Array to CC wiring question

Dell

New Member
Array to CC wiring question. Technical wiring question for 7 400 watt panels in parallel. These panels are listed as 50.4 VOC and 9.74A. Run is 70ft. 8AWG’s the largest cable I’m aware of using MC4 connectors. 8AWG’s rated at 55 amps. Can someone please comment on the best way to accomplish properly wiring this parallel array with a Victron TR 150/100?
 

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NMNeil

Solar Enthusiast
Wire 3 panels in series to give 150V and put 2 of these strings in parallel to give just under 20A.
At that current and voltage, and allowing for a 3% voltage drop over 70 feet you should be able to use 8 AWG, perhaps even 10 AWG.
Putting all 7 in parallel to get just under 70 amps is going to be difficult to work with.
 

Dell

New Member
Thanks for the response Neil. Are you saying only use 6 of the 7 panels?

(Also, there is a shading situation)
 

iamrich

Solar Addict
2S3P using three sets up 10awg for 70' and then into combiner box and then 4-6awg from combiner to Victron?
 

iamrich

Solar Addict
Thanks for the response Neil. Are you saying only use 6 of the 7 panels?

(Also, there is a shading situation)
You could run 7 runs of 12awg parallel, but that's a lot of wire. You still need to come into a combiner box I would think.
 

GXMnow

Photon Sorcerer
I agree, you need to series in at least pairs. Can you fit an 8th panel? 7 is a tough number being a prime, 6 or 8 allows a few options, 7 does not. All in parallel comes out to 68 amps. That is a lot of current, especially at just 41 volts. You would need to run 3 full runs of #10 or #8 wire. Is the shading predictable? Will some panels never be shaded while others will always have shade pass across? Panels that are in series should see the same shading at the same time. If one is shaded, and then later the other is shaded, it is a problem. With 6 or 8 panels, you could parallel the panels where the shade will pan across, and series that group with another parallel group that has the shade pan across. This way the amount of full sun panels in each of the series sections is about equal. And you might get a bit more total energy if you parallel in that 7th panel on the group that usually sees a bit more shade. That would be 4 in parallel with some shade, in series with only 3 in parallel but with less shade. Not ideal, but it could work well. This does limit your maximum current to about 3P or 34.09 amps. That is too much for #10, and borderline for #8. I would probably run 2 runs of #8 to reduce losses on a 70 foot run. Your voltage doubles to 100.8 VOC and 82.2 VMP. Those seem well in range of an MPPT 150|100 with nearly 50% voltage headroom. You did not mention your battery voltage, so I can't tell if your current is safe. 400 * 6 = 2400 watts max (The 7th panel in this setup can't really make more power, but it could extend the time you get full power with one of the parallel panels being shaded. On a 12 volt system, 2400 watts would be 200 amps, not good. On 24 volts, it is 100 amps, so just making it on the 100 amp rated controller. At 48 volts, it drops to just 50 amps so you would have room to spare. You would have to look up to see if the Victron is able to handle over paneling on the 12 volt setup, the 24 and 48 should be completely fine.
 

Dell

New Member
I agree, you need to series in at least pairs. Can you fit an 8th panel? 7 is a tough number being a prime, 6 or 8 allows a few options, 7 does not. All in parallel comes out to 68 amps. That is a lot of current, especially at just 41 volts. You would need to run 3 full runs of #10 or #8 wire. Is the shading predictable? Will some panels never be shaded while others will always have shade pass across? Panels that are in series should see the same shading at the same time. If one is shaded, and then later the other is shaded, it is a problem. With 6 or 8 panels, you could parallel the panels where the shade will pan across, and series that group with another parallel group that has the shade pan across. This way the amount of full sun panels in each of the series sections is about equal. And you might get a bit more total energy if you parallel in that 7th panel on the group that usually sees a bit more shade. That would be 4 in parallel with some shade, in series with only 3 in parallel but with less shade. Not ideal, but it could work well. This does limit your maximum current to about 3P or 34.09 amps. That is too much for #10, and borderline for #8. I would probably run 2 runs of #8 to reduce losses on a 70 foot run. Your voltage doubles to 100.8 VOC and 82.2 VMP. Those seem well in range of an MPPT 150|100 with nearly 50% voltage headroom. You did not mention your battery voltage, so I can't tell if your current is safe. 400 * 6 = 2400 watts max (The 7th panel in this setup can't really make more power, but it could extend the time you get full power with one of the parallel panels being shaded. On a 12 volt system, 2400 watts would be 200 amps, not good. On 24 volts, it is 100 amps, so just making it on the 100 amp rated controller. At 48 volts, it drops to just 50 amps so you would have room to spare. You would have to look up to see if the Victron is able to handle over paneling on the 12 volt setup, the 24 and 48 should be completely fine.
Thanks for responding GXM.

8th panel would be too much wattage.

Batteries are setup up as 24 volt.

Shading’s predictable, from trees.

1/O cable is rated at 85 amps.

Is 1/O a viable option for wiring all 7 in parallel?

VOC would be ‘low’ at ~50.4 total, high enough to flow into 24 volt battery set up however.
 

Dell

New Member
Thanks for responding GXM.

8th panel would be too much wattage.

Batteries are setup up as 24 volt.

Shading’s predictable, from trees.

1/O cable is rated at 85 amps.

Is 1/O a viable option for wiring all 7 in parallel?

VOC would be ‘low’ at ~50.4 total, high enough to flow into 24 volt battery set up however.
 

GXMnow

Photon Sorcerer
Yes 1/0 cable would do the trick, but 70 feet (140 total) is going to get expensive.
You can over panel the Victron a bit without damage. Read note 1a (If more PV power is connected, the controller will limit input power) So you will max out at 2900 watts of charge power. With your shading issues, it is unlikely the 8 panels will ever top 2900 watts anyway. The input current limit is 70 amps. You are very close to that with the 7 in parallel, but going to 2 series, 4 parallel, your input current drops to just 40.72 amps short circuit current. That is a lot easier to deal with.
 

rickst29

Solar Enthusiast
Thanks for responding GXM.

8th panel would be too much wattage.

Batteries are setup up as 24 volt.

Shading’s predictable, from trees.

1/O cable is rated at 85 amps.

Is 1/O a viable option for wiring all 7 in parallel?

VOC would be ‘low’ at ~50.4 total, high enough to flow into 24 volt battery set up however.
I guess my really big question is: WHY is the battery bank a mere 24-volt setup? But my second question is: What will be using all of this power? If you're gonna run a giant Inverter with it, then you might simply switch to an off-grid residential scheme. A small Sunny-Boy handles up to 3000w just fine, includes the Inversion to single-phase AC, AND handles 600V PV input Voltage. About $1000 bucks, you could wire all 7 of your panels in series with no problem. ~360V(oc) with only 9A needs only small wires, though you obviously use conduit and warning stickers at that voltage.

With a battery bank, you simply add on a compatible battery management unit, or buy a 3-way unit (battery Solar, and Inversion) right from the start. Although I'd be inclined to use SMA, other upper-end builders like SolarEdge have comparable offerings.

After you've got the batteries charge by your "pretty big" Solar Array, what is the application? Does it really WANT to be at only "24V"?
 
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Dell

New Member
Yes 1/0 cable would do the trick, but 70 feet (140 total) is going to get expensive.
You can over panel the Victron a bit without damage. Read note 1a (If more PV power is connected, the controller will limit input power) So you will max out at 2900 watts of charge power. With your shading issues, it is unlikely the 8 panels will ever top 2900 watts anyway. The input current limit is 70 amps. You are very close to that with the 7 in parallel, but going to 2 series, 4 parallel, your input current drops to just 40.72 amps short circuit current. That is a lot easier to deal with.
Yeah, I just looked at 1/O cable prices and 140 ft. is cost prohibitive for sure.
 

Bud Martin

Solar Addict
Yes 1/0 cable would do the trick, but 70 feet (140 total) is going to get expensive.
You can over panel the Victron a bit without damage. Read note 1a (If more PV power is connected, the controller will limit input power) So you will max out at 2900 watts of charge power. With your shading issues, it is unlikely the 8 panels will ever top 2900 watts anyway. The input current limit is 70 amps. You are very close to that with the 7 in parallel, but going to 2 series, 4 parallel, your input current drops to just 40.72 amps short circuit current. That is a lot easier to deal with.
+1
 

Hedges

Photon Sorcerer
3 panels in series is too high a voltage, will kill the charge controller.
3 x 50V = 150V even at 25 degrees C, higher when cold.
You can only put two of those panels in series.

You can never have too much wattage. If the SCC doesn't want the watts, it won't use it.

"Max. PV short circuit current: 70 Amps"
This is the other limit to obey, besides Voc (at record cold temperature for your location.)

Can you orient some series strings of 2 panels SE for morning sun and some SW for afternoon? If aimed at say 10:00 AM and 4:00 PM (daylight savings time), the 90 degree angle between them means only 0.7 times as much area presented to the sun. You can over-panel with 150% of rated wattage; SCC will only see 100% of its rating but for more hours so you get more power. Or tilt some for summer and some for winter. That isn't as large an angle, but will have some effect.
 

Dell

New Member
I guess my really big question is: WHY is the battery bank a mere 24-volt setup? But my second question is: What will be using all of this power? If you're gonna run a giant Inverter with it, then you might simply switch to an off-grid residential scheme. A small Sunny-Boy handles up to 3000w just fine, includes the Inversion to single-phase AC, AND handles 600V PV input Voltage. About $1000 bucks, you could wire all 7 of your panels in series with no problem. ~360V(oc) with only 9A needs only small wires, though you obviously use conduit and warning stickers at that voltage.

With a battery bank, you simply add on a compatible battery management unit, or buy a 3-way unit (battery Solar, and Inversion) right from the start. Although I'd be inclined to use SMA, other upper-end builders like SolarEdge have comparable offerings.

After you've got the batteries charge by your "pretty big" Solar Array, what is the application? Does it really WANT to be at only "24V
 

Dell

New Member
For a small hunting camp in FL.

3000 watt, 24 volt Reliable inverter

4 BB 100ah LiFePo in the mix
 

Dell

New Member
Yes 1/0 cable would do the trick, but 70 feet (140 total) is going to get expensive.
You can over panel the Victron a bit without damage. Read note 1a (If more PV power is connected, the controller will limit input power) So you will max out at 2900 watts of charge power. With your shading issues, it is unlikely the 8 panels will ever top 2900 watts anyway. The input current limit is 70 amps. You are very close to that with the 7 in parallel, but going to 2 series, 4 parallel, your input current drops to just 40.72 amps short circuit current. That is a lot easier to deal with.
2 series, 4 parallel might be the best way within the context. Keep the extra panel for a spare. I’m not sure about the shading situation though. There’s shaded sun in the morning and late afternoon.

The avg. total power needed per 24 hr. is about 14,000 watt hours.
 

Dell

New Member
2 series, 4 parallel might be the best way within the context. Keep the extra panel for a spare. I’m not sure about the shading situation though. There’s shaded sun in the morning and late afternoon.

The avg. total power needed per 24 hr. is about 14,000 watt hours.
(not including recharging the batteries)
 
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