Hi, I bought 2 solar panels 100watt 20v with 5amp max at sticker (mono), I connected it in parallel.

It gave me (both) only 3.5 amp, and some time (after heating up) about 2 ampere, as I expected it should be more than 6 for both of it.
I measured it by millimeter with 10A (short circuit) directly for each panel, only about 1.5 amp for each
and I measured it both as short circuit too.

Is my panels are damaged, do I damaged it, my bad I have no warranty.
Is it kind of bad panels and the vendor cheated me?

Can Bypass diodes be broken and waste power?
do i need that bypass diodes with panel connected in parallel?

I read here in the forum and internet about solar panels and diodes but I am confused, what is my fault.

Thanks in advance.

 

What is the size of one of the panels.
If charging batteries, yes, you will need the diodes.

 

one panel size is 110 * 55 cm (4*9 cells)

 

Is that current with the panels directly facing the noon sun with no haze?

 

it was about 11am, yes facing the sun without shade or cloudy

 

Lets go over how you measure these. By "both" do you mean both panels in parallel? Did you put your meter directly across the panel output to measure the short circuit current?

I would back up and measure each panel in turn. This checks if say one works but the other is stealing some current.

Also, what does the open circuit voltage read?

The diode is a series diode between the raw solar panel and it's output. While this is a source of power loss it is typically part of the panel. It is actually common to use a solar panel to directly charge a lead acid battery directly just depending on this diode to keep the battery from discharging at night back into the panel.

 

Lets go over how you measure these. By "both" do you mean both panels in parallel? Did you put your meter directly across the panel output to measure the short circuit current?

Yes, and i am afraid that damaged my panel?

But i measured it alone, each one, one gave me 1.8 other 2.2amp maximum

Also, what does the open circuit voltage read?

Open voltage 21v

 

the sun must be 90 deg to the panel.
My 100W panels Put out 60W new and 5 years later 35 to 50 W
Also the wattage was taken at 14v charging the batteries, not shorted I never tested them shorted so I don't know.
panel current at 14v was 3 to 4 amps depending on which of 45 panels I was testing

 

Connecting a short across a solar panel is the recommended way to make it safe for maintenance. It will cause no damage to the panel.

Member N11778 Just posted his solar system he has been running for several years. He also reports the actual power he gets is around 40% of the exaggerated marketing spec.

I suggest you make nice to him then ask him a boat load of questions. ;-)

 

Comparing my 15 W panel by size to yours, you might expect about 36 W. Loaded =15 V @ 2.4 A ??