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The battery monitor I purchased appears to be junk.

It tells me that overnight I drain 150 AH from the house bank. If the refrigerator were running constantly it will still only deplete about 60 AH and it's not running constantly. My estimate is that I use about 20 AH between sunset and sunrise ... so this thing appears to be off by a factor of 7.

I obviously need a new one. I expect that all I really need is something that will accurately track amps used and amps replaced so I can make a reasonable estimate of SoC at any point in time. Really, the only thing I _need_ to know is whether the SoC is low enough that I should run the engine for a while (in the event that the solar can't keep up for some reason).

So ... recommendations?
 

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For lead SoC, not Ah counting

Merlin SmartGauge

Lead or LFP, Ah counting

Victron BMV-712
Xantrex Link Pro
Bogart Trimetric TM-2030*

Balmar SG-200 but IMO too new.

If you want integration with shore charging, Magnum w/ 'Advanced' remote control ARC / BMK

Go here https://marinehowto.com And CTRL-F for battery monitor and read closely those three articles
 

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I have the Victron BMV-712. It’s been a solid purchase. The phone app is quite nice and I’ve used it to really dial in the necessities and what their impact is to our battery.
 

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Link20 seems to be OK for 2 banks. All the fancy functions like SOC are hard to use and keep synchronized. Ammeter and voltage function work beautifully... and that's really all you need.

Your system needs to be properly set up... batteries of the capacity to match typical loads without repeatedly going to deep discharge - charge cycles. That's what shortens battery life. Essentially you'll want a lot more battery capacity than typically needed. Alt charging sources are a good thing to have as when you are away from the boat they are topping up your batteries and you don't rely on a alternator.

Discontinued product...
 

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Have a phillipi system. Monitors solar and wind input individually as well as both banks. Get running count of input from each source, instantaneous input, voltage and %of charge of each battery bank. Also the shunts measure current input/draw from the batteries. Input from alternator and generator isn’t split but can be inferred by which one is running.
Information is helpful as you get an idea not only about your batteries but also draw from each piece of equipment and your various inputs.
Also get via ultrasound amount in each of 4 fuel tanks, 2water tanks and 2holding tanks.
Takes awhile to set up but then one and done. Biggest plus is tank monitors actually work and everything is accessible on one little (~3 x3”) screen.
Also have voltages on the electrical panel.
 

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Second the Victron 712. Reasonably priced
Easy to read and understand.
 
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I've been using a Blue Sea System, M-2 1834 battery multimeter and it works flawlessly to monitor exactly what goes into and the draw on my house batteries.
 
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I've been using a Blue Sea System, M-2 1834 battery multimeter and it works flawlessly to monitor exactly what goes into and the draw on my house batteries.
That is a DMM, V&A instantaneously only, no Ah totalizing.

Usually to call a given gadget a BM, needs to at least be trying to guesstimate SoC.
 

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That is a DMM, V&A instantaneously only, no Ah totalizing.

Usually to call a given gadget a BM, needs to at least be trying to guesstimate SoC.
If I wanted Ah totalizing, I guess I would have purchased a different unit. Sometimes all the add ons are just gimmicks and with proper monitoring, like one might do if one lived aboard full time in the Caribbean, unnecessary.
It does exactly what I was looking for. Personally, I don't need some bit of tech to tell me how many amp hours I have left in my battery bank any more than I need one to tell me CPA.
 
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Yes I am not saying you or anyone on particular "needs" a BM.

Maybe 90% of boaters certainly don't.

Just clarifying the terminology for those might not be as au fait.
 

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So what do members thing the mission critical data about their electrical system is?

I would say accurate to at least 0.1 precision volts and amps (input - charging, and output - loads).
 

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For me, the most important thing to know is cumulative Ah. This is a singularly terrific troubleshooting and system monitoring measurement. I don't even use these as battery monitors in the typical sense that others do for determining SOC or when charging can be terminated.

For the first time, we are without this datum because we bought a SG200 that doesn't have it. The SG200 was a big mistake, and it is about to get replaced with a Victron 712. I wanted to like the SG200, and had hopes that they would bring cumulative Ah to it in the near future, but it is basically a random number generator that is only a very expensive basic voltmeter/ammeter at best. There is absolutely no way you can trust or rely on the SOC or SOH numbers coming from that thing - particularly since they change so drastically depending on how you charge the batteries each day. Ironically, the only way to really troubleshoot or corroborate the SG200 is to know cumulative Ah, which it doesn't provide.

Mark
 

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Well there are bank types where even the alpha-stage SG-200 SoC was judged very accurate.

Super-accurate V&A are critical when you need that level of precision, but SoC accuracy is the only metric I care about in a BM.

But as MS details, that does usually require ongoing attention, and ideally periodic load testing as capacity declines.

That last bit being automated by SG-200 is the real game-changer when/if it works.

But I agree that that BM seems to have issues with some chemistries / batt models, or at least it needs to be proven by a lot more community collective experience in coming years.
 

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You should look in the SmartGauge experience thread. I posted my experience with a $30 Bluetooth battery monitor that is perfectly fine for a simple solution.
 

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Here is my initial post in that thread;
I just came across this device in another forum; https://www.amazon.com/LPHUS-Bluetooth-Wireless-Automotive-Diagnostic/dp/B07LBDZ5SG/ref=cm_wl_huc_item



For ~$31 it is about 1/10th the cost of a Smartgauge and it gives you much more information via BlueTooth.

From what I can read it reports SOC, Real-Time Battery Voltage and graph of BV over time, Real-Time Charging Status... The only drawbacks that I can see are that it reads 0.03V low in several YouTube reviews, and does not understand batteries other than FLA.
...

...

The BlueTooth device above graphs voltage over time which is something that the SmartGauge does not do. If I am understanding the directions, this doo-hickey also records up to 35 DAYS of information at 10mS intervals AND it makes this information available via BlueTooth, which means that I don't have to stop whatever it is that I am doing at any given time to push a button on the SmartGauge or mess with the probes on any of the several DVMs that I keep aboard.

The ability to graph battery voltage over time at the sampling interval will allow me to analyze; how powering my cellphone and the pilot light are really affecting the battery voltage over time, how running my 12VDC refrigeration impacts my battery bank voltage - that is when I choose to run it, how *exactly* my alternator's output (Leece-Neville 90A) affects my battery, and what happens to my battery when I am at anchor.
So far, despite that it does not support other chemistries, I am happy with it.

No affiliation with the manufacturer, or seller of this product. I'm just a happy customer.
 

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Why wouldn't it support another chemistry?

It just reads volts and amps, no SoC gauge functionality, so should "work" in that sense with any type battery.
 

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SOC is the only feature that would not be accurate for chemistries other than FLA.
 

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I’ve monitored battery voltage for years and it has worked for me. I have 3 banks that are read out on my panel. I’ve thought about a more sophisticated battery monitor, but haven’t felt the need. Maybe I have to make mental notes about the effect of loads on the decline in battery voltage over time, but it isn’t much of a mental exercise.
 
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