testing solar cells

[bcroe]

Bruce can you please attach the design or photos of your jig i will be very grateful

The picture is earlier in this same thread. Those who would rather see (almost) short circuit
current instead of some power delivery, can replace my load resistors with shunts in the
20-50 mv at 5A range, along with a more sensitive voltmeter. Bruce Roe

[Sunking]

The picture is earlier in this same thread. Those who would rather see (almost) short circuit
current instead of some power delivery, can replace my load resistors with shunts in the
20-50 mv at 5A range, along with a more sensitive voltmeter. Bruce Roe

Bruce you do not need a shunt to measure current, just a DVM. The meter provides the shunt. Depending on what type of meter you may not even need to switch leads to test Voc and Isc, just toggle via selector switch.

[inetdog]

It is hard to tell for sure without a schematic but from Bruce's verbal description it sounds like he is separately testing for current in both metalized tabs of a two tab panel. To do this properly he has to have approximately the same repeatable resistance in each of the two (or three?) circuits. That cannot easily be done with a single DMM in ammeter mode.
Instead it requires one load resistor (or one shunt) per circuit, and a switch to move the DMM, on a voltage range, from one place to another in the circuit.
Whether the information obtained this way is worth the added complexity depends on just how much you want to know about each cell that you are testing, beyond just the single Voc and Isc with all tabs of the same polarity on the cell connected in parallel.

[bcroe]

It is hard to tell for sure without a schematic but from Bruce's verbal description it sounds like he is separately testing for current in both metalized tabs of a two tab panel. To do this properly he has to have approximately the same repeatable resistance in each of the two (or three?) circuits. That cannot easily be done with a single DMM in ammeter mode.
Instead it requires one load resistor (or one shunt) per circuit, and a switch to move the DMM, on a voltage range, from one place to another in the circuit.
Whether the information obtained this way is worth the added complexity depends on just how much you want to know about each cell that you are testing, beyond just the single Voc and Isc with all tabs of the same polarity on the cell connected in parallel.

The above pretty much describes it. I wanted to test a lot of cells, and quickly. Connecting and
disconnecting leads is time consuming; meanwhile the light is heating up the cell & changing
the reading. Turning the bulb on and off burns it out faster.

Even just switching an ammeter around is a problem, because the high currents
and low voltage means standard switch resistance isn't negligible anymore. Bruce Roe

[Sunking]

My bad guys, should have looked at the testing rig. My only question left is what can you tell from an artificial light, rather than a reference source of known w/m^2 or noon sun?

[SunEagle]

My bad guys, should have looked at the testing rig. My only question left is what can you tell from an artificial light, rather than a reference source of known w/m^2 or noon sun?

I think bruce is looking for consistency from one cell to another as opposed to V & I mp of the cell. At least if all the cell "test" have similar results then you can "assume" (I hate that word) they will work if properly connected together.

[elhifnawyplast]

schematic please

without a schematic it is not perfectly clear for me,if please attach a schematic for testing or sorting a 4.5w solar

[bcroe]

without a schematic it is not perfectly clear for me,if please attach a schematic for testing or sorting a 4.5w solar

Try this. The load is chosen to put the voltage around 80% of Vmp on a good cell. Letting
the voltage rise a lot higher won't draw enough current for the best test. A couple 0.1 ohm
resistors (in parallel) are generally easier to find than a single 0.05 ohm 3 watt resistor.
Voltmeter wires are attached directly to resistor wires to avoid wiring drop error (Kelvin
connection). For reading cell overall, I use 100 ohm resistors to average the lead voltages.
Bruce Roe

[elhifnawyplast]

schematic

Thank you for the schematic you sent to me,i am trying to understand it as much as i can as i am a mechanical Engineer and my electrical knowledge is limited