Junction two solar panels

[wander]

Hello,

I have a question about the connection of two solar panels on the same controller.
The problem is that they are different solar panels and measuring the voltage of the first, gave something around 17.3V, 19.4V already presented in the other.

What to do?

System data:
cmp12 charge controller
Stationary Battery Freedom Df1000 12V 70AH
Inverter Morningstar SureSine reverse 300w

Grateful

[Logan5]

if you wire your panels in series for 33.7 volts you will have no problem. that into most "quality" charge controllers will charge a 12 or 24 volt battery bank of the appropriate amp hour rating. I would not wire different voltage panels in parallel.

[wander]

So the best solution for my case is to connect the panels in series? My charge controller will bear this tension?

Data Sheet
• Model: CMP12
• Rated Voltage: DC12V / 24V
• Max Current: 10A
• Full Charge Cut: 13.7V / 27.4V
• Low Voltage Cut: 10.5V / 21V
• Temp compensation: -3mv / ℃ / cell
• Zero Load Loses: ≤20mA
• Min Wire Size: ≤20mA
• Min Wire Size: 2.5mm ^ 2
• Voltage Drop: <210mv

[Logan5]

that is a junk charge controller. not to trust your expensive and heavy batteries on this unit. replace immediately. do not risk your batteries.

[Sunking]

if you wire your panels in series for 33.7 volts you will have no problem. that into most "quality" charge controllers will charge a 12 or 24 volt battery bank of the appropriate amp hour rating. I would not wire different voltage panels in parallel.

Logan it is a Series Voltage regulator like a PWM controller. He can only wire the panels in parallel. However you are correct the box the controller came in, is worth more then the controller.

[garybeck]

Hello,

I have a question about the connection of two solar panels on the same controller.
The problem is that they are different solar panels and measuring the voltage of the first, gave something around 17.3V, 19.4V already presented in the other.

What to do?

System data:
cmp12 charge controller
Stationary Battery Freedom Df1000 12V 70AH
Inverter Morningstar SureSine reverse 300w

Grateful

it all depends on your battery.
if your battery is 12V then you MUST keep everything in your system at 12V nominal.
if that is the case, do NOT wire your panels in series, unless you have a fancy/expensive MPP controller which is probably not the case for a system this size.

if your system is 12 V, wire the panels in parallel.

if both panels are 12 V nominal, it will work. it is not ideal to have them be sligthly different voltages, but it won't break anything.

ciao,
gary (aka the solar bus guy)

[inetdog]

A PWM CC will pull the voltage coming in from the panels to a volt or two above the battery voltage at the moment. (Almost a fixed offset by CC design but may increase somewhat as the total current increases.)
So any difference from one panel's Vmp or Voc to the other panel's as long as both are above that voltage point will not prevent both panels from contributing full current.

[MisterMechanic]

Don't take a risk of it. Use different controllers for two different solar panel of different voltage.

[inetdog]

Don't take a risk of it. Use different controllers for two different solar panel of different voltage.

That is completely unjustified advice to give in this situation. A two volt difference out of 20 volts is minor.

[jflorey2]

I have a question about the connection of two solar panels on the same controller.

You should connect them both in parallel then connect them to the charge controller. Make sure the Impp of both panels combined is not over 10 amps.