Elejoy Adjustable 400W Solar Boost MPPT

[offGridDownUnder]

... as sold by Grin Technologies and others.

The manual (on page above in 'Product Attachments' seems contradictory.

On page 2 of the manual, it states the device will not turn on with an input voltage of less than 14V.

On page 4 it shows a table that suggests it will work with a 'nominal 12V' solar panel.

On page 5 it shows a table stating that 'Minimum Voltage' for Solar input is 18V.

I'm not aware of a nominally 12V solar panel that guarantees output of 18v minimum. I would expect 14V so it can charge a Lead-Acid car battery.

My question is - what solar panel can work with this device? What specification ensures the panel can do the job?

In my case, I want eventually to charge a 36V or 48V Lithium battery, if that makes any difference in the solar panel required to work with this device.

 

[offGridDownUnder]

From Grin support:

It will work fine with 12V nominal solar panels, which are always around 18-21 volts open circuit. I reread the manual and there is no contradiction here. Page 5 is the open circuit panel output, page 2 is the minimum voltage at which the display lights up. If you want to charge 36V batteries eventually, you just need to make sure that the open circuit panel voltage is less than 36-ish volts.

 

[harrisonpatm]

You'll want to check the back of a solar panel for the label that lists all the power specs. 12V nominal is just that, "nominal," in that it's not actually 12V. Panels will have two lines that list voltage: open circuit voltage, or VoC, this is the voltage read across the leads with no load applied. For most 12V nominal panels, this is in the area of 20-24V. Once a load is applied, voltage will sag. How low it drops depends on how much current is being drawn, leading to the next voltage spec to look for , which is voltage at max power point, or usually Vmp.

My 100w panels, which are 12v "nominal," have open circuit voltage of 22v, and I pull them down to 15-18v depending on cloud cover. So, in your case with this controller you are considering, this is still above the 14v minimum device requirement.

The takeaway should be that a "12V solar panel" isn't actually 12v. When shopping for what panels will work in your application, you'll need to look for VoC of less than 36V, and Vmp of more than 14V. And since it's a 400w controller, you'll want to stick to less than 400w of solar panels, in any arrangement. Sticking to 300w would be better for the life of the controller.

Since this is a boost-only controller, it can only charge a battery which is a higher voltage than the solar panel being used. If you give the controller 60V of solar to charge a 48V battery, it won't work.

Does that help?

 

[offGridDownUnder]

Does that help?

it does.

Cheers.