Solar Panel Current

[Tom Mathews]

What is the typical % of the ISC current should a solar panel generate?

I have a brand new mono type solar panel. On a sunny day with the panel is fairly angled to the sun, I measured the input current coming directly from the solar panel over a 10 awg 10 ft wire is 4.6a. Given the ISC is 5.81a, is the 4.6a that I measured is considered low? 4.6a is only 79% of the 5.81a ISC. If so, something wrong? Thanks.

 

[Bud Martin]

All the panel spec are done in the lab condition with calibrated equipment.
Did you do the Isc test by connecting the panel cables directly together and use the Clamp-on DC Amp meter to take the reading?
I do not think you have problem with the panel since you do not have perfect setup to do the test.

 

[time2roll]

Yes on a perfectly clear day, close to solar noon, pointed at the sun.... the panel should produce very close to Isc.
Could be your connection or measurement.

 

[Tom Mathews]

All the panel spec are done in the lab condition with calibrated equipment.
Did you do the Isc test by connecting the panel cables directly together and use the Clamp-on DC Amp meter to take the reading?
I do not think you have problem with the panel since you do not have perfect setup to do the test.

Yes, I use the clamp-on and the panel is connected to a portable charger and charging a battery. Wondering what is your current and ISC?

 

[Supervstech]

Yes, I use the clamp-on and the panel is connected to a portable charger and charging a battery. Wondering what is your current and ISC?

ISC and MPPT amps will be far different. Keep in mind, ISC is a dead short amp production value. Near zero volts... and maximum amps. Measuring a load your amps multiplied by the solar output volts would show you the watts. I bet it is fairly close to the rated watts of the panel.

 

[Tom Mathews]

Yes on a perfectly clear day, close to solar noon, pointed at the sun.... the panel should produce very close to Isc.
Could be your connection or measurement.

I stripped down everything to bare minimal. One solar panel connected to a portable solar charger. I used clamp-on between solar panel and the charger and measurement shows 4.6a. Even the portable charger show only 65w input out of that 100w panel. Perhaps, solar panel is extremely inefficient? Or is this normal range? I brought it brand new. Wondering what is your current v.s. ISC? Thanks in advance.

 

[Bud Martin]

Yes, I use the clamp-on and the panel is connected to a portable charger and charging a battery. Wondering what is your current and ISC?

You will short the PV cables directly together, I.E. if it has MC4 then you just plug them in together and read the current. The way you are doing is not short circuit current reading, you were measuring the load current being pulled from the panel

 

[fratermus]

Even the portable charger show only 65w input out of that 100w panel. Perhaps, solar panel is extremely inefficient?

Panels will very rarely make their lab-rated output in the real world; there are many complicating factors.

Example: when the battery is full and floating (no loads) the controller might demand only a few watts from the panel. My batteries are in late absorption right now accepting 33w. Add in about 75w of additional loads and my system is idling along making 14.5% of rated wattage. Completely normal for my system under these conditions.

 

[JeepDaddy]

Imp is a better number to use than Isc for testing purposes. Isc is not a meaningful number as it is the current during a short circuit (at 0 volts). Imp is the current at optimal power output.

 

[mikefitz]

measurement shows 4.6a. Even the portable charger show only 65w input out of that 100w panel.

If the solar controller is a PWM type this is to be expected, typically you lose about 30% of the panels output.

With a MPPT controller at the same level of input current (4.6A), you could expect over 80 watts of power.

Mike