DVCC, Multiplus and MPPT

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southsideph asked May 11, '22

DVCC, Multiplus and MPPT

Hi

There have been similar posts but not really answered my concerns. I have 2 x MPPT, BMV712 and Originally IP43 charger, these were all connected using VE.Smart Networking.

I have 2 x MPPTs as I use one for the integral Solar Panels and the second allows me to add additional portable solar panels when static for a period of time (e.g. a show). Using VE.Start Networking it allows the MPPTs to synchronously charge batteries from both.

I have a GX device fitted now and my understanding is that you can't use both VE.Smart Networking and GX devices, which is fine in principal, why would you, also now have Multiplus installed.

My question really is, with the VE.Smart Networking disabled and the GX device set for DVCC, I have noticed on more than one occasion a disparity between devices, one MPPT showing on GX console as being in absorption, the other being in float or the Multiplus being in storage/bulk/absorption.

My assumption, incorrectly is that all these devices will be synchronised and charge stages managed by the GX device, they should all be in one or other stages but in unison, charge rates managed based on SOC, temperature etc by the GX device. Especially all devices are actively charging which can often be a scenario

thoughts please

Rgds

MPPT Controllers Venus GX - VGX multiplus ve.bus DVCC

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Answer 1 · 2022-05-11T08:33:47Z

klim8skeptic answered · May 11, 2022 at 08:33 AM

My assumption, incorrectly is that all these devices will be synchronised and charge stages managed by the GX device, they should all be in one or other stages but in unison

Not really. Distributed Voltage and Current Control is more about all connected devices sharing a common Voltage reference, and some control over absolute battery charging current should you need it.

I occasionally see my 2 mppts in different charge states. Why is this so??

The simple answer for me, is that 1 of my mppts is old and slow (to react to changes). The other mppt is newer, quicker to react and has a larger pv array.

I think the GX device sends updates to connected devices in a serial (individual device) update, rather than to all devices in a parallel (all devices at once) update.

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Answer 2 · 2022-05-11T11:56:27Z

JohnC answered · May 11, 2022 at 11:56 AM

Hi @SouthsidePH

With a BMV you have a battery current reading that DVCC's SCS can pass to the mppts. They can terminate Absorb at their own set Tail (in Amps) from that reading, effectively at the same time. This works in addition to the Fixed or Adaptive settings. One proviso.. the max Tail setting is 10A, dunno why.

As for syncing the mppts with a Multiplus charger, time to take a step back and take a hard look at why you'd actually want to do that. You may well have a reason, but best managed depending on circumstances. You don't mention battery type, but this can also affect what you set up.

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southsideph commented · May 11, 2022 at 12:25 PM

Thank you for your reply,

Often can be in the situation where both MPPTs and Multiplus on grid are charging the batteries, although limited charge current.

Currently using AGM batteries, often because of "use scenarios" I could potentially have 3 charge sources in parallel, as such avoid overcharging batteries as effectively there is no BMS, solely reliant on the BMV/GX to manage this. I could manually turn devices off but this is not always practical. So it is more the interaction between the devices, 2 x MPPT and 1 x Multiplus when all three are active.

I'm now using the Virtual Switch to ignore AC on certain conditions to mitigate this to some degree

Rgds

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JohnC ♦ southsideph commented · May 11, 2022 at 01:33 PM

@SouthsidePH

You could also consider setting the Multi to a flat V, no Absorb cycle at all. With it's target V set just 0.1V under the mppts' Float. That way all mppt charge will have priority and the Multi will handle all loads and charge too when needed, just more slowly. (with DVCC's SVS to make sure all units are seeing the exact-same V.)

There's also Assistants and even ESS to expand on VS capabilities. You've taken the step up from BT, and you have much wider options. Explore them, the sync thing is really a non-issue.

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