre

Solar Enthusiast
Circuit breakers are supposed to be 1.56 times the amps to avoid nuisance tripping. So with my 100 watt panels, that could push 6 amps at 18 volts. I use a 10 amp circuit breaker. With 9 amps, there could be some nuisance tripping.

So yes you could put more in series, but the 195 watt panel may be to big for the 10 amp circuit breaker. May need to get a 15 amp circuit breaker or something between 10 and 15 if available.
Point well taken.
The combiner box has 10a fuses and I haven't had one blow yet (one year)
If one does a 15a fuse maybe the thing to do
 

wiseacre

Solar Enthusiast
AH, unexpected but the seller just responded.
Confirmed I can up the voltage of each string
As I thought, mixing different voltage panels with what I already have is a no no. There goes the bigger panels into the sunset.

Thank all for the help, it's greatly appreciated
 

chrisski

Photon Sorcerer
In my signature block, there’s a link for “Mixing and Matchingpanels” that will show how much would be lost for parallel and series for mixing voltages and wattages. Short answer is the closer, the better the results.
 

wiseacre

Solar Enthusiast
In my signature block, there’s a link for “Mixing and Matchingpanels” that will show how much would be lost for parallel and series for mixing voltages and wattages. Short answer is the closer, the better the results.
If I understand correctly
adding a higher voltage panel to my existing panels is possible

I'm not sure what adding a 400watt, 41v 10a panel would be reduced to but considering I can buy something like that for less than I paid for the original 195watt panels I wouldn't be wrong using them
 
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