Need help wiring a 20 year old panel

[ambersun]

I picked up 2 old Mobil RA-220 panels, these have 4 junction boxes on the back of them, one near each corner, with a single lead in each box. its just the metal ribbon from the panel connected to a wire, with no diode. I'm trying to figure out how to wire these up. It seems that one end of the panel is positive and one is negative. each set measures aprox. 9 volts. i was hoping to wire each panel in series to get 18v from each panel. instead i got zero volts. i had it wired with a wire going diagonally across the back to connect the +/- together, and then connected the free + and - to my voltmeter.

I'm not sure if i caused any damage by test wiring them this way. after i disconnected everything i noticed the resistance between the two positives is 0 and same for the 2 negatives. is this normal? do i need to be using any diodes with this type of panel or connection? i think i might have fried something and can just connect the two panels together in series to get the 18v but want to be sure i understand how i should be wiring the diodes if i need to be using them. thanks for any help!

[foo1bar]

I don't think you can damage a solar cell by shorting it out. Which is what I *think* you did.

Do you still get 9V if you go back to what you measured previously? (with any connections you had made undone)

[ambersun]

Yes it's still giving 9v at each connection. There's 2 + and 2 - terminals. Do these need to be connected together with a diode? I'm just confused that I'm able to measure 0 ohms + to + and - to -.

[foo1bar]

Are the two + terminals just connected with a wire?
(ie. two wires both going to the same + connections on the solar cells)

If so, then connecting across the diagonal would be shorting the + and - together.
And I wouldn't expect that to cause damage. It'd be the "Isc" - short circuit current - going through that connection but probably that's not that big a deal.

And *if* that's what you have, that'd mean you have a pair of 9V panels - you can get 18V out of the two of them together, but not 36.

[ambersun]

There are two metal tabs sticking out the top, which are both positive, and two metal tabs at the bottom. It seems the two pairs are internally connected because the resistance is zero between them with no external wiring attached. I wired it to my mppt controller with the two panels in series and got around 15v but only around 1a. So I'm not sure if I need to externally bridge the two hot and ground tabs, or if it's maybe something in the controller keeping the amoerage too low. Controller indicated battery was not fully charged so assuming it's charging in bulk mode.

[foo1bar]

or if it's maybe something in the controller keeping the amoerage too low.

Was it in full sun aimed directly at the sun at solar noon?
15W *might* be expected output, depending on what the light conditions were, and how much the panel has degraded.

Could also be controller picked a poor operating point - not enough info provided to know if the controller is able to operate properly at ~15V input.

[ambersun]

It's an epever tracer 3210a 30a controller with a flooded 12v marine battery connected. I was expecting a power loss as these were originally 220w so maybe 120w each? How much loss is typical after this much time?

[Steve R]

Have the 3210A ... find instructions confusing.
Can anyone help with providing advice on setting up system.
I have a 200w panel tha I will be connecting to a 12v battery box.
Only propose to use it in camping situation and connect and use during daylight hours for re-charging.
Thx Steve