question

Ceki Gabay avatar image
Ceki Gabay asked

DVCC vs Smart Network in order to sync two mppts.

Hi all,


After reading manuals still I am little bit confused about which one to use.

My installation as follows on our sailboat.


A non victron inverter/charger combi

4x160 agm non victron service batteries

280watts solar array charging service batteries via victron mppt smart 100/20

340watts solar array charging same battery bank via victron mppt smart 100/30

A bmv 712 monitor

a venus gx have connection to 100/20, 100/30 and 712 with ve.direct cables.


my problem is two mppts are

ok and works fine in bulk phase,

then they are ok passing to and work in parallel in absorb phase

afterwards they are ok passing to float phase. however in some shady days 100/30 stays in float which is normal, 100/20 turns back to bulk mode which is not normal.


manuals says do not use smart battery sense or smart networking between mppts if there is a gx product in the system. Do I have to use dvcc in order to get two mppts synced. Or can I use smart networking while dvcc is off.


thanks in advance

smart solar set-up helpDVCCSmart Battery SenseVE.Smart Network
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JohnC avatar image
JohnC answered ·

Hi C. DVCC can't sync them, and unless you have some specific reason to use it, perhaps best left off anyway.

This 'syncing' seems to be something that people 'crave', but all can live without.

Seeing one mppt in float and the other return to Bulk state might conceivably result from beginning their solar day at different times, maybe locking in things like Abs time and temp compensation at slightly different levels. Maybe one might decide to do a short 'reAbsorb', and the other hasn't picked up the need to do that?

In the washup, what happens over the course of a day with your batt V's is the important thing. If it's doing what you want, then rest easy.

If you have VRM, perhaps post up screenshot(s) of the relevant stuff, and we can take a look.

I don't know how far this 'syncing' thing needs to be taken. Some endusers may well have (say) 4x mppt's, a wind genny, hydro, grid & generator, even conceivably all running together. To sync them is impractical (meaningless?), and 'priority' is usually the issue anyway then. That can all be managed with kit/settings, but at the end of the day what the batts get is the target.

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Ceki Gabay avatar image Ceki Gabay commented ·

Thanks for the answer.

The thing is one of the mppts stays in float state. That is ok. However the second one starts to fluctuate between 13.8 and 14.4V as lt is in bulk state It cannot go to absorb and float state as it has not enough power for charge and supply the load. I am little bit disturbed about over voltage till sun drops. I am curious whether I am damaging batteries within these hours.


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JohnC avatar image JohnC ♦ Ceki Gabay commented ·

Yeh, I can understand why you may be concerned, but it's not necessarily an issue.

Make sure your units are set to exactly the same charge algorithm. I think the newer firmware can be set to a fixed Abs time rather than an adaptive one, so both will experience that together.

If you were pushing into very small batts, maybe an issue, but you're not. With even all your panels at full spec you're not even 0.1C (Ah). With one mppt falling away, you're well less. So what defines 'overcharging'?

It's hard to explain, and subject to personal preference too. Airy-fairy it is. As an example, in poor winter weather my own system may spend all of the day in Bulk mode, never reaching Abs, but most of the day above Float level. After dark I can see how well they're charged by the V they settle to, and usually fall just that little bit short. So all day they've been 'chasing' the chemical reaction within the batts, rather than 'forcing' it at Vabs. I don't call that overcharging. Personal view, I can wear any dissent, ha.

Some people, even on this forum, demand Victron provide a longer Bulk phase. Personal preference again, and that's usually achievable by limiting Amps.

So the Science can become a bit of an Art. It's why I love my VRM graphs so fondly, don't use SOC much, nor auto genny start to top up after a bad solar day.

Hope this drivel makes some sense. Hard to explain Artistry.. :-)


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DVCC chapter in GX manual  

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VE.Smart Networking Manual