Array to CC wiring question

[Dell]

Is 2400 watts enough to do it?

 

[Hedges]

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)

What, you're going to draw 14,000 watt hours while the sun shines, plus another <unspecified> amount from batteries at night?
Or, you expect total consumption in a 24 hour day to be 14,000 Wh, whether drawn day or night? In that case, the only extra you need is to make up for round-trip inefficiency of battery. (and charge controller, and inverter if you haven't accounted for that.)

LiFePO4 and other lithium is fairly efficient, don't know the exact percentage lost to heat. Lead-acid is much less efficient, could be just 70% to 90% so requires considerably more watts to recharge what was used. Lead-acid gets noticeably hot when charging at a high rate. I hear lithium does not. With high discharge rate, higher internal resistance of lead-acid means more I^2 R losses.

Summer or winter? Consult an insolation calculator. Might be 5 hours effective sun in summer, 2 hours in winter.
Figure PV panels deliver actual PTC power about 80% of their STC rating (more or less, apparently some brands perform better.)

14,000 / 2 / 0.8 = 8750W (STC) of panels needed to deliver that much power in winter,
14,000 / 5 / 0.8 = 3500W (STC) of panels needed to deliver that much power in summer.

Is 2400 watts enough to do it?

Nope.

Better get more panels.
Or one of these:



Or reduce power consumption.

 

[Dell]

What, you're going to draw 14,000 watt hours while the sun shines, plus another <unspecified> amount from batteries at night?
Or, you expect total consumption in a 24 hour day to be 14,000 Wh, whether drawn day or night? In that case, the only extra you need is to make up for round-trip inefficiency of battery. (and charge controller, and inverter if you haven't accounted for that.)

LiFePO4 and other lithium is fairly efficient, don't know the exact percentage lost to heat. Lead-acid is much less efficient, could be just 70% to 90% so requires considerably more watts to recharge what was used. Lead-acid gets noticeably hot when charging at a high rate. I hear lithium does not. With high discharge rate, higher internal resistance of lead-acid means more I^2 R losses.

Summer or winter? Consult an insolation calculator. Might be 5 hours effective sun in summer, 2 hours in winter.
Figure PV panels deliver actual PTC power about 80% of their STC rating (more or less, apparently some brands perform better.)

14,000 / 2 / 0.8 = 8750W (STC) of panels needed to deliver that much power in winter,
14,000 / 5 / 0.8 = 3500W (STC) of panels needed to deliver that much power in summer.



Nope.

Better get more panels.
Or one of these:

View attachment 44883

Or reduce power consumption.

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

(not including recharging the batteries)

 

[Dell]

(not including recharging the batteries)

Total for everything except recharging batteries is about <14,000 watts per 24 hrs.

(basically <600 watts per hour)

 

[Dell]

Total for everything except recharging batteries is about <14,000 watts per 24 hrs.

(basically <600 watts per hour)

About how fast should the batteries recharge during ~8 hours of sun?

 

[Hedges]

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

(not including recharging the batteries)

Recharging the batteries means putting back in them the power you drew from them (at night, or during the day when you turned on a microwave and drew more than PV was producing at the moment.)

That 14,000 watt-hours ought to be total consumption, whether from battery or direct from PV. That is used to size your PV array.
It is useful to also determine how much will be consumed at night. That is used to size your battery.

About how fast should the batteries recharge during ~8 hours of sun?

In a typical summer day of 12 plus hours sunshine, you get 5 or 6 equivalent full-sun hours. One full sun is 1000 W/m^2. A 120W panel produces about 100W in typical conditions, heated by the sun but cooled by a slight breeze, and aimed directly at the sun. Angle of sun on panel varies during the day, and early/late in the day, suns rays are less intense because they travel through 1.5 x as much air. Figure 5h x 100W = 500 Wh typically produced on a summer day by a 120W panel.

If you have 2400W of panels they may produce about 2000W peak, and about 10,000 Wh/day.

 

[Hedges]

Total for everything except recharging batteries is about <14,000 watts per 24 hrs.

(basically <600 watts per hour)

< 600 Wh/hour or 600W average is of course a small number.

Larger number is peak consumption, which your inverter, fuse, BMS, etc. has to carry. and a brief higher starting surge if anything has a motor. Most components tolerate a few seconds surge, but for motors it is about 5x their nameplate current which can be a problem.

 

[Hedges]

Total for everything except recharging batteries is about <14,000 watts per 24 hrs.

(basically <600 watts per hour)

< 600 Wh/hour or 600W average is of course a small number.

Larger number is peak consumption, which your inverter, fuse, BMS, etc. has to carry. and a brief higher starting surge if anything has a motor. Most components tolerate a few seconds surge, but for motors it is about 5x their nameplate current which can be a problem.

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?

You show a 400W Trina panel.
Somebody said PTC (real-world power) output of the Trina panel is 300W, which is just 75% of its 400W (STC) rating. This means you need to oversize the array a bit more than you would for some other brands of panels.

 

[Dell]

< 600 Wh/hour or 600W average is of course a small number.

Larger number is peak consumption, which your inverter, fuse, BMS, etc. has to carry. and a brief higher starting surge if anything has a motor. Most components tolerate a few seconds surge, but for motors it is about 5x their nameplate current which can be a problem.

You show a 400W Trina panel.
Somebody said PTC (real-world power) output of the Trina panel is 300W, which is just 75% of its 400W (STC) rating. This means you need to oversize the array a bit more than you would for some other brands of panels.

So I kinda need the 7th panel in the equation if possible? Like the 7 panels in parallel?

 

[Dell]

So I kinda need the 7th panel in the equation if possible? Like the 7 panels in parallel?

~<14,000 is a theoretical number based on ~<600 watts draw, in reality it would be less. 1/2 hour on and 1/2 hour off for small window A/C (500 watts) during the non-sun hours. This would leave the batteries basically drained the next day, how fast should they recharge?
Within about 8 hours if there is 2400 watts of panels and average conditions?

 

[Dell]

~<14,000 is a theoretical number based on ~<600 watts draw, in reality it would be less. 1/2 hour on and 1/2 hour off for small window A/C (500 watts) during the non-sun hours. This would leave the batteries basically drained the next day, how fast should they recharge?
Within about 8 hours if there is 2400 watts of panels and average conditions?

(and the appliances drawing about 600 watts)

 

[Hedges]

So I kinda need the 7th panel in the equation if possible? Like the 7 panels in parallel?

Even that would be a bit short of your 14 kWh/day, even in summer
7 x 400 = 2800W (STC)
If Trina panels really only produce 300W (STC) (check the data sheet), then for 3500W you would need 12 panels.

See if you can reduce that 14 kWh/day number, and can it be much less in winter?
Seems high for an RV unless you're running A/C. If it is for A/C, you should find a way to run it only while the batteries are at a fairly high state of charge.
The other think about A/C, is if you park in the sun so PV panels get sunlight, you need more A/C. If you park in the shade, RV doesn't build up as much heat but panels don't produce anything.

~<14,000 is a theoretical number based on ~<600 watts draw, in reality it would be less. 1/2 hour on and 1/2 hour off for small window A/C (500 watts) during the non-sun hours. This would leave the batteries basically drained the next day, how fast should they recharge?
Within about 8 hours if there is 2400 watts of panels and average conditions?

If 500W running 50% of the time, that's 250W average x 24 hours = 6 kWh, and that only in the summer. Much better. About 1200W of PV for 5 hours gives you that, so 2400W of panels sounds good.

How much battery? You said 24V, so 2400W would be about 100A. If those are 280 Ah LiFePO4, then charging around 0.4C which sounds reasonable.

Anything you can do like an awning, other shade to keep sun off parts of roof without panels should help.
Some people have a few portable panels they can deploy out in the sun, while RV is parked in the shade.

 

[Dell]

Even that would be a bit short of your 14 kWh/day, even in summer
7 x 400 = 2800W (STC)
If Trina panels really only produce 300W (STC) (check the data sheet), then for 3500W you would need 12 panels.

See if you can reduce that 14 kWh/day number, and can it be much less in winter?
Seems high for an RV unless you're running A/C. If it is for A/C, you should find a way to run it only while the batteries are at a fairly high state of charge.
The other think about A/C, is if you park in the sun so PV panels get sunlight, you need more A/C. If you park in the shade, RV doesn't build up as much heat but panels don't produce anything.



If 500W running 50% of the time, that's 250W average x 24 hours = 6 kWh, and that only in the summer. Much better. About 1200W of PV for 5 hours gives you that, so 2400W of panels sounds good.

How much battery? You said 24V, so 2400W would be about 100A. If those are 280 Ah LiFePO4, then charging around 0.4C which sounds reasonable.

Anything you can do like an awning, other shade to keep sun off parts of roof without panels should help.
Some people have a few portable panels they can deploy out in the sun, while RV is parked in the shade.

~500W running 50% of the time,{during non-sun hours}.

4 Battle Born 100ah LiFeO wired to make them 24 volts.

 

[Dell]

~500W running 50% of the time,{during non-sun hours}.

4 Battle Born 100ah LiFeO wired to make them 24 volts.

4 100 Ah 12V LiFePO4 Deep Cycle

 

[Hedges]

~500W running 50% of the time,{during non-sun hours}.

4 Battle Born 100ah LiFeO wired to make them 24 volts.

4 100 Ah 12V LiFePO4 Deep Cycle

200 Ah, 24V. With 2400W of PV, that's 100A charge current or 0.5C. 50A into each battery.
Check their specs. That is probably OK at 25 degrees C. Whether or not their spec gives a different charge current for 5 or 10 degrees C, it should be reduced to something less than maximum charge current at 25 degrees C.

200 Ah x 24V = 4800 Wh.
500W load running 50% of the time is 250W average. 4800Wh / 250W = 19 hours (to drain from 100% to 0%)
That should support 12 hours of run time with minimal other loads.

 

[Dell]

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 you thoughts on this situation GXM.

Each 400W panel has #12 (12AWG) factory wire (~4.6’) in MC4 connectors.

You think it’s ok to have 1 string of 4 in parallel (using #12 or #10 wire for the leads?) in a set of 4 to 1 MC4 branch connectors and one string of 3 in parallel with (#12 or #10 wire for the leads?) in a set of 3 to 1 MC4 branch connectors, and then use 2 sets of #8 to make the 70 ft. run?

(9.74 amps per panel and #8 wire is rated at 55 amps)

 

[Hedges]

Do you mean 4s (four in series) and 3s (3 in series), then connect those two in parallel?
The 3s will conduct current coming from the 4s, pulling it down to about Voc of 3s. This heats the 3s panels more and doesn't give very much more power than 3s2p.

I think I already figured out that 3s is too high a voltage for your charge controller. Unless something has changed in your equipment selection, or I made a mistake, don't do that.

Array to CC wiring question

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...

diysolarforum.com

Wire the panels as 2s3p. Take the 7th panel and use it with a separate charge controller. Or pick up a one more panels of similar voltage/current and wire all 8 panels 2s4p. (If more than 2 strings in parallel, use a fuse for each string.)

Now if by "one string of four in parallel" you meant "four in parallel" (the word "string" is generally a synonym of "series"), then voltage would be OK.

4p + 3p gives same voltage as 2s, 2s2p, or 2s3p. But 4p + 3p won't really give much more power than 3p + 3p or 2s3p. Current will be limited to about 3 x Imp.

So I still say 2s3p is the way to go.

 

[GXMnow]

The odd ball connection I had suggested was using a parallel group of 3 panels, and another parallel group of 4 panels, with the 4 being the ones that get more shade issues. The idea being, the 4 with shading might make as much current as the 3 with less or no shade. Then put those 2 groups in series. If any 1, 2, or 3 panels in each group is getting full sun, it will work just fine. Any light hitting the other panels can still add some current. If all 7 do have good sun, then the ones in the 4P group will be working at less than ideal with their current limited to the 3P group, but it could still make a little more total power than just using 6 of the panels. Basically, this allows one panel of the 4P group to be heavily shaded, and the other 3 will stay working well with the other group of 3 in parallel. Sure, it is not ideal, and adding the 8th panel would be better. But if he already has 7 panels, and knows there will be shading, I think this is a very god compromise to make the best use of the gear he has. The 2S voltage is very good for that charge controller, and the "3.5P" current is good as well. This only really will help over the 2S3P or 3P2S when there is a shadow that will traverse across the 4P group. You can theoretically keep getting 3P performance from the 4P group with a moving shadow taking out one panel at a time. Obviously, no shadows would be better.

 

[rickst29]

Thanks for you thoughts on this situation GXM.

Each 400W panel has #12 (12AWG) factory wire (~4.6’) in MC4 connectors.

You think it’s ok to have 1 string of 4 in parallel (using #12 or #10 wire for the leads?) in a set of 4 to 1 MC4 branch connectors and one string of 3 in parallel with (#12 or #10 wire for the leads?) in a set of 3 to 1 MC4 branch connectors, and then use 2 sets of #8 to make the 70 ft. run?

(9.74 amps per panel and #8 wire is rated at 55 amps)

8 AWG, supporting 35A @ 82 volts V(mp) on a 70 foot run loses around 4.6% in wiring losses (AKA "Voltage Drop", the SCC receives only 78.1 Volts of difference.) 6 AWG would lose about 2.9%, at rated panel output. The number of strands creates small differences in these figures. I don't know if you need type UF, or whether everyday building wire will be OK. 70 feet seems like a kinda long run.

 

[Hedges]

Here would be a way to deal with the prime number "7" panels of 50 Voc, and to make "70 foot run" short rather than long, with low losses using just 12 awg (600V charge controller)

Schneider Electric 865-1034 Conext MPPT 100 Amp 600VDC Solar Charge Controller

NOTE: In order to program this controller, you will need the Schneider InsightHome Energy Management Device 865-0330.

www.solar-electric.com