BMV-700 value differences between CCGX and modbus

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mario79 asked Nov 24, '22

BMV-700 value differences between CCGX and modbus

Welcome! I'm new to this forum.

I'm a happy owner of an off-grid setup: Quattro 48/8000, BMV-700, MPPT 250/85 (15 solars @250W), Sunny Boy 2.5 (10 solars @250W), CCGX, and lead-acid 48V 800Ah. The setup has around 5 years.

Recently I discovered Home Assistant (the main goal being to automate car charging only when batteries are full and there is a surplus of energy). The first tests are very positive :)

Incidentally, I discovered a potential glitch...
I'm using Modbus to integrate CCGX in HA, and the values I used for Wallbox are correct (at least similar to what I see in CCGX), that is:
- com.victronenergy.battery Battery voltage
- com.victronenergy.battery Current
- com.victronenergy.battery State of charge
- com.victronenergy.system AC Consumption L1

But when I started (out of curiosity) to play with Charged Energy and Discharged Energy (from BMV history) the Modbus gave me very strange values...

The values I see in HA:

the definition of sensors in HA:

and the templates to apply scalefactor:

The definition in HA is fairly simple (and it works fine for other values), so I wonder if it can be a Modbus or BMV issue?

BMV Battery Monitor Modbus TCP lead-acid

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1669321356066.png (7.4 KiB)

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wkirby answered · Nov 24, 2022 at 09:56 PM

How come you are using a template to scale the values?
Surely it would be easier to scale them directly in your modbus.yaml?
Try something like this and see if that will be any better:

- name: "Battery Voltage"
scan_interval: 5
unit_of_measurement: "V"
slave: 225
address: 259
scale: 0.01
precision: 1

- name: "Battery Current"
scan_interval: 5
unit_of_measurement: "A"
slave: 225
address: 261
scale: 0.1
precision: 1

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mario79 answered · Nov 24, 2022 at 10:41 PM

Thanks @WKirby !

I'm new to HA, I felt my config is not optimal :)

scaling in modbus.yaml works indeed :)

Anyway, with the (dis)charged energy numbers, it's simply because the high-order bits are discarded while converting to uint16... and then when converting back to a signed type, if the most left bit is 1, the value becomes negative... No more questions :)

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Modifications Space

Node Red Space

Answer 1 · 2022-11-24T21:13:38Z

mario79 answered · Nov 24, 2022 at 09:13 PM

ok, I just realized that the range of those 2 values in Modbus is 0 to 6553.5, and the real values I can see in BMV are way out of that range...

Any idea how to make use of out-of-range values?
The negative value wonders me the most ;)

Is resetting the BMV history the only option?

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