The Balmar Smartgauge
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This article is quite in-depth but much less so than it could have been. I have given a very brief overview of my actual testing procedures but enough to explain the methodology. Other than the EnerSys white paper this is the only other independent testing of this product that I know of.
Unlike EnerSys I tested new, used and even well-used marine batteries. If the product had failed my testing, this article would not be here. I don’t believe in writing articles to simply bash a product, unless of course it is a safety hazard.. The Smartgauge really surprised me and I am not easily satisfied. To be 100% honest I went into this testing with a slight bias that it would not or could not work. I was proven wrong.
Ah / Coulomb Counters:
For many years I have been a big proponent of Ah or Coulomb counting battery monitors and still am, for the right owner. These devices calculate and keep track of the current flowing into and out of a battery bank so you can attempt to keep track of SOC & Ah’s consumed, or at least get a rough approximation.
Coulomb counters give you lots of useful information; voltage, current, Ah’s consumed and SOC to name a few. Some can even give you historical data. These are nice features all packed into one compact unit. They are however not the easiest devices to program, not the easiest to wire and lose accuracy at an alarming rate, if not kept on top of.
Ah counters can be so problematic to use correctly that I had to write an entire article on installing and wiring them properly as well as a sister article to that one on proper programming. Despite both of these articles people still email me because they are confused. The Smartgauge is a simple two or three wire hook up!
Despite their complexity Ah counters have led almost every one of my customers to longer battery life, when properly used & wired. However, in some cases they have become so out of synch that they have led to erroneous readings that are simply meaningless.
Last summer I had a link 2000 reading -1100 Ah’s on a 65 Ah starting battery… (smirk) That can’t really happen now can it….? (wink)
Up until recently, this type of battery monitor was the best we had. The only other option was an ROCV reading (resting open circuit voltage) or SG measurement (specific gravity) neither of which lend themselves to prudent practical use or accuracy when actually using the vessel.
The problem with traditional Ah or Coulomb counters is keeping them accurate. As batteries age their capacity changes, the charge efficiency changes as does the Peukert’s constant. A battery is an ever moving target, so the 100Ah battery you bought three years ago may now only be a 75Ah battery.
If your battery monitor is still programmed for a 100 Ah capacity, and you are drawing 50% of the assumed Ah capacity out of it, based on this 100Ah’s, you are really drawing the bank to just 25% SOC, rather than the well accepted safe discharge level of 50%.
Follow me on this one.
- You had 100Ah programmed into the Ah counter for a 100Ah battery
- Your battery, due to age and use, is now 75Ah’s not 100Ah’s
- You now draw an assumed 50% of 100Ah’s out of the battery
- Instead of being at 50% SOC you wind up at 25% SOC
75Ah - 50Ah = 25Ah remaining or approx 25% SOC.
Now if you threw Peukert’s exponent into the mix you may actually be lower or higher depending upon the actual load at which it was drawn.
Holy cow Ah counters are confusing???? (head bonk)
This is but one example where an Ah or Coulomb counter easily and regularly become inaccurate.
A trick many of us in the industry might use is to start with a lower programmed Ah capacity than the bank is rated for. The best option is to physically test the batteries for 20 hour capacity, but this is expensive and time consuming.
For the 100Ah battery I might initially program it at 95Ah’s so the owner is never actually drawing to 50% SOC that first year (self protective feature). The next year I might remove another 3% – 5% off the capacity etc. etc.. These are just rough guesstimates, but they are never perfect. I then also count on the fact the battery bank is being drawn at average currents that are below the 20 hour rated load. This can lead to slightly more usable bank capacity, but again this gets CONFUSING for the average boater to understand any time we bring our good friend Mr. Peukert into the equation.
The only way to accurately know the actual battery capacity is to perform a physical 20 hour load test. This is complicated, time consuming, and very few boaters are willing to do this.
To be honest I don’t know of a single boater who actually has conducted an accurate 20 hour load test. Ah / Coulomb counters rely on the actual 20 hour capacity figures being accurate, to actually remain accurate, over time. No accurate 20 hour capacity figure, no reasonable accuracy in the Ah counter, only a “close enough” range. This may not be half-bad but is a a long way from accurate.
Unfortunately the scenario I laid out for a Coulomb/Ah counter is just one of the many ways these devices can become tripped up and lead to inaccurate readings. There are many more “gotcha” scenarios that can rear their ugly head, including shunt wiring mistakes, battery temperature, false re-synchs caused by solar or wind, incorrect programing etc. etc.. For the last 20+ years however, these are all we’ve had, and they are certainly better than nothing at all.
I suspect the big reason they are, and have been better, is because they make owners more aware of their bank. More awareness of your bank and charge source performance is important, and can play a larger role than we may otherwise assume.
For years I have been trouble shooting and helping owners try to use these devices in a smarter and more accurate manner. When owners understand it they can be very useful and as I said most all of my customers have had longer battery life as a result.
- FACT: Traditional Ah / Coulomb counters become LESS ACCURATE as time goes on when related to SOC.
- FACT: The Balmar Smartgauge gets MORE ACCURATE as time goes on for SOC
The Balmar Smartgauge is a major paradigm shift in battery SOC monitoring! Read on to find out why..