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fbo avatar image
fbo asked

Turning off MPPTs intentionally

Dear Victronians,

my setup is a GX, some Multiplus II and some Smartsolar MPPTs using ESS which avoids to feed power into the grid. I'd like to turn off the MPPTs from time to time to implement an upper SOC limit. This document

https://raw.githubusercontent.com/victronenergy/dbus_modbustcp/master/CCGX-Modbus-TCP-register-list.xlsx

shows a writable modbus variable ( "/Mode" , 774) which affects the MPPTs in the way I want. But: Is it safe to write to it often (is the state stored in a flash)?

Optimally, I'd like to set the MPPTs maximum charge current/power but there seems to be no way to do so. Is this correct?

Thank you for any advise.

Frank

ESSMPPT SmartSolar
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2 Answers
andrii-podanenko avatar image
andrii-podanenko answered ·

It is safe

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fbo avatar image fbo commented ·

Hi Andrii,

thank you very much. Do you know of a source, where to find information like that? I'd love to make a map "modbus address" to "flash or not".

Best regards

Frank

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alexander-uhde avatar image
alexander-uhde answered ·

Hi Frank,

wouldn't it be better to use "max charge current" for that?
I have implemented a node-red function to restrict SOC to certain limits from time to time.

Using modbus this should be register 2705 for an ESS.
I guess this should be safe to be written often, since it seems to be used by ESS regularly when nearing certain SOC limits.


Regards

Alex


Edit:

"Optimally, I'd like to set the MPPTs maximum charge current/power"

Sorry, I did not read this one carefully enough the first time.

"max charge current" exactly does this one.

You can set it in 1A steps from zero to whatever maximum is possible.
This value can be overwritten by your BMS, if your desired value is higher than possible.

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fbo avatar image fbo commented ·

Hi Alexander,

2705 seems to be a Victron setting which means, it's defined in /data/conf/settings.xml and updated there. Unfortunately, my use case requires frequent writes (e.g. once every 5 minutes) which is a bit much for my GX's flash storage

Best regards

Frank

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alexander-uhde avatar image alexander-uhde fbo commented ·

Hi Frank,


I am afraid I cannot give detailed advise on that.

In my use case I am shifting this value only 3-4 times a day during the summer and maybe 2 times a day during winter.

(I own a MP2 5000 GX with a MPPT250/100 and two additional SMA inverters connected to Ac-out).


Victron seems to use this in their own implementation of Venus OS large (Node red).

I checked the behaviour just some minutes ago. If I am changing the affected node in OS large, I can also see this change in register 2705 via modbus.

Normally I am not using modbus to communicate to victron, just using node-red.


Did you have a look at this already?
https://www.victronenergy.com/live/ess:ess_mode_2_and_3


Victron sugessts to use 2705 in this one as well, but unfortunately I could not find a statement for write cycles of the GX`s flash at all.


Best regards and have a nice week

Alex

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fbo avatar image fbo alexander-uhde commented ·

Hi Alexander,

I actually found some additional variables: /Settings/ChargeCurrentLimit and /Link/ChargeCurrent on the MPPT's DBUS service. It doesn't have a modbus address but it can be written to via MQTT. Unfortunately the first one seems to be flash based (in the MPPT) while changing the second one starts a flame war with the DVCC service.

Best regards

Frank

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