question

kmt85 avatar image
kmt85 asked

How many modbuss writes until mtbf

Hi,

Is there a write limit for writing to the Multiplus modbus registers via Cerbo GX ?

I have custom ESS running for 6 months now via Node-Red and almost 10.000.000 writes to the registers.

Is this unlimited ?

Modbus TCP
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2 Answers
nickdb avatar image
nickdb answered ·

Why would you think there is a limit on local access?

The community isn't a support site, so please don't request direct help from staff as per our guidelines, especially on functionality that is not directly supported. Thanks.

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Alex Pescaru avatar image
Alex Pescaru answered ·

Hi @kmt85

It depends on which registers are you writing to and other factors like OS drivers, MultiPlus firmware, etc...

Generally speaking many modbus registers are tightly connected to some d-bus paths on the operating system.

Now, some of those values are ephemeral, some are stored on the Cerbo's OS non-volatile file system and some are stored on the MultiPlus non-volatile config.

Firsts are no problem, the second ones depends on the endurance of the Cerbo's non-volatile storage system and last ones depends on the eeprom's endurance inside Multiplus.

Cerbo's using some kind of eMMC drive which endurance could be over 10TBW, so no worry here, but the MultiPlus config eeprom could pose a problem, if the Cerbo's OS is not wisely exploiting that resource.

So, in the end, like I've said, it all depends on which registers are you writing to and to the endurance of the media on which they are written to, so to speak.

Think from where that value is taken at system cold boot. From Multiplus's config, from Cerbo's config or is a dynamic value entered later.

Alex

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kmt85 avatar image kmt85 commented ·

Hi Alex,


Thanks for your detailed explanation.

I'm writing the L1 / L2 / L3 setpoint registers to control charging / discharging of the battery depending on how much solar power there is available.

So let's hope it is a dynamic value so that writing to it is nearly unlimited.


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