Need to Reduce solar voltage!!

[SamDeleted]

I can’t do 3s2p. The distance is too far and the voltage will be too low for my 10 gauge wire. I need the voltage to be on the higher side to keep amps down to get away from running long distance. That’s why I went with 2s3p. If I was to running 3s2p then I will have to run 8-6 gauge wire to be under the 3 percent voltage drop.

Couldn't be clearer . Lol ?

 

[vashkoproimage]

Very grateful to those actually trying to help Happy Thanksgiving y’all.

 

[Ampster]

The distance is too far and the voltage will be too low for my 10 gauge wire.

To be more clear, I would have said that the current would be too high for my 10 gauge wire. In a 3P2S configuration that would be on the borderline for 35 Amps for 10 gauge wire. However in a 2S2P configuration the current would not be too high and physically two groups in parallel would be all that you could do, given the physical limitations of your layout. I am not trying to get you to change your mind. I am hopeful that future readers may benefit from this dialogue and realize that stating the issue more clearly might have made the thread more productive.

 

[ghostwriter66]

To be more clear, I would have said that the current would be too high for my 10 gauge wire. I am not trying to get you to change your mind. I am hopeful that future readers may benefit from this dialogue and realize that stating the issue more clearly might have made the thread more productive.

And thus why many just read the first and last page of a post ... LOL

 

[Ampster]

And thus why many just read the first and last page of a post

Yes and the longer the thread the more likely that will happen. That just increases the need for some repetition of some fundemental constraints even though it might be redundant and a pain for the OP but stuff happpens in life that we cannot control.

 

[pollenface]

It was never a concern about the wiring I have set up. Concern was about lowering voltage from current setup without rearranging current setup.

You've said you're going for 2s3p as your wiring is sufficient. That's great, problem solved ?

 

[vashkoproimage]

You've said you're going for 2s3p as your wiring is sufficient. That's great, problem solved ?

Yes correct. Wire is good for my 3s2p setup. ?

 

[pollenface]

Not possible to do 2 panels in series.

Yes correct. Wire is good for my 3s2p setup. ?

Now I'm confused again.

 

[SamDeleted]

Now I'm confused again.

The details are fuzzy ?

 

[wme]

Choices..
a bigger (more v) controller
run 2s2p in the winter and 3s2p in the summer... I know thats backwards for production. but!!
chance it and run 3s2p and see how long the controller lasts.
Move 1 panel to the other mount and then run 2s3p

 

[SamDeleted]

@vashkoproimage I see you are a professional photographer


I hope your wedding snaps turn out clearer than your forum posts! ?

 

[vashkoproimage]

Choices..
a bigger (more v) controller
run 2s2p in the winter and 3s2p in the summer... I know thats backwards for production. but!!
chance it and run 3s2p and see how long the controller lasts.
Move 1 panel to the other mount and then run 2s3p

Yes. Hit that hammer right on the nail. ? was the exact options I was looking at before. I posted this question here to see option like (out of the box ideas) just as Hedges and other said (shorting the diode). Too bad it’s NOT an option due to it be glued in.

 

[vashkoproimage]

@vashkoproimage I see you are a professional photographer


I hope your wedding snaps turn out clearer than your forum posts! ?

Yep. ?

 

[vashkoproimage]

Thinking of just going with a Victron 250v controller for temporary use. Any other options with charge controllers with higher voltage? Must be a 48v battery bank. Might get lucky finding one for decent price for Black Friday.

 

[Hedges]

Remove one panel from one array. Mechanically splice it onto the other array. Then you can do 2s3p.

You keep saying you would need heavier wire to keep voltage drop under 3%. Why 3%? Let it be 10% or 15%, that's fine too.

 

[Hedges]

Thinking of just going with a Victron 250v controller for temporary use. Any other options with charge controllers with higher voltage? Must be a 48v battery bank. Might get lucky finding one for decent price for Black Friday.

Midnight Classic is good.
You can use the 150V one all the way up to 150V, and not worry if it goes over in cold.
They also have 200V and 250V models. Those cost more per watt.

 

[vashkoproimage]

Remove one panel from one array. Mechanically splice it onto the other array. Then you can do 2s3p.

You keep saying you would need heavier wire to keep voltage drop under 3%. Why 3%? Let it be 10% or 15%, that's fine too.

When I researched while ago, wire sizing for solar arrays was told that it’s best to keep under 3% voltage drop. I’m very open minded. Educate me if I’m wrong.

 

[Hedges]

3% voltage drop wastes 3% of power, but when sun is low and makes half as much, only 1.5% of smaller amount is wasted.
10% voltage drop wastes 10% of power, but when half as much power is made, only 5% of smaller amount is wasted.

Running 2s2p instead of 3s2p wastes 33% of power all the time.

Running 2s3p instead of 3s2p boosts current 50%, causing 1.5^2 = 2.25 as much power loss. 3% x 2.25 = 6.75% power loss.
Better to lose 6.75% during peak times than 33% all the time.

 

[vashkoproimage]

3% voltage drop wastes 3% of power, but when sun is low and makes half as much, only 1.5% of smaller amount is wasted.
10% voltage drop wastes 10% of power, but when half as much power is made, only 5% of smaller amount is wasted.

Running 2s2p instead of 3s2p wastes 33% of power all the time.

Running 2s3p instead of 3s2p boosts current 50%, causing 1.5^2 = 2.25 as much power loss. 3% x 2.25 = 6.75% power loss.
Better to lose 6.75% during peak times than 33% all the time.

So running my panels 2s3p will be at 83.66v 38.37 amp going into controller. And running 3s2p will be 125.49v 25.58 amp. These are normal conditions. So you say 2s3p is better with higher amps and lower voltage? I always thought to keep voltage higher to get away with running thinner wire longer distances.

 

[Hedges]

Yes, Higher voltage, lower amps is better for wiring loss. Up to what insulation can withstand and electronics can handle.
Most of my equipment is rated 600V, and operates at 380 Vmp. A couple charge controllers are 145V or 150V. Some people have 1000V equipment. In both cases, this is straight to AC, GT PV inverters.

MPPT operation is more efficient with less voltage delta, so PV closer to battery or to AC voltage is better. More efficient also means electronics runs cooler, extending its life.

I was just saying that losing several percent more is no big deal, a good tradeoff against cost of heavier wire and to avoid over-voltage of electronics. 3% is a good target, I think mine is 1% (panels were more expensive 20 years ago so it mattered), but much higher loss is OK for PV strings.

 

[vashkoproimage]

This is my current 48v battery setup. Was planning on adding 8 more battery’s but ran out of space. ? Maybe you see anything I did wrong? It’s 4/0 cable running all though out system. Center stack has input and output cables going to controller. These are agm batteries 140ah. Charge controller charging them all the way to 56.8v and holding voltage there for a while slowly releasing charging current till the end. I have no control of charging parameters on this system. I guess it auto detects battery’s for charging.

 

[Hedges]

Measure charging system behavior (voltage, time, current), compare to specs for the batteries.
Is there a temperature sensor? If not, are they kept at moderate temperature?

The only auto-detect is 12/24/48V. SCC can't know if FLA/AGM/Gel, NiCd, LiFePO4, etc.

We would prefer to have a charge controller with everything settable, and then we set for what is wanted.


I think you have charge controller & inverter connected to bottom 4 batteries, then others daisy-chained. Each string will get a different amount of current due to wire resistance. Connect them diagonally, e.g. to positive terminal of bottom 48V string and negative terminal of top 48V string.

 

[vashkoproimage]

Measure charging system behavior (voltage, time, current), compare to specs for the batteries.
Is there a temperature sensor? If not, are they kept at moderate temperature?

The only auto-detect is 12/24/48V. SCC can't know if FLA/AGM/Gel, NiCd, LiFePO4, etc.

We would prefer to have a charge controller with everything settable, and then we set for what is wanted.


I think you have charge controller & inverter connected to bottom 4 batteries, then others daisy-chained. Each string will get a different amount of current due to wire resistance. Connect them diagonally, e.g. to positive terminal of bottom 48V string and negative terminal of top 48V string.

I see what you’re saying. Currently the center/middle rack has the negative and positive connected. Will it affect charging the way I have it setup? I should have done that from the start, was planning on finding space for remaining battery’s.

 

[Hedges]

The middle battery would get more discharge/charge.
Diagonal corners should be a bit better although not perfect.
If 2 or 4 strings, there are ways to make wire length identical. To do it with 3, I think that would take 3 matched wires.
Right now I have just single strings of AGM, will be doing one with 2 strings (2p8s x 6V for 48V).
One of my inverter setups has 3, but balance there isn't so important.

Recharging sufficiently, and with proper parameters, is the most important.

Are these around 100Ah, so 300 Ah 48V, 15 kWh?
Probably wants around 0.2C, 3kW charge rate.
Is this charged by your 6x 535W panels? Only hits 0.2C under ideal conditions.
Lower charge rate is OK for my batteries according to manual, but the recommend longer absorption.
And of course you need to supply loads as well, and recharge something like 120% of what was drawn from the batteries.
More panels would probably help, especially during shorter winter days. Unless you don't use much.

 

[vashkoproimage]

The middle battery would get more discharge/charge.
Diagonal corners should be a bit better although not perfect.
If 2 or 4 strings, there are ways to make wire length identical. To do it with 3, I think that would take 3 matched wires.
Right now I have just single strings of AGM, will be doing one with 2 strings (2p8s x 6V for 48V).
One of my inverter setups has 3, but balance there isn't so important.

Recharging sufficiently, and with proper parameters, is the most important.

Are these around 100Ah, so 300 Ah 48V, 15 kWh?
Probably wants around 0.2C, 3kW charge rate.
Is this charged by your 6x 535W panels? Only hits 0.2C under ideal conditions.
Lower charge rate is OK for my batteries according to manual, but the recommend longer absorption.
And of course you need to supply loads as well, and recharge something like 120% of what was drawn from the batteries.
More panels would probably help, especially during shorter winter days. Unless you don't use much.

All my wires are the same length except for the upper side string wires. I had to make few inches longer because of the height difference of the shelf built.

These are 135-140ah battery’s. So I have around 20,736wh available. At 50 percent discharge 10,368wh available as current setup.

Yes these are charged by current 4 panels connected. Should be 6 but 2 unplugged. Today for example it started charging at around 7:30am. By 12pm they were fully charged and charging watts were dropping slowly while holding the voltage 56.8v. That’s the voltage my agm should be charged. Never over 14.4v because they start gassing.