question

seriusrod avatar image
seriusrod asked

Why my MP2 doesn't draw up to the configured Grid amount?

Overnight I run all my big loads and charge the battery. The system never approaches the 32A configured grid limit. And when the HVAC starts heating the water tank at 5:20, the charge reduces.
Why this happens? Is there anything I can do to fix it?

[Battery is blue, EV is green, HVAC is orange, Grid voltage is red]

1701268068554.png

Edit: This is an ESS system, with smart batteries, but not configured as controlling.
SmartShunt as battery monitor. The environment temperature is 16ºC


Exhaust temperature, charge and grid draw

1701344433151.png

ESS
1701268068554.png (168.3 KiB)
1701344433151.png (66.0 KiB)
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1 Answer
nickdb avatar image
nickdb answered ·

That chart is difficult to read.

Is this an ESS?

What is the temperature?

Charging reducing at the same time of loads would indicate the inverter hitting limits and possibly derating. Specs are at an internal temperature of 25C, unless you have very cool ambient temps it may be reducing charge.

That is typically the issue, assuming the batteries aren't limiting charge.

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seriusrod avatar image seriusrod commented ·

Thanks @nickdb for your help.

What you say is so interesting. I've seen in the VRM that the exhaust temperature of the MP2 during the night starts at 31ºC, increases to 41ºC in a short time and ends the night charge at 47ºC. I have a temp sensor inside the top output air outlet.
Shouldn't inverter limiting temp be independent from the charger ones?

My battery BMSs (2p), while they are integrated in the Cerbo system, is not configured as "controlling BMS".


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nickdb avatar image nickdb ♦♦ seriusrod commented ·
The system is a converter, so if it gets hot both will be constrained.
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JohnC avatar image JohnC ♦ seriusrod commented ·
@seriusrod

The Multi's inverter and charger are essentially the same device, just running in 'reverse'. They don't run together, so if it's charging, the ac loads are in passthrough from the grid. And if it's inverting, there's not enough grid to serve loads, so no charging.

I can't pick out from the graphs enough to compare to that 32A limit. In practice there's a bit of a safety limit applied to allow for surges. This may be as much as 10%, so I wouldn't expect more than 30A, so like 6600W. Or even less if you have loads with a poor power factor.

Are you absolutely certain you have it set to 32A? It won't be set there by default.


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