diy solar

diy solar

Did I Make a Mistake?

J

Josh M.

New Member
Joined
Sep 15, 2022
Messages
52
I was just told by a guy running a solar booth at a Self-sustainability Expo this past weekend that I should not have hooked up my 8 100w panels in series because I have a PWM charge controller. As I mentioned in another thread, I have a 60amp PWM charge controller from Eco-worthy. The controller will handle up to 1800w under a 24v system like what I have set up. The owners manual says Max Solar energy input voltage <55v. Max voltage at the battery end <34v. My panels are 12v each and they also say VOC: 21.6v. Not sure if that's relevant.
The guy I talked to said I probably already messed up my charge controller. How would I know if its ruined? There is nothing different showing on the display now than from the day I hooked the system up, and there are no error codes.

Thanks in advance for any help!
 
Josh M. said:
The owners manual says Max Solar energy input voltage <55v.
Click to expand...
8x 100W panels in series is about 8x 17V (136V).
Look on your panels, you will see that the Vmp is NOT 12V (that's a marketing term).

You got good advice.

Is your PWM still working and not smoldering?
 
It "appears" to be working. No funky readout on the display and no error codes popping. Temp has stayed constant from day 1 (obvious variations based on outside temps).

I am asking this because I had described to him that all of a sudden, once the outside temps started dropping below freezing overnight, my batteries are just not lasting through the night like they used to. We are dead in the water by about midnight. The only major change is our furnace in our 5th wheelrv runs more often. I suppose that is probably a big drain on the system.
The other odd change I have seen is that during the day, I carry between 27v and 29v. Typically by 4pm to 5pm, I'm at an average 27v in the batteries. As soon as the sun is off the panels by 5:45pm, the voltage drops dramatically even with only my fridge plugged in. By 7pm, I'm down to about 25v in the batteries.
 
VOC of 21.6V, x 8 = 172.8V
What is the full spec of the panel?
The PWM SCC will supply what the max current the panel can supply, so if your panel is rated at around 5A each and you put them in series, the max charging current will never be more than what the panel deliver, 5A, because it is buck converter topology that converts high Voltage low current to charging Voltage and high current.
MPPT SCC vs PWM SCC
www.cleanenergyreviews.info

MPPT Solar Charge Controllers Explained — Clean Energy Reviews

Solar Charge Controllers are one of the most affordable and effective devices used to charge battery systems using solar. We explain how a MPPT charge controller works and how to select the right size solar charge controller for your solar system.
www.cleanenergyreviews.info www.cleanenergyreviews.info
 
Last edited:
Josh M. said:
It "appears" to be working. No funky readout on the display and no error codes popping. Temp has stayed constant from day 1 (obvious variations based on outside temps).

I am asking this because I had described to him that all of a sudden, once the outside temps started dropping below freezing overnight, my batteries are just not lasting through the night like they used to. We are dead in the water by about midnight. The only major change is our furnace in our 5th wheelrv runs more often. I suppose that is probably a big drain on the system.
The other odd change I have seen is that during the day, I carry between 27v and 29v. Typically by 4pm to 5pm, I'm at an average 27v in the batteries. As soon as the sun is off the panels by 5:45pm, the voltage drops dramatically even with only my fridge plugged in. By 7pm, I'm down to about 25v in the batteries.
Click to expand...
What does the display show for the Battery charging current?
 
Last edited:
If you end up restarting…

Look for a mppt charger you will also want your panels in a series parallel combo -

Something like a Victron mppt 100/50 with panels connected as 4s2p or 2s4p or if you have room for one more panel a 3s3p. IF you have three or more strings in parallel be sure and fuse each string. There are MC4 fuses that will just clip in.

Also, a battery monitor is very good (I would say essential) - something like a Victron Smartshunt or BMV712.

The battery monitor will let you know if the batteries are mostly full or mostly empty. In RV’s it is easy to use more power than what we collect from solar - especially as winter arrives.

Good Luck

Ps - I really like the info you get from the Victron app. Helps to solve problems.
 
If actually connected in series, I would expect voltage to kill the transistors. As soon as the transistors try to turn off.

Disconnect the panels immediately!

"The owners manual says Max Solar energy input voltage <55v"
"Max voltage at the battery end <34v"

"during the day, I carry between 27v and 29v"

Maybe battery voltage never got high enough for SCC to try to switch off. If it did I think it would kill itself.

"8 100w panels in series"

Should be 2s4p, based on the specs you've given us.
 
Last edited:
Bud Martin said:
VOC of 21.6V, x 8 = 172.8V
What is the full spec of the panel?
The PWM SCC will supply what the max current the panel can supply, so if your panel is rated at around 5A each and you put them in series, the max charging current will never be more than what the panel deliver, 5A, because it is buck converter topology that converts high Voltage low current to charging Voltage and high current.
MPPT SCC vs PWM SCC
www.cleanenergyreviews.info

MPPT Solar Charge Controllers Explained — Clean Energy Reviews

Solar Charge Controllers are one of the most affordable and effective devices used to charge battery systems using solar. We explain how a MPPT charge controller works and how to select the right size solar charge controller for your solar system.
www.cleanenergyreviews.info www.cleanenergyreviews.info
Click to expand...
20221117_131628.jpg20221117_131628.jpg
Here is the spec sticker on the back of the panel.
 
Hedges said:
If actually connected in series, I would expect voltage to kill the transistors. As soon as the transistors try to turn off.

Disconnect the panels immediately!

"The owners manual says Max Solar energy input voltage <55v"
"Max voltage at the battery end <34v"

"during the day, I carry between 27v and 29v"

Maybe battery voltage never got high enough for SCC to try to switch off. If it did I think it would kill itself.

"8 100w panels in series"

Should be 2s4p, based on the specs you've given us.
Click to expand...
I believe I'm connected 2S4P. Each 2 panels are connected together, pos on one to neg on the other, then the other 2 pos/neg cables of that pair going into a 4-string combiner box. So, 4 pairs of panels.
 
You need to shut this down. 8 of those panels in series is 172.8vdc open circuit. Your PWM controller is likely damaged, and if you leave it connected your batteries, and other equipment may end up damaged, if they are not already.

You need an MPPT controller that can handle 200+ voltage on the PV
 
Josh M. said:
I believe I'm connected 2S4P. Each 2 panels are connected together, pos on one to neg on the other, then the other 2 pos/neg cables of that pair going into a 4-string combiner box. So, 4 pairs of panels.
Click to expand...

We'll that changes everything. Your first post said 8 in series.

You're good if you have them wired in series/parallel like you just said.
 
Rocketman said:
If you end up restarting…

Look for a mppt charger you will also want your panels in a series parallel combo -

Something like a Victron mppt 100/50 with panels connected as 4s2p or 2s4p or if you have room for one more panel a 3s3p. IF you have three or more strings in parallel be sure and fuse each string. There are MC4 fuses that will just clip in.

Also, a battery monitor is very good (I would say essential) - something like a Victron Smartshunt or BMV712.

The battery monitor will let you know if the batteries are mostly full or mostly empty. In RV’s it is easy to use more power than what we collect from solar - especially as winter arrives.

Good Luck

Ps - I really like the info you get from the Victron app. Helps to solve problems.
Click to expand...
I was looking at that exact MPPT, but unfortunately, I'm stuck with my PWM for now, as my budget is far sort for what I really want and need for this set up. Ultimately, I'd love to have the MPPT, 8 330w grid-tie panels, 3500w Inverter, and 6 12v 210Ah LiFpo batteries.

But, again, budget. So, I'm just trying my best to figure out how to get the most out of what I have, which is 8 100w panels, a 60 amp PWM SCC, 1500w Inverter, 4-string combiner, and 4 12v 105Ah Deep Cycle standard lead acid batteries (hooked up 2S4P).
 
BradCagle said:
We'll that changes everything. Your first post said 8 in series.

You're good if you have them wired in series/parallel like you just said.
Click to expand...
Sorry about that. It wasn't until I read that post I made this reply to about 2S4P that reminded me how I had them hooked up.

So, you say that changes everything. What exactly do you mean by that?
 
That 2s2p is good because you Voc for the system is 21.6 *2= 43.2v. Are those other four panels in a 2s as well? If they are just in 4p your wiring needs changed. All strings need to be wired the same (for Voltage and Amps).

However your PWM charger is not helping you. You need a MPPT charger. You will harvest almost 1.5x as much power if you change out the Solar Charge Controller to a good mppt.

Look at a Victron 100/50 or Victron 150/60. (There are other brands too).
 
Rocketman said:
That 2s2p is good because you Voc for the system is 21.6 *2= 43.2v. Are those other four panels in a 2s as well? If they are just in 4p your wiring needs changed. All strings need to be wired the same (for Voltage and Amps).

However your PWM charger is not helping you. You need a MPPT charger. You will harvest almost 1.5x as much power if you change out the Solar Charge Controller to a good mppt.

Look at a Victron 100/50 or Victron 150/60. (There are other brands too).
Click to expand...
8 panels, wired up in pairs. each pair is connected to one of the 4 ports (pos/neg) in the 4-string combiner box. I was told this is 2S4P.
 
Josh M. said:
It "appears" to be working. No funky readout on the display and no error codes popping. Temp has stayed constant from day 1 (obvious variations based on outside temps).

I am asking this because I had described to him that all of a sudden, once the outside temps started dropping below freezing overnight, my batteries are just not lasting through the night like they used to. We are dead in the water by about midnight. The only major change is our furnace in our 5th wheelrv runs more often. I suppose that is probably a big drain on the system.
The other odd change I have seen is that during the day, I carry between 27v and 29v. Typically by 4pm to 5pm, I'm at an average 27v in the batteries. As soon as the sun is off the panels by 5:45pm, the voltage drops dramatically even with only my fridge plugged in. By 7pm, I'm down to about 25v in the batteries.
Click to expand...
You are likely not getting enough charge into your batteries now that the days are short and the nights are long. The voltage reading during charge can be high without the battery being fully charged as would be if the voltage was at a resting state. Thus the sudden voltage drop once the sun is down.

From your other post"s description the SCC is working OK.
 
Mattb4 said:
You are likely not getting enough charge into your batteries now that the days are short and the nights are long. The voltage reading during charge can be high without the battery being fully charged as would be if the voltage was at a resting state. Thus the sudden voltage drop once the sun is down.

From your other post"s description the SCC is working OK.
Click to expand...
Thanks for the explanation! With my current setup, is there a way for me to get more charge into my batteries?
 
Mattb4 said:
Make sure that you have no shading of the panels between 10am and 4pm.
Click to expand...
There's none at all from10:30am until dark. I just don't have the cable length to get them out of the shade before 10:30. They do get partial sun from about 9:30 to 10:30, just not full sun.
 
Josh M. said:
There's none at all from10:30am until dark. I just don't have the cable length to get them out of the shade before 10:30. They do get partial sun from about 9:30 to 10:30, just not full sun.
Click to expand...
Cable length? This comment intrigues me. How are the panels mounted, and at what tilt angle?

BTW what kind of production (watts) do you get from your solar panels at peak sun? You should be seeing around 75% of rated panel wattage. Thus your 800w worth of panels should be producing around 600w.
 
Mattb4 said:
Cable length? This comment intrigues me. How are the panels mounted, and at what tilt angle?

BTW what kind of production (watts) do you get from your solar panels at peak sun? You should be seeing around 75% of rated panel wattage. Thus your 800w worth of panels should be producing around 600w.
Click to expand...
Panels are mounted on a moveable frame at a 30 deg angle. Not sure on the production number. Is that a reading I should be able to get from my SCC?
 
Most SCC will have a display of PV volts and watts. Some will also tell you charging amps and battery voltage. There are a few that have no display and you would need to use a clamp on amp meter and a DMM to get voltage. W=VA
 
Putting panels in series will not give you more power when using PWM SCC, the charging current will be the current of the panel current rating, as shown in the link I provided, I.E. 100W panel with 5A of current connected them two in series you will only get 5A charging current using PWM.
Do 4p setup and you will see you will get the same charging current as 2s4p.
 
You must log in or register to reply here.

Similar threads

Consumerbot3418
Did the DC Solar engineers make a rookie mistake paralleling the batteries?
Replies
8
Views
513
NevadAdobe
N
S
Help! Inverter not happy.
Replies
8
Views
372
seneysolar
seneysolar
millsan1
I am a solar nerd. Eco-worthy 25w x 2 on my side by side utv
Replies
3
Views
360
millsan1
millsan1
T
What am I doing wrong with setup
Replies
3
Views
170
robbob2112
robbob2112
L
Charge controller problems
Replies
4
Views
236
time2roll
T

diy solar

diy solar
Back
Top