question

John Biggin avatar image
John Biggin asked

Is DVCC essential or not?

Recently connected up our new system as follows (UK system, approved by DNO)

AC coupled PV (from existing FIT setup) feeds into house Consumer unit

Multiplus 2 5000/50-70 (latest firmware) Connected by AC in from consumer unit

Cerbo GX (latest firmware)

ET112 grid meter, hardwired

Fogstar Rack battery system 48v (3 x 100Ah Lifepo4 batteries 15kw) Connected by Canbus cable type B . The cells contain 16 x grade A Eve cells and use PACE BMS. (The batteries are set up to use the Victron protocol and report on the GX as Victron)

Using ESS assistant all setup to store excess PV, and invert when drawing from grid

All appears to work as it should....however after 48 hours, having had lots of nice sunny weather started to get lots of cell imbalance warnings, cell overvoltage warnings etc.

I found that by enabling DVCC and setting a maximum charge voltage of 54.8v, the number of overvoltage warnings subsided, but still got imbalances.

Using the battery software and supplied cable, i was talked through adjusting the point at which cell balancing begins.

over a number of days, the difference between cell voltages became wider, with a couple of cells hitting 3.65 volts way before the majority, and that was causing the alarms, and ultimately the battery would go offline.

Interestingly if you look at the nice lcd screens on the rack batteries , number one(master) reports 92% SOC, whilst 2 and 3 report 99%. (seems quite a large difference)

So today as a last resort, i have disabled DVCC, and rebooted the sytem to reset the VE bus, and lo and behold after a couple of hours of sunshine, the batteries are all back to the matching SOC on their screens, and when you use the software to look at the battery cells, you can see they are far more balanced, in fact it shows the balancing at work.

So question is....is it safe to leave DVCC disabled as it appears to work smoother...so far, or am i doing any harm?

I have scoured forums, and pestered Fogstar who now dont reply to emails or phone calls.

Multiplus-IIDVCCess settings
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3 Answers
nickdb avatar image
nickdb answered ·

The DVCC section of the cerbo manual has enough guidance to answer your queries.

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mark-callaway avatar image
mark-callaway answered ·

Sorry not an answer. I have just commissioned the very same system ( historic ac pv with fits 10 years ago). Fogstar recommend using the victron protocol as they said if would work better, but I’ve currently got them set to pylontech as that’s what they came with and need a windows based laptop to change. After just 36 hours the batteries are beginning to drift apart in terms of SOC but the cell voltages seem to be ok. How is your system going on the victron protocol. Are you still disabling DVCC

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nickdb avatar image nickdb ♦♦ commented ·
DVCC is pretty much mandatory for managed batteries. The docs highlight the use and don’t use cases.

When a supported battery is recognised (or one that spoofs a supported battery) DVCC is forced on, this is so an intelligent battery can control its charge.

It is one of the control foundations of the victron ecosystem.

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lee-taylor avatar image
lee-taylor answered ·

I have a similar setup using Pylontech batteries. If you read the Victron guidance on Pylontech they do state that Pylontech set their max charge voltage relatively high. Victron suggest a lower voltage as there is little to be gained by setting it that high. I had a number of over voltage readings initially with DVCC set up without enabling limit managed battery charge. I enabled it and and set my max charge voltage to 52.4 (now 52.5) and I dont see these errors now.

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nickdb avatar image nickdb ♦♦ commented ·

These warnings are common on many new batteries, in most cases it resolves quickly and the guidance is to leave it on keep charged for a couple of days. Limiting voltage is only needed on a severe imbalance. In any case , this has nothing to do with dvcc, which is forced on, it merely provides centralised control to enforce additional limits beyond what is manually set individually on the chargers or requested by the battery.

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