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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. :)

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.....