Harbor Freight panels

[sanjosanjo]

I bought two of these Harbor Freight 1.5W panels and I'm getting horrible performance.

http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=44768

In direct sun, with the panel facing the sun I get:

V(open circuit) = 23volts

I(short circuit) = .5mA

I don't know how the current could be so bad.  They are spec'ed to be 150mA.  Does this seems possible?  I get the same performance on both of them.

[johnlm]

I suspect you are doing something wrong on the current measurement.  Did you try another meter?  Try connecting a 10 ohm resistor across the output and measure the voltage across the resistor (you should get around .75 to 1 V or so and then use I=V/R to calculate the current.  I have a couple of those panels and they dont put out what they claim but they will put out about 80 to 90 mA short circuit current.

Johnlm

[tce]

Check your meter setting. Most meters are funny about measuring current. Also, make sure that the angle of the panel to the sun is correct. The panel has to be perpendicular to the sun.

Tony

[ghurd]

Do you have a HF meter?  A new battery may help.

It takes 'Good Sun' to get the rated ma.  It won't do it in the morning, evening, or indoors.

G-

[sanjosanjo]

I'll try the 10 ohm resistor method.

Is it okay to be inside but right next to the window?  I assume that the photons are getting through my window, right?

What's an HF meter?  Mine is a cheapo unit from Sears.  I'm measuring more

[ghurd]

HF = Harbor Freight.

Figured you maybe got a $3 / $12 meter when you got the panels.  Not too bad, but the batteries are often low, and it causes all kinds of strange readings.

The panels will be much happier in direct sun. Aimed straight at the sun.

Cloudy days need maximum exposure to the 'whole' sky.

Some windows restrict the light more than others, but I wouldn't expect very good output indoors either way.

G-

[tce]

What is unusual is the high voltage reading. The wattage formula is W=IxE. If E=23 and I=. 05, your wattage comes close to the rated panel output, considering that maximum output is never achieved unless you are in perfect sunny conditions. The 23 volts also indicate that the panel is getting plenty of light. I suspect that it's either the meter or your method of reading the current.

Tony

[alcul8r]

Tony,

If you are willing to accept open-circuit volts and Short-circuit current in the equation I can get get real good power out of your panels.  

The most power available should be calculated measuring under load.

Rex

[Volvo farmer]

I did an experiment a while back and found that low-e glass definitely drops the available power from a panel. This was with one piece. If you have a modern low-e 2-pane window in front of your panel, the glass is likely hurting your output somewhat.

[Clifford]

Specs:  http://www.harborfreight.com/manuals/44000-44999/44768.pdf

I misread this at first...   But, I think you have your units off...

Reported current is 0.5 Milliamp (short circuit)

I.E.  1/2 of 1/1000 amps...

0.0005 amps.

So,

0.0005 amps * 23 Volts = 0.0115 watts  (11.5 mW)  (less than 1/100 of the rated 1.5 W)

Of course,

(Short Circuit Amps) * (Open Circuit Volts) = (Not a very realistic number, but should be within an order of magnitude (*10) of your target)

So, he is running quite low on the current (by over a factor of 100).

Try connecting the system to a 12V car battery and recheck the Volts and Amps readings (meter between one lead and the battery).  It is possible that your panel doesn't like the Short Circuit Amps reading.

I would vote for double checking the meter reading, & purchasing a new $4 meter at Harbor Freight and trying it out (meter with battery costs about the same as a new battery alone).

Another part that can go bad in the Harbor Freight / Cummings Tools meters is that they have a fuse.  I believe that if you plug the negative into the 10A hole, then touch the + & - to a 12V battery (no matter what the meter is set on), it will instanteously blow the fuse.  The voltmeter may still be accurate, but the the ammeter will not function properly.

I am trying to think of a mechanism that would produce normal voltage and ultra-low amps.

• I am not sure a single bad cell could knock it out like that (without also significantly affecting your VOC).
  
• A bad diode would also likely affect neither or both.
  
• You might get relatively normal VOC in the shade or a cloudy day, but see 1% to 10% Amps.  Perhaps you could have a uniformly bad panel (or bad glass) that would act similarly to a shady day.
  

[tce]

Rex,

I stand corrected. YOu are right. I got caught up in the discussion and didn't notice the decimals in the current reading in the original message. However, short circuit current always reads higher than current under load. So if the meter and panel are working  correctly, under full sun the scircuit current should still provide a high reading. Under load, we would see a drop.....

Tony

[ghurd]

The test resistor would be better at around 180 ohms.

Brand new PVs like those operate at a higher amps.  It falls off in a month or 2.

Into a battery I would guess 120ma when new, 90ma after a few months use.

G-

[farmbo]

northern tool has 12v 1 amp 15 watt panels i bought 16 at $79.99 /free shipping and an earlier purchase of 16 at $99.99/free shipping.all will be hooked up this summer to an xantrex 48v grid tie inverter. now i am looking for tracking equipment. these panels work great...