You can short circuit a PV panel indefinitely no worries at all mate :) - Page 1
Forum section: electronics / beginners

author: @rt
author_rank: Super Contributor
timestamp: September 22, 2020, 11:07:54 am
content: Otherwise I lost a bet/argument, etc.I think you can short circuit a PV panel safely because the panel and it’s wiring (including cell interconnects) couldn’t tell any difference between having it’s output shorted,or providing it’s maximum current to charge a battery.However, later it occurred to me that a typical load such as a charge controller and battery would dissipate some heat, so now I’m not sure if that same heat wouldn’t be dissipated in just the PV panel and it’s cabling if it were short circuit.... making it less safe for the PV panel and wiring.

author: Psi
author_rank: Super Contributor
timestamp: September 22, 2020, 11:13:47 am
content: The power will be pretty tiny under short circuit conditions due to almost zero volts.So I can't see it damaging the panel if shorted permanently.I'm no export on the subject though

author: Ed.Kloonk
author_rank: Super Contributor
timestamp: September 22, 2020, 11:36:15 am
content: I wanted flames.

author: Kleinstein
author_rank: Super Contributor
timestamp: September 22, 2020, 11:43:23 am
content: The panels should not have a problem with a short. Under normal use the current would be at around 90% the short circuit current. A short may pose slightly higher load to the reverse polarity protection for the weaker cells. However they get tested from time to time anyway with a partial shade (e.g. bird, plane or cloud coming in).Efficiency of the PV is a around 15% so some 15% more warming of the cells from the sun than normal. It would be the same if the battery is full and not more current drawn.

author: sleemanj
author_rank: Super Contributor
timestamp: September 22, 2020, 11:51:34 am
content: If we look at an IV curve....we can see that the short-circuit current is basically the normal operating current anyway.So in short-circuit you are not doing anything other than collapsing the voltage, the panel is totally capable of handling the current.

author: @rt
author_rank: Super Contributor
timestamp: September 22, 2020, 12:12:37 pm
content: Thanks allI don’t want flames lol!

author: samnmax
author_rank: Regular Contributor
timestamp: September 22, 2020, 12:34:28 pm
content: Recently we discovered one of the panels on our roof (~6kW installation), was disconnected from any string and shorted to itself, for YEARSI was also wondering if it would be OK or if it would be damaged. We added it to the corresponding string and everything seems to be fine.

author: @rt
author_rank: Super Contributor
timestamp: September 22, 2020, 02:01:23 pm
content: It’s good to hear it’s true in a real case.Nobody would run the experiment on purpose for years with an expensive panel and it’s wasted real estate

author: Ed.Kloonk
author_rank: Super Contributor
timestamp: September 22, 2020, 04:39:04 pm
content: Quote from: samnmax on September 22, 2020, 12:34:28 pmBut did you notice a spike that correlated with the panel's inclusion with the string?

author: David Hess
author_rank: Super Contributor
timestamp: September 22, 2020, 11:23:06 pm
content: The panels have a lot of surface area so any additional heat dissipation is easily handled. They already see worse by being in direct sunlight.

author: samnmax
author_rank: Regular Contributor
timestamp: September 24, 2020, 12:05:44 pm
content: Quote from: Ed.Kloonk on September 22, 2020, 04:39:04 pmI think it was in a very cloudy day, so it was difficult to assert that the panel was really contributing. Measures done in later days showed a small increase in production, so we concluded it was OK.I wonder if there are safe and easy ways to measure voltages on a solar string when functioning, the weather-proofed cables and connectors prevent the use of a normal multimeter.I guess given the equal current, the good panels would give a higher voltage than the bad ones.

author: TimFox
author_rank: Super Contributor
timestamp: September 24, 2020, 12:26:24 pm
content: A photovoltaic cell is basically a current source (current proportional to incoming solar power level) in parallel with a parasitic diode (polarity to forward-conduct from photocurrent), as shown in the curves posted above. The parasitic diode limits the voltage available from the single cell. Short-circuiting a current source is permissible, as is open-circuiting a voltage source.

author: Renate
author_rank: Super Contributor
timestamp: September 24, 2020, 12:37:03 pm
content: It's not a good idea to short a PV panel.There's no reason to do that and in cases of faulty panels could start a fire.A specific case is the Renogy flexible solar panels.There were problems with the connections between individual cells.An increase in resistance at the connection would cause the full power of the panel to be dissipated at a small point.There have been cases of melting and burning.See:https://www.cpsc.gov/Recalls/2016/rng-recalls-bendable-solar-panelsI was looking for a great photo of a panel burned through, but I can't seem to find it.

author: Psi
author_rank: Super Contributor
timestamp: September 25, 2020, 09:20:50 am
content: Quote from: Renate on September 24, 2020, 12:37:03 pmThat's true, but if you were using the panels you'd almost definitely get a fire anyway.The damage might be 50% slower to manifest, since you would have two loads trying to draw current, the real load and the faulty connection.But 50% of a burning short is usually still a burning short.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: September 25, 2020, 02:28:57 pm
content: Note that shorting *a* panel doesn't do much (it gets a few percent hotter), but shorting one panel in an array may be a rather poor idea, for which it matters what backflow/safety protection there is. In short, if you're actually shorting out the array, not just the one panel, that's obviously a bit more current than normal.Tim

author: Renate
author_rank: Super Contributor
timestamp: September 25, 2020, 03:44:13 pm
content: The whole thread is pretty silly.Why don't we discuss whether it's sensible to stick a metal fork into the neutral of a wall socket?I mean, if it's wired correctly you won't kill yourself.The point is, there is no compelling reason to stick a fork in an outlet.There is no compelling reason to short a PV panel.

author: Siwastaja
author_rank: Super Contributor
timestamp: September 25, 2020, 03:54:29 pm
content: Quote from: Renate on September 25, 2020, 03:44:13 pmThis response well demonstrates why this thread is clearly necessary. Newsflash: a PV panel and a wall socket are fundamentally very different types of power sources.But, you can always choose to ignore the possibilities to learn.Yet, especially for safety, understanding, not just trying to follow rules, is crucial.With rules, context is everything, because they carry a lot of hidden assumptions.

author: Seekonk
author_rank: Super Contributor
timestamp: September 25, 2020, 04:41:44 pm
content: I do have a little problem with this. Panels are just crappy diodes with faults. I've seen FLIR images of panels operating well below the power point voltage and then when this extreme condition is removed. It is very clear the weakest cells take the brunt of the heat. Over the years I've had several panels fail. In theory shorting shouldn't be a problem. But, this is real life and I have to believe stressing weak cells has to lead to some increase in failure.

author: Phaedo
author_rank: Contributor
timestamp: December 25, 2023, 05:09:35 am
content: Hello all,Pretty old post, I know.Just wanted to have some feedback. I got a solar panel, it delivers about 18V ~ 20V when open. When I short it through a DMM, I am getting about20mA. Is this a dud panel or some kind of limiting effect when the panel is dead shorted ?Cheers and happy holidays !

author: Andy Chee
author_rank: Super Contributor
timestamp: December 25, 2023, 05:24:56 am
content: Quote from: Phaedo on December 25, 2023, 05:09:35 amWhat's the size of the panel? Your numbers are probably ok for a 5 watt panel.

author: Phaedo
author_rank: Contributor
timestamp: December 25, 2023, 08:19:10 am
content: QuoteThis is what the website claims :50x35cm Solar Panel 12V 30W Rectangle Shape × 1

author: Andy Chee
author_rank: Super Contributor
timestamp: December 25, 2023, 08:54:09 am
content: 20mA short circuit for a panel of that size, I think there is definitely something wrong with the panel. Should be able to get over 800mA at least.

author: amyk
author_rank: Super Contributor
timestamp: December 25, 2023, 09:25:47 pm
content: Quote from: Andy Chee on December 25, 2023, 08:54:09 amDepends how much light it's under...