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New Balmar SmartGuage experience

26K views 296 replies 21 participants last post by  Bleemus 
#1 · (Edited)
Installed this at the beginning of the season and calibrated it to 100% charge and set it to GEL battery type, as the house was fully charged at the slip all week. My first few trips off the dock were short, so the batts never discharged below 80%.

Being away for the weekend more often now, I see discharge levels down in the 50s after a couple of days. But only twice at that level of discharge.

My odd experience, however, has to do with recharging, which may have nothing to do with the gauge.

Previously, all I had to identify charge was the Xantrex remote panel, which has three idiot lights for Bulk, Absorb and Float.

Now, I'm checking the new toy all the time, to see actual voltage and charge percentage.

The SmartGuage was not showing much increase in charge level, after running the generator for an hour or two. Previously, that would be about all I felt I needed to recharge a full days usage. It's been showing an increase of maybe 10% of capacity on a 400ah house bank. This is concerning, because I use more than that per day and I wouldn't think I would need to run the generator for more than two hours per day to keep up.

Then I noticed something on the original idiot gauges. They marched their way up from bulk to float, but the SmartGuage still said the bank was only 84% charged. Float should be 98-99, if I understand this correctly.

Could it be that the SmartGuage hasn't "learned" the house parameters yet? Remember, I've also considered that the idiot lights are wrong too.

Final symptom..... When plugged into the dock, I measure 115volts at the AC receptacles. When running the generator, I only measure 106 volts. However, in both scenarios, the SmartGuage seems out of synch with the idiot lights.
 
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#237 ·
So just ignore it dood.

The case of sitting at a dock on Float is so bog-standard normal for 99.9% of boats, there's no way that alone would cause Gibbo's design to get out of whack.

Sorry not to go searching, but what is the Ah counter? Great you have a point of comparison. . .
 
#238 ·
....Sorry not to go searching, but what is the Ah counter? Great you have a point of comparison. . .
It's the Magnum inverter/charger Advanced Remote, which adds a shunt to the package. This morning, the shunt monitor now says we've used 55 amps and should be at 86%. The SmartGauge says 77%. Battery voltage is 12.65, while only drawing 2 amps. As a capacity rule of thumb, the SG would be nearly correct (12.65=75% for gel), if that voltage was resting, but it's not, suggesting resting voltage and capacity are higher.

For those 55 amps to truly represent a decline of 23% of capacity, the bank's total capacity would have to decline from 400 amps to 239 amps, ignoring pheukert, which at these draw rates would not have accelerated the decline anyway. That would be destroyed and impossible to believe, after one year of use and well charged. I'm not even sure they'd take a charge, if that hurt.

As I've said, my real issue now is whether the SG will recognize the recovery to 100%, when I recharge.
 
#239 · (Edited)
For those who find this unnecessary, imagine the comical irony that you took the time to write that. :)

Several have been very helpful in this odyssey, for which I’m appreciative.

The recap allows me to document the analysis for myself. It’s necessary, because I’d like to be sure I’m maximizing capacity on a power hungry boat. The two that I most hope will read it are Balmar and the guy on this forum, who sold it to me.

I’m very open to have made a mistake, but this $300 gauge is marketed as “screw it on and let it learn for a few cycles”. That’s been far from my experience, other than a few moments of encouragement.

The current experiment is having manually reset the SG to 100%, after acceptance amps in Absorb voltage dropped below 0.005c and then below 0.0005c in Float voltage. I’ve shut the charger off to record drain over time. Next I’ll recharge to see if the SG re-recognizes 100%.

No need to follow along, if not interested. I don’t read 75% or more of the threads here. For some posters, who have even claimed to call the USCG about me, that’s 100%. :wink
 
#241 · (Edited)
Weird twist from folks who don’t want to discuss the subject of the OP, huh.

Waited for the SG to read 69%, and voltage now reads 12.5v under load. The battery monitor says we’ve used 71 amps and the bank should be at 82%. It took almost 24 hours of normal non-sailing usage (with just two of us aboard) to discharge to this point.

I turned the charger back on in Bulk and it began accepting 80 charging amps, into the batteries. It only took 5 minutes to get to Absorb voltage and switch over. Still accepting 80 amps. The fast Bulk stage suggests to me that it was not down to 69%, as the SG thought. Note: this SG was booted up at the beginning of the season and has made at least a dozen cycles off the dock by now.

We’ll see what happens when charging flips to float, which I expect to take many hours.
 
#242 · (Edited)
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.

Heck, I just ordered one.
 
#245 ·
I just came across this device in another forum
…
From what I can read it reports SOC
I do not see how it can do that last, just reading voltage,

but it does look interesting and thanks for the link.
The SmartGauge also reports SOC based on voltage input and some internal black magic.
 
#244 ·
Why did you start the recharge at such a shallow DoD?

I thought the current hypothesis we're testing is, the SG is not learning well enough from your usual dockside usage pattern.

Making the goal now to manually control cycling to ensure the next 12-20 cycles go down to 50% or so, for enough deep cycles in a row for learning.

Just for testing the hypothesis, to get the SG tuned in, trying to get meaningful SoC numbers must require some "exercising".

Let the bank carry the loads without charge input until that point, then reconnect manually.

If you just keep doing what you've been doing, likely you'll just get the same results?
 
#248 · (Edited)
Both the device that I posted about above, and the SmartGauge use voltage as the only inputs to determine State Of Charge. SmartGauge has some special-proprietary-seceret sauce that makes it, and it alone, better?



Minne's and my experience with the SmartGauge show that we are not true connoisseurs of SOC gauges. In my case, I have become skeptical of the device. Several other posters here that have experience with the device seem to be of like mindset.



I will conceed that the SmartGauge has provisions for alternate battery chemistries, but the question raised by Minne in this thread is how accurate the magic inside the SmartGauge is at translating from the voltage input into SOC. After having a SmartGauge on my boat for the past five years I now have my doubts as well. In my experience the SOC seems to drop precipitously from the mid-90s to the mid-70s when I have applied little to no load (keeping my cellphone above 80% charge and powering an LED pilot light for about 2 hours) on my 220AH House bank.

For reference- my SmartGauge was installed with AWG 14 wire, and uses an ATC 3A fuse on each lead to the battery bank's positive lead. There are no shunts or inverters in my electrical system, and my boat spends most of the time in the summer on a mooring.

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.

Your comment about my "wasting $30 on this unit's bells and whistles" makes me suspicious. What is YOUR connection in Balmar or SmartGauge? My relation to SG is that I am a customer, and I have helped sell a couple of them to my clients. Before I decided to purchase my SmartGauge I spent several hours reading everything at their UK website: SmartGauge Electronics - SmartGauge battery monitor

My experience is this: after I spent/invested/wasted $331 for a SmartGauge in April of 2014, I have never feelt "warm and fuzzy" about the SOC that the SG tells me that I have in my battery bank. I believe that the <$32 spend/investment/waste to record and analyze battery voltage history with this device is worth it to me. YMMV.:)
 
#247 ·
John, I've already cycled the batteries down to near 50% more than once this season, which has me at this stage.

I decided I would recharge, when the SG said 70% (although the amp counter said 82% SOC). 24 hours with out recharging is a pretty normal cycle for us, so it's real life.

The verdict........ crap again.

Took the charger somewhere between 2 and 3 hours to get the bank back to accepting <2amp, ie 0.005c and switch to float. What's the SG say? 85%. Same as it was before I manually reset it to 100. It simply thinks Full is 85%.

I recall @Maine Sail talking about incredibly accurate bench testing. I wonder if it's ever really been tested well IRL, plugged into shore power most of the time in Float and cycles that rarely get all the way down to 50%. That's is, until now.
 
#249 · (Edited)
I've already cycled the batteries down to near 50% more than once this season
I believe the SG may need in this case a dozen true deep cycles to complete its learning after your 100% calibration.

Ideally in a row, but at least within a few weeks if interspersed with your usual pattern barely-cycles.

Maybe more, possibly less, varies by all the factors unique to your setup. But "more than once" in a season, or anything like your usual automated patterns, IMO just won't cut it for learning purposes.

Once dialed in, then hopefully no need to worry about it.

Meantime ignore its readings, go off the Ah counter, voltage and your gut, but lower SoC the better each cycle.

48hrs, five days without charging whatever, or if you want put an intentional high load on to speed things up.

This is IRL testing, not of its usual accuracy, but for the purposes of facilitating its **learning** process.
 
#252 · (Edited)
The SG installation manual is bad. That should have been a sign. I originally attached it to opposite ends of my bank, but not the same ends as the takeoffs for the load. I only did this to reduce connections, but MS later posted they needed to be on the same side. Not that anything changed, when I moved them.

The SG manual is also written badly. There are some setup instructions, prior to it telling you how to get into the setup menu. It’s illogical.

I’m going to try another experiment. What the heck, I own the ballast now. I’m not too interested in trying to manage a dozen cycles down to 50 SOC. They just don’t time well with my usage and forcing heavy loads to get there quicker is undesirable. I get there in daylight hours, if I have multiple people aboard, we sail all day, with all the nav/comm on and lots of lights, fans, heads flushing, etc.

When I disconnected the charger this past experiment, the SG dropped from the manual 100% SOC I set (where it was still in Float and accepting between 0.0 and 0.2amps) to 95% almost immediately. Then it dropped to 90% very shortly afterward, while I was only drawing a few amps on a 400 Ahr bank. IOW, as the batteries voltage declined from Float voltage to a stable 12.9v, it decided the SOC declined too. This initial delta between its calculated SOC and the SOC suggested by the amp counter then held fairly constant the rest of the way. I’m going to turn off the charger, wait a half hour for voltage to stabilize, then reset to 100% again.

None of this is as advertised. On Amazon, I’d give it 1 star, maybe 2, since the voltage meter works, but not the SOC.
 
#256 ·
as the batteries voltage declined from Float voltage to a stable 12.9v, it decided the capacity declined too.
Not a substantive point, I'm sure you know this, just clarifying semantics for others:

SoC is what the SG measures, how "full" the battery is, a fraction expressed as a %.

Capacity is something else, the maximum Ah the bank will hold, the denominator of that fraction.

So drawn down 100Ah out of 400Ah is 75% SoC, the capacity remains at 400Ah.

As the bank ages, to the extent capacity is reduced is its SoH, as a % of what it was at install time.
 
#253 ·
Well I find it telling when people who have paid to drink the koolaid say they don't like it. Normally people always defend a tech purchase because they "spent money on it".

SG doesn't sound very smart.
 
#254 ·
I'm not saying that the SmartGauge is worthless, but I do think it is worth less than the ~$300 that they charge for it. For the past five years it has HELPED me to better maintain my batteries than I could have with the old analog gauge that was included with the boat.

The problem, for me at least, comes down to this; NO ONE KNOWS how the SOC calculation in the damn thing works. Therefore, no one KNOWS how to use the SOC function.

Stevie Wonder sang; "When you believe in things that you don't understand then you suffer. Superstition ain't the way. No, no, no."

Our friend, Maine Sail, ran multiple bench tests with calibrated multimeters, power supplies, data logging, known loads, etc., for a couple of months and walked away impressed with the results. However, after all his tests he posted that he didn't understand how it worked [in my technical training days we used to call this "F.M."]. I didn't understand the SmartGauge either but I bought it anyway. I placed my faith in RC's testing (and my wallet suffered to the tune of ~$300).

RC states the following on his web page (where he is selling the thing);
But RC how does it work?"

You've got me..? I have no idea how it works, at least at the programing/algorithm level (proprietary stuff), but it is reportedly designed to track voltage. Many internet posters have assumed, posited and suggested, that it checks internal resistance and pulses across the battery etc.. It may, but I have not seen evidence of this on the power / volt sensing wires, even with an Oscilloscope. If I had a tracking o-scope I may have seen something but I don't.

As near as I can tell it simply tracks voltage, up to 1500 times per second, to detect trends and compare it to internally programed data models. I do know it uses computer modeling of actual batteries in real world situations and then feeds this data into an algorithm that can "learn" the bank as time goes on. This modeling must have been time intensive to get to this level of accuracy and this sort of programing minutia is way to complex for a guy like me who can hardly figure out an iPhone.

The Smart Gauge may pulse the battery every so often, and I just missed it..? All I can say is that over time it seems to adapt to learn your bank and give significantly more accurate SOC readings than an Ah/Coulomb counter can, as programmed and used by the average installer or boat owner.

How it actually does this is as closely a guarded a secret as the Frosted Flakes recipe that Tony the Tiger protects.
Albert Einstein is credited with saying; "If you can't explain it simply, then you don't understand it well enough."

I have now been using a SmartGauge on my boat with a VERY simple electrical system for the past five years. The bottom line is that I don't trust it when it tells me 98% SOC vs 72% SOC. After seeing the SOC, I ALWAYS push the voltage button because I don't understand or trust, and no longer believe the stated SOC.

I can't explain the SOC, but I grok the SmartGauge's voltage reading. Therefore, the $30 bluetooth voltage tracker seems like a better solution for me. I'll have to see how it works on my boat before I reccommend it to anyone.
 
#255 ·
#260 ·
Glad to hear that new device seems to be working. I’d consider it, but we’ll see. Does it have a setting for Gel?

Before leaving the slip yesterday (awesome wind and sailing), I turned off the shore charger and waited several minutes for the battery voltage to decline from float. The SG was reading 85%, when acceptance amps prove it was just Full. I enter the setup menu. Battery type comes up first and is correct. Then comes SOC, which I manually adjust to 98%, then press set. Next are some settings for alarms, which I don’t use and are already indicating Off.

At this point, I try to Exit the setup menu, but it won’t. I wait for the two minute timeout, but it’s still on the alarm setting. I wait 10 more minutes. IT’S FROZEN! What a total POS.

The only way to correct was to pull the fuse, which loses all its learning memory, not that any of it was correct anyway. I boot it back up and manually set 95% as the SOC (it defaults to 75% at startup), then go out sailing.

Naturally, it doesn’t match the amp hr counter this morning, after a night off the dock. Of slight interest is that it still reads about 10 percentage points below the amp hour counter, like it did after its previous couple of months of “learning”. I’ll be curious to see what happens, when I plug it back in later today. Albeit, the same curiosity one would have watching a squirrel trying to cross a busy four lane highway.

I’ll be out cruising for a few weeks starting next Fri. I’m betting the squirrel doesn’t make it.
 
#261 ·
The device is only configured for wet-cell batteries, but I don't place a lot of faith in the claimed SOC. I believe that the SOC as reported by the device is from this table;

However, the ability to see a voltage over time plot is VERY useful to me, and that would work regardless of battery chemistry. I can see how engaging the starter affects the voltage, and what the alternator does for the batteries. I believe that you could come up with a similar table to the one above for your gell cell batteries

Hey, for <$30 it seems like a winner.
 
#263 ·
Remember, amps acceptance rate at Absorb V is relevant to establishing 100% Full point not Float.

I think if you aren't able to give it a dozen true deep cycles to learn, in order to determine whether you just have a faulty unit,

you should probably just make do with a $40 coulomb counter.

Or maybe try a Xantrex Link Pro or 712-BMV if you're inclined to throw more money at it.

The SG-200 has a learning curve as well, and maybe too new to know its accuracy for your bank type.
 
#266 ·
I think if you aren't able to give it a dozen true deep cycles to learn
If I had to take my bank through a dozen deep discharges just to get a battery monitor "learned", I'd throw the monitor away. Balmar's information on this does not match your advice. There are many examples on the internet of people having this same issue with their smart gauges, even after many deep cycles. Also examples of it working well - so who knows? I have a friend with two of them. He has identical in all ways split banks that get regularly cycled, and each bank has a smartgauge. One SG works perfectly, while the other gives him all sorts of random information and is never correct.

This is off-topic, but we just installed the new Balmar SG200 on a lithium bank. So far, it is a random number generator, and I have been deep cycling the bank every day for 3 weeks now. Throughout the day, I will see SOH jump to 97% to 25% to 50% - at any time it will be at any random number. Often, it just presents --- instead of a number. The SOC value sometimes reaches 100% right when the batteries reach 100%, but other times reaches 100% hours before the battery, or never reaches 100% at all. Sometimes after reaching 100%, and charging is turned off so that loads draw, it immediately drops to 90% SOC. Perversely, the SOH often jumps up dramatically at the same time. How/when it reaches 100% SOC, and the specific SOH it gives at any time seems to be dependent on how I charge the batteries. The numbers it presents when 150A of mains charging is used are different than the numbers it gives when 20-40A of solar is doing the charging. The voltage seems to be always correct, so at least I have a $250 voltmeter.

To answer the expected questions calling out the installation or operator knowledge, the shunt is the only thing connected to the negative terminal, and it is located 4" from that terminal connected with 4/0 wire. All charging and load sources are connected to a bus bar located 10" from the shunt and connected to it with 4/0 wire. The terminal connections were done professionally with the correct crimper and dies, and I watched them being made (one advantage of living 2 miles from GeniuneDealz). All wires, connectors, bus bars, etc are brand new. I recently did a capacity test on the bank, so know its SOH, and since this is LFP, it is very easy to determine when 100% SOC is reached. Independent voltmeters and current meters were used to make measurements right at the batteries, and they match what is being presented by the SG200 in both charge and discharge modes. Like mentioned, I have the time and ability right now to daily discharge these batteries below 50% SOC and then immediately recharge them to 100% - and they have been cycling like this for 3 weeks.

My initial inclination was to buy the Victron BM, but decided to be a pioneer with the SG200 given the good press about it as well as the promised SOH monitoring. What I really want in a monitor is coulomb counting, which this doesn't do at all. I'm very close to throwing in the towel and buying the Victron. Sometimes the pioneers do get the arrows (and the expensive lessons).

I am working with Balmar, changing some parameters, and hope that this begins to work better. But now I'm left with lingering doubt about the numbers it presents to me, and how accurate they really are or will be. There are no doubts with good coulomb counters, particularly with LFP. I thought SOH would be the killer reason for this over a coulomb counter, but now I know that if in the future it presents me with a worrisome number, I'm going to have to do a capacity test to check against it anyhow. So it isn't very useful for that. SOC is a pretty useless parameter to LFP, because I don't really care what SOC it is in, and would know that anyway with a coulomb counter.

Mark
 
#264 ·
Yes, Absorb V was below 0.005c before Float. I find, if that’s not the case, by the time it switches over to Float, then float says it’s accepting higher amps and never catches up. For float to be accepting minuscule amps , Absorb has to have done its job. My experience anyway.

I leave to go cruising on Fri. That will give it some learning time. I’ll be off the grid for the first ten days. Uncharacteristically, I have two transient slips booked along the way, after that, to meet family. That will get me intermittently back to 100% too. If that doesn’t “teach” it, then it’s junk. By now, I hold no hope, but I’d be happy to report back otherwise.
 
#265 ·
Smartgauge Battery Monitor | Balmar

According to Balmar's website, the SG is "Accurate within 5% after just a Few Cycles". That's not a dozen. Marketing?

Goes on to say "proven in independent testing by Enersys® to be accurate within 3% after 6 months of use". How did time become a factor and not cycles?

And for folks like me :) ......... "even the most technically challenged crew member can understand just how much power is left in the battery."

The installation diagram, on this web page, also shows the pick ups for the parallel bank, both on one end of the bank. I have the pos on one end and neg on the other, just like the power pickups.

Truth is, I think I understand this stuff better than the average bear, which wasn't always the case, but I'm no pro.
 
#267 ·
There may well be circumstances where more learning cycles are needed, others where fewer are enough.

I am not saying 12 is some magic number, just like ensuring each cycle hits both 100% and 50% SoC, may or may not be needed or helpful with a given bank.

Nor do I think that Enersys sentence was meant to imply anything about the required learning period, just saying that they put it through a very long and thorough proving trial.

Finally, I think it's clear that having very high expectations of any BM is a mistake.

Even if another make & model are proven to be "the most accurate" on the market for a wide range of batteries, that is a very low bar to clear.

Just because you decide to spend an extra few hundred, does not guarantee any such device will deliver **you** tremendous utility, end up being greatly valued in **your** use case.

And if not, does not mean others won't find it the best thing since sliced bread, vive la différence, what makes the world go 'round.
 
#268 ·
I don't think you are understanding the problem being presented here. It is not one of "high expectations", nor is it one of "most accurate", nor is it one of relative utility, nor of expense, nor of value.

It is a case of giving random, completely incorrect, totally unusable in any way results.

This is very different from "vive la difference".

If your refrigerator thermostat caused the interior temperatures to range around randomly during operation, and what you set it at in any given time causes it to perform differently than it did the last time you set it there, and it was so untrustworthy that you needed to bring in a second thermostat to monitor and correct the first one, would that just be a case of relative value and vive la difference?

Mark
 
#270 ·
If your refrigerator thermostat caused the interior temperatures to range around randomly during operation, and what you set it at in any given time causes it to perform differently than it did the last time you set it there, and it was so untrustworthy that you needed to bring in a second thermostat to monitor and correct the first one, would that just be a case of relative value and vive la difference?

Mark
If your beer kept randomly changing temperature it would be a more serious problem that expecting this SG thing to work. If you needed a SG to determine if the beer was 34 degrees or only 36 degrees would you really have any use for it?
 
#269 ·
I was not speaking to any one instance, nor any specific model BM.

And for this case, I did state the unit may be faulty, and hence my suggestion, also several times, to ensure as thorough a test as possible.

A given owner would be advised to make that sort of determination while with their refund period, so if the testing effort is taking "too much" time and effort for their taste they can choose to take another path at just the shipping cost of returning their unit.
 
#273 ·
I’ve been off the grid for over a week. The banks would generally run down to what the SG thought was low 60s, but the amp hr counter thought was low 70s. Recharging took various forms, from running the generator to intermittent engine use. Twice I ran the generator until Absorb acceptance amps got as low as 0.5%C. I let the bank rest, for about 30 mins, after the generator was shut down, and manually reset the SG to 95%. Despite this forced learning, it would only read 85% on subsequent charges back to Absorb=0.5%C. It just seems to like that level, as noted above.

Odd thing happened yesterday. I had to run the engine for 4 hours, underway. I noted that acceptance amps declined to well under the 0.5%C level, more in the range of 0.1%. I do not have a smart alternator, so it essentially maintains a permanent Absorb level charge. The SG, after those 4 hours, now indicated 93%. Still, it was clearly 100%, but I found it interesting that the SG would only recognize charge over 85%, if Absorb went far past where it should.
 
#275 ·
I've been off the grid for over a week. The banks would generally run down to what the SG thought was low 60s, but the amp hr counter thought was low 70s. Recharging took various forms, from running the generator to intermittent engine use. Twice I ran the generator until Absorb acceptance amps got as low as 0.5%C. I let the bank rest, for about 30 mins, after the generator was shut down, and manually reset the SG to 95%. Despite this forced learning, it would only read 85% on subsequent charges back to Absorb=0.5%C. It just seems to like that level, as noted above.

Odd thing happened yesterday. I had to run the engine for 4 hours, underway. I noted that acceptance amps declined to well under the 0.5%C level, more in the range of 0.1%. I do not have a smart alternator, so it essentially maintains a permanent Absorb level charge. The SG, after those 4 hours, now indicated 93%. Still, it was clearly 100%, but I found it interesting that the SG would only recognize charge over 85%, if Absorb went far past where it should.
Like you, I do not have a "smart" regulator on my alternator (Leece-Neville 8MR series). I have 2 x 110 AH FLA wet cells connected in parralel as my house bank. I have been playing with a 60 Watt solar panel (actually 4 x 15 Watt panels), and the MPPT controler that was included with the panel to "charge" my house bank. My observation is that the solar panel does not bring the house bank voltage up to 14.x VDC when I connect it. Instead, the voltage starts at 12.xVDC, and as the battery slowly charges from the solar panels, the voltage displayed on the SG slowly raises. As a result the SG does not seem to recognize this as charging the battery at all! The SOC stays right where it was when I connected the solar panel to the batteries. However, if I start my motor, the 90A alternator quickly jumps the voltage over 14 VDC, and the SG SOC starts to rise.

Interestingly, the SOC reported by the $30 BlueTooth battery monitor (BTBM) does recognize the increase in SOC when the solar panel is charging the batteries. Frequently the SG will report 78% SOC and the BTBM will report 80%. While they don't always match the reported SOC, they never seem to be off (in my limited experience) by more than 10%, and are usually within 5%.

Another observation is that the BTBM seems to recognize anything above 13.2-ish (I am not really sure of this number) VDC as charging. Therefore if my batteries are fully charged, such as when I first shut my engine off, this el-cheapo battery monitor will identify the surface charge as charging until the surface charge drops. The BTBM does NOT report SOC while the batteries are charging - this is something that the SG does.

My working hypothesis is that the SG looks at the battery bank voltage only. If the battery bank voltage is over some seceret threshold the SG believes that the battery bank is being charged. The SG then quantifies the TIME above that threshold, and begins to increase the reported SOC as time elapses. If the voltage falls below another threshold then the SG starts to decrease the reported SOC. The further below that threshold the faster the SOC decreases.

Unlike you I am not trying to figure exactly how the SG will report with some exoctic battery chemistry. My goal is simply to keep my house bank viable for as long as possible. For $30 the BlueTooth device seems to meet that need.
 
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