Checking Used Solar Panels

nigtomdaw · October 2007

Hi, Ive just bought 8 Sharp 162 Watt solar panels that are 1 year old. Apart from physical inspection what is the best field way to check each unit. I can take a 24 volt battery and I have a very good mm with DC clamp. Just like the experts to run through a series of tests so I avoid costly errors. Ive a 7 hour one way drive to get these panels and it will be buyer beware so any help will be apprieciated. Model number and spec for sharp panel is

ND-162E1F
Pmax 162w
Power +10% -5%
Voc 28.8
Isc 7.95A
Vpm 22.7
Ipm 7.14A
Max System Voltage 100v

Next question having just typed in these figures and Im now aware these panels came from a large array system in Morrocco are these panels suitable for my 24 volt system the Voc and Vpm look low for 24v nominal voltage or will I need to run these through a MPPT CC.

Thanks Nigel

nigtomdaw · October 2007

Re: Checking Used Solar Panels

Max System Voltage should read 1000v not 100v edit wouldnt work ?

mike95490 · October 2007

Re: Checking Used Solar Panels

Test each panel individually, open circuit should show close to Vmax (depends how hot it is)
and then swap your meter leads around, and configure for amps, measure amps the panel can put into the meter, and let it run for about a minute. You should have the SAME amps after a minute. Amps should be 70%- 80% of rated amperage, when perpendicular to sun, unless you have a lab & STC setup, would be 100% Record for each panel. Lather, Rinse, Repeat.

Note, if using a DC clamp, short the panel + to - and measure short circuit current in the loop.

Do 1 panel at a time.

Voltage will droop as panels heat up, but amps should stay same, if lighting (sun) is steady. Amps fluctuating is not good.

No need to haul a battery along

(when EDITing a post, use the [GO ADVANCED] and then the edit will work.

niel · October 2007

Re: Checking Used Solar Panels

i'll just mention 2 things in addition here when measuring current.
1> the leads of some meters could add a voltage drop if they are cheap or old and could reduce the net current seen by the meter.
2> keep in mind that you will be holding a sustained short circuit and to make very sure your meter can handle the amount of current you are placing through it and note that some things could get warm or hot.

nigtomdaw · October 2007

Re: Checking Used Solar Panels

Mike..... Thankyou very much. I think Ill do the current test with the clamp meter, its very accurate
Neil..... Thanks also the meter I use is only 2 years old it was a present from my son he is a qualified electrician and the unit was over $300. The Dc amp clamp hasa 40 amp and a 400 amp dc range and is very accurate and reliable.

They only concern about these panels appears to be the Max Voltage ratings I intend to use a MPPT controller with them so no real problem and thus probably wire them at 48volts at 8 x 162 watts = 1296 watts @ 24v = 54 amps should be OK with a XW or MX .

crewzer · October 2007

Re: Checking Used Solar Panels

Nigel,

The MX60 is rated to handle a 1,600 W STC array with a 24 V battery system. The XW is of vitually identical electrical specs, so I would expect it to comfortably handle such an array size as well.

Either one will handle your opportunity 1.3 kW array without any difficulty. Assuming the 22.7 Vmp spec is correct, just configure your array in a 2 x 4 configuration (45.4 Vmp x 28.6 A Imp) and you'll be good to go.

HTH,
Jim / crewzer

Solar Guppy · October 2007

Re: Checking Used Solar Panels

crewzer wrote: »

The XW is of vitually identical electrical specs, so I would expect it to comfortably handle such an array size as well.
Jim / crewzer

Bit of a nitpick, the WX is thermally superior to the MX60 and can handle higher loads at large Vin/Vout differentials ... hence the thermal tempature at which the "identical" specs are listed at.

nigtomdaw · October 2007

Re: Checking Used Solar Panels

Sorry SG that went airborne on me please explain?

BB. · October 2007

Re: Checking Used Solar Panels

I believe that Solar Guppy is saying that once the MX 60 gets in a warm room, it starts reducing its current capacity (derating) to prevent over heating...

Whereas the new WX can, with the same electrical specs. (current/voltage) operate at a higher ambient temperature (without fans) before it starts to derate (to prevent damaging overheating).

Also, the Vin/Vout ratios... Vin (Panels) can be a variable, but high voltage, but the Vout is fixed by battery voltage... Since the charge controller takes Iin*Vin=Power of Solar Panels=Iout*Vout for battery charging--a high Vin means that Iin is relatively low (low current), but when charging batteries at a lower Vout voltage, Iout must increase (example 120vdc*10amps in = 1,200 watts = 24 VDC * 50 amps out to battery--just made up numbers--don't know the WX specs.)...

Heating is (I^2)*R... So as the current rises, the heat generated goes up by the square (10 amps input vs 50 amps output, 5x the current but 25x as much heat loss).

That is about as much tea leaves as I can read in SG's post... It is difficult to design a high efficiency (and cool running) charge controller (or inverter) as the things that make for high efficiency (big FETs and Lots of large copper wire) are pretty costly (and, for example, labor intensive to wind some types of transformers--like toroids, if used in the WX) and sell it for a competitive price.

-Bill

Checking Used Solar Panels

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