question

Kristina Elaine avatar image
Kristina Elaine asked

Number of Panels for Solar Charge Controller?

I currently have a Voctron MPPT 100/20 with four 100 Watt solar panels. I have four more I would like to hook up. Can the 100/20 handle that and how? Or do I need to get a larger one? Thanks in advance!


Edit* it's a 12v system. We don't get good sun. Really just want to know if I CAN put 8 panels on that controller and if I can, how?

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Alexandra avatar image Alexandra ♦ commented ·

https://mppt.victronenergy.com/ will help you work this out as you are more familiar with where you live and what the specifications are of your panels.

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Justin Cook avatar image
Justin Cook answered ·

Hi @Kristina Elaine, will you please specify your battery nominal voltage (ie, 12v or 24v)? This will affect the ideal panelling for your SCC.

Also, what charge current have you seen from your current setup? I ask because, no matter how many panels you connect to your existing 100/20, you will never see more than 20A of charge being put into the batteries simply because that's the maximum charge current of the particular model you have.

If you're using this array to charge a 12v nominal battery system and you're in an area that gets good sun a lot of the time, you're possibly already wasting a decent amount (5-9A) of charge current just because your controller can't put out what your panels could possibly harvest; this depends on your battery bank nominal voltage, though, so a few questions:

1. Battery bank nominal voltage

2. Total Ah capacity of battery bank

3. General geographic location so we can reference how much sun is actually hitting the panels

4. Intended purpose of the array- ie, are you running heavy loads that are dragging down your batteries and you need a lot of solar to recharge, or are you mostly just topping your batteries up from light usage, or...

5. VOC and Imp ratings of both the panels you currently have as well as the panels you would like to add (if they're different panels)

Given those datapoints I'm sure I or another person here will be able to advise you on your best likely course of action!

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