Victron 712 to batteries in parallel

[Yellowjacket]

Originally Posted by MichelleWhy

Your parallel wiring for sure is not the common way, but is ok and does its job.
Make sure all wires are more or less equal length.

Here is how you should install the shunt. The connections on the shunt are marked -Load and -Battery. Make sure you connect the bus bar wire to the -Load connector and the wire coming from the battery goes to -Battery. Not easy to have both wires from the two batteries connected to the one connector. Depends on thickness of wire terminals. Good luck.

Attachment 183685

Thank you Michelle. This solution made sense to me, given the original wiring. Considering what others have written, that orginal wiring may be more complicated than usual, but that's not uncommon on this boat.

Since I will have more than one BVM, it seems I could connect two of the old ones directly to neg and positive posts of each battery to monitor separately, with the Victron 712 as you have drawn (using my drawing as a base!) to monitor and convey info on the entire bank. Amps would not be measured by 712 but would be trivial. Thoughts?

[john61ct]

The whole point of the BM is the shunt measuring AH.

A voltmeter only costs 1/10th the price.

[Yellowjacket]

Originally Posted by john61ct

The whole point of the BM is the shunt measuring AH.

A voltmeter only costs 1/10th the price.

John, I stated poorly what I meant. The amps draw of the additional volt meters would be trivial. Yes, the point of the BM is to measure and convey AH. And voltage. And temperature.

[MichelleWhy]

Originally Posted by Erik Dolson

Thank you Michelle. This solution made sense to me, given the original wiring. Considering what others have written, that orginal wiring may be more complicated than usual, but that's not uncommon on this boat.

Since I will have more than one BVM, it seems I could connect two of the old ones directly to neg and positive posts of each battery to monitor separately, with the Victron 712 as you have drawn (using my drawing as a base!) to monitor and convey info on the entire bank. Amps would not be measured by 712 but would be trivial. Thoughts?

You're welcome.

Sorry, I maybe don't understand your question. Do you want to monitor each of the two batteries separately? If so, why?
It wouldn't make much sense when they are wired up in parallel, because they must be seen as one battery. Look at the drawing (the one I tweaked) again. The whole current flow from all your loads are calculated/measured with this one shunt. And that makes sense because you surely want to know how much current is flowing in or out of the battery and probably also want to look at SoC/Voltage etc.
As long as they are wired in parallel, the voltage at the battery terminals are equal, thus makes no sense to have a second BMV...unless you want to measure the current flow from each of the batteries separately. But that doesn't make sense either. But what you can do if you have a spare BMV is connect it to your fridge or some other load to see how much this individual load is drawing independent of all the other loads.

[john61ct]

Originally Posted by Erik Dolson

John, I stated poorly what I meant. The amps draw of the additional volt meters would be trivial. Yes, the point of the BM is to measure and convey AH. And voltage. And temperature.

My point is, using only one BM is plenty.

KISS is an important goal, from my limited understanding of your description of your system, IMO you should strive to simplify rather than adding more complexity.

Your surplus BMs are worth selling, or keep as spares.

[Sailshabby]

I just had this conversation with Victron, after adding a starting battery to my system (PO relied on the two house batteries for everything). I added an echo charger for the starting battery and kept the 1-2-All-Off switch for the two AGM house batteries (for no good reason other than I was tired of throwing stuff away). I’m running the 702, and in a nutshell, they said to add the capacity of both house batteries and treat them as one, assuming I’m keeping the switch in the BOTH position.

[Yellowjacket]

Originally Posted by MichelleWhy

You're welcome.

Sorry, I maybe don't understand your question. Do you want to monitor each of the two batteries separately? If so, why?…
As long as they are wired in parallel, the voltage at the battery terminals are equal, thus makes no sense to have a second BMV...unless you want to measure the current flow from each of the batteries separately. But that doesn't make sense either. But what you can do if you have a spare BMV is connect it to your fridge or some other load to see how much this individual load is drawing independent of all the other loads.

I am convinced.

My thought was to measure current flow separately and possibly be able to isolate a problem to one battery or the other, and to compare readings over time for consistency to get a better "feel" for behavorial patterns inherent in the system. But if there could be no possible difference in batteries wired in parallel then that's just a silly waste of time.

Between John's KISS (really, one reason I chose this boat was its relative simplicity) and your suggestion, Michelle, to perhaps use the extra BM to look at refrigeration load, it's time to just get this done.

Back story: When I bought the 25 year old boat, I was completely ignorant of electrical systems and the boat had three battery monitors: One in the Mastervolt Mass Combi, one in the panel, and a small round monitor labeled "Balmar" that only retired Balmar techs remembered and for which Balmar has no information anywhere. I asume it was sourced from another OEM.

None of the three ever agreed with either of the other two as to voltage or current. And, I wasn't sure if the little round guage wasn't actually connected to the start battery given that unlabeled wires run everywhere.

Let's not get into the two huge alternators hung off the main engine and driven by 2 too small V-belts impossible to adjust and a dumb regulator. Boy, did they eat belts. Even a Blalmar smart regulator didn't cure that (serpentine, did, with one larger alternator. KISS, right John?).

Oh, the genset regulator was installed such that the "dripless" shaft seal could toss salt water right at it. Talk about random issues! Genset exhaust was plumbed into a cockpit drain, which made for noisy and really smelly evenings on the hook. The tach didn''t need to be replaced despite the insistence of a tech who aparently didn't grasp open circuit vs volatage under load, and a main engine that would not start until, again, all ground contacts were sanded and tightened.

So, if three guages don't tell the story, get a 4th! Bought a Balmar Smart Guage and wired it myself to one battery of the house bank so that I would absolutley know where and how. This BM agreed with the voltage of the round Balmar guage which also gives amps draw. They were consistetly .2 volts higher than the old panel monitor, which also seems to report amps randomly between 2 and 200, which I put down to age/shunt issues, and a refrigeration system that the main panel ignores completely. But as long the differences were consistent, I wasn't worried. I was ignorant, almost as good!

That left the Mastervolt, which agreed in volts with the two Balmars when it was not charging, but was way off when it was. It also was not fully charging the batteries from shore power, I realized later, though my main engine (now through a Balmar 614) and Genset (now with a Balmar 612) did, once those regulators were installed. Mastervolt issue led to the discovery of a loose ground during the process of sanding engine room bus bar connections.

Then came solar and the Victron App, a Victron Battery Sense that does not broadcast beyond it's own low profile shadow, and hence the 712 and this dicsussion.

It's amazing to me, and yes, I'm talking to fellow members of a very small choir here, how frustrating this can be and at the same time, how much I love this stuff! I really mean that. What an education.

Like discovering after almost threeee yeeears and uncountable episodes of wiping up diesel while chasing the perfect flame that my Dickenson Diesel Heater doesn't just want good draft, it really prefers positive cabin pressure! What a hoot!

Thank you everyone for all your suggestions and support.

[john61ct]

Lemme know if you want to sell any excess BMs.

Also looking for old BSS CL-style ACRs, now discontinued, haven't been showing up so often on CL or eBay anymore

[CatNewBee]

Originally Posted by john61ct

Lemme know if you want to sell any excess BMs.

Also looking for old BSS CL-style ACRs, now discontinued, haven't been showing up so often on CL or eBay anymore

https://www.obelink.de/nds-imanager-kabellos.html

This may ba a gadget if you stick with FLA, AGM or GEL,
pretty simple display, not too techy, manages 2 independent house batteries, even of diffetent sizes, makes etc.

Auto-combines them in charging and high loads, separates them otherwise and switches seamless in between. It isolates the batteries, so a failure of one does not wreck the other.

Had it installed in my RV before moving to the LFP path.

https://www.obelink.de/images/thumbn...S-imanager.jpg

Manufacturer web site in Italy
https://www.ndsenergy.it/prodotto/imanager/?lang=en

Max current is 150A.

If you are too overwhelmed with all the settings of a Victron, this is a very simple, but effective device in small installations. It runs automatic or in manual mode and shows Voltages and currents individually per battery, also graphically the SOC, not too accurate, but sufficient to get an idea.

[john61ct]

??? Not sure how that pertains?

BSS 7600 is the device I meant, specifically for its current limiting.

But will also take SmartGauges and BMVs.

Or did you mean to address the OP?

[CatNewBee]

It is about combining batteries / isolating batteries of a house bank instead having them parallel all the time and having individual gauges per battety.

That one works with Lead Acid.