Battery Monitor, which brand, which type

[Davidhoy]

Take a look at the Blue Sea M2 SoC monitor. It comes with a shunt to measures amps in a single bank, but also measures voltage on up to 3 banks. I am installing one of these on my boat. No battery monitor is perfect, but this one seems to combine the best features of the Balmar Smartguage and the more common battery monitors. I've been very impressed with Blue Sea gear in general, hopefully this will be as good. It will let me monitor the main bank, as well as voltage of the engine start bank and windlass/thruster bank.

https://www.bluesea.com/products/1830/M2_DC_SoC_Monitor

-David


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[jbinbi]

Originally Posted by smac999

I doubt the shunt is in the right spot... the feeder cable is too small. it should likely be between battery and switch. on the big cable. it's likely only capturing one thing. like panel draw. where does the big cable on the top of shunt go?

I am not at the boat, but pretty sure that this goes to the panel and breakers only. However, that is mostly what I am concerned about draw. The only things using As are electronics, lights, fridge, pumps. Not worried about windlass etc.

Hard to believe a brand new boat from one of the largest boat manufacturers wouldn't have the shunt wired correctly.

So 2 questions. If I need to see A out of the Solar Panels, or more accurately, from the MPPT controller, and not have to stick my head down under the berth, I am assuming I can just get an old style analog A meter and a shunt and put it between the battery and the controller's neg connection. If that is the case, then I can just continue to use the panel meter to read V of the battery, and a table for SOC. Is this correct?

2. If I want to use a Victron and leave my current system in place as suggested, does the Victron shunt go in parallel to the current shunt? I had assumed this, but in thinking some more, not quite sure about it.

[DeepFrz]

It looks like they are using that bottom wire as a fuse.

[Matt Johnson]

Originally Posted by DeepFrz

It looks like they are using that bottom wire as a fuse.

Odd that the feed wire is such a small gauge while the other side of the shunt looks more appropriate.

Matt

[ErikFinn]

Originally Posted by shufti

I'm happy with my Nasa battery momnitor. But almost twice the price of the Victron metioned above.

GBP 105, at today's fx it should be about 135 bucks. That's cheaper then a 160 bucks Victron, no?

Clipper BM-1 Battery Monitor - Nasa Marine Instruments

[mitiempo]

Originally Posted by jbinbi

Thanks for all the replies.

In re thinking this some more, since my current monitor shows V , as Dockhead says (and great post , thanks!), just a table would show SOC fairly well.

However, I really want to know if the solar is outputting and how well. I have learned that even though my panels each output 20As, I have hit this only once, when the sun was directly overhead at the stern. Other times I have checked the controllers, which I explained getting to them is a major major PITA, it turns out I am getting 1/4 to 1/2 of that because the mainsheet is shading or the sun is not direct, etc. etc. issues of solar.

So I guess I really want to have a remote monitor for my panels. And to know what is going out as well. Possibly an ammeter as dockhead and others have said. @smac, the shunt I have is correct, see pic below. New boat, this is installed from the factory. Or maybe just Victron 700.

How do I wire in the second shunt (thinking practicality). In the pic, the bottom of the shunt is coming from the neg battery switch (we have been through this in another thread, typical of French manufacts, Bene, Lagoon, Juneau to have this switch).

With new shunt in parallel, I would probably bypass the switch, attaching another low guage wire up from bottom of the switch where the batteries are attached. However, to connect the top of the existing shunt to a new shunt, I need to wire across with inflexible low gauge wire. Basically this is a bar with insulation that needs to be a few inches away. Any tips on wiring this gauge wire?

I agree with the others - it looks like the shunt is incorrectly wired.

What solar controllers do you have?

[botanybay]

Originally Posted by jbinbi

My boat's setup is as follows.

1 house bank of 420Ah and 2 start banks, one for each engine.

The instrument panel has a battery monitor that lets me select each one of three to show its corresponding voltage level. It also shows As crudely on the top corner, though but only outflow, not inflow.

There is a shunt for the battery monitor.

Since adding solar, I am very keen on knowing how much is going into (and out of) the battery. The MPPT controllers have a LCD display that cycles between V and A, and AH, but the controllers are under a berth, to see them I need to unmake the bed, take off the mattress(es), slide back a piece of wood, and lean over. Not very convenient.

So I am thinking of adding a monitor. I have looked at the Victron, and Balmar Smart Gauge. The smart gauge would be easy to install, and also let me use my current setup to monitor both start batteries. I can leave all wiring in place, including the shunt, the Balmar just connectors to my house bank's terminals. BUT, it doesn't show Amps.

The Victron requires me to substitute its shunt for the current one, not a big deal, but then I can't monitor both of my starts, as the Victron only has the capability to monitor 1 extra battery. But it will show current in and out!

For those with solar, how important is it to know just SOC vs. current used as well. I have read reviews on both of these, mainesail highly recommends the Balmar for SOC. Sorry for the long post, but interested in hearing what others have used and pros and cons. Thanks.

The victron works fine with other shunts.

When I installed mine I tied into the existing shunts. Programmed the mv per amp and worked great.

In my case the old shunt had a different screw pattern so I used twisted pair jumpers for a couple of inches.

Great unit!


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[Matt Johnson]

Originally Posted by botanybay

The victron works fine with other shunts.

When I installed mine I tied into the existing shunts. Programmed the mv per amp and worked great.

In my case the old shunt had a different screw pattern so I used twisted pair jumpers for a couple of inches.

Great unit!


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As long as the shunt has the same mV reading. There are some that are 25, 50, 75 and 100mV. Bluesea and a lot of others use 50mV.... the cheap eBay ones are 75mV.


Matt

[smac999]

Originally Posted by jbinbi

I am not at the boat, but pretty sure that this goes to the panel and breakers only. However, that is mostly what I am concerned about draw. The only things using As are electronics, lights, fridge, pumps. Not worried about windlass etc.

Hard to believe a brand new boat from one of the largest boat manufacturers wouldn't have the shunt wired correctly.

.

it's wired as a panel draw meter. like I said. it's in the correct spot for a panel draw meter. it's in the wrong spot for a battery monitor. if you add the victron the new shunt will go next to the battery instead. the existing one can be left as is.

[Dockhead]

Originally Posted by Davidhoy

Take a look at the Blue Sea M2 SoC monitor. It comes with a shunt to measures amps in a single bank, but also measures voltage on up to 3 banks. I am installing one of these on my boat. No battery monitor is perfect, but this one seems to combine the best features of the Balmar Smartguage and the more common battery monitors. I've been very impressed with Blue Sea gear in general, hopefully this will be as good. It will let me monitor the main bank, as well as voltage of the engine start bank and windlass/thruster bank.

https://www.bluesea.com/products/1830/M2_DC_SoC_Monitor

-David

I like Blue Sea gear too, but that battery monitor does NOT indeed determine state of charge like the SmartGauge does. It is an ordinary amp-counting meter just like the Victron. The only difference is it can measure voltage in three places, instead of two for the Victron, which in my opinion does not make it worth twice the price.

The volts and amps readings are useful, but amp-counting state of charge is, in my opinion, worse than useless, for the reasons I stated above.

For $300, you'd be a lot better off buying a simple volt/amp meter with shunt and two voltmeters, and spending the $260 you have left over in the pub. In my opinion, of course.

[Stu Jackson]

Originally Posted by jbinbi

...........................................

2. If I want to use a Victron and leave my current system in place as suggested, does the Victron shunt go in parallel to the current shunt? I had assumed this, but in thinking some more, not quite sure about it.

This might help you understand how shunts work:

Ammeters & Shunts 101: Ammeters & Shunts 101

WADR, forget "go in parallel" (and that's not the case here at all, either) - what you REALLY need to do is figure out what you want to measure and where the shunt needs to go.

A shunt is a flow meter, simple.

Most of us with coulomb counters know exactly what the draw of each component of our loads are. My fridge is 4.9A when it runs. I know what all the lights and pumps do when they run, because the meter shows that.

Most battery monitor meters monitor the NET current.

So all you have to do is shut down your loads whenever you want to know what the panels are producing, or, even simpler, do the math in your head.

[botanybay]

Originally Posted by funjohnson

As long as the shunt has the same mV reading. There are some that are 25, 50, 75 and 100mV. Bluesea and a lot of others use 50mV.... the cheap eBay ones are 75mV.


Matt

The Victron BMV702 is definitely programable.

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[botanybay]

For my system the estimate of state of charge is useful because it can cause automatic actions to take place. For example shutting down the inverter output if the soc gets too low or load shedding the hot water heater if the support function of the inverter is loosing ground (say 90% soc).

Works extremely well for what I ask of it. No, it may not be sufficiently accurate for partial state of charge long term cycling. Knowing an instruments limitations is always important.



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[Matt Johnson]

Originally Posted by botanybay

The Victron BMV702 is definitely programable.

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Having not owned a Victron, I didn't know about this feature. I just looked in their manual and sure enough, you can have up to a 9999A and/or 75mV shunt. It's programmable in the start-up wizard. Very cool!

Matt

[Dockhead]

Originally Posted by botanybay

For my system the estimate of state of charge is useful because it can cause automatic actions to take place. For example shutting down the inverter output if the soc gets too low or load shedding the hot water heater if the support function of the inverter is loosing ground (say 90% soc).

Works extremely well for what I ask of it. No, it may not be sufficiently accurate for partial state of charge long term cycling. Knowing an instruments limitations is always important.

This could be done using the SmartGauge alarm output function, which can be set to give two different alarms, one upon reaching a certain SOC threshold, and the other for a low voltage threshold.

It will be much better with the SmartGauge than with an amp-counting meter, and you've inspired me to think about it. Just setting up alarms would probably serve the function -- to alert me to switch stuff off. I could theoretically set up some relays to shut some stuff off. I'll think about it; thanks very much. It's definitely an argument for having a SmartGauge instead of just a voltmeter.


Edit: This is actually a great idea. I burned up my alternator one time because I had the inverter on while operating my 10hp bow thruster. This could have been prevented with a simple NC relay which would shut down the inverter whenever voltage goes below x (say 23.5 volts). This would be a very simple modification.