Buying Used Solar Panels
Some commercial arrays will
change out large parts of a system because they have had too many panels fail.
Those that are sold will have been tested, they may or may not perform to full
rating.. but they work and pricing us usually god. Older panels
from an individual that's modernizing their system may be a good deal or not .
Sometimes hear from our clients that they've purchased their solar
panels from someone who is upgrading their system and wants their panels to be
of the same shape, colour and form, and prefers to
start over rather than to display a mix of panels. Solar farms
purchase many pallets of unused panels and sell off cheaply those they did not
install. There are deals to be found!
Panels to
Avoid
Unless you're willing to take a
risk and are prepared to work on them avoid panels with:
- cracked
glass,
- condensation under the glass
- delamination
- broken connections
- discoloration is usually not
a problem
Test PV Panel Output
Before you go to see the panel
check out what the specifications for that panel are and bring them with you.
Bring your multimeter with you, set it to DC volts, and test the used solar panel
by measuring across
the open-circuit (OC) voltage by measuring across the positive and negative terminals.
If you're not going to to the location during the day or on a cloudy day you're
taking your chances. A 12 volt panel should
produces approximately 17 volts in full sun. A Larger 72 cell panel has an
OC voltage of around 47V.
Next measure DC amperes; again
measure the short circuit current in full sun between the positive and negative
terminals. Watts = Amps x Volts. To determine actual
panel Watts multiply the current (amps) you measured by the panel's rated
voltage. If you don't know the panel's rating multiply your measured amps
by 17 for a 12V panel.
You'll need strong alligator
clips on your multimeter, but remember to tap and giggle the panels while you're
testing them. Intermittent problems can be difficult to both trace and
rectify. Unfortunately you won't be able to check the panel under a
variety of temperatures. Some intermittent problems are due to temperature
changes.
For a 12 volt panel, multiply your current by 17
volts to get watts. (17 volts is the rated voltage of most 12 volt panels.)
We can't advise you what a good
price is for used panels. Just remember that 20 year warranty
applies only to the original purchaser. The price had better be a good
deal!
Discolouration
Some panels change colour over
time. Don't concern yourself about panel discolouration.
Measure the
actual power output, and make your decision based on Watts.
Electrical Problems
Of the electrical problems to
resolve yourself of, loose connections on the output leads, corroded connectors and
breaks within the insulated wire at the strain relief, all causing intermittent
problems, are the simplest to rectify. Problems within the panel cells can
be repaired but require substantially more commitment and expertise on the
part of the buyer.
Bypass diodes sometimes
fail as a result of a nearby lightning strike. If they are shorted out
they will significantly reduce the solar panel output. Diodes can be
frequently be changed with relative ease diodes of an amp rating of
the panel; look for a voltage rating of 400V or better.
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