suavek avatar image
suavek asked

DVCC without BMV on a boat installation

I plan to enable DVCC. My configuration consists of one or two (second is planned) Smart Solar MPPTs, Multi, AGM batteries, no BMV. To save some power Multi is switched on only from time to time only when there is a need to use an inverter or when in a port connected to shore power. What How will Smart Solar work under DVCC when the Multi will be switched off? Should I use a shared voltage sense? What voltage Smart Solar will use?

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1 Answer
Mark avatar image
Mark answered ·

If the Multiplus is totally switched OFF it will not send any data to the Venus device for DVCC.

So if DVCC was enabled with some data (such as SVS) being provided from the Multiplus but then the Multiplus is suddenly turned OFF, the MPPT will revert back to its own internal measurements.

However, I have found a workaround for this - if you switch the Multiplus to 'Charger Only' mode (instead of OFF) then it only draws ~3w and will still keep communicating with the Venus device. A CCGX draws ~5w when operating in the background, so the total standby consumption is ~8w.

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suavek avatar image suavek commented ·

@Mark, what can be the purpose of not relying on MPPT's voltage measurements when you don't use the inverter or generator?

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Mark avatar image Mark ♦♦ suavek commented ·

Hi Suavek,

I suppose that the effect depends on what you are actually sending to the MPPT via DVCC - battery voltage and temperature or just voltage alone.

If you have high losses in the cables between the MPPT and battery, then the MPPT will stop receiving the real / accurate battery voltage (worse at higher charge current).

How much of a difference this makes depends on how much losses you have in your MPPT cables. You should be able to calculate the approximate voltage drop if you really want to quantify it.

If the Multiplus is used to provide this data to the MPPT via DVCC, then you really should be using the voltage sense terminals on the Multiplus with wires running direct to the battery terminals.

I am still using one of the old Venus 2.30 beta/test firmware versions on my system that allows me to provide my MPPT with temperature data from my Multiplus via DVCC - STS, that's why I leave my Multiplus in 'charger only' mode when I really want it turned off.

STS using the Multiplus temperature sensor was cancelled last minute prior to the Venus 2.30 FW release (due to some complications), but my understanding is that it should be possible again in a future formal release.

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suavek avatar image suavek Mark ♦♦ commented ·

In my case voltage drop between the MPPT and a battery is not a problem (short wires and big enough size) but STS is the thing that I need most. There are big temperature difference in battery compartment within a day.

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