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mihlit avatar image
mihlit asked

Negative MPPT power in node red and MQTT

Right now, Cerbo shows pv production jumping between 0 and -5.3 W. I guess that negative value means there is some wrong formula in the sw that should be fixed.

I get the negative value both in Node-red
node "Venus system | MPPTs - power (W)" and MQTT at

N/<id>/system/0/Dc/Pv/Power

Venus OS version is v3.00~42

MQTT history log:

07/17/2023 8:44:29 PM(-2.02 seconds) 

{"value": -5.256000215649607}

07/17/2023 8:44:23 PM(-6.03 seconds) 

{"value": 0.0}

07/17/2023 8:44:21 PM(-1.98 seconds) 

{"value": -5.258000261455777}

07/17/2023 8:44:07 PM(-14.03 seconds) 

{"value": 0.0}


Note: During the day, when there was enough sun, values were correct - matching expectation. On the other hand, I can spot 0 jumping to -5 easily, but would not notice 5 W jumps on high values.

cerbo gxMQTTbug report
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smallsolar avatar image smallsolar commented ·
Are you using the load outputs on the mppt or are they on? Mine shows the same, but I have some loads on the load outputs of the mppts and the load is always on.
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mihlit avatar image mihlit smallsolar commented ·
No, I don't use load output.
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2 Answers
d-ferdi avatar image
d-ferdi answered ·

hello,

what mppt does you use?

i have this only with mppts with a connected load or mppts which are powered from accu.

is this the power from pv or from accu?

goodby

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mihlit avatar image mihlit commented ·

I'd say usual 48V setup. First MPPT is SmartSolar 100/20 with 2p2s 1.16kWp, second one SmartSolar 150/85 ve with 1p3s 1.18kWp atm, both connected to LFP battery, nothing on 100/20 load terminals (150/85 does not have those) and no other DC load except MPII inverter.

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d-ferdi avatar image
d-ferdi answered ·

hello,

which pv-voltage have you? is the mppt in off-state ?

get you power from mppt if you remove the data-connection to the gx-device?

if you have bms connected to the gx, check the bms-parameters. this can prevent the system from charging. my bms set the charge current to 0 if accu is full. but this can also happens, if something is wrong like a very unbalanced accu.

bulk is ok, but which charge current do you have. in this case the mppt should transfer the hole pv-power to the system. if not, there must be a current-limit active.

i think, you can check that with the victronconnect-app and check the batterie settings. normaly the gx will overwrite this, but it can only overwrite the voltage with a hight value, not the current!

the only way to get the actual parameters is with an own program or terminal-program over a vedirect-connection. you must read registers 2001 voltage and 2015 current. some samples are in the vedirect hex docu.

goodby

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