Balmar SG200, a good battery monitor gets better

Balmar’s Chris Witzgall stands with the SG-200 display at IBEX

I recently judged the Innovation Awards at the International Boat Builders’ Exposition (IBEX) and we selected the new Balmar SG200 battery monitor as the winner of the Electrical Products category.  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 first generation Smartgauge differed from almost every other battery monitor on the market by measuring a battery bank’s State of Charge (SoC) using just two voltage wires.  This meant that while the Smartgauge could tell you how charged your batteries were — somehow with more accuracy than more complex current counters according to power expert Rod Collins — it couldn’t tell you how much power was being used or replaced in real-time.  This lack of insight into consumption and charging was a significant limiting factor to many users.  Coupled with a very simple numeric-only display and the lack of support for lithium battery chemistries, there was definitely room for an update.

Enter the SG200.  Balmar has streamlined the user interface to a 2-inch, sunlight-readable color display.  It links to a sensor module named the SmartShunt via a 4-pin network connection called SmartLink. Since SmartLink allows the connection of 32 devices, you can monitor a large number of battery banks with displays located throughout the boat.  Each SmartShunt can also monitor voltage for two auxiliary batteries, like engine start or similar non-deep-cycle applications.

With the SG200, Balmar has begun measuring your battery bank’s State of Health (SoH), which is delivered as a percentage representing the battery bank’s current capacity versus design capacity.  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.

Balmar says the SG200 can accurately measure State of Charge and State of Health for all major battery types including Lead Acid, AGM, Carbon Foam, TPPL and LiFePO4.  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.  Unlike the original Smartgauge, the SG200 purportedly doesn’t lose accuracy while charging, and over time the system will get more accurate withut requiring calibration like typical coulomb counting shunt-based monitors.

Balmar’s planned options for the SG200 system include a Bluetooth gateway that will support a mobile app and a NMEA-2000 gateway that will make battery status and other metrics available on connected N2K instruments and MFDs. The basic SG200 gauge and shunt kit sells for $239 with limited availability until January, and the gateway prices aren’t yet known. Balmar has put up a good SG200 video here.

I’m hoping to install a SG200 on Have Another Day soon and look forward to reporting on the monitor’s ability to deliver on all the promise it shows.

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Ben Stein

Ben Stein

Publisher of, passionate marine electronics enthusiast, completed the Great Loop in 2017.

52 Responses

  1. Balmar’s new Smartguage looks really good to me. For one thing, a battery bank’s State of Health is quite important because you can not have accurate State of Charge if the bank no longer has the capacity it was meant to.

    Also, I’m happy to report that the SG200 is doing well so far in lab testing by Rod Collins: “It is pretty cool and so far on LiFePO4 the thing is posting within 1% on both SOH and SOC. That to me is quite amazing. One will be going on my own boat as soon as I can get a production model as Ah counters just don’t cut it.”

    Support Rod’s work here:

  2. According to Balmar’s Facebook page, the SG200 is “currently under a limited release…with full production launching January 1st” and those units are only available at PKYS:

  3. Lauren says:

    I would be curious to see how this works for people who run 100% renewable as for the charging. We lived on the hook for several years with both LiFePO4 batteries and a large solar array. the variable charging nature of solar and wind really seemed to confuse algorithms used. We cruised a few years ago, so had a link 20 and a BMV602, and after months of tweaking, found the victron to be slightly closer to the truth, but there were times where both got confused and reported wrong, but different situations confused them differently so having a second opinion was nice! Luckily we we had way more solar than we needed to keep charge and I understood what was going on, but I am curious if Balmar’s secret sauce actually works better in this scenario.

    • Well, the original Smartgauge definitely has an unusual way of tracking SoC — apparently termed “active impedance compensation” (I learned while editing this entry) — and according to Rod Collins there’s just no way that current counting alone can maintain accurate SoC over time.

      In my experience the 1st gen Smartgauge can get slightly confused when solar gain is high, but once the sun is down it’s much more accurate than my boat’s BMV (though it has umpteen adjustments I may have wrong ;-). Hopefully, the SG200 has it all completely right.

  4. Richard Cassano says:

    So, how do you program 32 devices? Is this done with push button codes? The Smartguage buttons are a nightmare to work with – some button presses work and sometimes not. I’ll wait for Rods report before I upgrade. Right now I’m happy to at least see the voltage on my house bank and starter battery.

    • Ben SteinBen Stein says:


      Although the system has capacity for 32 devices, it’s hard for me to see a scenario where you’d be programming more than a small handful of SmartShunts. The new display has a single button and during my brief time at the booth using a demo unit I didn’t find any difficulty in getting it to respond to button pushes. Balmar uses a combination of short taps to change settings and long presses to confirm. It worked fine but is obviously quite limited in what settings can be changed this way. I’m guessing the mobile app will probably allow greater customization like naming of banks and the like.

      • Richard Cassano says:

        Great, that’s what I was hoping for, an App that allows programming rather than button pushes. I’ll never be programming 32 devices but for those with complex systems a programmable App would be welcome. Button pushing seems so primitive.

      • Actually, Balmar’s video briefly shows an SG200 app screen where you can custom name the shunts, the gauges, and the gateways. The narration also mentions that you can put shunts on loads like thrusters or refrigeration, so I think it’s possible to get that little display to show some sophisticated information in plain English. Check 2:44 here:

  5. Tim Leighton says:

    I’m encouraged that Balmar has joined the newer “family” of smarter shunt-based battery monitors. While I was happy with my SmartGage on our old sailboat I always wished it provided more information. Last spring the LINK system on our new-to-us Krogen 48 trawler died and I opted for the Victron 702 monitor which was very easy to install and has worked extremely well for us. I wonder what the differences are between those two systems.

    • Ben SteinBen Stein says:


      The biggest difference is that the Victron system is strictly coulomb counting. As a result it’s prone to drifting out of accuracy and doesn’t have any idea what age has done to the capacity of the battery bank it’s monitoring. If you told it you have a 1,000ah bank but age has reduced your capacity to 800ah it’s still assuming you have 1,000ah available.

  6. Leslie Troyer says:

    I ordered one in Annapolis – hope they make the Bluetooth API available. It would be nice to track this with Signalk. They said it will be delivered end of this month.

  7. Grant says:

    “…and a NMEA-2000 gateway that will make battery status and other metrics available on connected N2K instruments and MFDs.”
    That’s maybe the best news of all – right now, trying to monitor multiple battery bank voltages using NMEA2000 requires buying a separate NMEA2000 voltage monitor for each bank. The only product I know of that does that is Maretron’s DCM100 at $495 MSRP – plus an additional Maretron device to program them (USB100, etc.)
    For a twin-engine boat with genset, its not uncommon to have 4 battery banks – so that’s over $2,000 just to read battery voltage on a NMEA 2000 display! I’m glad somebody finally addressed this, to say nothing of the other capabilities of the SG200. Looking forward to seeing it soon!

  8. Rick R says:

    Can this be used to trigger an Automatic Generator Start at say 50% SOC, and is there an audible alarm to draw attention to a fault or alert? I didn’t see either in the owners manual.

    Balmar needs to hurry up and include bluetooth with every unit, since Victron 702 has had this feature for several years. Hopefully the SG 200 prompts Victron to add a battery State of Health feature.

    • Ben SteinBen Stein says:

      Looking through the specs and wiring diagrams I don’t see a relay output of any sort. That would be one way to enable generator starting at a given SOC. Without that, I think the most likely way to achieve this would be with NMEA-2000 output and then use a device that monitors the PGN for SOC and takes action when it crosses a threshold. Not a simple solution.

      Right now it seems like Balmar is on the same path as Victron was with the 702, Bluetooth being an add-on option (on the BMV-702 it connects to the VE.NET port) but the BMV-712 now has it built in.

  9. Anonymous says:

    Whats the relationship to Merlin Equipment, who made the original smartgauge, as Balmar were just rebranding it for the US market.

    I’m in the UK, will I be able to get it from Merlin, or are they not involved in the SG200?

    • Ben SteinBen Stein says:

      My understanding is that Balmar has engineered the SG-200 themselves and I don’t believe Merlin was involved. I haven’t heard anything about any agreements with Merlin for them to sell it in the UK but I’ll reach out and ask.

  10. Saffy The Pook says:

    I sure hope that every configuration setting can be made without the need for the app & bluetooth module. I have no need or desire for the bluetooth module otherwise and having to pay extra just to set the thing up is a deal breaker for me.

  11. Hi all, I’m the funny looking guy at the top of the post. I figured I would attempt to answer a few of the questions here. While there are some similarities at how the original SmartGauge calculates SoC compared to the SG200, there are some big differences. Note we are not calling this SmartGauge 2, or something like that.

    Active Impedance Compensation is not something the SmartGauge does, only the SG200. It should have no issues with Solar and lower amperage charging sources. Although we may find a use for it in the future, Peukert is not used to calculate SoC. This is important because it is actually kinda hard to get this number right, and it is actually not constant, but varies as batteries age, and as even as they charge and discharge. We are currently only using it for Time Remaining.

    A N2k and or Canbus connectivity is something we anticipate adding in the future. Although there is a State of Health PGN, the only place I think it is view-able is on a Maretron display.

    Additional shunts are viable to use to monitor any load or charging source, but when it comes to SoH on a battery or bank, we need to see a cycling, both charge and discharge over time, to make that calculation. This is why we are not recommending a Separate SmartShunt for starter batteries.


    Programming the devices is pretty darn simple. Just select a chemistry, and then the design capacity of the battery or bank. That is it. Additionally, you can define alerts for the difference SmartShunts. There is currently no audio buzzer or sound alert, only on screen. We have some ideas about a I/O or relay module, this could be incorporated in that.

  12. Grant Jenkins says:

    Chris, thanks for the clarifications. Really hoping you can program it to output at least a basic PGN (127506 or 508) containing even just DC Volts for display on other NMEA2000 displays. Look forward to seeing the product at the Seattle show perhaps in January?

  13. Ted Arisaka says:

    I hope the BT connected app technology can be leveraged to program a future version of you MC614 external regulator. I stole Rod Collins idea of programming it off the boat, but I still need the instruction manual in front of me and that darn screwdriver with the magnetic tip 🙂

  14. Ian Kelly says:

    Hmm – seems like a move in the right direction
    is it know if this device will talk with the original smart bank ? ( the brother to the smart guage?)
    major pity if this didn’t have this funcionality

  15. Leslie Troyer says:

    Got the display installed today an the cable run to the battery compartment. Next is shunt install and testing.

  16. Saffy The Pook says:

    Any idea what the shunt resistance is? I have an existing 50mV/500A shunt for my inverter/charger and would have to either put it in series with the Smart Shunt (which I don’t want to do) or just use the SS in place of my current shunt and have it do double duty by putting the charger’s sense wires across the Smart Shunt but I could only do that if it matches the specs of the current one.

    • Ben SteinBen Stein says:

      Saffy, I’ve reached out to Balmar to see if they can provide that information. I’ll let you know if i hear back or Chris might chime in directly here.

    • Saffy,

      While our shunt is compatible from a resistance standpoint, this is not something we have tested for and it very well could really mess things up with some of our internal calculations done in the SmartShunt. We are measuring a very tiny voltage at a high degree of accuracy, anything that throws that would be very detrimental to the SG200 operation. Much more so than a traditional coloumb counting shunt.

      Having said that, there is no issue with putting the SmartShunt in series with another shunt.While i may not be the most elegant solution, we have done this with no inpact to the SG200 performance.

      • Saffy The Pook says:

        Thanks, Chris. Series is an option if there’s no alternative.

      • Jorgen says:

        I also look forward to replacing the smarthauge (and perhaps even Maratron ) with this new devise.
        But why is it that this new design does not use coils (such as Maretron) to measure current so that the user do not have to cut the conducting cable?

        • Ben SteinBen Stein says:

          Perhaps Chris will chime in on this but I believe (at least part of) the reason is that in order to measure resistance as the SG-200 does they need hard connections to the battery and not just the flow of current as a typical CT does.

  17. Saffy The Pook says:

    Thanks, Ben.

  18. Peter Jung says:

    My house battery bank (2, 8D AGMs) is now two years old, and has undergone significant charge/discharge cycles in those two years. Short of doing a 20-hour rate discharge test on my existing battery bank to establish the current SOH of my bank, how will it determine SOH of an “experienced” battery bank such as mine?

    • Ben SteinBen Stein says:

      According to Balmar that’s the magic of the SG-200. Their algorithms will know what the characteristics of an aged battery look like and evaluate your battery based on those characteristics to determine its actual capacity. I haven’t had the chance to evaluate that on my boat yet but expect to do so in the next month or so. I also have an experienced bank made up of 8 FLA GC2 batteries.

    • Pete and All,
      Pete sent in a request for this information to our support email so I responded to him there. I am posting it here, since he asked here too:


      I received your request for more information about how the SG200 works, specifically when connected to aged batteries. Over several charge/discharge cycles, the Monitor will establish the SoH of the battery or bank. The number of cycles is not set in stone, but typically is from 2-6 cycles. Note that the accuracy of this is will be skewed if the battery does not receive at least one full charge, all the way to the top. For instance, it it calculated that your SoH is 92%, but the charging was stopped when 2% of the usable capacity was not “Charged’ then the SoH will be off by that 2%.

      Based on some continuing testing we are doing, we may be able to document a procedure to shorten the time needed to get a good SoH figure.


  19. Anonymous says:

    Hi Ben,

    Well, huh. I’m hopeful Balmar will provide some amplifying details of how their algorithm “queries” the battery bank to determine SOH. I’ve asked them, no answer to date. As I expect the algorithms and hardware are intensely proprietary, I’m not hopeful for much of an answer. Perhaps Rod Collins will weigh in here, or on his web site.

    If Balmar’s assertion proves to be correct and accurate, seems like a further variant of the SG200 would obviate 99% of the SOH “battery testers” currently in use today by battery retailers, auto repair shops, Harbor Freight, NAPA, and a myriad of others. The vast majority of which, IMHO, seem simply worthless.

    The SG200 seems REALLY promising, and I’m tempted to acquire one ASAP. Kudos to Balmar! And thanks to you for the heads up on this instrument.



  20. Happy to report that I encountered two more battery monitors claiming to deduce battery State of Health at METS. One is a Scheiber Intelligent Battery Monitor kit now being sold in the U.S. by MarineBeam, who also explain it well:

    The other is not yet described online but Sentinel Marine Solutions has new IBS (Intelligent Battery Sensor) that can output results over NMEA 2000 as well as off boat:

    • Hi Ben,
      The Sentinel Marine unit seems to be simply a voltage sensor – it would let you know if you are low/high (along with lots of other things – it seems to be primarily a security device). The Scheiber unit looks more interesting, but appears to be limited to post-type batteries, as mounting their sensor on a tab-type battery like my Lifeline 8Ds wouldn’t work without significant kludgery 🙁 .

      It strikes me that many of the folks looking at these units probably already have one or more shunts installed for an existing amp-counter device — it would be nice if these things could be configured to use these existing shunts, making installation much simpler!

      • We actually had an early prototype that mounted directly onto a battery stud (Not post). We moved away from that, mostly because it made the battery installation taller, and from my experience that was something that would limit installation in many circumstances. We also made the choice not to use an already available automotive sensor for performance (max Amp draw etc).

        If we were just measuring current flow, then using existing shunts would have been an option. However we are also making other measurements including impedance, and we require a factory calibrated package for our performance targets.

        • Hi Chris.
          I do understand regarding a standardized connection.
          Two questions: first, are the terminals on the SmartShunt 3/8″? Second, your diagram seems to show that the start/aux battery negatives run through the shunt – wouldn’t the starting (or running, like for a thruster) current and charging current to the start/aux batteries confuse the readout of other currents in the system?

          • Leslie Troyer says:

            The shunt in the SG200 is what Balmar calls a smart shunt. It does contain a normal shunt, but also contains a microprocessor that does all the math and necessary calculations for monitoring the battery. The microprocessor must have two “spare” analogue to digital converters.
            The unit uses thes to measure the voltage of the other batterie sets. Electrically they are isolated from the actual shunt proper.

          • Hi Leslie,
            That’s what I would have thought, but if you look at the diagram above (it’s also on BalMar’s website) you will see that they have wired the start/aux battery negatives through the shunt as well. Perhaps this is a drafting error, but it could be significant.

          • On a standard installation utilizing the auxiliary leads, we assume that there is a common ground. If not, then additional leads will need to be installed from the aux battery back to the SmartShunt. If you read the note, it states “Negative leads on Aux. Batteries are Only Needed on Isolated Ground Systems”.
            This won’t be the case on most installations, It will work fine just running one of the orange aux leads to the positive side of the aux battery. Don’t forget to install a fuse there, sized for the wire run (there is no appreciable current flowing.)

            An additional note about fuses. Some may wonder why we include a 10a fuse for the shunt/system power, when it draws much less power. The fuse is sized for the wire properly, and we have found that there is a decent different between the resistance of a 1a fuse and a 10a fuse, so the voltage readings are a bit more accurate.

  21. Ian Kelly says:

    Hey Anonymous Pete – its probably not BALMARS IP – they have been using the smart gauge monitor from the UK for years see – – my guess is that this bit of magic actually belongs to Merlin. again a guess they will be manufacturing under license condition.

  22. Jonathan Woytek says:

    Someone had previously asked about differences between the SG200 and the Victron BMV 700 series devices. In addition to the important tech differences, it is interesting to note that the BMV712 specs quote a 1mA draw, and the SG200 specs quote a 10mA draw in sleep mode (both at 12V).

    I’m currently evaluating battery monitors for a new-to-me sailboat. The existing DC system is pretty simple with an older shunt-based energy monitor installed. Im going to be adding some new loads with nav electronics, and have an eye to install some solar charging in the future. I want to have a good handle on the existing battery bank first, though. Thanks for bringing the SG200 into my evaluation process!

    • Johnathan,

      There are some savings in power we can implement, it is on our future development list. While I am not sure we will ever get down to 1ma, it should be a good percentage savings. Our processor is much more capable (needed for our performance criteria), but that comes at a cost.

      • Jonathan Woytek says:

        Thanks for the reply, Chris! That’s great to hear that there could be some future savings there, too. Certainly, 10mA is not a deal-breaking number. It represents only about 240mA per day, or about 7A over the course of a month. In my use case, since I live in an area that freezes over the winter, the boat will be on the hard out of season, and I’ll be depending on doing some solar-based battery maintenance while out of the water.

        Does the unit have an automatic low-voltage shutdown to avoid killing a battery in the event of loss of long-term loss of charging current?

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