first 24v

[jBrew]

Trying to get a second opinion on a setup i want to build. I built a 12v system before but this is a 24v.

4 x 200w 24v solar panels: 2 in a series and 2 in a parallel
Victron MPPT 100|30
4 x 12v chins 100ah: 2 in a series and 2 in parallel connected by 4 gauge wire (24v 200ah bank)
ill probably add a 24v inverter also with a 4 gauge wire

i guess my biggest question is about the solar panels.
With this setup dont i get 48v in the solar panels ?
Will this work with the Victron MPPT 100|30 ?

 

[MisterSandals]

With this setup dont i get 48v in the solar panels ?

The MPPT will convert the higher array voltage to your charging voltage.

The question is whether the Voc of your panels, x2, is too close to the 100V max input voltage of the 100/30.
What do your panels show on the label for Voc?

 

[MisterSandals]

probably add a 24v inverter also with a 4 gauge wire

The size of the wire will depend on wire length and the watts/amps of the inverter. Fuse size too.

 

[jBrew]

Thank you for such a quick reply and i apologize for not giving enough information
the solar panel info:
+ Maximum Power(Pmax): 200W
+ Maximum Power Voltage(Vmp): 37.6V
+ Maximum Power Current(Imp): 5.36A
+ Open Circuit Voltage(Voc): 45.4V
+ Short Circuit Current(Isc): 5.83A
+ Maximum System Voltage(Vmax): 1000VDC
+ Temperature Range: -40°C ~ 90°C
+ Max Series Fuse Rating: 15A

the length between the battery bank and charge controller will be about 10 feet (planning on using the 4 guage)

the inverter: Giandel 24 Volt 2000W Pure Sine Wave Power Inverter DC 24V to AC120V with Dual AC Outlets with Remote Control 2.4A USB and LED Display
and the inverter will be the most 5 feet from battery bank.

 

[MisterSandals]

+ Open Circuit Voltage(Voc): 45.4V

So your 2S2P array will be 90.8V, rated at 25C. (77F)
This voltage will increase .3%for every degree C the temp drops below 25C.

100-90.8 = 9.2V leeway
9.2V = 90.8V x .003 x temp change C
temp change = 34C
So 25C - 34C = -9C = 15.8F

If the temp ever drops below 16F, your panels will exceed the 100V limit of your Victron 100/30 and very likely damage it.

 

[rmaddy]

With those panels in 2S2P they will be over 100Voc at temperatures below -5ºC. You never want to exceed the max input voltage of the SCC. So the 100/30 SCC will not be a good choice if you will ever encounter temperatures below freezing. Those panels in 2S2P can also generate close to 37A output from the SCC which is obviously over the 30A supported by that SCC. But in that case the extra amps will simply be unused.

 

[pollenface]

You could get away with 1s4p with 72cell panels, the Vmp is still 7-8v higher than your fully charged batteries in 24v

 

[MisterSandals]

the length between the battery bank and charge controller will be about 10 feet (planning on using the 4 guage)

4awg is plenty. Only .27% voltage drop (needs to be below 3% drop)

Voltage Drop Calculator

This free voltage drop calculator estimates the voltage drop of an electrical circuit based on the wire size, distance, and anticipated load current.

www.calculator.net

 

[rmaddy]

the length between the battery bank and charge controller will be about 10 feet (planning on using the 4 guage)

The Victron 100/30 only accepts wire up to 6 AWG. 4 AWG won't fit.

 

[jBrew]

Will MPPT 150|35 work better in this case?
and if 4awg is plenty, can I use 6awg for that length?
for the same set up as the start of the thread
to connect the batteries ill use 4awg and use 6awg between the bank and the MPPT

or is there more optimal set up?

 

[12VoltInstalls]

6ga at that length is good for as much as 60A or 70A. 8ga is 40A which would be my choice because it’s one size bigger than 10ga which does 30A snd should be enough.

 

[jBrew]

6ga at that length is good for as much as 60A or 70A. 8ga is 40A which would be my choice because it’s one size bigger than 10ga which does 30A snd should be enough.

i wont be pulling many amps from the bank (maybe the most is 30). its going to be turned into 12v anyway.
Thanks

 

[jBrew]

With those panels in 2S2P they will be over 100Voc at temperatures below -5ºC. You never want to exceed the max input voltage of the SCC. So the 100/30 SCC will not be a good choice if you will ever encounter temperatures below freezing. Those panels in 2S2P can also generate close to 37A output from the SCC which is obviously over the 30A supported by that SCC. But in that case the extra amps will simply be unused.

how do i generate 37A?
i guess im doing the math wrong

45.4V x 2 = 90.8V (series)
5.83A x 2 = 11.6A (parallel)

i understand that the voltage and the amps will go up, but up to 37A?

 

[12VoltInstalls]

i wont be pulling many amps from the bank (maybe the most is 30). its going to be turned into 12v anyway.
Thanks

I was referring to solar panel wires. 8ga is fine.

A 2000W inverter has a 4000W surge. The inverter therefore needs a cable set capable of withstanding a potential current of ~165A for which 1/0 will work at 24V.
If you are now going 12V batteries, the inverter cables should probably be 2/0

30A from the bank as you say is like 360W/3A at 120V from the12V you mention. But you should use wiring to support the load (2000W at 86A for 24V) not what you think you might use.

Maybe I’ve lost track but 12V or 24V batteries predicate what inverter you use and I am not sure what voltage you are going with at this point

 

[Northernchateau]

1

how do i generate 37A?
i guess im doing the math wrong

45.4V x 2 = 90.8V (series)
5.83A x 2 = 11.6A (parallel)

i understand that the voltage and the amps will go up, but up to 37A?

1st you Do Not have 24v panels as you stated. Those panels can charge 12v or 24 v depending on your charge controller.
2nd switching your 2s2p configuration to 1s4p will yield:
max VOC of 45.4v
max power voltage of 37.6V
max current of 5.83 x 4 = 23.32 amps

not sure where rmaddy came up with 37amps

 

[jBrew]

1

1st you Do Not have 24v panels as you stated. Those panels can charge 12v or 24 v depending on your charge controller.
2nd switching your 2s2p configuration to 1s4p will yield:
max VOC of 45.4v
max power voltage of 37.6V
max current of 5.83 x 4 = 23.32 amps

not sure where rmaddy came up with 37amps

ah so looks like 1s4p is a better setup.
for some reason i wanted to keep the amps low but with 1s4p if i use Victron MPPT 150|35 it will work just fine.
i can also reuse the 10awg wire from solar to charge controller, since it can take over 30amps up to 10 feet
thank you

 

[chrisski]

the length between the battery bank and charge controller will be about 10 feet (planning on using the 4 guage)

Even though voltage loss is not an issue, 4 AWG is pretty skinny ampacity wize. 4 AWG will need 90 C insulation to handle below the max draw, and you want to go to 105 C if its higher. Depending on how much you’re going to use the full 2000 watts, you may want to go even thicker than that to help wires from heating up. If this were mine to cover surge wattage plus a DC appliance or two on already, I would size this to 1/0. 2 or 4 AWG may work, but not for any growth or the careless guest you may have that does the unthinkable about plugging in a hair dryer while the microwave is running. The inverter should shut off, but I try not test that. Fuses take some time to blow also.

Edit: I’m not sure where your system is going, but I wish I’d bought the 150 volt Victrons instead of the 100 volt VIctrons. THe 150 volt can do 12, 24, and 48 volt systems, but the 100 can only do 12 and 24. Had I had those, I probably would be doing a 48 volt upgrade instread of a 24 volt upgrade.

 

[rmaddy]

how do i generate 37A?
i guess im doing the math wrong

45.4V x 2 = 90.8V (series)
5.83A x 2 = 11.6A (parallel)

i understand that the voltage and the amps will go up, but up to 37A?

not sure where rmaddy came up with 37amps

If you plug the numbers into Victron's MPPT calculator you will see that the SCC could generate up to 37A output with those panels.

ah so looks like 1s4p is a better setup.
for some reason i wanted to keep the amps low but with 1s4p if i use Victron MPPT 150|35 it will work just fine.

According to Victron's MPPT calculator, if you go 2S2P with those panels you will want the 150/35. If you go 1S4P you will want the 100/50. The 100/30 would work at 4P but you would be giving up some amps so going with the 100/50 lets you take full advantage of the amps it can generate with the panels. And it gives you room to upgrade to 5P if you wanted.

i can also reuse the 10awg wire from solar to charge controller, since it can take over 30amps up to 10 feet

the length between the battery bank and charge controller will be about 10 feet (planning on using the 4 guage)

Between the SCC and the battery you have 20 feet of wire round trip. If you use the 100/30 or the 150/35 you need 6AWG to safely pass 30A or 35A over 20'. If you go to the 100/50 then you want 4AWG to pass up to 50A over 20'. But the 100/50 only accepts up to 6AWG so I'm not sure how that works.

 

[Northernchateau]

If you plug the numbers into Victron's MPPT calculator you will see that the SCC could generate up to 37A output with those panels.

His panel lable states: Short Circuit Current(Isc): 5.83A
Someone will need to explain how a fused 15amp panel can generate 37a

 

[rmaddy]

His panel lable states: Short Circuit Current(Isc): 5.83A
Someone will need to explain how a fused 15amp panel can generate 37a

It's the output of the SCC, not the current of the panels. Plug the numbers into the Victron MPPT calculator and you will see what I'm talking about. It's labeled "Ibat max @ Impp" (maximum battery current at panel maximum power point current).

The potential Ibat max @ Impp will be capped at the max current of the SCC (30A for a 100/30 MPPT SCC for example).

The rough formula is string Vmpp times Impp divided by system voltage where each of those first two values is adjusted for temperature. In this case (2S2P), at STC, Vmpp = 75.2V (2S), Impp = 10.72A (2P), system voltage = 24V.

75.2V * 10.72A / 24V = 33.6A

At -5ºC it works out to about 37A.