The new Smart Shunt vs BMV-712

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valden asked Mar 17, '20

The new Smart Shunt vs BMV-712

Hello everyone.

Re the newly announced Smart Shunt, I'm wanting to understand what it doesn't do compared with the BMV-712.

I'm working with my boat builder to design and install a large Victron lithium battery and electricity management system, based around 4 x 12.8V 300Ah Smart LiFePO4 batteries. I had specified a BMV-712 and its included shunt (500A/50mV).

The documentation on the new Smart Shunt says:

Differences compared to BMV712 Battery Monitor

- No programmable visual and audible alarm.

- No programmable relay.

Questions I have are:

- if the Smart Shunt is connected to a Cerbo GX and GX Touch Display, can visual and audible alarms be set by using those? Or some other way?

- what clever things can be done with the BMV-712's programmable relay that I might be missing out on?

In summary, I like the idea of using the Smart Shunt, but I don't want to give up on features of the BMV-712 that could be important to my system. Eyes wide open ...

Thanks.

cerbo gx BMV Battery Monitor system design

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Answer 1 · 2020-03-18T05:36:22Z

JohnC answered · Mar 18, 2020 at 05:36 AM

Good question(s) @Valden . Been considering the same myself..

I doubt alarms are a real issue. The GX has plenty options, and VRM has a horde which can email you too.

Probably ditto for relay options. What do you think you might be missing out on? :)

For me, I don't need the little BMV screen. And I don't really fancy BT either. But will if I must (just to change settings)..

The alternative is maybe a Victron Connect f/w beta via VenusOS. Now we're discouraged from talking about this (for good reason), but if that ever arrives on full release it will be a good day for me.

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valden commented · Mar 18, 2020 at 06:16 AM

JohnC wrote - What do you think you might be missing out on? :)

Well, my main problem with the lithium battery system is the way it will cause my diesel engine's alternator to overheat while recharging it. Then there's the vulnerability of the alternator regulator to voltage spikes when the batteries (or more precisely, the BMS) stop accepting charge. I was wondering if the BMV-712's relay function might be of some help in managing the alternator's vulnerability in this respect.

I know of two ways to protect the alternator (using an Orion battery to battery charger to limit the rate of charge, or using a BP 200 with clever fusing to do the same), but still, I'm loath to give up the relay functionality of the BMV-712 without knowing its full potential.

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JohnC ♦ valden commented · Mar 18, 2020 at 07:09 AM

DVCC could probably cover your alternator fears admirably.

I'm not sure whether you already have some of this kit, or you're doing due-diligence. It's described here (Section 4): https://www.victronenergy.com/live/ccgx:start

And it's free..

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valden JohnC ♦ commented · Mar 21, 2020 at 09:21 AM

JohnC wrote - I'm not sure whether you already have some of this kit, or you're doing due-diligence.

Due-diligence, during system design with my boatbuilder.

DVCC has me stumped. Can you expand that please? Nope - found it. Distributed Voltage and Current Control. I'll study it. I'm thinking the Cerbo GX will be able to do this too. To be confirmed ...

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Answer 2 · 2020-03-19T18:08:49Z

gbarnaud answered · Mar 19, 2020 at 06:08 PM

Hi Valden

Have you considered this ? https://www.victronenergy.com/upload/documents/VE.Bus-BMS-to-BMS-12-1200-alternator-control-cable-EN.pdf

Better explained here : https://www.victronenergy.com/upload/documents/Datasheet-BMS-12-200-EN.pdf

Be aware than the negative of starter battery and house battery shouldn't be bonded apart through this item. By the way there should soon be released a BMS12/200 operating on positive lead.

Regarding the BMV screen, I also don't think you will miss anything that you couldn't find at least double with the Cerbo.

I don't trust the Battery Protect regarding alternator charging interruption as opening the power leads of an alternator during operation would result in an immediate damage on its regulator. And the BP isn't designed for battery to battery charging.

Last but not cheap : Buck Boost !

Bye

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gbarnaud commented · Mar 19, 2020 at 06:15 PM

By the way, this new item is released ! Called Smart BMS CL 12-100

https://www.victronenergy.com/upload/documents/Datasheet-Smart-BMS-CL-12-100-EN.pdf

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Justin Cook ♦♦ gbarnaud commented · Mar 19, 2020 at 07:36 PM

Well, announced, not actually released yet.

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valden gbarnaud commented · Mar 21, 2020 at 08:45 AM

Oh Wow! This thing is the ducks guts! (That means it's good, in Oz slang). Well done Victron. When will this hit the streets?

If I'm reading things correctly, this Smart BMS CL 12V-100A could possibly do the jobs of the following, to care for the lithium batteries and protect the alternator:

- a VE.Bus BMS (though this might still be needed for AC detection, at least)

- a Smart Battery Protect 220; and

- an Orion-Tr Smart 12-12/30 Battery to Battery Charger, placed between the alternator/engine-start battery and the lithium batteries.

Have I got this right?

And, the Smart BMS CL 12V-100A will allow a higher charging current; not limited to 30A as per the Orion.

But what stops the alternator from overheating? Does the Smart BMS CL 12V-100A act as a current limiting device? Yes - from the tech data sheet:

Alternator and battery protection

The input current is electronically limited to approximately 90% of the fuse rating.

I'm thinking this is a more elegant solution for alternator protection than what I was planning (listed above), or the VE.Bus BMS to BMS 12-200 alternator control cable solution. Bewdy!

Thank you very much for the heads-up on this G. :-)

Edit: I can see that I will still need the Smart Battery Protect 220, to sit between the lithium batteries and the loads.

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