Solar panel short circuit current V installed on a solar charger - Page 1
Forum section: electronics / general

author: ziplock9000
author_rank: Regular Contributor
timestamp: June 04, 2020, 01:56:22 pm
content: Hey guys is it normal for the short circuit current of a panel to be a lot higher than what it is when it's connected to a solar charger?For example when the 100w panel is just by itself and it's a really sunny, Open Voltage=21.59v and Short Circuit Current=6.04A (~130w).But when it's connected to the EPever Tracer controller, with a battery that needs charging, the input current of the panel never gets above roughly 0.9, although the voltage seems right.I've checked that the input and output of the charge controller are ok relative to each other, and they seem to be, the output is about 90%+W of the input.It's just the input current is a lot less than when it was tested under short circuit.Thanks.

author: fourtytwo42
author_rank: Super Contributor
timestamp: June 04, 2020, 04:32:13 pm
content: Quote from: ziplock9000 on June 04, 2020, 01:56:22 pmYES, ISC is not the mpp operating point for the panel, that is IMPP that for your panel would typically be 5.5A and VMPP around 18V.However IMPP is directly related to how bright the sun is.But most importantly of all the current taken from the panel will depend upon the batteries state of charge, in other words in bright sun if it is less than 5.5A then your charge controller doesn't think the battery needs charging at the maximum rate, or your battery voltage is to high (you dont say what battery you are using) ?Ahh I see your charge controller auto switches 12/24 batteries, are you perhaps using a 24V battery with insufficient PV voltage (see user guide) ?

author: ziplock9000
author_rank: Regular Contributor
timestamp: June 04, 2020, 05:08:41 pm
content: For now it's a single 12v lead acid car battery that is not in the best of condition with a 100w PV.Even when the battery was low (11v) the current supplied was never more than 1AIt's a new system and the weather here in the NE of England is crap, so I can't do further testing.If your saying this is normal to have lower current than when short circuit, that's great, thanks.

author: Photon939
author_rank: Regular Contributor
timestamp: June 04, 2020, 05:50:13 pm
content: If it works the same as the Epever Tracer I have, then it should work as follows: Bulk charge to somewhere around 14v up to the current output limit of the charge controller (10A in my case) assuming you have enough solar panel to get there. Once the battery hits 14.something volts it will switch to float charging around 13.6 at a fairly low amperage.But if you're saying you have 11v on the battery and it's only drawing 0.9A from the panel with over 6A available (assuming full sun) then either the controller is bad or you have a wiring problem.Current will be substantially less if the sky is cloudy, like 5-10% of full sun current.

author: ziplock9000
author_rank: Regular Contributor
timestamp: June 04, 2020, 09:01:28 pm
content: Quote from: Photon939 on June 04, 2020, 05:50:13 pmThere's 6A when the panel is completely disconnected from the controller and it's short circuit current is measured.Yes today is a poor day weather wise in the NE of England to do any comparisons to that peak day.

author: fourtytwo42
author_rank: Super Contributor
timestamp: June 05, 2020, 09:40:08 am
content: Quote from: ziplock9000 on June 04, 2020, 05:08:41 pmSounds like your battery is kaput to me (high impedance), ask a neighbor to borrow a regular charger or use a bench psu set to 13.8V and see how much current it can absorb. You can get around the sunlight problem as your panel is not to big and portable with a few desklamps or similar, not to be recommended as a permanent solution however

author: ziplock9000
author_rank: Regular Contributor
timestamp: June 05, 2020, 01:44:02 pm
content: Quote from: fourtytwo42 on June 05, 2020, 09:40:08 amI've just tested it and the car battery charger is only putting ~0.6A* into the battery when I think it's range it 5-8A depending on normal or fast charging mode.Dead battery then it seems. Thanks.*Yes the battery is under voltage and being charged