How to optimize what I already have??

B3nn

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Oct 26, 2021
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18
So I built a backyard office. I'm a software engineer and maker.
I have 3d printers, laser cutter, multiple computer screens, a mini bar fridge and a few small electronics.

I have a 12v system.
4* 100w 12v panels in parallel
400w 12v wind generator (not connected yet)
A 40a 12v/24v charge controller
Connected to 2* 200ah agm batteries in parallel
A 2000w 12v pure sine wave inverter.

I live in a place that's often fog covered. During foggy days I get a couple amps of charging all day.
On sunny days I have seen up to 16amps of charging if I'm lucky.

Is there going to be any benefit to switching everything to be in series and swapping my inverter for a 24v inverter?

Or any other suggestions to make this a more capable system?

I also have 2 portable lithium battery packs that are 777wh each, that I have started plugging things into, then plugging them into my solar system.
That way if the power goes out then my critical items have plenty of time before they lose power.

I also have a pro-logix 20a charger that runs from my house (which is also solar but not off-grid) and it overheats often and turns itself off as a safety feature.
 

smoothJoey

mumble...
Joined
Nov 30, 2019
Messages
9,317
So I built a backyard office. I'm a software engineer and maker.
I have 3d printers, laser cutter, multiple computer screens, a mini bar fridge and a few small electronics.

I have a 12v system.
4* 100w 12v panels in parallel
400w 12v wind generator (not connected yet)
A 40a 12v/24v charge controller
Connected to 2* 200ah agm batteries in parallel
A 2000w 12v pure sine wave inverter.

I live in a place that's often fog covered. During foggy days I get a couple amps of charging all day.
On sunny days I have seen up to 16amps of charging if I'm lucky.

Is there going to be any benefit to switching everything to be in series and swapping my inverter for a 24v inverter?

Or any other suggestions to make this a more capable system?

I also have 2 portable lithium battery packs that are 777wh each, that I have started plugging things into, then plugging them into my solar system.
That way if the power goes out then my critical items have plenty of time before they lose power.

I also have a pro-logix 20a charger that runs from my house (which is also solar but not off-grid) and it overheats often and turns itself off as a safety feature.
Since the devil is in the details please post product links for
panels
wind generator
charge controller
agm batteries
inverter

Also a picture of the setup and a topo diagram would be helpful
 

time2roll

Photon Sorcerer
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Mar 20, 2021
Messages
2,222
No I don't think 24v will make anything fog resistant. If the fog tends to lift in the afternoon it could help to face the panels more to the west to get the afternoon sun. Otherwise you need more battery and more panels to get you through the days of less sun.
 

B3nn

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Joined
Oct 26, 2021
Messages
18
No I don't think 24v will make anything fog resistant. If the fog tends to lift in the afternoon it could help to face the panels more to the west to get the afternoon sun. Otherwise you need more battery and more panels to get you through the days of less sun.
For sure!
Not trying to be fog proof. Just making sure I'm optimal before buying more panels and batteries.

And if I end up swapping batteries, then I was going to weigh out switching to lithium. I don't believe there's a way to run agm and lithium together
 

B3nn

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Oct 26, 2021
Messages
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This sounds too small for your setup.
The fridge actually hasn't.cause any issues.

But I agree I need a bigger system, I just want to make sure I'm being the most efficient before adding panels. I only have so much real estate for panels. So just looking for efficiency tips for my setup.
 

smoothJoey

mumble...
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Nov 30, 2019
Messages
9,317
I see you have 2 different kind of panels.
Hopefully you have 2 of 1 kind and 2 of the other.
Depending on the wire used and the length of the runs you might be able to reconfigure you panels to 2s2p to decrease the voltage drop between the panels and the solar charge controller.
I sure there a bunch of small tweaks we can suggest but that will have to wait for the diagram.
 

B3nn

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Joined
Oct 26, 2021
Messages
18
Ya. I bought them in pairs.
The first pair wasn't sold anymore so I bought the same 12v 100w with the second pair, thinking that's what mattered to have match.

What's 2s2p. The cable that goes from the charge controller to the panels is 20 ft.

And I connected the panels with splitters. So all the positives merge into one and all the negatives merge into one.
 

smoothJoey

mumble...
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Nov 30, 2019
Messages
9,317
Ya. I bought them in pairs.
The first pair wasn't sold anymore so I bought the same 12v 100w with the second pair, thinking that's what mattered to have match.

What's 2s2p.
Its a short form notation for 2 strings comprised of 2 panels in series.
The cable that goes from the charge controller to the panels is 20 ft.
I will guess the wire is 10 awg but please confirm.
Also will guess that the voltage per panel will be ~20 volts and the typical amperage is 5 amps.
That makes the voltage drop .2 volts on 20 volts vs .2 volts on 40 volts.
2 string of 2 panels in series is slightly more efficient.
Not a world changer :)
4 panels in series is a bit close to the solar charge controller's max voltage so I will leave that on the table.
 

Hedges

I See Electromagnetic Fields!
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Mar 28, 2020
Messages
8,397
The fridge actually hasn't.cause any issues.

But I agree I need a bigger system, I just want to make sure I'm being the most efficient before adding panels. I only have so much real estate for panels. So just looking for efficiency tips for my setup.

I think he meant a mini-bar fridge doesn't hold enough booze ;)

I see the battery spec says 60A max charge rate (0.3C)
Not sure its preferred rate; my AGM wants 0.2C
You have two batteries in parallel, 400 Ah, and 16A charge is 0.04C
Many more panels would be good.
 

B3nn

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Oct 26, 2021
Messages
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I think he meant a mini-bar fridge doesn't hold enough booze ;)

I see the battery spec says 60A max charge rate (0.3C)
Not sure its preferred rate; my AGM wants 0.2C
You have two batteries in parallel, 400 Ah, and 16A charge is 0.04C
Many more panels would be good.
What's 0.4C?
 

B3nn

New Member
Joined
Oct 26, 2021
Messages
18
Its a short form notation for 2 strings comprised of 2 panels in series.

I will guess the wire is 10 awg but please confirm.
Also will guess that the voltage per panel will be ~20 volts and the typical amperage is 5 amps.
That makes the voltage drop .2 volts on 20 volts vs .2 volts on 40 volts.
2 string of 2 panels in series is slightly more efficient.
Not a world changer :)
4 panels in series is a bit close to the solar charge controller's max voltage so I will leave that on the table.
Ya. That cable is 10 awg.

Not sure I follow the rest of what you said though ....
At you saying to put each pair of panels into its own series. And then parallel the two series??
 

12VoltInstalls

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Jan 18, 2021
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Many more panels would be good
If I were you I’d max that controller out with like 4 or 5 two-in-series strings that provide 24V to the controller and hits the batteries with lots of amps at 12V.
I’m running a 400W system myself but I have 5 fla batteries which is just about enough - in summer. I think you need two more batteries with the extra solar and you’ll be better off by a lot.

I don’t think the foggy days can be fixed but more batteries is more headroom and the amphours of input from more wattage will recover them nicely on good days. Low voltage for long periods is what kills lead batteries
 

Hedges

I See Electromagnetic Fields!
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Mar 28, 2020
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What's 0.4C?

Charge (or discharge) rate per hour 0.4 x battery Ah capacity.
That would be 40A per 100 Ah of battery.
Yours isn't at 0.4C, rather 0.04C

You have 2x 200 Ah 12V batteries for 400 Ah 12V
16 amps you say - 16A / 400 Ah = 0.04C

Sealed lead-acid batteries should be OK with a range of charging rates, although for my SunXtender, it says if charged at less than 0.2C then modified absorption cycle needed to get them fully charged. Check detailed documentation for yours. After charging to end of day, disconnect batteries and let sit a few hours, then check resting voltage vs. documentation to see if they did get fully charged.

The "C" rate for discharge also affects what voltage is seen vs. SoC, and how much capacity can be used before voltage gets too low (partly due to voltage drop across battery internal resistance at high current, partly I guess due to chemistry which I don't have an understanding of.)

For lead-acid, you need to get them completely, fully charged periodically if not every single cycle.
You should limit depth of discharge, and recharge soon rather than sitting discharged.
Cycle life depends on depth of discharge, although down to 70% DoD or so, number of Ah per cycles x number of cycles is fairly constant. Down towards 100% DoD, what you get from the battery is reduced.
The trick is how to measure DoD and shut off loads to avoid completely discharging. Some inverters have a low-voltage shutoff, which isn't a perfect measure (varies with temperature and current draw.)
Simplest is to size the system so overnight draw won't be too low, and PV will fully recharge in the day. Then you still have to address inadequate recharge in winter or poor weather.
 

Hedges

I See Electromagnetic Fields!
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Messages
8,397
At you saying to put each pair of panels into its own series. And then parallel the two series??

That should work.
SCC spec says "Max Solar Input Voltage: 100 VDC" so two panels in series x Voc of panels is well below that limit.
Vmp of panels is 17.47V and 18V, so all 4 in parallel or 2s2p are matched well.

SCC will require PV input to be somewhat above battery voltage. Not sure how much for this model. Some need 2V, some need 5V headroom.
PV panel Vmp drops lower when hot.
AGM batteries need higher absorption voltage than FLA. Don't see it listed on the page, but probably 14.5V
Connecting the two panels of one brand in series, two of the other brand in series, then those two in parallel (2s2p) ensures voltage is quite sufficient for charging a 12V battery.
 

B3nn

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Joined
Oct 26, 2021
Messages
18
That should work.
SCC spec says "Max Solar Input Voltage: 100 VDC" so two panels in series x Voc of panels is well below that limit.
Vmp of panels is 17.47V and 18V, so all 4 in parallel or 2s2p are matched well.

SCC will require PV input to be somewhat above battery voltage. Not sure how much for this model. Some need 2V, some need 5V headroom.
PV panel Vmp drops lower when hot.
AGM batteries need higher absorption voltage than FLA. Don't see it listed on the page, but probably 14.5V
Connecting the two panels of one brand in series, two of the other brand in series, then those two in parallel (2s2p) ensures voltage is quite sufficient for charging a 12V battery.
Ya. On the charge controller it says there's 18v input. I assumed that was what it was reading from the panels at real time. But now I'm questioning if that's what it is, or if it's the max option for my config
 
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