Does the SmartGauge provide an indication of current battery condition? In other words, if my batteries were originally 225Ah, and they have "aged" to an effective 112Ah, will it tell me that they are only half what they once were?
No, but it will give you an accurate SOC and you will realize that you can no longer run as long as you did originally and you can develop a
sense of over all health. They make a product that does give battery health but Balmar chose not to import it. For trying to get the most out of a bank SOC is the only real measure we need to be cognizant of. Whether you decide on 50%, 60% or 70% SOC's as your deepest draw the SG will more accurately accurately track this, far better than the vast majority of installed Ah counters can..
Ah's is only a good measure if it matches up with your batteries. Most times it does not. This is because a yearly capacity test has not been performed, an accurate Peukert is missing or the battery temp has been programmed incorrectly for the avg temps in the battery box.
I get that the SmartGauge will "adjust" so that it tells me the correct state of charge. But what I'm looking for here is an indication of the need to replace them. If my batteries are getting to 50% SOC quickly, is that because I need to use less juice, or does it mean I should replace the batteries.
It is not about how much juice per se but how long you used to be able to go before you hit XXX SOC vs. how long you can go now. It takes getting used to compared to other means but it works well. Any bank not capable of delivering approx 80% of its rated capacity is ideally due for a change. Can they be pressed further? Sure but the risk of failure gets higher.. The only way to
accurately know this is via a capacity test..
An interesting twist on the SmartGuage is that it does not tell you how much electricity you have used, but rather the SOC. SOC tells you when you need to recharge, but a "use gauge" tells you how well you have managed your use. Kind of like my car. I get 350 miles on a 10 gallon tank, and so I should get 175 miles when the gauge reads half a tank. If I find I'm only getting 150 miles on a half a tank, does that mean I'm using more gas, or does it mean someone put an 8 gallon tank on the car?
Harry
It is designed to be simple & accurate something the typical Ah counter is not... Current can be a good tool to have as can Ah but they really need to be accurate for the readings to be meaningful.. I am constantly programming and re-programming battery monitors..
This was a discussion I recently got involved in and I think sums it up fairly well:
Quote: "100 hours out of a 220 AH battery is 55% SOC, out of a 180 AH battery is 45%. Nevertheless it is still 100 AH that has to be replaced by some means, for a sailboat cruiser this is what is important."
It is not, unless you drew it out at 75-80F, at the 20 hour rate and had that capacity to begin with, which most batteries don't, once used.. This is pretty simple stuff... Loads are very, very rarely discharged on house banks at anywhere near the 20 hour rate thus we have to rely on Peukert corrections and temp corrections to get a more accurate idea of SOC/DOD...
The upside is that early on in the banks life we draw the banks down less than we "assume" we did so our SOC is actually usually higher than we assume it is, if the bank has the capacity it is programmed for. However as the battery ages and loses capacity we often get to a flip/flop point where we begin drawing the bank lower and lower that we
assume....
220 Ah Bank Peukert 1.25 Assumes 75-80F battery temp, load constant
100Ah's at 100A = Peukert Corrected Load 173A - Bank Capacity at 100A load = 126Ah
100Ah's at 50A = Peukert Corrected Load 73A - Bank Capacity at 50A load = 151Ah
100Ah's at 30A = Peukert Corrected Load 39A - Bank Capacity at 30 load = 171Ah
100Ah's at 11A = Peukert Corrected Load 11A - Bank Capacity at 11A load = 220Ah
100Ah's at 5A = Peukert Corrected Load 4.1A - Bank Capacity at 5A load = 268Ah
If one were to use just the Ah screen, as MANY boaters do, with a 100A load, you would be way off..
If one were to use the Ah screen even at just 5A you would also be a bit off....
If not doing manual resets when the bank is
known full these counting errors only tend to get worse and compound... If you don't know the current
actual capacity of the bank, at this point in time, the readings are even further off.
Of course loads vary widely on boats so the Ah screen alone is really only a hip shoot....
If someone is
competent enough to use an Ah counter then they are terrific tools and wonderfully accurate for a period of time until capacity, temp etc. changes again.
The vast majority of boat owners, in my experience, are not skilled enough or willing enough to get
good accuracy out of an Ah counter but they are still great tools because they most often err on the side of caution, due to Peukert, and bring more awareness to the bank ..
The point is that 100Ah out of 220Ah battery is only 55% SOC if the temperature, load and capacity all line up with what you
assume to be correct.... The only way to use an Ah counter, and get good accuracy, is to use the SOC screen, or equivalent, which accounts for temp & Peukert.
The Ah screen is just a guess, and may even be close, but won't be accurate unless proper programming has taken place and temp and Peukert are accounted & corrected for.
Some elcheapo Ah counters predetermine the Peukert constant for you. This really sucks when you get into a bank of Rolls batteries, or some Odyssey TPPL's, and there is no way it is going to be accurate.
All this does not even begin to touch on "
gotcha" issues like solar or wind replicating the "charged parameters" and resetting the Ah counter to 100% well before the bank is even close to full. I see this one all the time, especially with solar..
It also does not even touch on charge efficiency, which also changes with age, or self discharge, which a Coulomb counter can not
accurately predict.
All of these lead back to manual control &
known full resets as a primary way to keep these devices close to accurate.
Even for the Link Pro used on my LiFePO4 bank I had to calculate the Peukert by conducting physical load tests. Because the Peukert of this bank is so low I ideally could use the Ah screen but on a bank with a 1.25+ you will really get lost if the Peukert correction is not used...
The Link Pro is now quite accurate in relation to my Li bank but it is still always manually re-set and the bank undergoes yearly capacity tests to ensure the Link Pro is giving as accurate data as possible (actually it has had 8 capacity tests in 24 months due to accelerated cycle testing). If they could develop a Smart Gauge type device that worked for Li I would use it in a heart beat.
The best counting error I saw was on a Sabre. The Ah counter was reading -1100Ah's on a 65Ah starting battery and the owner had long ago given up on the Ah or % charged screen and simply reverted to voltage.....
Remember that 50% is not a magic number. The shallower the discharge the more cycles you get and Ah counters on large house banks tend to trend in favor of shallower discharges, for a while, until it flip flops, as battery capacity diminishes, the capacity has not been reprogrammed, and then it really begins to snow ball.......
I had one customer with a 690Ah bank with a 1.27 factory stated Peukert. His average load was about 8.5A. He wanted to cycle to 60% SOC and used the Ah screen to do so not the SOC screen.
Problem is that at his average load his bank was closer to 1000Ah's not the 690Ah's he was doing the math on by looking at the Ah consumed screen. He was discharging far less than the 60% SOC he wanted to be at before starting the motor. As a result he ran the motor far more than he wanted to and was in the very inefficient absorption charging range rather than bulk like he wanted/assumed he should have been..
The reality for me is that I see so many Ah counters wired wrong, programmed wrong, wrong assumed capacity etc. etc. that the Smart Gauge is going to be a great tool for many boaters who don't have the ability to use an Ah counter as accurately as they would wish..
It could also be argued that an accurate SOC is really all one needs to maximize cycle life of the bank and even at that it really only needs to be known once per day to adjust usage & charging...
I offer capacity testing for my customers with expensive banks such as GEL, AGM, Rolls batteries, L16's etc.... I have yet to have even 5% of the batteries tested line up with the "20 hour rating" and I have tested well over 100 batteries in the last few years...
A few weeks ago I capacity tested a pair of AGM batteries, for a new customer, that had 178Ah's out of the 220Ah they are rated for. His battery monitor was still programmed for 220Ah, a Peukert of 1.25 (incorrect) and an average battery temp of 80F, this time of year his batts are in the low 50's...
His shunt was also miswired and had at least three wires "sneaking" around it. He, like many boaters, who don't fully understand
the rest of the story, swore his Ah counter was accurate...
His Ah counter will be much better programmed this year but due to wiring and programming issues, among some other issues, his bank is already pretty toasted.
Is the Smart Gauge perfect? No, ideally I would love to see a Smart Gauge with a current screen, but then we are back into more complicated wiring, and the SG was designed and intended to be simple..
For the vast majority of boaters who want to know SOC, so as not to go below their safe threshold for the best cycle life, then the SG makes a lot of sense due to its amazing simplicity and rather remarkable accuracy.
For knowing your batteries current condition, capacity test them...
