2x100W in parallel issue.

[rafi]

Hello!

I have an issue with the solar system I am trying to install in my RV. I purchased 2x100W panels from HQST and a morningstar 30 amp charge controller (with lcd screen).
I installed the solar panels in parallel to get the same 12V voltage and supposedly add the amps from both panels.

THe problem is I am getting right now with both panel a reading of about 4 amps jumping up and down of solar amp. It's not a lot and the jumping around seems weird (sun is shining 100% right now).
When i disconnect 1 panel from the pair, I get a very stable 5.2 AMPs on the screen. (both panels outputs about 5.2 amps on their own)

What could be wrong ? I dont get it I used standard Y MC4 connectors to link them up, and i tried other Y connectors too without any changes.

Thank you!!

[jflorey2]

I have an issue with the solar system I am trying to install in my RV. I purchased 2x100W panels from HQST and a morningstar 30 amp charge controller (with lcd screen).
I installed the solar panels in parallel to get the same 12V voltage and supposedly add the amps from both panels. THe problem is I am getting right now with both panel a reading of about 4 amps jumping up and down of solar amp. It's not a lot and the jumping around seems weird (sun is shining 100% right now).

You are most likely seeing the charge controller cycle. If you have a PWM controller it will turn on (full current) and off (no current) rapidly to maintain the right voltage. To your meter it will look like the current is "jumping."

[rafi]

it still seems strange that i get less solar input amp on the reader of the charge controller with 2 panels than with 1 ?
My problem is with 1 panel i get 5.2 amps, with 2 conntected , I get 4 amp jumping.
I tried to look for the voltage input on the charge controller (full sun, winter) : with 1 panel 18.5V, with 2 in parallel 19.7
Specs for my panel: Optimum Voltage : 18.5
open circuit : 22.5V
100W

hope it helps

[jflorey2]

it still seems strange that i get less solar input amp on the reader of the charge controller with 2 panels than with 1 ?

You're not.

One panel cannot quite push the voltage to the setpoint - so you see 5.2 amps.

Two panels do push the voltage to the setpoint - so you see 10.4, then zero amps, then 10.4A. But since your meter isn't fast enough to catch all that, you see 3.1A 1.8A 5.1A 0.8A 4.6A etc. on the display.

My problem is with 1 panel i get 5.2 amps, with 2 conntected , I get 4 amp jumping.
I tried to look for the voltage input on the charge controller (full sun, winter) : with 1 panel 18.5V, with 2 in parallel 19.7

What is the voltage on the battery with 1 and 2 panels connected, and what is the setpoint?

[Sunking]

If your controller is MPPT, your first mistake was wiring them in parallel, and completely defeated the purpose of a MPPT Controller. Other than that as Jeff indicates, nothing is wrong.

If your controller is PWM means you must use very expensive low voltage panels wired in parallel and only have a 130 watt system.

Hint:

PWM Output Current = Input Current
MPPT Output Current = Panel Wattage / Battery Voltage
Power = Voltage x Current.

So do some math. Look at your panels Imp current rating. For a 100 watt low voltage battery panel should be around 5.5 amps with a Vmp of 18 volts. Two panels in parallel on a PWM controller gives you 11.0 amps and with a PWM controller means its maximum output = 11 amps x 12 volts = what?

Did you answer 132 watts?

With MPPT your max output would be 200 watts / 12 volts = 16.7 amps.

One more Q/A for you that might help. How many amps does a charged battery draw from the charger?

0 AMPS, and 0 amps x 12 volts = 0 watts.

Now with a MPPT controller you could wire your panels in parallel if you do not know better. You wil not gget quite as much power because you doubled the current on the input wiring, thus double your wire losses on the input. To overcome those losses and for safety you have to use larger more expensive wiring. Additionally with with more than two strings in parallel requires you to use expensive combiners and fuses. panels in parallel.

Now you understand why I said if your controller is MPPT, you threw all those advantages, money, and some power away.

[Wy_White_Wolf]

Discharge the battery some or turn on loads that total at least 10 amps and then tell us what the system does.

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