incorrect battery SoC & incorrect load display - Quattro/VenusGX/BMV712

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daniel1957 asked Mar 19, '19

incorrect battery SoC & incorrect load display - Quattro/VenusGX/BMV712

my system consists of a new Quattro, new VenusGX and new BMV712 connected to an existing bank of 2000 Ah 48v gel cells.

The BMV712 reports

95% 52.1v -408w.

The Quattro through the VenusGX incorrectly displays the following

AC LOADS 284w Battery 100% discharging 317w 52.1v

Am I correct to assume that the Quattro is using 317w to create 284w? ie an inefficiency of 33w overall in operation.

Therefore what is the 408w that the BMV712 showing?

The only other connected loads are the BMV712 & VenusGX.... surely they are not consuming 91w??

the 100% SoC is definitely incorrect.

I notice that Victron Connect through the VenusGX for the Quattro has a setting for battery monitoring but it can't be changed from 'auto'...

Currently I can only connect to the VenusGX through my android phone/WiFi/Victron Connect app.

SOC

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Answer 1 · 2019-03-19T04:09:10Z

JohnC answered · Mar 19, 2019 at 04:09 AM

Hi Daniel. The Quattro (and other kit) readings are just a 'best effort' attempt to provide info for the user without adding to cost. Victron have freely admitted that in the past, and is probably the reason the BMV was introduced in the first place. You can safely ignore them now you have a BMV.

The SOC figures are calculated too, even on the BMV, so aren't cast-in-stone. They're tunable though, mostly via 'Peukert' and 'Round trip efficiency', so you can fiddle with those on the BMV to make it represent what you will learn to know about your batts and their condition.

Sorry if this answer seems vague, but it's the nature-of-the-beast. This issue may even peak in systems where batt BMS, BMV, and GX invariably disagree on SOC. Victron have actually recommended to installers that they allow just a single SOC to clients to help prevent confusion and complaints. Bad thing? For you to judge, but it is as it is..

I don't even use SOC myself, as I've discounted it's usefulness in my own mind somewhat. The VRM graphs of all the rest is essential for me though. :)

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Answer 2 · 2019-03-21T02:11:49Z

daniel1957 answered · Mar 21, 2019 at 02:11 AM

OK thanks.

if that is the case, then why on earth does Victron Energy facilitate the venusGX through VictronConnect to show the SOC on the Quattro when it remains at 100% when it is nowhere near that level.

It is clearly incorrect and misleading.

It may be OK for tech savvy personnel to distinguish which is correct and which is not but the whole purpose of the monitoring system is to allow non tech savvy, such as my wife in my case, to monitor and utilise the system properly.

If what you advise is correct then such monitoring is not possible using Victron Energy equipment and I have wasted many hundreds of dollars.....

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boekel ♦ commented · Mar 22, 2019 at 12:44 PM

Because for some systems the Multi's internal battery monitor is sufficient, and you don't need to invest in a BMV for those systems.

There is a reason there are training days for installers, and experience is needed to correctly setup big systems. some things need good understanding of components and general electric knowledge to correctly install and setup.

There are so many different setups to be made with different components and use cases it is just impossible to have one answer to fit all.

The BMV can be setup to match the 'real' SOC quite accurately, but needs tweaking as there is a lot of difference in batteries, and when they age the specs change also.
(most of the times a 'safe' setting is used that will show a little lower SOC so the customer doesn't discharge the batteries too far, also a choice depending on the client)

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