victronmeldrew avatar image
victronmeldrew asked

Charging Issues - SmartSolar 100/20 - One Solar Panel (245w) - 12v System

I have been having issues with my charge controller.

I have one solar panel (specs below) connected to the "Victron 100/20 SmartSolar MPPT" charge controller. When I tested the panel directly, the multimeter was reading 37.2v.

There are 2 x 12v leisure batteries (haven't been charged in a while) wired in parallel to the controller. The controller light flashes blue when the batteries are connected, but no change when the solar panel is connected.

Solar Panel specs:

Maximum power (pmax +10%,-0% - 245w
Short Circuit Current (Isc) - 5.86a
Open circuit voltage (Voc) - 53.0v
Maximum power current (Imp) -5.54a
Maximum power voltage (Vmp) -44.3v
Mamimum system voltage -1000v

Readings from charge controller:

Battery: 12.49v
PV: 12.3
Load: 12.49v

I tested it again after a few hours and the Load was 12.45v.
Are these the reading I should be getting? Or is something in my set up wrong? I was told this controller would work in creating a 12v system (very important, don't want 24v).

"Nominal PV power, 12V - 290W":,-75-15,-100-15,-100-20,-100-20_48V-EN-.pdf

Any help would be much appreciated.
Thank you.

Solar Panelerrorsmart solar set-up helpcharge controller compatibility
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2 Answers
JohnC avatar image
JohnC answered ·

Hi V. That panel is well suited. There's not much really you can do wrong hooking it up, but there is one thing to check first..

Panel polarity. Beg, borrow or steal a cheapo multimeter and check the V on your PV terminals. Pull the PV wires from the mppt to test them.

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victronmeldrew avatar image victronmeldrew commented ·
Hi, thanks for your reply. I checked the polarity and it's definitely correct. I've done a few solar set ups in the past, and this one is quite simple which is annoying it isn't working. It is also indoors (on dryland), so not much in terms of wind/environment would affect any connections.

The panel is making 30v, but when connected to the controller, the reading drops to 12.3v. The panel is a brand new Panasonic, still in packaging; the controller was also new. I was extra careful when making the connections. Have also been connecting/disconnecting in the right order; batteries connected first, then the panel.

All I can think of is that the panel isn't making enough amps or there's a software setting I need to set (bluetooth app).

Any more suggestions would be amazing.
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JohnC avatar image JohnC ♦ victronmeldrew commented ·

Yeh, good you're experienced. I doubt there's anything in the settings of the mppt that could do that, and if you haven't changed anything there deliberately, the defaults can usually be relied upon.

Try testing your panel disconnected in full sun. 30V isn't it's rated 53V in open circuit, and it should get up near there even in weak sun.

Maybe even find a (disposable) 12V lightbulb to see if the panel can blow it. 200W could do that easy if the panel was ok.

Sure I live in the bush.. :)

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Justin Cook avatar image
Justin Cook answered ·

@victronmeldrew, in addition to @JohnC's comments, I would check your MC4 connectors to ensure that they're making a good connection. I've seen several installations in which a bad crimp inside one end or the other of the MC4 causes erratic behavior only certain conditions, such as when the MPPT puts a load on the panel. This would potentially explain why you're showing good voltage until you connect to the MPPT... voltage=good but when the MPPT puts a load on the panel the bad crimp heats up, raises resistance, and the voltage drops off.

Obviously with Panasonic panels it seems unlikely, but sometimes it's the simple things that go overlooked.

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