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Dual MPPT PV setup


Sidewinder

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Morning all,

I'm in the planning phase of expanding my system. Since the Infinisolar V 5kW can take up to 6kW of PV, and I have found myself short daily with the current 3.6kW.

I have enough roof space to add another 12 x 300W PV. I have sorted out my early morning deficiency with winter shading by topping a few fairly high tree growth.

My biggest problem lies in the fact that my roof is 14 deg east of north (=-14deg?), so I loose solar production quickly after 4pm.

So instead of adding 12 PV's on existing roof, I was thinking of adding 9 x PV on the roof, and the last 3 (I use 3 PV's in my strings) on the Western side of the house, using a custom 45 deg bracket against the wall. This wall gets full sun in winter as well as summer till sunset

What I want to know is will a West string(900W) combined with a North string work? I'm hoping this setup is OK, as it is the ideal, so that I can add a good 500W or so to my afternoon PV generation pool.

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I've done exactly this. I have a North and a North-North-East string in parallel (bit of a no-no really, but it works well enough). Around 3:30PM the NNE string gets shadow and it takes the North string with it. I already have the cable pulled in AND an extra MPPT installed to remedy this situation, just have to find the time to actually do it. Then I can tell you if it makes much of a difference... but... I'm pretty certain it will.

In other words, from personal experience, I can tell you not to combine your N and NW strings.

I also added 600W pointing NW. Same reasoning, since the other array starts dropping out before 4PM, I wanted something to pick up the late afternoon sun. It has its own MPPT. I don't ever get full power on that side, it peaks at 500W (out of 600) around 14:30. But then again, this time of year... that's actually not bad. I get two thirds of the rated power for most of the afternoon, but by 5PM it makes only a quarter of it's rating. So not getting much extra out of it past 4PM, which is your requirement, but it definitely does better than the shaded strings.

Your plan will work, just put it on a separate MPPT. I understand that that adds a good 4k to the ticket though...

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1 hour ago, plonkster said:

Your plan will work, just put it on a separate MPPT. I understand that that adds a good 4k to the ticket though...

Sidewinder has the new dual MPPT offering from Voltronic which has eventually hit our shores. Now this  is an inverter to tempt me to swop out my Axpert. It is an Axpert with real hybrid capability and a second MPPT thrown in for good measure. It is a 5kW unit rather than the standard 4kW.

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Now if there only was a way to combine(parallel) the Infinisolar with the Axpert, but that is a big no-no, not willing to experiment that one!.

Just a note on the V, they are not equiped with the parallel card, as my Axpert was, but I'm pretty sure they can be swopped out.

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@Don, Haha, no not stuggling, just havent been around to commission properly. I did manage to switch the unit on via dual circuitry from my batteries last week, before the York Rally in Sabie required my attention. Just need to tidy up the AC side and cut over the PV. hopefully the second set of PV will arrive before the longweekend, which I plan to spend on the roof!

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