Voltage from panels ok?

[ddw867]

Hello, new small off-grid solar setup in progress. Have 4 100 watt panels mounted and wired in parallel, just checked voltage from the leads that will go into the charge controller and am getting a little over 20 volts, like about 20.3.
I have a 30A Wanderer charge controller and just want to make sure i'm not doing something wrong
There's 2 Renogy panels I bought new and 2 Sungoldpower panels I got from a friend moving away, here are the specs:

SUNGOLDPOWER SG-100WM PANELS:

Production tolerance: ±3%

Maximum Power Current (Imp): 5.24A

Maximum Power Voltage (Vmp): 19.1V

Short Circuit Current (Isc): 5.57A

Open Circuit Voltage (Voc): 22.1V

Maximum System Voltage: 800V

RENOGY PANELS:

Maximum Power at STC: 100W

Open-Circuit Voltage (Voc): 24.3V

Short-Circuit Current (Isc): 5.21A

Optimum Operating Voltage (Vmp): 20.4V

Optimum Operating Current (Imp): 4.91A

Maximum System Voltage: 600V DC

Was just wondering if this is normal, I guess I was expecting only 12v. Thanks!

 

[chrisski]

Sounds good with 4 panels wired in parallel.

In my signature block there’s a link to panels in parallel and the math behind mismatched panels if you want to see how much is lost. I doubt it’s 20 watts so with the panels you have should be fine.

 

[ddw867]

Ok, thanks!

 

[ungrounded]

Hello, new small off-grid solar setup in progress. Have 4 100 watt panels mounted and wired in parallel, just checked voltage from the leads that will go into the charge controller and am getting a little over 20 volts, like about 20.3.
I have a 30A Wanderer charge controller and just want to make sure i'm not doing something wrong
There's 2 Renogy panels I bought new and 2 Sungoldpower panels I got from a friend moving away, here are the specs:

SUNGOLDPOWER SG-100WM PANELS:

Production tolerance: ±3%

Maximum Power Current (Imp): 5.24A

Maximum Power Voltage (Vmp): 19.1V

Short Circuit Current (Isc): 5.57A

Open Circuit Voltage (Voc): 22.1V

Maximum System Voltage: 800V

RENOGY PANELS:

Maximum Power at STC: 100W

Open-Circuit Voltage (Voc): 24.3V

Short-Circuit Current (Isc): 5.21A

Optimum Operating Voltage (Vmp): 20.4V

Optimum Operating Current (Imp): 4.91A

Maximum System Voltage: 600V DC

Was just wondering if this is normal, I guess I was expecting only 12v. Thanks!

Your panel specs are 22 and 24volts. Why would you expect 12 volts? Looks about right.

 

[Hedges]

Is your battery 12V? 30A SCC x 12V = 360W.

Wanderer Li 30A PWM Charge Controller

The Renogy Wanderer-Li is a 30A PWM solar charge controller that incorporates efficient PWM crediting boost battery life and improving system performance.

www.renogy.com

https://www.renogy.com/content/RNG-CTRL-WND30-LI/WND30-LI-Datasheet.pdf

30A PWM charge controller. For lithium, it says.

An MPPT charge controller you can usually overpanel, but PWM it is important not to.
These four should total about 22A, so OK there.

25V max. To avoid exceeding that in freezing weather, I'd rather not use panels above 21.6Voc (at 25 degrees C.)
Ironic that the renogy brand panels have highest Voc

Open-Circuit Voltage (Voc): 24.3V

With all four paralleled, voltage may be pulled closer to the lower ones. You read still lower, but likely on a hot day.
It'll be ok in mild weather, but a chance of going slightly above 25V in colder weather.

Happen to know what the battery/BMS can tolerate, in case SCC fails shorted?

An MPPT SCC would be an improvement. Work with higher voltage, you could wire the panels 2S2P, might get a bit more power from them.

 

[ddw867]

Thanks for the replies, it's just a backup system in case of power failure, had a bad ice storm last winter and trees were down everywhere.
I'm using 4 mighty max sealed batteries ML-35-12 so not much power there, its just for running our wireless router and charging laptops, cell phones and TV right now, maybe briefly a fridge or chest freezer. Most of the year, if not all year, it's just keeping the batteries topped off, so an MPPT is probably overkill right now i'm guessing(?)
Next step is possibly a lithium battery so we can discharge it down farther although the system is out on the patio so it won't charge in really cold temps, our wireless security cameras won't below about 20 degrees. Or are solar lithium batteries different?
I'm new to this and just working with what I have at the moment, thanks for your patience and help, much appreciated!

 

[Hedges]

Inverters have a no-load draw, which batteries would have to supply in addition to the loads you want backed up.
If router and other critical loads work off 12V, may be able to power directly from a fused battery connection (not sure if voltage regulation is important, probably just feeds regulators.)

To power the freezer you could connect an inverter temporarily.

I have an AC backup system that powers the house, but want to set up a 12V DC backup fed by both that and PV panels, for our router & modem.

Sealed lead acid is good for backup system. KISS. 35Ah x 4 = 140 Ah. What does manual say about charge current and voltage? Adjust SCC to match voltage. If 0.2C, then 28A charge rate, similar to your system.

If you orient some panels towards morning sun and some towards afternoon, it would start charging earlier and keep it charged later, so battery doesn't drain as much overnight.

SCC "Discharge limit voltage 10.8V" - can that be adjusted? Best to select what depth of discharge you want and have loads shut down to limit it, like 50% or 70% DoD. If not adjustable, determine current draw by loads and calculate what it would be, see if OK. Or operate on solar for a day, measure battery voltage in the morning.

Calculate PV production summer & winter, must be sufficient to power loads and recharge battery, including additional ~ 30% of recharge for battery round-trip inefficiency.

"Most of the year, if not all year, it's just keeping the batteries topped off"
How does it switch between grid powering electronics and PV/battery powering them?

 

[Rednecktek]

With 400w a MPPT really starts showing its value. You don't even need a fancy one, just a 40a or higher to turn solar DC into battery DC.

Spend the little bit more on a LFP battery with low temp protection and mount it in a cheap cooler. Unless it gets butt-nugget cold out there the battery should be able to generate enough heat to keep itself above freezing. If you want to buy yourself some safety, get a 12v heating pad and wire it to a basic thermostat to kick on at 2c and off at 10c or the like. A 20 or 30w pad under the battery should be more than plenty and it's a pretty cheap way to get a LOT more capacity.

With your current batteries you're only effectively getting 70Ah/840Wh with all 4 batteries. A single LFP will gain you 30% usable power for the smaller & lighter battery.