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Looking for battery monitor recommendations

7K views 53 replies 20 participants last post by  john61ct 
#1 ·
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?
 
#6 · (Edited)
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...
 
#7 ·
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.
 
#14 ·
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
 
#15 ·
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.
 
#16 ·
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.
 
#17 ·
Here is my initial post in that thread;
I just came across this device in another forum; https://www.amazon.com/LPHUS-Blueto...e-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.
 
#37 ·
Here is my initial post in that thread;

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.
Hm, when I click on the link you list in your post it goes to an item on Amazon that looks completely different from what your posting is showing. Is that the same thing?
 
#19 ·
SOC is the only feature that would not be accurate for chemistries other than FLA.
 
#20 ·
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.
 
#22 ·
It is a Blue Sea 1830 ...

Guidance on what the wiring issue could be would be greatly appreciated. The part that confounds me is that the instantaneous amp draw that the monitor displays at any point in time is correct (when compared to a clamp on meter) or at least close enough to correct that it doesn't explain how far off the % is.

To put that another way: at any point in time, I feel that looking at the monitor to see how many amps are being added or removed from the batteries at that instant is correct.

However, the % full of the bank goes down far too quickly for the amp draw that the meter is reporting.

Concrete example:
The bank is 300 AH. That's what I have programmed into the monitor.
Leaving all charge sources on for several days, I am confident that the batteries are 100% full.
Turning off all charging sources, I monitor power draw:
Without the refrigerator running, draw is always less than 0.5 amps (running some fans that are always on)
When the refrigerator is running, total draw is between 4 and 5 amps.
These two amp draws were measured by the monitor and double checked with a clamp on meter at the batteries.
If we assume that the refrigerator runs 100% of the time (which it does not) then leaving the system off charge for 12 hours should result in a maximum of 60 amps used out of the bank. That would put the bank at 80% charge. A more realistic value is 90% charge because the refrigerator actually runs less than 1/2 the time.
However, 12 hours later, the battery monitor claims that the bank is somewhere between 50% and 70% of capacity (I've done the experiment more than once)

The wiring is not particularly complicated: twisted pair to the shunt. I would expect that if I'd done that wrong somehow that the instantaneous reading would also be incorrect, but I'd be happy to be corrected if that assumption is wrong.
 
#25 ·
I think so. Peukert definitely isn't it because I've tried varying it slightly according to the guidance in the little manual to try to get it just right, and that hasn't changed their behavior. I can't remember about charge efficiency but will check into that tomorrow because this is really starting to bug me. Odd that in summer the AH goes continuously down, but in winter plugged into AC power with constant battery charger, the AH goes up until it plateaus at approximately +200 instead of blinking and resetting when it got back to zero and the charging amps are below the required threshold. I equalized once in the fall and again in the spring before unplugging from AC power so I don't have to use the generator for so many hours straight.

If something were wired to bypass the shunt, wouldn't that cause the AH used to be a smaller number than actual because those AH's that snuck by the shunt wouldn't have been counted? But all summer the AH used number is higher than actual. If I still had any appreciable amount of hair I'd be tearing it out by now!

As a result, I just go by how high the voltage is with no load ((around 1 amp for things like stereo backlighting or phone charging) and no charging source and that's been getting me by. But on my previous boat I had a Link 10 and it worked perfectly for about 8 years until I sold it.
 
#26 ·
Some followup:

I ran through the settings again this morning, and the meter is set for FF Oasis batteries, which appears to configure all the other values, and thus should be correct for my bank.

However, there is some setting about using voltage to adjust battery SoC (sorry, I forgot the actual name of the setting). I didn't connect the voltage leads when I hooked it up because, frankly, I didn't care. For right or wrong, I only cared about amps in/out being used to estimate SoC. Apparently my desire to simplify things resulted in breakage. Interestingly, there's an option to turn this feature off. So I did. Knowing that the monitor is capable of considering battery voltage as well, I'll add it to my project list to run leads to the voltage probes on the meter, but first I'll see if turning that feature off improves accuracy.

Interesting ...
 
#28 ·
Well, the answer to that last question is that I didn't realize that it was running sophisticated algorithms. And running yet more wires is work I'm not going to do if I don't know that it's necessary.

Anyway, to follow up. Simply turning that feature off doesn't seemed to have done anything to improve the accuracy. So, this morning I'm going to add in wires to the voltage probes and turn it back on. We'll see if/how much it helps.
 
#30 ·
I use a Bogart Engineering TriMetric model 2020. Works fine. Battery monitors that track amp hours became prevalent in home solar systems. So they're well developed and affordable outside the marine market.
It tracks the amp-hours discharged and charged into the battery. It also converts that to a % discharged and % charged number. The monitor allows adjusting battery capacity as that changes with life. The monitor tracks charging voltage and current and indicates when a charge has been completed. It informs you of the time since the last charge and when an equalizing battery charge is due. It tracks the highest voltage charged and lowest voltage discharged. It also has indicators when battery voltage has dropped to the point of risking battery exhaustion. B.
Then amp hour meter senses house battery discharge from a shunt resistor
 
#32 ·
To wrap up this thread (in case someone finds it later and wants to know what I happened ...)

Actually doing something about this finally came to the top of my TODO list. As a first step, I wired up the voltage sense wires to the BlueSea M2 meter (that didn't appear to be working properly) and ...

That fixed everything.

After a few days of charge/discharge cycles, the monitor is reporting values for SoC that match calculated values of usage. I am now confident that I can stop obsessing over power usage and trust what the monitor is telling me.

The lesson, I guess, is to hook up all the wires, even if you don't think you need them.
 
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