LiFePO4 capacity test

[Paul L]

Originally Posted by transmitterdan

Of course it is about marketing. That’s how it works many times in business. Indeed, that’s how companies stay in business most of the time.

The original SG did not have a shunt. So people who were needing (or at least desirous) to know how much current their batteries were receiving or delivering were buying another meter. The clever people at Balmar recognized a market existed for a smart device that also included the current measurement feature. So they had one designed and that is the SG200. The original SG has a good reputation so they kept the name.

Then they worked with some reputable marine service providers like Rod Collins to get their feedback. After many months of outside testing and probably some tweaking of their algorithm these outside testers gave it a thumbs up. So for most of us we can look at their experience and decide whether the device is “good enough” for our own use. I have to say that the endorsement by people like that is worth a lot more than random chatter on the internet.

Over time reputable alternator vendors have gradually expanded their literature. For years the alternators were rated on initial current output (so-called cold amps) because flooded lead acid batteries have a current profile that shoots up and falls rapidly. Then people started building huge AGM banks and ultimately LiFePo banks that will accept huge charge current for a long time. In this new application the alternators had to be derated. The technical advice Balmar gives today is pretty honest and straightforward about how to use their alternators and regulators.

If we objectively look at history I think we can see that the old version of Occam’s razor is often correct. Be not quick to ascribe malice when ignorance is the more likely explanation.

I agree with your Occams razor comment. If you look at the current pdf brochures for the series6 alts it says that a 100a alt will put out 80-93a when hot. Pretty unlikely you'll get anything like that continuosly or for an extended period of time from the small frame. I sure don't on my Yanmar. I'm not asking them to pull a miracle out of a small frame alt, just to be up front with the marketing.

If it is attributable to ignorance, it is willful ignorance. Something that is very popular in the marketing realm.

I too like to see the recommendations from actual expert testers - probably as much as the marketing guys like those recommendations. It isn't unreasonable to ask for some error ranges or tolerances for the product. Test it and put it in the spec. Then I can look at my situation and see how valuable I feel the product might be to me.

[john61ct]

Originally Posted by transmitterdan

According to the manufacturer the SG200 is not a redesigned version of the SG. It is a new product not based on the SmartGauge.

No one has claimed otherwise, why would you even bring that up?

The "Active Impedance Compensation" part is a similar measurement technology, but unlike SmartGauge they combine its algorithms with the more traditional Ah-counting.

Which is what allows it to work with non-lead chemistries.

> The original SG did not have a shunt.

Just call it SmartGauge. That wording is confusing, implies a connection between the two. Even better, Merlin SmartGauge, since Balmar was just a reseller, had nothing to do with its development.


> The original SG has a good reputation so they kept the name.

No, the full name is SG200. There is nothing to indicate that is supposed to stand for SmartGauge, that it is just something you are inferring.

Originally Posted by transmitterdan

If we objectively look at history I think we can see that the old version of Occam’s razor is often correct. Be not quick to ascribe malice when ignorance is the more likely explanation.

Hanlon is the modern one, Occam lived in the 14th century

[john61ct]

Originally Posted by Paul L

That makes it clearer So the accuracy spec is clearly stated as unique. That's purely marketing, not engineering.
…
The new version is superior as it added a shunt.??

The "unique" aspect is the combining of the two algorithms.

With the new SoH measurement, yes, very unique, in the consumer arena.

I only know of Merlin's more recent designs which I believe are intended for military customers, and too expensive for us.

You are correct to be skeptical, only time will tell, I'm sure someone at Maine Sail's level will publish CR-style objective test results comparing its accuracy to other meters one day.

But that accuracy will vary depending on the battery type & model maybe age, usage patterns, temperature, etc.

You should probably hold off buying one.

But the more others do, willing to be the pioneers, the quicker we later adopters will get their feedback.

[john61ct]

Originally Posted by CatNewBee

Can we agree to disagree.

I outlined the standard and 100% objective definition of SoH above.

The relationship between that hard data and the decision as to when you want to replace your bank, I agree is subjective.

> You may have an SOC of 80%, but still have the full capacity usable.

No, that is nonsense.

Yes there is room for **a little** wiggle room, a difference between how the maker defines 0% and 100%, and what the owner uses as her setpoints for those labels in daily cycling.

But any given SoC point can be accurately measured through load testing to a standard zero-definition, and I have never come across anyone defining "their usage 100%" at any significant distance from the result of using the vendor's definition.

Maybe 3-5% at most, measured through load testing.

Of course none of the above is using SoC meters as canonical, even the best most accurate such devices are just guesstimating during cycling, only load testing can be relied upon when testing accuracy is critical.

[john61ct]

Now choosing your zero point to be at 20% SoC rather than ever going lower, that would result in a big boost to longevity, certainly makes sense.

Just not taking that much off the top end.

[CatNewBee]

Originally Posted by john61ct

...
> You may have an SOC of 80%, but still have the full capacity usable.

No, that is nonsense.
...

You got me. Typo, I mean 80% SoH

[Paul L]

Originally Posted by john61ct

The "unique" aspect is the combining of the two algorithms.

With the new SoH measurement, yes, very unique, in the consumer arena.

I only know of Merlin's more recent designs which I believe are intended for military customers, and too expensive for us.

You are correct to be skeptical, only time will tell, I'm sure someone at Maine Sail's level will publish CR-style objective test results comparing its accuracy to other meters one day.

But that accuracy will vary depending on the battery type & model maybe age, usage patterns, temperature, etc.

You should probably hold off buying one.

But the more others do, willing to be the pioneers, the quicker we later adopters will get their feedback.

The vendor is marketing this device to cover most battery types. Of course the accuarcy will vary based on conditions. That doesn't negate the need to spec accuracy ranges for the two key parameters the device is designed to deliver. Like most accuarcy ranges, there are multiple parameters associated with them. Sometimes to make them clear and sometimes to assist marketing obfuscation.
This is turning into beating a dead horse.

[rgleason]

Catnewbee
Your statement ....use a real ... says volumns about your "opinion" about this instrument, each to his own, however your statement

" Same for the battery SOC. You may have an SOC of 80%, but still have the full capacity usable"

I don't believe this is a accurate statement about the sg200 and believe Chris would take issue with it.

[newhaul]

Originally Posted by Paul L

The vendor is marketing this device to cover most battery types. Of course the accuarcy will vary based on conditions. That doesn't negate the need to spec accuracy ranges for the two key parameters the device is designed to deliver. Like most accuarcy ranges, there are multiple parameters associated with them. Sometimes to make them clear and sometimes to assist marketing obfuscation.
This is turning into beating a dead horse.

agreed this thread has progressed about as far as it is going to

[Delfin]

Originally Posted by CatNewBee

You got me. Typo, I mean 80% SoH

With respect, I don't think that a battery at 80% SoH could deliver full capacity, since the algorithm involves the device's calculation of how much capacity has been lost, based on how many Ah it will absorb influenced the time it takes to reach terminal current absorption. At least, that is how I understand the calculation.

By definition, a SoH lower than 100% is going to have some degradation of original capacity.

[CatNewBee]

Originally Posted by Delfin

With respect, I don't think that a battery at 80% SoH could deliver full capacity, since the algorithm involves the device's calculation of how much capacity has been lost, based on how many Ah it will absorb influenced the time it takes to reach terminal current absorption. At least, that is how I understand the calculation.

By definition, a SoH lower than 100% is going to have some degradation of original capacity.

Not really. Some friends and I have experienced, that the cells from Winston exceed the nominal capacity by 20+%, I have charged my nominal 1000Ah cells to full at 3.65V and have discharged then to 2.9V in a 12V configuration measuring the Ah / Wh by 2 independent instruments drawing 15kWh after the inverter and discharging almost 1300Ah at the battery, that is a over-provision of 30%.

If you set up your coulomb counter to the nominal capacity of 1000Ah, you can have a degradation of 300Ah and still have 100% nominal capacity despite your meter shows 80% SOH.

I guess, this is how they guarantee 5000 cycles at 80% DOD, just having enough reserves upfront. They provide the cells for professional installations, consumer market is not their focus.

[rgleason]

So in this case, with Winston batteries, if you enter 1000ah in the settings, and the batteries actually have 1200ah, one would expect there to be recognition of this in the sg200 after a reasonable number of cycles.
I suppose the capacity setting could be automatically increased, or the SOH be shown as 120%, or perhaps some other adjustment. They probably have this explained in the manual, but I don't have it available

[CatNewBee]

Originally Posted by rgleason

So in this case, with Winston batteries, if you enter 1000ah in the settings, and the batteries actually have 1200ah, one would expect there to be recognition of this in the sg200 after a reasonable number of cycles.
I suppose the capacity setting could be automatically increased, or the SOH be shown as 120%, or perhaps some other adjustment. They probably have this explained in the manual, but I don't have it available

I doubt it, because you never go that deep if not on purpose for testing. I usually draw between 300Ah and 600Ah, so the SG200 (if I had one) would think I have a 600Ah battery or whatever I set, it will never experience full and also never empty. The calculation is than flawed, based on PSOC and internal guessing. Also the battery and the battery monitor never run isolated, there are sources like solar and loads connected all the time. So best guess is Ah in to Ah out multiplied with an estimated (variable to inner resistance, load and temp) efficiency factor which can be compromised by BMS balancing losses, that are out of reach from the SG200. I am not saying, it is bad, I am saying it cannot be perfect, there is no magic inside - it can adapt and approximate, but it can be also as wrong as any other battery computer if not synchronized from time to time.

The BMS has better knowledge at cell level about SoC and SoH than any external gauge can provide anyway. The SG200 is a pack level monitor, SoH can differ at cell level.

[Q Xopa]

Originally Posted by Delfin

With respect, I don't think that a battery at 80% SoH could deliver full capacity, since the algorithm involves the device's calculation of how much capacity has been lost, based on how many Ah it will absorb influenced the time it takes to reach terminal current absorption. At least, that is how I understand the calculation.

By definition, a SoH lower than 100% is going to have some degradation of original capacity.

Yes agreed that an SOH less than 100% is lower its 'orginal capacity'. However a clearly defined 'orginal capacity' SOH 100% is not known, by us. So by extension we can really know how relevant the SOH %number is?
Obviously we can deduce more is better for SOH, but not what number should cause what action or worry.
The same is true of the SOC number. Which 100 and 0% definitions are being displayed is not known so how can we be sure its the ones we want to use?

Im not saying its not good. In fact from what we are hearing so far it is.

However I, like most here, like being able to verify this information as much as we can.

Lets suppose its working fine, then suddenly doesnt. Its going to be harder to see, or determine. Worse still is it slowly missreading.

Having blind faith in a black box is not the way most of us are comfortable.

[john61ct]

So use multiple boxen, and benchmark both measures with manual load tests.

The better SoC units let you calibrate Peukert and CEF , keep at it until they agree with each other, toss out the hopeless cases, or maybe just keep the one that guesstimates most accurately.

And be sure to post your protocols and results back here!

For those who think the above would not be worthwhile (much less fun), no need to say so.

But I think any of the respected meters are still better than flying blind. . .