MPPT 150/45 Voltage Too High Alert

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Tobias Franklin asked Jan 18, '23

MPPT 150/45 Voltage Too High Alert

I have 6 420W panels of this type https://static.trinasolar.com/sites/default/files/AU_Datasheet_DuomaxTwin_DEG15MC.20(II)_2020C.pdf

I have them in 2 strings of 3 - at the time I put them together I thought that was sufficient to stay under the 150v ceiling, but in very cold sunny weather (around zero degrees c and below) it can spike to 153v (highest I've seen).

I don't imagine that's enough to cause any damage, but it does shut the MPPT off until the error clears.

Am I right in thinking that I'm best of re-wiring these panels into 3 strings of 2 panels and that would not only sort this issue but give me bucket loads of headroom too?!

MPPT Controllers voltage

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JohnC answered · Jan 18, 2023 at 12:48 PM

Hi @Tobias Franklin

You'll destroy the mppt if you don't rewire the panels. That 130V that looks ok is the lower Vmp under production, not Voc when the batts are full. And when the mppt tracks every 10 minutes it will also cover the whole V range. Best fix this ASAP.

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Tobias Franklin commented · Jan 18, 2023 at 01:22 PM

Thanks for the heads up, my panels are pretty easy to get to so il get them rewired this week!

In the meantime il make sure there’s plenty of room on the battery/just turn the whole thing off at the breaker.

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JohnC ♦ Tobias Franklin commented · Jan 18, 2023 at 01:33 PM

@Tobias Franklin

You mean turn the panels off at the breaker. And I wouldn't restart them until they warm up a bit. That tracking will still happen though, and you can watch it happening on Victron Connect Trends with it's per-second logging. Take care..

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Tobias Franklin JohnC ♦ commented · Jan 18, 2023 at 02:06 PM

"panels off at the breaker" exactly - I have a DC breaker in front of the MPPT which I would turn off before any re-wiring fun takes place.

thanks for the assistance!

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Modifications Space

Node Red Space

Answer 1 · 2023-01-18T12:15:36Z

Tobias Franklin answered · Jan 18, 2023 at 12:15 PM

Update - I waited for it to warm up (now 4 degrees) very sunny out in the UK today!

Switched the DC breaker, on - voltages totally fine;

put the washing machine on, figures all looking fine.

I presume it's still worth sorting this though, otherwise il be forced to turn off my system during such weather rather than letting it manage itself with suitable tolerances...

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Answer 2 · 2023-01-20T08:37:42Z

jetlag answered · Jan 20, 2023 at 08:37 AM

You have to distinguish between Open Circuit Voltage Voc and the Maximum Power Voltage Vmpp.

The Voc is always higher, and in this case for this modules it is definitly way to high. It is 49,5V @ 25°C. And at 0°C it is already 52,6V (0,25% of increase each degree). And this will in some point destroy your MPPT as it was already mentioned above.

The point is, that this Voc is the the voltage the MPPT "see" first time before it can start to search for a Vmpp (to say it in simple words). If it once finds a maximum power point, the voltage is dropping down to Vmpp and this is what you see in the remote console when there is also power drained out of the modules.

It's up on you, put I also would strongly recommend to change to a 2s3p configuration!

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Answer 3 · 2023-01-23T14:22:44Z

Tobias Franklin answered · Jan 23, 2023 at 02:22 PM

Just to let y'all know - I updated the panel wiring to 2s3p configuration;

Peak voltages now WELL below where they were and the 150V MPPT maximum. I have two panels that can get shaded in the winter so paired them together and I seem to be getting better evening performance because of it.

When I originally set this up I didn't realise at all that panel temperature would play a part in affecting the voltage. I just checked the VoC values on the spec sheet, saw they were just under 150v in a 3 panel string and thought that was ok.

I don't see this talked about much online (I didn't notice it) but it certainly does play a considerable factor, maybe in some climates more than others.

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