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How many MPPT/chargers would I need


PlanB
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I suppose my question will reveal just how little I understand, but please be patient.

I have a Victron setup (5Kw Multiplus II, a 150/100 MPPT, and the color control GX and 12Kw of BlueNova LifePo batteries) On the roof I have 8 x 420 watt panels (4x2 strings) all facing the same direction (about north)

As I lose a lot of morning and afternoon sun I'm thinking of adding a 4x panels that face a bit more east and a 4x that face a bit more west.

Would that require 2x more MPPT (one for east and one for west) or can one MPPT devise mange the additional set of 8 panels.

or don't I need to add a MPPT and can I just wire the new strings into the current MPPT?

 

 

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3 hours ago, PlanB said:

Would that require 2x more MPPT (one for east and one for west) or can one MPPT devise mange the additional set of 8 panels.

or don't I need to add a MPPT and can I just wire the new strings into the current MPPT?

Firstly buy the exact same panels a stated above. Your 150/100 MPPT can take 5800w of solar = 14 x 420

Improtant just keep your 2 string configuration as to not exceed 150v

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17 hours ago, starmage said:

you will loose efficiency.

You loose very little. We are talking <5% so it is not worth buying an extra MPPT.
I have a MPPT where the one string face East and the other string West and this works great. All panels on the same string have to face the same direction though.

 

18 hours ago, PlanB said:

150/100 MPPT  
4x2 strings

A assume this is 2S4P (4 strings of 2 panels in each string). You should be able to do 3 panels in each string (check your panel's spec for the Vmax). On paper your Vmax (the open circuit one) might be more than 50V which would limit your strings to 2 panels only, but in practice here in SA it is never so cold that you will get to that value. 

If you have been running your current install for more that 1 year you would have done a typical winter. So go check the stats on your MPPT in the Remote Console. Under Overall History you will see what the very max Voltage is your MPPT ever reached. If for 2 panels per string this is < 100V with some margin I will say it is safe to add a third panel to each string to get closer to the 150V

Here is my 100/20's history with 2x 425W panels per string.
The best thing is that even if you did go over the max for a little bit, your Victron SmartSolar has over voltage protection and will not break anything, but just shut down safely until the overvoltage has cleared. This is not true for all other manufacturer's MPPT though.

image.png.f01f7d98f62f0aed9bb385328dd94b81.png

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53 minutes ago, Louisvdw said:

You loose very little. We are talking <5% so it is not worth buying an extra MPPT.
I have a MPPT where the one string face East and the other string West and this works great. All panels on the same string have to face the same direction though.

 

A assume this is 2S4P (4 strings of 2 panels in each string). You should be able to do 3 panels in each string (check your panel's spec for the Vmax). On paper your Vmax (the open circuit one) might be more than 50V which would limit your strings to 2 panels only, but in practice here in SA it is never so cold that you will get to that value. 

If you have been running your current install for more that 1 year you would have done a typical winter. So go check the stats on your MPPT in the Remote Console. Under Overall History you will see what the very max Voltage is your MPPT ever reached. If for 2 panels per string this is < 100V with some margin I will say it is safe to add a third panel to each string to get closer to the 150V

Here is my 100/20's history with 2x 425W panels per string.
The best thing is that even if you did go over the max for a little bit, your Victron SmartSolar has over voltage protection and will not break anything, but just shut down safely until the overvoltage has cleared. This is not true for all other manufacturer's MPPT though.

image.png.f01f7d98f62f0aed9bb385328dd94b81.png

Thanks for this very helpful information.

I have not gone through winter yet, I only installed this setup in October2020 

these are my stats:

image.png.7564388bc1c3d0a47975f6a242a06542.png

Do you think strings of 3 panels will be OK on the Victron MPPT?

 

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No this will not work well for you. With 2 panels your 102.98V gives you 51.5V per panel and with 3 panels this will be 154.5V (will be even higher in winter). That is a bit too much over your limit. Your MPPT will shut down too much and you will loose production. I suggest you stay with 2 panels.

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