question

mitsenoj avatar image
mitsenoj asked

250/100 MPPT topping out at 5300W

So for the first time my panels are pushing out more than 5kw (first summer)- but have recently noticed that the nice parabolic curve I had a month ago is now getting its head chopped - max is 5200-5300W as reported by VRM portal.

At first I though it was temperature of MPPT related - but there seems to be no correlation between MPPT surface temp and throttling though- see graphs below.

When I check the MPPT through Bluetooth it says it is pushing out 5800W - so why is VRM recording 5300W?

My system is Grid tied to any excess should get sent there.


screenshot-2020-12-03-174402.png

whatsapp-image-2020-12-03-at-153010.jpeg

whatsapp-image-2020-12-03-at-153037.jpeg


MPPT Controllers
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6 Answers
janvd avatar image
janvd answered ·

I am no expert, but i think you are bound to your battery voltage. In this case probaly 53V x 100A: maximum charge power = 5300W, if you want more power output, you have to rise your battery voltage which is probaly bad for the lifetime. Bluetooth give you the input, VRM the limited charger output.

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dgnevans avatar image
dgnevans answered ·

As Janvd has said. you are limited to the max 100amps output on the mppt. the mppt will not charge or output more than 100 amps. So it will throttle your solar down. there is also a certain amount of power lost to heat. the only thing you can do is add a second mppt and split the panels between. this may only improve your peformance slightly during peak months but will not offer much change in other months.

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mitsenoj avatar image
mitsenoj answered ·

Thanx guys - agree its not such a big deal in terms of lost energy (I am overproducing anyway now) - was just wanting to understand the reasons - will do some more monitoring to confirm, but think you guys are right

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mitsenoj avatar image
mitsenoj answered ·

@JanVD @dgnevans , so I have looked carefully at the logs - max voltage I am seeing when it plateaus is 55.8V - this matches my ESS settings for Float voltage (which is correct battries normally in float near midday - Grid feeding) - but max Amps is never higher than 93 Amps though .... mistery. At this point it is Grid feeding so I woudl expect 100Amps x 55.8 = 5580W which is about max rated power for this MPPT...

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dgnevans avatar image
dgnevans answered ·

You also need to remember that the temperature of the mppt will be affecting the output. it is rated for full output at 40 degrees. so this may affect your top end slightly. I cannot find documentation that quantifies by how much unfortunately.

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mitsenoj avatar image mitsenoj commented ·

Accepted - but I dont think thats the reason - there doesnt seem to be correlation between tempreture and the throttling - graph above is a good example

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klim8skeptic avatar image klim8skeptic ♦ mitsenoj commented ·

Given your second screen shot. PV max power / battery max voltage = close enough to 100A output max for each day.

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thomasw-1 avatar image
thomasw-1 answered ·

Did you size your solar panels and MPPT with Victron sizing tool?
I assume that your configuration exceeds limit.

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