Balmar SG-200 Battery Monitor

[two-rocks]

Originally Posted by john61ct

To me, the SoC percentage should reflect the actual current capacity of the bank.

Does it not do this? Using the SoH in it's calculations for SoC

Originally Posted by john61ct

Even if SG200's automatic SoH estimating will reduce the required frequency of (or in theory even eliminate) that requirement for accuracy (in my sense), are you saying it does not offer that feature?

My reason for getting this meter was to eliminate that "feature"

[john61ct]

Originally Posted by two-rocks

Makes replacement easier to justify - i.e. I'm hoping the reading rates the bettery at <70% SOH once it gets a few fill ups and full 'downs' If not, I'll just use them like I stole them [emoji3]

LOL

To me higher SoH is always better.

If setting out on years-long RTW travel in primitive locations might upgrade to a longer-lived bank even if the current one's just fine.

All depends on context, I feel no need to justify anything if I think it's worth it. But then my life partners don't outrank me unless they're paying my way 8-)

[john61ct]

Originally Posted by Paul L

The benchmark would be the accuracy specification that the vendor states.

But there is **no way** to know what the actual accuracy is!

Other than comparing a "known more accurate" instrument measuring **that same battery at that time**.

[nebster]

Originally Posted by john61ct

And again, exactly what more-accurate standard measurement could it compare its estimate to, in order to judge its own estimate is now "accurate enough"?

Well, it could compare its estimate to its previous estimate(s) and observe the rate of change. When that change gets low enough, it could decide that it has converged enough and indicate that.

Or, it could keep track of how many charge/discharge curves it has seen, and/or how many data points it has evaluated within those curves. That sum could be compared to a table of typical cycles needed for reasonable convergence*for a given chemistry, programmed in by the manufacturer. When the sample size exceeds a predetermined quantity, the unit could show it.

Or, it could use any number of statistical measurements derived from its curve-fitting algorithm. We don't know exactly what technique it is using, but most of these have metrics that attempt to quantify the performance of a new sample run against the cohort.

[john61ct]

Originally Posted by two-rocks

Does it not do this? Using the SoH in it's calculations for SoC

I would also hope expect so! Certainly do not want to have to "interpret" that 88% is actually 100% in the sense of "highest this batt can go this season", with different numbers meaning that next year.


> My reason for getting this meter was to eliminate that "feature"

I agree, but would still want it available.

If the SG200's "Active Impedance Compensation" algorithms turns out not to be so accurate for a given model / chemistry,

thus falling back to plain old coulomb counting,

a manual reset at the top will help keep good accuracy.

Hopefully not needed at all. But maybe at least does not need to be so frequent.

And if nothing else, ideally used in any case to help speed up the learning process of its AIC side.

[Paul L]

Originally Posted by john61ct

But there is **no way** to know what the actual accuracy is!

Other than comparing a "known more accurate" instrument measuring **that same battery at that time**.

Like I said, the vendor should spec the accuarcy and tell you what the conditions are for that accuarcy. How can you tell if the device is working properly if you don't know the spec? If the device is designed and sold as +/-10% accuarcy and it reads 90%, then a reasonable user can infer the actual range is 80 to 90%. Then if some more advanced user wants to test against a 20 hr test, they can determine if the particular reading is accurate within the specd range and the device is working as marketed.

The selective cherry picking of the readings, sometimes agreeing with them and sometimes saying they aren't accurate yet is not going to help a typical user. The device reads 90% and we can say it is accurate and the lead acid battery isn't broken in yet, or we can say the reading is 85% and say oh it hasn't been through enough cycles to be accurate.

[john61ct]

Originally Posted by nebster

Well, it could compare its estimate to its previous estimate(s) and observe the rate of change. When that change gets low enough, it could decide that it has converged enough and indicate that.

Or, it could keep track of how many charge/discharge curves it has seen, and/or how many data points it has evaluated within those curves. That sum could be compared to a table of typical cycles needed for reasonable convergence*for a given chemistry, programmed in by the manufacturer. When the sample size exceeds a predetermined quantity, the unit could show it.

Or, it could use any number of statistical measurements derived from its curve-fitting algorithm. We don't know exactly what technique it is using, but most of these have metrics that attempt to quantify the performance of a new sample run against the cohort.

I suppose. But new information coming along could result in a different estimate curve.

Given all the hundreds of wildly varying batteries in use globally,

only a very small subset used in development of such a device even assuming unlimited resources available,

with new brands and chemistries being released all the time,

and the fact such algorithms will not improve actual measuring accuracy, just add complexity for the sake of an "I think I'm done learning now" indicator,

seems to me an unrealistic expectation.

The key is to remember, the actual phenomena being measured are not precise in the first place, so there is no point other than marketing, in encouraging the customer to believe in precision indicators beyond the 3-5% range.

[nebster]

Originally Posted by john61ct

To me, the SoC percentage should reflect the actual current capacity of the bank.

Let A = the user-specified capacity.
Let B = the capacity the SG200 currently calculates from its fitting algorithm.

SOH is displayed as B / A.

You wrote, above, that SOH should "adjust" to 100% over time, even if it comes up lower in early tests.

With a battery that never delivers the specified capacity, B will never equal A.

I guess you could put in a fake A if you'd rather have the "health" start at 100%. It's just a convenience fraction.

[john61ct]

Originally Posted by Paul L

to test against a 20 hr test, they can determine if the particular reading is accurate

That is the only practical measure IRL, and only applies to **that** battery in **those** conditions.

[Paul L]

Originally Posted by john61ct

That is the only practical measure IRL, and only applies to **that** battery in **those** conditions.

BS. Then why even have an SG200 if it isn't a practical measure?
You want to play both sides of the game, claiming the device is accurate and a must on a cruising boat, and that only a complex test that very few actual cruisers ever do is required.
I guess when its all just theoretical to you and you have no cruising electrical experience, mimicking what you read online as if its gospel is the best alternative.

[Maine Sail]

Originally Posted by john61ct

To me, the SoC percentage should reflect the actual current capacity of the bank.

SoC by itself is not and does not have any relation to SoH in terms of deliverable Ah capacity. You can't infer that a battery is at 100% SoH because it can attain 100% SoC.. This is why SoH and SoC are different.

We have tested batteries that can barely must 30% of their Ah rating yet can achieve a chemical 100% SoC based on both open circuit voltage and specific gravity. The owner of one bank, and an original Smartgauge, knew his SoC was plummeting way too fast (time @ X load) and this is what gave him insight into his failed bank. So yes his battery was being charged to 100% SoC but it had an actual Ah capacity of less than 30% of rated or less than 30% SoH but it could still achieve a chemical 100% SoC. The SG200 removes the mental time equation by adding SoH to the mix..

Just because a battery can charge to 100% SoC this does not tell you anything about the batteries SoH in relation to Ah capacity unless you examine other variables.

Originally Posted by john61ct

That is the goal implied in your three BM articles on marinehowto, right?

Umm not at all.... You don't seem to fully understand what you are discussing? The goal of those articles is to help owners not be mislead by screen data that can be incorrect, out of sync with the battery & to explain how this data can become incorrect, how to properly wire to not create inaccuracies etc.. Here is but one glaring example of a typical Ah counter being grossly inaccurate.

Battery Voltage = 12.70V or almost 100% SoC


-264Ah on a 70Ah battery sitting at 12.7V, not even possible:

Originally Posted by john61ct

Isn't that how SmartGauge operates? without any Ah capacity input from the owner.

The original Smartgauge tells you SoC very accurately, unlike a traditional Ah counter. But SoC, without other measurements, such as time to 50% from 100%, and at what load, tells you only the SoC not the SoH. For most boaters basic SoC and achieving 100% SoC often enough is really what is most important for battery life. I have run tests on the original Smartgauge for SoH and it wound up within a few % using SoC + time + load as the indicator. Not bad really but still not as easy as the SoH screen.

Originally Posted by john61ct

And, as with most BMs, there is the ability to reset the 100% point when the owner knows the bank is Full via measuring tapering endAmps.

Lets not confuse SoH and SoC. How do "end amps" work when the battery starts to sulfate? The whole idea with the SG200, or original Smartgauge, is to remove this level of fiddling from the equation and replace it with a learning algorithm that stays accurate even as the bank ages without any human input.. It is all about simplicity for the owner.

Originally Posted by john61ct

Even if SG200's automatic SoH estimating will reduce the required frequency of (or in theory even eliminate) that requirement for accuracy (in my sense), are you saying it does not offer that feature?

John why do you enter discussions acting as an expert, chronically using absolute statements, when you have little knowledge or practical experience of what you are actually discussing? What you just said above is about as gobbledygook as I have read in a while, it does not even make sense..

Originally Posted by john61ct

I concede we are discussing a high level of care here, what most owners consider unrealistic or not worthwhile in practice.

Lets keep this simple, the SG200 can take the guesswork out of it for most owners. Program your rated capacity, go use the bank, pretty soon it will be telling you an SoH that is much more accurate than any device we've seen thus far. It won't do this immediately or with 5% discharge cycles but it is darn simple.

[john61ct]

Originally Posted by nebster

Let A = the user-specified capacity.

Which is known to be inaccurate, unless the result of a recent load test.

> Let B = the capacity the SG200 currently calculates from its fitting algorithm.

Which accuracy is unknown, unless compared to A.

> You wrote, above, that SOH should "adjust" to 100% over time, even if it comes up lower in early tests.

The **only** two SoC% points **known** to be accurate for sure, are

0% (10.5V under a light load, nominally .05C), and

100% (point tapering current hits "endAmps Full")


> SOH is displayed as B / A.

Wut?

only if A is a fixed number intended to indicate either vendor rating (which we know rarely accurate), or the "maximum ever" capacity determined by a benchmark load test after the commissioning / breaking in period.


The SoC% number displayed should IMO be a relative "countdown", with the 100% mark matching the definition above.

[john61ct]

In addition, IMO the user should be able to reset the scale at the **bottom** end as well, with the 0% point self-defined as "the DoD point below which I do not want to let the bank go."

Thus if an occasional incident or emergency forces us to go past that Zero point, the display could flash the voltage reading in red or something, just spitballing there of course.

[john61ct]

Originally Posted by Paul L

BS. Then why even have an SG200 if it isn't a practical measure?

I did not mean as a measure of SoC nor SoH.

A measure against which your idea of "accuracy" can be benchmarked.

This is a discussion of ideas here, there is nothing gained by attacking me in person.

Address the points of the argument neutrally, if I make a statement that anyone believes is in error,

I am very happy to be corrected by those whose expertise I trust, I learn new things every day and strive to help the community by remaining objective, have no ax to grind, not promoting any products nor any one way of accomplishing our shared objectives.

Is Balmar or any other vendor a sponsor of these forums?

[john61ct]

Originally Posted by Maine Sail

SoC by itself is not and does not have any relation to SoH in terms of deliverable Ah capacity.

Exactly.

The 100% SoC point is IMO best defined as the point at which that battery, at that time is Full, as indicated by holding Absorb voltage until current tapers down to the endAmps condition, ideally both spec'd in the mfg datasheets.

Easily and objectively verified by any owner with an ammeter.

Which I guess you are here calling "chemical 100% SoC"?

And of course that measurement does not have anything to do with SoH, no one is saying otherwise.

> I have run tests on the original Smartgauge for SoH and it wound up within a few % using SoC + time + load as the indicator.

And it does indicate 100% in the sense I am advocating here. And afaik every other BM does the same, maybe different underlying methods,

but the meaning of 100% SoC does not change as SoH does,

the draw-down is measured relative to whatever the top is, that battery is capable of achieving without overcharging.

I am inferring from your previous post that SG200 is going to do something different?