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Warwick Bruce Chapman avatar image
Warwick Bruce Chapman asked

Clarifying DVCC

I want to just make sure I have my thinking correct here:

DVCC is only relevant in systems with an external BMS. With batteries that do not have BMS Comms eg. lead or unsupported Lithium, whether DVCC is on or off, the programmed parameters on the inverter/charger/mppt are used and any limits set in the DVCC menu are ignored.


Is this table accurate:

1664876374651.png


Further to this, the presence of a SmartShunt has no effect on DVCC at all.


We have a site with a Lithium battery (in a golf cart) which does not have BMS comms and we want to use DVCC to set charge current limit between MPPT and MultiPlus but it is being ignored. We noted also that programmed Maximum charge voltage in DVCC was ignored when we tried to lower the voltage from DVCC menu. We have a SmartShunt installed.

DVCC
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3 Answers
JohnC avatar image
JohnC answered ·

Hi @Warwick Bruce Chapman

I think that chart is pretty right, DVCC doesn't have need to pass on a lot of the parameters with unmanaged batteries. Including the selection for max charge V, which actually states for 'managed batteries'.

From memory the literature on SCS is a little sparse, but with it showing 'Active', for me the Smartshunt value seems to be used for limiting the charge current selected in the DVCC screen. And it's also passed across to the mppt for it's Tail function.

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nickdb avatar image
nickdb answered ·

With multiple charge sources DVCC should be used even for dumb batteries. We used it successfully for LA batteries - to limit charge current and for shared temp sensors for temp compensation.

SVS may also have some value, depending on the install.

As far as I recall whichever is lower of the settings is honoured.

(there is an updated DVCC manual in the works as well)

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kevgermany avatar image kevgermany ♦♦ commented ·
Yes, I do this. I think it was @JohnC who recommended it to me
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Warwick Bruce Chapman avatar image Warwick Bruce Chapman commented ·
How do you use it for LA batteries? From what I can see without a BMS, DVCC parameters are ignored.
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nickdb avatar image nickdb ♦♦ Warwick Bruce Chapman commented ·

They aren't ignored. Shared current limits apply. You can use it to provide all the devices with shared temp/voltage sense data (temp compensation is important) from a shunt.

All mppt's will report as external control.

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Warwick Bruce Chapman avatar image Warwick Bruce Chapman nickdb ♦♦ commented ·
That's the behaviour I expected but Charge current limit and Maximum charge voltage were being disregarded.


I could only lower charge voltage by reconfiguring MultiPlus and MPPTs.

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nickdb avatar image nickdb ♦♦ Warwick Bruce Chapman commented ·

Voltage you may have a point but current limits should apply.

Even the docs state this:

Lead-acid batteries For systems with lead-acid batteries, DVCC offers features such as a configurable system-wide charge

current limit, where the GX device actively limits the inverter/charger if the solar chargers are already charging at full power, as

well as Shared Temperature Sense (STS) and Shared Current Sense (SCS).screenshot-2022-10-05-at-115313.png


Charge limit is ignored if ESS is installed and DC feed-in is enabled (even if set to 0)

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aphexer avatar image
aphexer answered ·

In case of standard (non-ESS), with normal battery: why are the MPPT solar chargers using their internal algorithm rather than being controlled by the inverter?

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JohnC avatar image JohnC ♦ commented ·
@aphexer

Because the inverter chargers often are needed to perform different types of charge function. Eg. A grid-supplied charge to top off a bad solar day might best be used at a lower 'float-type' V, to avoid duplicating a full charge cycle. Or a genset user might want max power to minimise runtime, so he could set Abs level just slightly lower than the mppt, so the mppt always has priority.

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Related Resources

DVCC chapter in GX manual