Balmar SG-200 Battery Monitor

[Stu Jackson]

Originally Posted by ontherocks83

I can't fault what you are saying, and I agree that I would have the budget figured out previously, what I also take into consideration is sometimes things change and I want to be able to see those changes that I know are coming. Eventually going from coastal to long range cruising is going to change your consumption along with crew size changes, children and most importantly things that go wrong like parasitic draws that creep up that you are unaware of.

No argument that things change. Oddly enough, though, you may well find that "...going from coastal to long range cruising is going to change your consumption..." may not be true.


Once you build a solid "base" that includes systems and equipment that uses energy, I would venture to say that little changes. Most of us, for example, know that 60% of a coastal cruiser's daily load is for refrigeration. 100 ah per day with a 5 A fridge that cycles 50% is pretty standard. Unless you make major changes to the equipment on any given boat, I simply don't see how a change from coastal to long range changes anything on the boat that uses power. Of course, any qualified energy budget has daysails, anchoring overnight and sailing overnight as the three main components. And overnight sailing always uses more.


Parasitic draws? I don't understand that one at all.


Good luck.

[ontherocks83]

Originally Posted by Stu Jackson

No argument that things change. Oddly enough, though, you may well find that "...going from coastal to long range cruising is going to change your consumption..." may not be true.


Once you build a solid "base" that includes systems and equipment that uses energy, I would venture to say that little changes. Most of us, for example, know that 60% of a coastal cruiser's daily load is for refrigeration. 100 ah per day with a 5 A fridge that cycles 50% is pretty standard. Unless you make major changes to the equipment on any given boat, I simply don't see how a change from coastal to long range changes anything on the boat that uses power. Of course, any qualified energy budget has daysails, anchoring overnight and sailing overnight as the three main components. And overnight sailing always uses more.


Parasitic draws? I don't understand that one at all.


Good luck.

Just to start, I agree with everything that you are saying. For me and its a personal OCD type of thing, is I like to have the extra info and monitoring to make sure that things are staying the same or like I said if I change a system that I can figure out what it is doing to my AH consumption. Not saying it is right or better at all, just extra monitoring for peace of mind. I am a tinkerer and am the type that needs to be constantly checking, working on, or monitoring whatever I am using, whether it be boat, car, motorcycle, or lawnmower.

Parasitic draws come from my time in the automotive industry where sometimes something goes wrong and a device starts to consume power when it is supposed to be off draining your battery prematurely. Now these are usually relegated to computer controlled items in cars, but for example if something is wrong with your reefer, or the insulation is bad, or a door seal is bad you would see an increase in your AH consumed per day telling you something is consuming more power then it used to. From there you have to start throwing circuit breakers system by system to try to isolate the cause.

Again not really mission critical in the grand scheme but it would be a small addition that would give me a little peace of mind.

[Stu Jackson]

I agree with you, good to have. I put a Link 2000 in my boat decades ago. I, too, check regularly to see that things are where I expect them to be.

[rgleason]

From the Manual:

CHARGE VOLTAGE and TAPER CURRENT are used together by the SG200 to determine when charge termination has occurred. This is indicated on the Display when a “+” sign shows on the SoC Display.

Charge Termination is defined as when the battery is fully up to 100% of it’s present capacity. Each of these values have defaults that are set per chemistry, but can be changed if required.

Selecting the CHARGING menu item brings up a sub menu, where the
following options can be set:

• Charge Voltage
• Taper Current
• Peukert

Alerts and Faults
Generally, Alerts are used to notify the user that a certain condition has occurred, and are not only used to signify a problem.

• Alerts (User Defined)
• Min/Max State of Charge (SoC%)
• Min/Max Current (A)
• Min/Max State of Health (SoH%)
• Min/Max/Voltage (V)
• Min/Max Aux-1 & Aux-2 Voltage (V)
• Min/Max Mins Left (minutes)

Faults

Faults are triggered when specific values have been passed that may have an impact on safety or the health of the battery. For example. draining a battery down to less than 5% SoC will trigger a fault, as it can adversely affect the life of a battery. Exceeding the safe current carrying ability of the SmartShunt will also trigger a fault. Faults can help a user identify behavior that will shorten the life of a battery

These features will be useful for User Defined LiFePo4 Bank Alerts.
However, this device will not activate relays or take any control action, like the Victron BMV712 does.

[rgleason]

Under section 8 of the SmartGauge there are Notes about Low & High Voltage Alerts and NO NC contacts.
-----I have not found this feature in SG200----

Assume the low voltage activation setting is set to 12.00 volts and the deactivation setting is set to 13.20 volts. The battery voltage is at 12.6 volts. The alarm output is not active. COM is connected to NC. NO is not connected to anything. The alarm LED is unlit.
2.
As the battery voltage falls eventually it will reach 12.00 volts. The alarm output remains as above. When the battery voltage falls to 11.99 volts (i.e. below the activation level) the alarm output will activate. COM is now connected to NO. NC is not connected to anything. The alarm LED will light up. An audible alert connected to the batteries via COM and NO will now beep.
3.
As the voltage rises to say 12.80 volts the alarm output remains in this state. The battery voltage rises to 13.20 volts, the alarm output deactivates, COM is once again connected to NC and NO is connected to
nothing. The alarm LED will go off again. The sounder will go silent. Operation of the standard low status alarm is identical to that of the low voltage alarm except, of course, that it operates on the charge status as opposed to the battery voltage. Timed low status operates slightly differently. (See Section 9.0 Addendum.)

[john61ct]

See also Merlin SmartBank, Lite vs Standard.

And remember all this "SG1" stuff has no design connection to the new SG200 gear.

[sailinglegend]

Originally Posted by witzgall

The SG200 was engineered entirely by our team in Huntsville, AL. Merlin has not been involved in the design at all. No Merlin code, no Merlin design work, No consulting, nothing.

Chris

Many thanks Chris for your input to this and other threads.

On Balmar's past records I'm sure your engineering team are very capable of doing an excellent job on this exciting new product, but it does leave some simple questions up in the air.

Is the SG 200 based on the 13 year old Smartgauge technology for it's SoC, or has this been updated by Merlin or Gibbo - to include new - and we hope future battery technologies? If it hasn't been updated then how can it so easily calculate SoC and SoH for LiFePO4?

I appreciate you may not want to answer these questions - so if you stick to your quote above - no Merlin Code....nothing - then either your boffins have cracked the Smartgauge code or written their own. You seem to be suggesting the latter.

[witzgall]

SailingLegend,

As I mentioned before, Merlin (nor any of their present or past employees) have not taken any part of the development process, it is entirely a Balmar effort. I am indeed stating that we wrote all of the code in-house. It has been a huge team effort, with many overtime hours by engineering. This was not a reverse engineering effort, we took a different approach to most everything, except at the end of the day all of this is governed by physics.

As an example, consider the battery testing needed to characterize each of the chemistries. A single cycle sometimes takes almost two days. We have automated much of this, but some still needed constant supervision, especially early on in the process. This meant second shift work for lab staff, for months. Our lead engineer on the project worked 6-7 day weeks for almost a year. And the work still continues, as we consider product enhancements, etc.

Chris

[sailinglegend]

Originally Posted by witzgall

SailingLegend,
As I mentioned before, Merlin (nor any of their present or past employees) have not taken any part of the development process, it is entirely a Balmar effort.

Chris

Many thanks for that.

I'm not surprised that you've managed to write your own code just 18 months after a poster on a UK forum gave his formula of how Smartgauge could work. I reposted this on Cruisers Forum and I copy it here to prove that it could be 'entirely a Balmar effort.'

[QUOTE=Toaster;2275929]Just thought I'd make a few comments about the idea of measuring state of charge with only voltage measurements and not current.

On their web site, the SmartGauge people say they use "computer modelling" for calculating SOC. I've done a lot of computer modelling (professionally) so here are some observations. Disclaimer: I am a physicist.

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 aging.

Smartgauge we know 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.

[john61ct]

So, there is the "SG1 style" algorithms, for directly detecting SoC via "active impedance compensation" techniques.

Let's call that AIC.

Then the more widely used "AH / coulomb-counting" methodology, which usually depends on 100% SoC resets for ongoing accuracy.

Let's call that AHC.

What is revolutionary here is that the SG200 combines information output, calculation results from these two different data sources, and then "integrates" them to derive its SoC estimate.

The AHC data overcomes the old AIC weakness of high precision only at rest, especially lower accuracy during charging.

Once the AIC learning process has settled down, that can help compensate for AHC's need for manual 100% resets.

Now if the AIC side still is not quite as accurate with LFP as it is with lead chemistries, the AHC methods also help with that issue.

> Combining both technologies this way, letting best-of-both-worlds each inform the other, certainly holds a lot of promise!

> In any case, great potential here, hope Bruce includes it in his comparative benchmark tests.

[sailinglegend]

Originally Posted by john61ct

.....What is revolutionary here is that the SG200 combines information output, calculation results from these two different data sources, and then "integrates" them to derive its SoC estimate......

'If' that is what it does then there will be severe errors introduced because a very large proportion of Battery Monitor installations have wired the shunt incorrectly - see Maine Sail's posts for figures. Balmar need to be aware of this and Maine Sail needs to be testing for this..

Subsequent installations of other equipment may well bypass the shunt. The SG 200 needs to have error detection software that can detect a varying +/- SoH which would show that 'all' the current discharges from the batteries are not going through the shunt.

This maybe not be the all singing all dancing answer to a SG1 and a separate Ah counter - as it doesn't seem to count Ah.

Balmar need to get it right because you can bet Victron and others will be hot on their heals.

[a64pilot]

You can’t design around an idiot, trust me. There is always a better idiot.
If its incorrectly installed, it’s unlikely to correctly work, that is true for everything.

Of course we are all theorizing, just like we did with the original SG.
Pretty much just best to assume it works off of PM and go with it.

[john61ct]

Originally Posted by sailinglegend

it doesn't seem to count Ah.

Sure it does. Both for live ammeter and AH counting

[Paul L]

Originally Posted by john61ct

So, there is the "SG1 style" algorithms, for directly detecting SoC via "active impedance compensation" techniques.

Let's call that AIC.

...
> Combining both technologies this way, letting best-of-both-worlds each inform the other, certainly holds a lot of promise!

> In any case, great potential here, hope Bruce includes it in his comparative benchmark tests.

I don't see where Balmar has said that they use the active impedance approach of the original Smartgauge at all in the new battery monitor. It sounds more like they have abandoned that approach and moved on with a far smarter amp counter approach.

[john61ct]

How else could SoH (residual capacity) be calculated?

See the Panbo puff piece cited in post #19.

Maybe not dictated by Chris directly, but I'd be surprised if it contained gross inaccuracies.

> The SG200 combines the goodness of the highly regarded original Smartgauge with a shunt to deliver a more complete picture of what your batteries are doing.

> The SG200 also reports on current consumption and total time remaining for the battery bank. A mix of what Balmar calls active impedance compensation and shunt-based monitoring is used to deliver this level of insight.

> According to Chris Witzgall, the product manager for the SG200, it takes about three charge cycles for the SG200 to fully learn your battery bank’s characteristics and be able to accurately report on its status.