Buying a Smartgauge

[CatNewBee]

Originally Posted by billknny

Just because YOU do not understand how it works does not mean is "simply cannot work. The world is a bit more complicated than you see...

A little knowledge is a dangerous thing. You are right when you say that you cannot use voltage alone to determine state of charge. But you are totally wrong when you assume that is the only possible measurement that the Smartgauge can make. It is NOT.

You know less than you think you do.

Well, the opposite is the case. Because I KNOW how a lead acid / Gel / AGM battery works, what their inner resistance is and how this affects the voltage while charging / discharging it with diferent loads, I can tell, that simply looking after the Voltage is not enough to guess the state of charge. It might work in static environments, where you have almost constant loads and also for some time constant amp charge sources, so you can interpolate and make an educated guess.

The reality is different, you have solar panels, the sky has some clouds, you never have constant charging and constant discharging, the whole ideal charge curves does not exists in real life, If you look at current and voltage diagrams collected during a real week you'll see a roller-coaster style values. You can compare the curves with a state of charge curve and you will also notice, that voltage and state of charge SOMETIMES correspond but often not, if you look at the Amps, you'll know why. The SmartGauge cannot tell you ANYTHING about your current capacity and how long it would last, that is the REAL reason, it works with ageing batteries so well - it has no CLUE about your capacty.


So this simple device called "SmartGauge" just measures Voltage, it CANNOT measure current (if it could, it would have a shunt in line or a induction sensor over a main line). Therefore it is SOMETIMES right, but often not. That's all I'm saying. Looking at the price tag - well, you can buy a REAL battery monitor system for less, that is smart and can adopt to ageing of the batteries. At least you'll have ALWAYS precise measurements of the Voltage AND the current at any time and a very good estimation of SoC / battery cycles, energy charged / discharged during the day to the battery bank and historic data, that lets you make educated decisions on your capacity needs and on the age / conditions of your batteries and devices connected.
It is just more bang for the buck. Lazy people that do not want to understand their electric will be happy with any gauge that has SMART in her name, so they can outsource this part to a gadget with three knobs.

[sailorboy1]

The past year I've met 3 types of battery users:

1 - pretty much ignorance beyond a basic concept of voltage
2 - knows enough and gives a reasonable amount of attention to their batteries
3 - knows too much, has all the toys to monitor their batteries, and watches and worries about them all the time

For the most part near as I can tell all 3 appear to be getting about the same life out of their batteries. In part it may be that the amount of shore power plugged in time, with #1 plugged in the most. For the most part there appears to be a high percentage of #3 on forums and they also appear to be willing to spend as much on monitoring batteries as they do on the batteries themselves. The biggest difference is that #1 knows when their batteries are dead pretty much on that day to a week away and #3 is concerned because the batteries are going to be dead in a year or so.

I'm a 2+ because I try to stop paying as much attention to the little boxes of lead and acid because they are CHEAP in the big picture, but I just can not stop thinking about them so much. I hope one day to become a 1+ to a 2 because that is all the batteries are really worth in time and money. Yes batteries are VERY important to a cruiser, but damn it they are here to serve the boater not the other way around.

I got my current set of batteries last year and wanted them NOW and paid a premium. So my 440AH bank was $550. If I get 4 years out them thats $11.46/month. NOTHING on a boat is so cheap, especially given the use and abuse, as a set of batteries! Is it really worth all the time and money for me to try to get 6 years out of them, which would save $3.82/month on battery costs???

And if you have one of those $1,100 set of batteries and still only get the 4 years instead of 6 that's still only $7.64/month extra cost so don't start with "But SB your batteries are cheap and mine are so expensive to replace!" And the truth is that a #2 above probably gets much more than 4 years.

So go ahead be a #3. Buy a SmartGuage, LiPO system (or whatever they are called, add an extra 500W of solar, get a wind generator, buy a honda generator, etc. etc. and made those batteries last longer to "save" that $3.82-$7.64/month and be happy that you are being frugal.

STOP THE MADNESS PEOPLE!

[john61ct]

Sorry, but you are just wrong.

The one person that isn't happy with their SGs performance, maybe has a bad one, maybe some other factor is causing the problem.

But in general it does work well, there are a lot more data points available at the terminals than just volts and amps.

SG gives more accurate SoC than anything else so far. Yes, even better with a coulomb counter if you want one of those too.

But ignorance of **how** it works is no excuse for dismissing it.

[john61ct]

Originally Posted by Kenomac

After reading this thread, I have to wonder how many of the Smartgauge fanboys are actually using the thing as full time anchorage liveaboards who monitor solar and generator production.

The Smartgauge works fine if one spends a couple of days per week plugged into shore power, but it's performance stinks when used by people like me who plug in once every six months. We need more accurate information from our system.

That is exactly the situation where AH counters are useless for SoC, and where SG excels.

Why your particular unit hasn't worked for you, we don't know.

[kenbo]

File this under how many angels can dance on the head of a pin or pin head...

If you contact the few battery manufactures that actually make lead acid batteries they will tell you the only way to confirm if your batteries are at 100% SOC is to monitor the change in charging current over time once the battery's post voltage is at the recommended absorption voltage.

One manufacturer states that you need to see less than 0.10A per HR CHANGE in charging current to indicate 100% SOC. That means you need to charge for an hour at absorption voltage while monitoring current AFTER you think the battery is full. Not many of us do that.

So after I learned that lesson the hard way, many times over, I've come to realize that there is little value in "smart" 3 step charging protocols. It's too hard to know when to go to float.

I've come to believe that the more rational approach to engine powered charging , either on propulsion engine or with a DC genset, is to use a hot rated large case alternator with internal regulation and battery voltage sensing (Delco 28SI, et al). Most modern internal voltage regulators now have a vSet of 14.5 or 14.6 and who cares about going to float.

Obviously, this approach is best suited to flooded and some AGM's but I believe it to be not only economical but much better for our batteries.

BTW the 28SI has a short reach mount case that can fit on many Yanmar engines with little modification.

[kenbo]

Originally Posted by sailorboy1

The past year I've met 3 types of battery users:

1 - pretty much ignorance beyond a basic concept of voltage
2 - knows enough and gives a reasonable amount of attention to their batteries
3 - knows too much, has all the toys to monitor their batteries, and watches and worries about them all the time

For the most part near as I can tell all 3 appear to be getting about the same life out of their batteries. In part it may be that the amount of shore power plugged in time, with #1 plugged in the most. For the most part there appears to be a high percentage of #3 on forums and they also appear to be willing to spend as much on monitoring batteries as they do on the batteries themselves. The biggest difference is that #1 knows when their batteries are dead pretty much on that day to a week away and #3 is concerned because the batteries are going to be dead in a year or so.

I'm a 2+ because I try to stop paying as much attention to the little boxes of lead and acid because they are CHEAP in the big picture, but I just can not stop thinking about them so much. I hope one day to become a 1+ to a 2 because that is all the batteries are really worth in time and money. Yes batteries are VERY important to a cruiser, but damn it they are here to serve the boater not the other way around.

I got my current set of batteries last year and wanted them NOW and paid a premium. So my 440AH bank was $550. If I get 4 years out them thats $11.46/month. NOTHING on a boat is so cheap, especially given the use and abuse, as a set of batteries! Is it really worth all the time and money for me to try to get 6 years out of them, which would save $3.82/month on battery costs???

And if you have one of those $1,100 set of batteries and still only get the 4 years instead of 6 that's still only $7.64/month extra cost so don't start with "But SB your batteries are cheap and mine are so expensive to replace!" And the truth is that a #2 above probably gets much more than 4 years.

So go ahead be a #3. Buy a SmartGuage, LiPO system (or whatever they are called, add an extra 500W of solar, get a wind generator, buy a honda generator, etc. etc. and made those batteries last longer to "save" that $3.82-$7.64/month and be happy that you are being frugal.

STOP THE MADNESS PEOPLE!

Man after my own heart!

[CatNewBee]

The problem is, you never charge-only or discharge only. You use power while charging, sometimes you even discharge the battery while "charging" - if the load is higher than your charger can provide. This is a complex dynamic system, the Voltage change is always ahead of SoC, how much ahead it is is a function of current going in or out and the capacity/resistance of the battery while charging / discharging - unfortunately the resistance is also a function of SoC, chemistry, geometry of the battery and temperature, with also depends on the environment and on the current / load.

If you want to have some more precise idea about SoC you must measure all of this components and calculate SoC and also adjust the capacity by each cycle. You also will have do sync to a 100% SoC when charging exceeds time and current decreases, and no load discharges for a longer time period. This period depends on the necessities of the chosen chemistry (absorption phase). For a GEL battery it could be several hours, for a wet battery or AGM it can be 30 minutes, a LiFeYPO4 it is almost instant.

Therefore good battery monitors have configuration options for this.

[sailinglegend]

Originally Posted by CatNewBee

.... I KNOW how a lead acid / Gel / AGM battery works, what their inner resistance is and how this affects the voltage while charging / discharging it with diferent loads, I can tell, that simply looking after the Voltage is not enough to guess the state of charge......

I have looked over all you previous posts and you have very few postings about batteries or charging so in no way are you a battery expert!!!! But keep posting the same message that it can't work without having tried it just alienates posters who do want to understand the facts.

Let me quote the designer Chris Gibson:

"Obviously I am not prepared to disclose how SmartGauge works. Anyone who asks me to do so is simply being totally unreasonable.
But to say that only voltage can be measured via 2 wires is *completely* incorrect.....

Pull a brief current pulse from the battery and measure the voltage drop, this will give an indication of internal resistance.

Present an AC voltage across the battery and measure the phase angle and amplitude of the resultant current. This will show the AC impedance of the battery.

Do the same thing with a wide variety of frequencies and analyse the results. This is know as AC impedance spectrography."

See also this post by 'Toaster' where he shows the SOC can be calculated without measuring current:

"Let's assume the SOC is some unknown function of voltage V, current I and time t. Also throw in battery parameters such as capacity and age, maybe even unknown things. We'll call those BP. Let's assume BP is a slowly varying function of time (they age slowly). And battery temperature is a factor too (also slowly varying).

So, SOC(t) = F(V, I, BP, T, t).

F is a gnarly function, most likely you could not write it down. But it exists.

First observation. The current I is likely to be a function of dV/dt (sorry, this is calculus). Q=CV so I = dQ/dt = dV/dt.C. Of course C may be a function of time but let's assume a slowly varying one (so that dC/dt is negligible). In plain speak, this means we have just eliminated the current I and no longer need to measure it. Magic!!

Then:
SOC(t) = F(V, dV/dt, BP, T, t)

Now, any well behaved function of t can be expanded like this:

SOC(t) = F(t) = A + B.V(t) + C.dV(t)/dt + D.d2V(t)/dt2 + etc., where A, B, C, D, etc are constants. This is just math.

In any computer model, aka simulation, that is based on time, you have to convert continuum physics into discrete computer steps. The longer the time steps (intervals) the more error creeps in. That's likely why SmartGauge measures V at a high frequency - they want to measure dV/dt. In fact, it is highly likely that their model also uses d2V/dt2 and higher derivatives. The higher the derivative, the faster they need the V data.

It's then a relatively simple task for a computer to take a time series of V(t), fit it to the equation and obtain the constants A, B, C, ..... Once you know those constants, the problem is solved, you can convert V(t) into SOC(t). Put in plain English, you can accurately calculate the SOC at time t, if you know the *history* of V.

An important point is that you don't even need to understand the physics of batteries to do this - you can do it by brute force using computers. All you have to believe is that batteries obey reasonable laws of physics.p

Give the little chip in the SmartGauge the right algorithm and a starting point, feed it some voltage data, and Bob's your uncle. My guess is it will make measurements, make a prediction for 30 seconds, check the prediction against reality, adjust the parameters, repeat ad nauseum, "learning" as it goes. This is probably how it adapts to battery ageing."

Smart gauge has 480 constants and measures the voltage over 1000 times a second so its algorithm must be a lot more complex than Toaster's.

Even though I don't fully understand the formula my degree in electrical engineering allows me to understand the principle. Please note that Toaster posted here about the Balmar conversion between UK metric voltage and US imperial voltage - great post!!!! I guess he was just piss*d off with so much dissent from so many people who don't understand the principle of why this device was designed in the first place.

I'm not being geeky - I just wanted to prove the point - again - that Smartgauge can work. As the designer says its not perfect but it is better than any shunt based battery monitor, and he worked for Link and was fed up explaining to unhappy customers why their expensive battery monitor didn't work properly after a couple of years.

I think that is where the problem lies - they believe in their battery monitor 100% - go and read MaineSail's excellent website about why they are so inaccurate.

[CatNewBee]

Well, as I told you, in a ideal world you indeed can calculate some approximation to SoC, in the real world you measure something, but not the resistance of the battery nor the AC Impedance, because the battery is part of changing circuitry containing high-amp devices, devices with inductivity and all the problems around, fast switching / high frequency inverters and many more, that are occasionally on or off, so pure integration over the time of the voltage by any model would not work.

Your perception is, the SmartGauge is accurate, because you believe so - well believers are often reluctant to reality. There is a difference between knowing and believing something, while believing is easier and more convenient - therefore superior.

It might be good enough for the average user, I agree, a CoC precision of 10% is more than enough for your every day live, and this can be done even with a Volt-meter alone when you turn off all loads for a few minutes. There is no magic at all. It does not matter if the SoC in reality is 5% higher or lower then the reading on the gauge - you cannot prove it anyway, and if you believe she is more accurate than a battery monitor - well your perception would be the monitor is probably 10% off.

It is the alignment of perception, believe, marketing, trust in superior computer models and hi-speed measurement - and in having something better than the others.

Well a good A/D converter measures also high-speed, but uses interpolation over many measurements to discriminate statistical errors and noise.

I do agree, in a lab you can even use temperature changes to estimate currents and use current to measure voltage if you have linear resistors or some with known U/I curve. This is what most voltmeters do, they close the circuit and measure the current trough a internal resistor, especially the analog instruments. They use a resistor cascade to switch to different resolutions. Event a shunt - Ammeter measures the current by measuring the Voltage Drop over the shunt by measuring current trough internal resistor.

SmartGauge is good on a pure discharge circuit, but will fail in an environment with dynamic charge sources like solar or wind gens - and also on batteries with very low resistance like Lithium..

[conachair]

Originally Posted by sailorboy1

The past year I've met 3 types of battery users:

1 - pretty much ignorance beyond a basic concept of voltage
2 - knows enough and gives a reasonable amount of attention to their batteries
3 - knows too much, has all the toys to monitor their batteries, and watches and worries about them all the time

You haven't met 4 yet then, - Knows a good deal about how the batteries work, knows easily as much if not more than 3 about whats going on with the batts without all the toys but with some basic accurate kit and doesn't worry as the batteries are being fully charged often. And has a good idea if they'll last another while so will know when it might be time to plan ahead a bit to be in a country where it's possible to buy good batteries easily.
If you're staying around home territory then you've a strong argument, but it's not all about money once you leave the marina behind you and head off across the oceans. Madness it ain't

[conachair]

Originally Posted by kenbo

File this under how many angels can dance on the head of a pin or pin head...

If you contact the few battery manufactures that actually make lead acid batteries they will tell you the only way to confirm if your batteries are at 100% SOC is to monitor the change in charging current over time once the battery's post voltage is at the recommended absorption voltage.

One manufacturer states that you need to see less than 0.10A per HR CHANGE in charging current to indicate 100% SOC. That means you need to charge for an hour at absorption voltage while monitoring current AFTER you think the battery is full. Not many of us do that.

So after I learned that lesson the hard way, many times over, I've come to realize that there is little value in "smart" 3 step charging protocols. It's too hard to know when to go to float.

I've come to believe that the more rational approach to engine powered charging , either on propulsion engine or with a DC genset, is to use a hot rated large case alternator with internal regulation and battery voltage sensing (Delco 28SI, et al). Most modern internal voltage regulators now have a vSet of 14.5 or 14.6 and who cares about going to float.

Obviously, this approach is best suited to flooded and some AGM's but I believe it to be not only economical but much better for our batteries.

BTW the 28SI has a short reach mount case that can fit on many Yanmar engines with little modification.

Same on solar, put the float voltage the same as absorption and be done with it.

[sailorboy1]

Originally Posted by conachair

You haven't met 4 yet then, - Knows a good deal about how the batteries work, knows easily as much if not more than 3 about whats going on with the batts without all the toys but with some basic accurate kit and doesn't worry as the batteries are being fully charged often. And has a good idea if they'll last another while so will know when it might be time to plan ahead a bit to be in a country where it's possible to buy good batteries easily.
If you're staying around home territory then you've a strong argument, but it's not all about money once you leave the marina behind you and head off across the oceans. Madness it ain't

That’s just a 2 to maybe 2+. The biggest advantage to being a 2 is that you know when batteries are starting to go, but that they still have have enough usable life that you can replacement them on your schedule.

[john61ct]

Originally Posted by sailinglegend

But keep posting the same message that it can't work without having tried it just alienates posters who do want to understand the facts.

Let me quote the designer Chris Gibson

Excellent research, great post, you can lead the horse to water,

But that thick-headed horse just won't drink.

Oh well knowledge is the light, will overcome ignorance every time.

[Dockhead]

Originally Posted by sailinglegend

I have looked over all you previous posts and you have very few postings about batteries or charging so in no way are you a battery expert!!!! But keep posting the same message that it can't work without having tried it just alienates posters who do want to understand the facts.

Let me quote the designer Chris Gibson:

"Obviously I am not prepared to disclose how SmartGauge works. Anyone who asks me to do so is simply being totally unreasonable.
But to say that only voltage can be measured via 2 wires is *completely* incorrect.....

Pull a brief current pulse from the battery and measure the voltage drop, this will give an indication of internal resistance.

Present an AC voltage across the battery and measure the phase angle and amplitude of the resultant current. This will show the AC impedance of the battery.

Do the same thing with a wide variety of frequencies and analyse the results. This is know as AC impedance spectrography."

See also this post by 'Toaster' where he shows the SOC can be calculated without measuring current:

"Let's assume the SOC is some unknown function of voltage V, current I and time t. Also throw in battery parameters such as capacity and age, maybe even unknown things. We'll call those BP. Let's assume BP is a slowly varying function of time (they age slowly). And battery temperature is a factor too (also slowly varying).

So, SOC(t) = F(V, I, BP, T, t).

F is a gnarly function, most likely you could not write it down. But it exists.

First observation. The current I is likely to be a function of dV/dt (sorry, this is calculus). Q=CV so I = dQ/dt = dV/dt.C. Of course C may be a function of time but let's assume a slowly varying one (so that dC/dt is negligible). In plain speak, this means we have just eliminated the current I and no longer need to measure it. Magic!!

Then:
SOC(t) = F(V, dV/dt, BP, T, t)

Now, any well behaved function of t can be expanded like this:

SOC(t) = F(t) = A + B.V(t) + C.dV(t)/dt + D.d2V(t)/dt2 + etc., where A, B, C, D, etc are constants. This is just math.

In any computer model, aka simulation, that is based on time, you have to convert continuum physics into discrete computer steps. The longer the time steps (intervals) the more error creeps in. That's likely why SmartGauge measures V at a high frequency - they want to measure dV/dt. In fact, it is highly likely that their model also uses d2V/dt2 and higher derivatives. The higher the derivative, the faster they need the V data.

It's then a relatively simple task for a computer to take a time series of V(t), fit it to the equation and obtain the constants A, B, C, ..... Once you know those constants, the problem is solved, you can convert V(t) into SOC(t). Put in plain English, you can accurately calculate the SOC at time t, if you know the *history* of V.

An important point is that you don't even need to understand the physics of batteries to do this - you can do it by brute force using computers. All you have to believe is that batteries obey reasonable laws of physics.p

Give the little chip in the SmartGauge the right algorithm and a starting point, feed it some voltage data, and Bob's your uncle. My guess is it will make measurements, make a prediction for 30 seconds, check the prediction against reality, adjust the parameters, repeat ad nauseum, "learning" as it goes. This is probably how it adapts to battery ageing."

Smart gauge has 480 constants and measures the voltage over 1000 times a second so its algorithm must be a lot more complex than Toaster's.

Even though I don't fully understand the formula my degree in electrical engineering allows me to understand the principle. Please note that Toaster posted here about the Balmar conversion between UK metric voltage and US imperial voltage - great post!!!! I guess he was just piss*d off with so much dissent from so many people who don't understand the principle of why this device was designed in the first place.

I'm not being geeky - I just wanted to prove the point - again - that Smartgauge can work. As the designer says its not perfect but it is better than any shunt based battery monitor, and he worked for Link and was fed up explaining to unhappy customers why their expensive battery monitor didn't work properly after a couple of years.

I think that is where the problem lies - they believe in their battery monitor 100% - go and read MaineSail's excellent website about why they are so inaccurate.

Chris Gibson irritates me, I must confess. He doesn't tell us how the device works, but invites us to speculate based on a lot of stuff which may or may not be part of the algorithm. "Measures voltage 1000 times a second" -- wow, must be accurate if it does that.

How can anyone say "it can't work" when we don't even know the operating principle?

I can't argue with a principle which hasn't been revealed to me, so I refrain from speculating. So that leaves us with nothing but practical experience. I can say from a few years of practical experience, that on my boat (maybe not on yours, I can only speak about mine), the SmartGauge works very well as long as there is no surface charge and no charge source attached.

Is it a fancy impedance spectrometer or just an averaging voltmeter, or what is it? God only knows.

[Paul L]

Originally Posted by john61ct

See?

> Even so most cruisers NEVER get their batteries to 100% regularly at anchor, even though a little light comes on saying full, or your BM or Smartgauge says 100%.

I think it is in fact true, most people have no way to get accurate SoC, are not tracking endAmps, and don't calibrate their charge regulators.

Likely most just leave settings at factory defaults.

Let me be more specific. I think it is false to say that most cruisers who cruise continually away from marinas do not charge their batteries to 100% periodically. Some may never get there, but many charge with multiple sources and have their regulator settings set appropriately. Sure it would be better if they got to 100% everyday, but that is not practical. Charging your Batts reasonably isn't an unattainable holy Grail or only accessible by experts.