The New Balmar Smart Gauge

[Maine Sail]

Hi All,

I know many have been emailing me and asking me about this product. It took a while but I have finally finished my review and in-depth testing.

After many MONTHS of testing my article on the Balmar Smart Gauge battery monitoring unit is finally finished (perhaps a few small tweaks if I see them)..

Bottom line?

If you want simplicity and accuracy in a battery monitor this is it....

The Balmar Smart Gauge - Review & Testing Results

 

[woodster]

thanks for the research Maine....will this work as good if you hook the wires up to the back of 1-both-2 switch on the panel or does it have to be direct to the battery post

regards

woody

 

[Maine Sail]

thanks for the research Maine....will this work as good if you hook the wires up to the back of 1-both-2 switch on the panel or does it have to be direct to the battery post

regards

woody

NO!!!!!

The leads MUST go direct to the battery terminals. This device is so sensitive, calculating as fast as 1500 times per second, it needs to be direct connected or it will be calculating, or rather miscalculating, based on voltage drop, which varies with loads. Direct to the battery terminals only.

 

[Stu Jackson]

Woody, mS's writeup is pretty clear, no?

IMPORTANT: DO NOT wire the Smart Gauge to any place other than the actual physical battery terminals! In order for the SGBMU to work properly the positive & negative leads from the SGBMU MUST go direct the the actual physical battery terminals not a positive or negative bus, or anywhere other than the actual battery terminals. Even if you have a traditional battery monitor you need to bypass the shunt and wire the neg to the neg battery terminal. The consumption draw/load of the SGBMU is so small a traditional Ah counter shunt can't even accurately see it or count it. The SGBMU will however track its own miniscule consumption, over time, even when a traditional Ah counter can not.

 

[woodster]

thanks guys .....i must have missed that part ..will read the write up again ....damn short term memory.......

regards

woody

 

[Maine Sail]

Woody, mS's writeup is pretty clear, no?

In defense of Woody that is a pretty long and in depth review of that product.... I felt it had to be that way because their would inevitably be doubters, like I was, before I tested it.....

 

[SailingHarry]

OK, I can't think of an anyone on the internet who I trust more than Maine. But I'm an engineer. I understand a coulomb counter, and I understand Peukert. But I sure as hell don't understand "magic smoke!" My coulomb counter still has a very secure job right now!

Now somehow I have to reconcile my high regard for Maine with the fact that he has been convinced by snake oil. This may take more than a little rum to get past....

Seriously, though, Maine -- thanks for the great write up.

Hasrry

 

[Maine Sail]

OK, I can't think of an anyone on the internet who I trust more than Maine. But I'm an engineer. I understand a coulomb counter, and I understand Peukert. But I sure as hell don't understand "magic smoke!" My coulomb counter still has a very secure job right now!

Now somehow I have to reconcile my high regard for Maine with the fact that he has been convinced by snake oil. This may take more than a little rum to get past....

Seriously, though, Maine -- thanks for the great write up.

Hasrry

I wish it was snake oil, would have been easier for me to write off, but somehow it works. The algorithm I am sure is very complex, and is a closely guarded secret, and I doubted it too.. If you can keep your Ah tracker accurate they can work fine, most however do not have the means or ability to keep them accurate. Close enough is good with an Ah counter but the SG is simply smarter and stays accurate. Regardless of battery age or condition if finds the SOC for the bank with rather astounding accuracy.......

If the Smart Gauge worked in LiFePO4 my Link-Pro would take a back seat real quick.

The Ah counter is being replaced on my brothers boat this spring by a Smart Gauge. My brother is not very technically savvy when it comes to boat electrics and I am the one having to keep his Ah counter accurate the Smart Gauge makes my job that much easier on his boat........

 

[walt]

Is the summary - we dont know how these work - only that it seems to measure accurately..

One question - can you use any lenght of wire between the monitor and the battery (as long as its hooked up to the battery correctly)? I think the gauge of the wire was mentioned but not the lenght.

And.. I think this was said regarding measuring currents on the order of 5 ma.

It should be noted that a traditional battery monitor using a 500A/50mV shunt does not have the resolution to even track this consumption.

This doesnt seem right to me.. I would think 5 ma or even lower would not be an issue.

Must be based on this from the Victron spec
High current measurement resolution: 10 mA (0,01A)

 

[Maine Sail]

Is the summary - we dont know how these work - only that it seems to measure accurately..

Yes the algorithm is a closely guarded secret that the designer is hold tight to the vest. The vast majority of the use of this product is not in marine but rather military use.

Merlin Equipment - Defense

The same exact technology used in the inexpensive marine Smart Gauge is used in the Military Vehicle Battery Monitor..

One question - can you use any lenght of wire between the monitor and the battery (as long as its hooked up to the battery correctly)? I think the gauge of the wire was mentioned but not the lenght.

And.. I think this was said regarding measuring currents on the order of 5 ma.



This doesnt seem right to me.. I would think 5 ma or even lower would not be an issue.

Must be based on this from the Victron spec
High current measurement resolution: 10 mA (0,01A)

I suspect the designer has upped the wire GA to 14GA to accommodate varying lengths. There is really no current to speak of on the wire that would cause drop so technically speaking 14GA is most likely a built in compensation for varying lengths? I have an email into the designer to get a more accurate answer.

All I can tell you about the Victron, was that with the SG in sleep mode it was unable to accurately track the standby draw over time. The Smart Gauge was smart enough to track its own self consumption....

 

[walt]

The 14 gauge requirement is a little odd..

10 foot of 14 gauge wire has a resistance of .025 ohm. For 10 ma of current, that would be a drop of .00025 volts.. Ie, pretty much zero.

On the other hand, if the monitor were doing some sort of current pulsing, the 14 guage would make more sense - but then so would a fixed lenght of measurement wire. I saw that you had looked with a scope and didnt see anything that might have looked like current pulsing (for impedance) and will just go with that.

 

[Maine Sail]

The 14 guage requirement is a little odd..

10 foot of 14 guage wire has a resistance of .025 ohm. For 10 ma of current, that would be a drop of .00025 volts.. Ie, pretty much zero.

On the other hand, if the monitor were doing some sort of current pulsing, the 14 guage would make more sense - but then so would a fixed lenght of measurement wire. I saw that you had looked with a scope and didnt see anything that might have looked like current pulsing (for impedance) and will just go with that.

I only watched it for a few hours total, and it is not a recording o-scope, but old school. I never saw it throw a pulse across the wire...

 

[walt]

This is one of those cases where we dont know the theory - but it works well (and.. its nice to have a credible source - ie, Maine Sail).. Better than having a great theory and it doesnt actually work.

If I were trying to look for the current pulse using a scope..

Just about any scope would work, just needs to have a "single sweep" or "single sequence" trigger mode - which is very common. You should be able to look either at the battery or the monitor side of the wire. Scope on AC and high resolution - like 100 mv/div horizontal and maybe 1 msec per division on the time base. Set the scope up single trigger. Set the trigger threshold so that it goes off maybe 50 mv below the DC level. If you dont see anything, start to move the trigger closer to the DC level (ie, less than 50 mv).

There was another product called the battery bug or something like that and it put out a 1 msec long current pulse to measure impedance- but only did this about once per second. If you were just looking at a scope normally, this would be difficult to catch. But on the single trigger and if set up correctly, you could easilly capture the pulse.

You may have already tried something similar....

 

[walt]

I guess I am becoming one of those internet posters who thinks that Balmer gauge must do impedance sampling of the battery in addition to the voltage reading. There are only two wires from the gauge to the battery - so no way to measure current. But two wires can be easily used for impedance measurement (with limitations) and I saw in the manual they want at least 14 gauge wires and the wires as short as possible. Both of these requirements point towards an impedance measurement.

Voltage measurement only? Say we have two electrical systems both with loads and charging. The difference is that the second system has 1/10 the battery capacity, 1/10 the loads and 1/10 the charging currents. The usage and timing of the loads and charging are identical. You can imagine just measuring voltage and seeing near identical voltage profiles of the two systems. Just based on voltage, the gauge might think the two systems are identical - but they clearly are not.

Add an impedance measurement to the voltage reading and this extra dimension adds a lot of information about the state of the batteries. Personally, I would like that meter a lot better knowing that it did an impedance measurement. There are lots of ways to do an impedance measurement such as a current pulse or a burst of a sin wave at some frequency. Some of these methods could be somewhat hard to detect.

If that instrument does do an impedance measurement (and I’m thinking it probably does), there would be a limitation to consider. In any method of impedance measurement, the meter would be looking at the impedance of whatever was connected to its terminals. This would include the wires to the batteries in series with the impedance of the batteries themselves. Since we don’t know the impedance of the wires (the length is not specified except to keep it short), we want this impedance to be small compared to the impedance of the battery. For example, if the impedance of the wire is 1/10 the impedance of the battery, what the meter measures is mostly the battery.

However.. if the wire between the battery and the meter gets too long or if the battery is very low impedance such as is likely with a large parallel bank, now the impedance of the wire could be significant compared to the battery and the accuracy of the measurement is reduced - since a large portion of the impedance measurement is the wire itself. Its also somewhat likely that the instrument assumes some nominal impedance of the wire and could take this into account. If the gauge of the wire and its lenght were specified, the instrument could almost exactly take this into acount. Its also possible that the instrument is very clever and even can somewhat learn what the wire impedance is and compensate for it.. dont know.

It looks like from the measurements done in the write up that a single battery was used along with a short 14 gauge wire - which are probably close to ideal. But I wonder what sort of accuracy you start to lose when either the measurement wire gets very long (like 20 feet) or you have a very large battery capacity (and very low impedance). I think if you have a large battery bank, I would pay a lot more attention to either very short wires or even going to a larger wire diameter than 14 gauge (assuming that the instrument does do an impedance measurement – which we are only speculating on).

 

[Maine Sail]

I guess I am becoming one of those internet posters who thinks that Balmer gauge must do impedance sampling of the battery in addition to the voltage reading. There are only two wires from the gauge to the battery - so no way to measure current. But two wires can be easily used for impedance measurement (with limitations) and I saw in the manual they want at least 14 gauge wires and the wires as short as possible. Both of these requirements point towards an impedance measurement.

Voltage measurement only? Say we have two electrical systems both with loads and charging. The difference is that the second system has 1/10 the battery capacity, 1/10 the loads and 1/10 the charging currents. The usage and timing of the loads and charging are identical. You can imagine just measuring voltage and seeing near identical voltage profiles of the two systems. Just based on voltage, the gauge might think the two systems are identical - but they clearly are not.

Add an impedance measurement to the voltage reading and this extra dimension adds a lot of information about the state of the batteries. Personally, I would like that meter a lot better knowing that it did an impedance measurement. There are lots of ways to do an impedance measurement such as a current pulse or a burst of a sin wave at some frequency. Some of these methods could be somewhat hard to detect.

If that instrument does do an impedance measurement (and I’m thinking it probably does), there would be a limitation to consider. In any method of impedance measurement, the meter would be looking at the impedance of whatever was connected to its terminals. This would include the wires to the batteries in series with the impedance of the batteries themselves. Since we don’t know the impedance of the wires (the length is not specified except to keep it short), we want this impedance to be small compared to the impedance of the battery. For example, if the impedance of the wire is 1/10 the impedance of the battery, what the meter measures is mostly the battery.

However.. if the wire between the battery and the meter gets too long or if the battery is very low impedance such as is likely with a large parallel bank, now the impedance of the wire could be significant compared to the battery and the accuracy of the measurement is reduced - since a large portion of the impedance measurement is the wire itself. Its also somewhat likely that the instrument assumes some nominal impedance of the wire and could take this into account. If the gauge of the wire and its lenght were specified, the instrument could almost exactly take this into acount.

It looks like from the measurements done in the write up that a single battery was used along with a short 14 gauge wire - which are probably close to ideal. But I wonder what sort of accuracy you start to lose when either the measurement wire gets very long (like 20 feet) or you have a very large battery capacity (and very low impedance). I think if you have a large battery bank, I would pay a lot more attention to either very short wires or even going to a larger wire diameter than 14 gauge (assuming that the instrument does do an impedance measurement – which we are only speculating on).

Again the designer has kept "how" it works a closely guarded secret other than computer models and a learning algorithm. My buddy who's o-scope I use, used to be a rep for Tektronix. He set it up based one what I told him I was looking for. We saw nothing but that does not mean we did not miss something either. I need to get myself a nice Rigol but have not yet cause he's always willing to lend his big old Tektronix......

It may do more than just voltage, but we were not able to detect that. If it did it only once or twice per day it could be easy to miss. Again Chris G., the designer, has been very elusive as to exactly how it works but he leads even their largest world wide distributor to believe it is voltage.

All I can say is that it works, that is all that really matters... It was also tested on a 440Ah series/parallel bank of Lifeline batteries and two GEL group 31's.....

 

[walt]

I wonder if there is a patent or patent pending number somewhere on the unit? You can then look these up (google or the US patent office) and the patent owner has an obligation to do a good job describing what exactly the invention is.

While I really like my "coulomb" meter (I guess this is now "old school") it does have all the limitations you mentioned in the write up. I know when my previous set of batteries were pretty much trashed, the amp hour meter would still say I had a lot of capacity left. I actually just never use the "capacity" reading as I don’t trust it for all the reasons you listed. I only ever look at amp hours used and voltage.. and really like to have the amp hour reading regardless of the actual state of the battery.

Its does look like a nice solution for keeping track of battery state..

 

[Maine Sail]

The Smart Gauge fills a real niche for boaters who want simplicity in an SOC meter. I still think a savvy boater, who can keep an Ah counter in synch, is probably well served with an Ah counter as it tells them the type of things they want to know. The SG is for everyone else who only wants to know the SOC of the bank so the don't over discharge.......

For me the real magic is that regardless of your banks age or condition it will find and tell you the SOC of the bank. If your batteries are 5 years old and only have 75% of capacity left the SG will simply tell you when you get to 50% SOC. This without you having to physically assume capacity & reprogram or test for actual Ah capacity..

 

[Rusty123]

This post (by Chris Gibson, Smartguage inventor, in 2005) might be of interest:

http://www.ybw.com/forums/showthread.php?73924-Smartbank-battery-management/page5

An excerpt:

"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.

These are very well known methods of battery measurements. They all involve "2 wires". There are *many* more that can be made with 2 wires."

 

[Exile]

thanks for the research Maine....will this work as good if you hook the wires up to the back of 1-both-2 switch on the panel or does it have to be direct to the battery post

regards

woody

I read the replies to this post as well as the Smartgauge manual where it says to wire directly to the battery posts. My house battery bank consists of two Lifeline 8D's which are only paralled together via the 1-2-ALL switch. All of the batteries' neg posts are wired together (incl. a separate eng start batt), but not the positives. What would be the easiest way to install the Smartgauge under this scenario, or would it require two? Thanks for all the research & effort checking this product out.

 

[mitiempo]

I read the replies to this post as well as the Smartgauge manual where it says to wire directly to the battery posts. My house battery bank consists of two Lifeline 8D's which are only paralled together via the 1-2-ALL switch. All of the batteries' neg posts are wired together (incl. a separate eng start batt), but not the positives. What would be the easiest way to install the Smartgauge under this scenario, or would it require two? Thanks for all the research & effort checking this product out.

I would parallel the 2 batteries directly, not through the 1-2-all switch. A larger bank is always more efficient, Smartgauge or not. The Smartgauge should be connected directly to the posts of the paralleled bank.