[p]I know this link is to a relatively old post, but the quick research I did seemed to show that the observations are still accurate today. Explains why the new monitor being installed by LL does not appear to be well received. Comments from the gurus appreciated:[/p][p]
[/p][p][a href="http://www.technomadia.com/2008/05/rv-battery-monitoring/"]http://www.technomadia.com/2008/05/rv-battery-monitoring/[/a][/p][p]
[/p][p]Besides the brands listed in this article, I also read good things on this one:[/p][p]
[/p][p][a href="http://balmar.net/smartgauge.html"]http://balmar.net/smartgauge.html[/a][/p][p]
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[quote source="/post/1912/thread" timestamp="1404913355" author="@funpilot"][p]I know this link is to a relatively old post, but the quick research I did seemed to show that the observations are still accurate today. Explains why the new monitor being installed by LL does not appear to be well received. Comments from the gurus appreciated:[/p][p]
[/p][p][a href="http://www.technomadia.com/2008/05/rv-battery-monitoring/"]http://www.technomadia.com/2008/05/rv-battery-monitoring/[/a][/p][p]
[/p][p]Besides the brands listed in this article, I also read good things on this one:[/p][p]
[/p][p][a href="http://balmar.net/smartgauge.html"]http://balmar.net/smartgauge.html[/a][span style="font-size:10pt;"] [/span][/p][/quote]The article is still accurate, and everyone who uses an RV should be aware of how the battery voltages fluctuate. However, my complaint about the monitor is not with the battery reading. Even the SeeLevel's battery reading is instantaneous voltage (and therefore only useful when combined with other factors). My issue with the monitor that LL installed is with the tank monitors... they're inaccurate and unreliable. Our previous trailer had that exact monitor and the black monitor was stuck at 2/3 within a year and the fresh and grey were too coarse to be useful. To use the analogy from the article, imagine if your car's gas gauge only updated every 1/3 of a tank.
That balmar gauge looks interesting, but it's also only voltage based. Maybe it works, but it's all up to their "proprietary test methods". I would want a little bit more of an explanation from them before I would purchase.
[quote source="/post/1912/thread" timestamp="1404913355" author="@funpilot"][p] Comments from the gurus appreciated:[/p][/quote][font face="arial" size="3"]Not sure I'm part of that august group but I'll toss my 2 cents worth in anyway. [/font][font face="arial" size="3"]First, the main objection to the KIB and any 4 light monitor is the probe tank monitoring system. There is no internal probe tank monitor that is at all accurate. External capacitive monitors are much better, but even those can give false readings. The external monitors such as SeeLevel seem to work well, but you have to be aware of their shortcomings too.
All 4 light battery monitors are basically useless. The KIB just seems worse than some others due to the levels they've selected for the lights. The best charge level monitor is a hydrometer. The second best, excluding the true AH integrating meter, is a digital voltmeter, but it has its limitations too. A digital voltmeter, used properly with a voltage vs charge table or graph, will give a fairly accurate indication. It's best to measure directly at the battery after the battery has been "resting" several hours. That said, here are some practical considerations:
[/font][ol type="decimal"][li][font face="arial" size="3"]Use a digital voltmeter. There are many inexpensive meters on the market. I use the one built into the SeeLevel monitor, but I also have this one: [a href="http://www.amazon.com/Equus-3721-Battery-Charging-Monitor/dp/B000EVWDU0/ref=sr_1_1?s=automotive&ie=UTF8&qid=1352484368&sr=1-1&keywords=battery+monitor+12v"]Voltmeter[/a].
[/font][/li][li][font face="arial" size="3"]Use the voltage reading; disregard the lights. Compare the voltage readings to the charts.[/font][/li][li][font face="arial" size="3"]Connect electrically as close as possible to the battery terminals. The best is physically right at the battery terminals. Second best is at the battery connection to the converter. Anywhere down the line, such as existing 12V outlets, can introduce errors.[/font][/li][li][font face="arial" size="3"]A circuit from the converter can be used if the monitor is the only active device on that line. My SeeLevel is connected to the TV preamp line, which has nothing else connected. With the preamp off and the TV disconnected the line is essentially a dedicated connection to the converter.[/font][/li][li][font face="arial" size="3"]Measure when everything possible has been turned off for a short time. No charging, no lights, no heater, no fan, etc. Unfortunately most RVs have a minimum load from propane monitors, radio, fridge control, etc. that cannot be eliminated. This is another reason to measure right at the battery.[/font][/li][li][font face="arial" size="3"]Temperature will have an effect, both on voltage and specific gravity. Corrections can be applied or ignored depending on the accuracy desired.
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So what's the conclusion? Use a digital voltmeter and forget anything with lights on it. Understand the conditions and limitations of whatever method you use. Don't lose sleep over it; that's for techies like me :D
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[p]Everyone says to let the battery "rest" for a while before measuring the voltage to determine state of charge. Some say 30 minutes, others longer. I did read one experiment where a boater took a battery, charged it up to float voltage and measured its "resting" voltage over a 24 hour period. The results were a little surprising. I will try to summarize.
Not surprising the voltage measured as soon as the battery charger was removed was in the mid 13s and was worthless in measuring state of charge. An hour later it was down to 13.0, still not much use. At 4 hours it read 12.8 which is closer to reality but not there yet. Only after 12 hours did it approach the theoretical 12.6 volts.
The same thing happens but the voltage stabilizes more quickly when you put a large, say 20 amp load on a fully charged battery for ten minutes. The voltage drops, depending on the amp hour capacity and for a Group 24 it can drop a half a volt. The voltage pops back up to about 12.6 in 15 minutes or so, but this illustrates that to really measure state of charge with a voltage reading you have to let the battery "rest" with no input and output at all, longer if you just took it off of the charger.
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[/p][p]Some years ago I cruised on a boat full time for 8 months. I did have a real integrating monitor, but since its display was out of the way, I got pretty good at estimating state of charge by factoring in the instantaneous current being drawn from the battery. If the refrigerator, anchor light and cabin light was averaging 5 amps, then I added a couple of tenths of a volt to the meter reading to get the current state of charge.[/p][p]
[/p][p]I suspect that is what the Balmar meter does with a microprocessor instead of my feeble brain. But how it gets current DC loads to enter in to that equation is beyond me. Measuring state of charge with only a voltage input takes more processing capability than I have between my ears;-).[/p][p]
David[/p]
[p]Here is info on the Balmer:[/p][p]
http://www.pbase.com/mainecruising/smart_gauge[/p]
From the article:
QuoteBut RC how does it work?
You've got me..? I have no idea how it works, at least at the programing/algorithm level (proprietary stuff), but it is reportedly designed to track voltage. Many internet posters have assumed, posited and suggested, that it checks internal resistance and pulses across the battery etc.. It may, but I have not seen evidence of this on the power / volt sensing wires, even with an Oscilloscope. If I had a tracking o-scope I may have seen something but I don't.
So apparently nobody knows how it works, but it seems to work for this reviewer. At $300 I'd still be uncomfortable getting it without a better idea of what's going on.
[quote source="/post/1923/thread" timestamp="1405009428" author="@tinkeringtechie"]So apparently nobody knows how it works, but it seems to work for this reviewer. At $300 I'd still be uncomfortable getting it without a better idea of what's going on. [/quote][font face="arial" size="3"]I don't see how it can measure SOC without knowing charging history, temperature, discharge rate, etc. Even internal impedance cannot be measured without accounting for the wire size and length, and then it would be iffy. If there was a way to measure SOC with only a voltage vs[/font][font face="arial" size="3"] time history the big battery users such as Telcos, utilities, solar guys, U.S. Navy Submarine fleet would have done it by now. That said I believe this device is very accurate in measuring wallet discharge rate :D.
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Here's a post from the inventor in another forum:
http://www.ybw.com/forums/showthread.php?73924-Smartbank-battery-management/page5
He hints at some ways that the battery can be measured using just two wires, but for me this is the most significant quote:
QuoteFor clarification, SmartGauge is not aimed at technically minded people. They can get along quite happily with an amp hours counter. Even when the unit runs out of sync, an experienced user can usually know this from the voltage and current readings. A non technical user cannot.
He even admits that he uses a amp hour counter himself. So basically the smartgauge is for people that can't (or don't want to) use an amp hour counter.
[quote source="/post/1925/thread" timestamp="1405011485" author="@tinkeringtechie"]For clarification, SmartGauge is not aimed at technically minded people. They can get along quite happily with an amp hours counter. Even when the unit runs out of sync, an experienced user can usually know this from the voltage and current readings. A non technical user cannot.
Quote
He even admits that he uses a amp hour counter himself. So basically the smartgauge is for people that can't (or don't want to) use an amp hour counter.[/quote][font face="arial" size="3"]"Not aimed at technically minded people." Well, TT, I guess that leaves you and me with our hydrometers, voltmeters, current shunts, microprocessors, charts, etc. Darn! No magic box after all. Not much better than the 4 light tank monitor combo..Camp on!
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LOL...sounds like it is perfect for me then. I really like even more that the 4 light model I should get will work fine for me. I guess when it goes to the second light I need to recharge???
Thanks for that post giving Chris Gibson's (the developer of Balmar's Smartbank Monitor) rebutal. I think he is too pessimistic about the usefulness of an integrating amphour monitor in the hands of a novice.
Most, maybe all such monitors reset net cumulative amphours to zero when it sees a voltage of 13.5 to 14.0 for a couple of hours. That is a pretty good indicator of full charge especially if the charging source is a smart charger or smart alternator regulator. On my cruising boat I would end up fully charging the batteries at least every 5 days or so. The battery monitor would then automatically reset and therefore learn about the battery bank's real capacity and/or Peukert coefficient with no "techie" input.
From Chris' post I do see a little of how Balmar's device does it: active polling of the battery's internal impedance for one thing.
But it is almost a hundred dollars more expensive than an integrating amphour monitor that also gives much more useful information, albeit only in the hands of us techies.
David
Here is another article that eventually says the Trimetric is pretty good. I did not mean to divert attention from my first post to the Balmar by having it by itself. Get a bottle of wine first as this guy is long winded. I have no technical skills to know if he is dead on or has been boondocking too long.
http://handybobsolar.wordpress.com/the-rv-battery-charging-puzzle-2/