DaveGood

Just so you all know, After sixty plus responses and no useful information ( I'm investigating dmr's hints as to another thread where the holy grail may be found ). I can state that the majority of you have been well meaning, some of you have promoted yourself as bearers of knowledge you don't poessess, none of you have been useful ( with the possible, still to be determined status of dmr ). I consider this thread closed and will not look at it again. It has been of no use at all. DaveGood.

dmr, I'm keeping an (amused) eye on you. This is a sixty plus thread, most of it we!l meaning waffle, some of it outright bull####, and the rest of it faux outrage that I dare question thier wisdom and knowledge. It's sixty plus waffle, BS, and grandstanding, zero on info and answers so far. I forget who it was who used the term "Non-Linear Relationship", a few posts back, (like he works at CERN ) in some kind of effort to demonstrate he knew what he was talking about, but I bet if whoever that was, if out of their sight for more then five days.... .....his mother, his wife, and his children will have forgotten him too. DaveGood

Rob, I live aboard, off grid. No shorepower, on a boat where it is a complete b*****d to get at the batteries to measure SG and confirm the state of charge that way. My boat is my home, it's either under charge or providing power. I have to rip out the back cabin to get at the batteries. To begin with I assumed that the voltage drop of X amps on Y amphours of lead acid batteries, within reasonable limits, would be easily found info. After all, it's technology over a hundred years old. Try finding it! So far I've tried four major battery manufacturers, two won't answer, one thanked me for my interest, and the fourth told me it was "proprietary information". Next I went to a number of websites that concern themselves with (among other things) battery usage. Look back through this entire thread, there's something like sixty responses, not one of them an answer. A lot of them deploy carefully worded explanations as to why a simple, straightforward physcal\chemical process is far too complicated for me to worry my pretty little head about. Oh, and the people saying this don't have the slightest clue what they are talking about. So they'll start referencing stuff they've never measured but heard mentioned, "magnetic fields" or, "non-linear relationship" is a dead giveaway. If you wanted to know, say, the equivalent question in an equally old technology. Such as.... " How much fuel does a diesel engine, (something built from scores of moving parts) burn per hour to produce 1 HP?" You'd get a correct answer delivered in one short sentence from dozens of people in a few minutes. DaveGood

Dmr, started the search, a shed load of possible threads. I'll work my way through every last one, And in advance, Thank you, DaveGood

Dave Clinton If I place a fully charged battery bank of 440 amp hours under a ten amp load, what voltage drop will I see? If you know, tell us, if you don't, can you find out and tell us? If you can't do either,any contribution you make to this thread should have a higher entertainment quotient. DaveGood PS if the mods don't ban me soon, Betty Boo will as soon as she sees this thread.

Loddon I read what you wrote, " roughly With no load and least two hours after charging..." Nicknorman, you made a very eloquent series of statements, which while useful, did not contribute anything I wasn't already aware of from my own reading, but utterly failed to answer the simplest of questions, if a battery bank of given amp hours is placed under a given amp load how much will the voltage drop? We all know batteries drop under load because we've all seen it. That must follow some basic physical law. But no, apparently I'll need access to a supercomputer to work it out while all smartgauge needs to work out SOC,a much more complex equation, is one number, voltage over time. You don't know now much a battery drops under load and you want me to believe it's fantastically difficult to work out, and would have no significance when calculating SOC if I did. DaveGood

Everything helps buzzard. DaveGood

Good info Loddon, thank you, But now consider the case of livesboards who, for whatever reason, cannot shut down thier electrical systems for two hours, this time of year. I've met some. DaveGood

Loddon, I know, or, not having one myself, accept from the evidence of others, that it is highly accurate, also highly expensive, there are useful solar panel systems out there that cost less. And I know there are many people on this forum who are not sure where to find the price of another two bags of coal to carry them through April, never mind be in a position to buy either a PV system or smartgauge. If I can work out a rough, rule of thumb method that will allow them to better manage their battery bank, without cost to them ,I will do so, but I'm getting no help here. DaveGood

Loddon, Naughty Cal, Do either of you know how much fuel your engine will use on half power for eight hours? I bet you do, and if you don't it'll take you less then ten minutes online to find out what your engine should burn in that time. My question is the same, but applied to batteries. This is stuff we all should know. DaveGood

If voltage drop under load is an inaccurate measure of battery SOC why believe the Merlin II or Smartgauge are accurate? They both take their main reference for judging battery SOC from the battery voltage whether under load or not. The arguement that you can take one or at most, two, parameters of any physical system and by subjecting that parameter to intense scrutiny over a long period of time you will gain a full understanding of the health of that system is a flawed one. I can monitor your blood pressure and your temperature second by second, it wouldn't tell me you were blind. All, I've done, here and other forums, is ask if anyone had any info on what voltage drop is normal for x amps applied to y battery bank. I've met with little but ignorance and disapproval. DaveGood

I agree with you PaulC, and with Nicknorman. What I don't understand is why one of the most basic parameters of battery performance, voltage drop when under load, is regarded as a taboo subject, dangerous to bring up, and absolutely noone had any idea what the answer is. Not one person has come here, or on other forums I've posted to with an answer. But there have been plenty of people who, while, not knowing the answer themselves, have told me it's pointless to know and seem offended I asked. DaveGood

By,eck The smartgauge gives a state of charge reading under dynamic load, so for that matter does your volt meter, your rev counter, and your temperature gauge. Which ones do you not trust when under "dynamic load", all, some, none? DaveGood

Nicknorman, If monitoring voltage alone, and peforming repeated calculations on that single piece of data , is sufficient to give an accurate reading of SOC, (which is what Smartbauge does). Why does monitoring voltage and amps and temperature and voltage drop when under load give a less accurate or misleading result? Why does more information and greater knowledge lead to a worse outcome? DaveGood

Perhaps so Keeping up. A piece of string can be any length, but an amp, a volt, an ohm, a watt cannot be changed to suit anyone's whim, or win an argument. DaveGood

Nicknorman, Lead acid battery technology is over 140 years. In essence it's a couple of conducting plates separated by an acid electrolyte. A two year old toddler who jams an iron nail and a lead pencil into a lemon has made a battery. There are no moving parts. Yet, it appears, the workings of one are so difficult and so complex we plebs are discouraged from seeking even the most basic information on how they function. To ask how big a voltage drop I can expect if I load x amps onto a battery of known ah is the equivalent of me asking what is the mpg of the latest ford focus. Instead of this basic info being widely available, I'm being told (It is being implied) that that information is irrelevant, I wouldn't understand it if I knew it, and it would mislead me if I did know it. And I'm being told this by people who they themselves, do not know. This technology is more then 140 years old, why is this info not widely known? DaveGood

Nicknorman, I understand what you are saying, but consider this, as far as "high resolution" measurement of voltage goes, the owner\ founder of "smart gauge" on his website says his device uses a voltmeter accurate to no more then 1 per cent. I've got voltmeters that accurate, so do most of us, it' the industry standard and they cost pennies. How does measuring volts over time differ significantly from measuring amps over time as a measure of battery usage and state of charge? It' amps we use, not voltage, though voltage responds quicker and therefore gives higher resolution. If it not possible (as the majority of posters here state) to get a volt reading that can be used to gauge SOC, unless the batteries have been disconnected for hours.... How does Smartgauge work? It either disconnects the users from all power in and out of the batteries for hours at a time, frequently, to get an accurate reading, or it doesn't need to, or it's a fraud. I'm betting its not a fraud. I'm also betting that since I know, to the same degree of accuracy as Smartgauge, what my battery voltage is at any given moment.... That I know what amps is being supplied to, or from the batteries at any given moment ( data smartgauge doesn't have.) That I know what temp the batteries are currently at, and a whole host of other factors smartgauge doesn't know and can't measure..... I can, using rule of thumb, off the top of my head calculation, work out that the current state of charge of my live board, in use day to day, battery bank to within five per cent soc. If only I had some accurate numbers on how far down a given amp load drags the voltage of a given ah battery bank. Which is information no one seems to have. DaveGood

What does the smartgauge itself measure? Far as I can tell it measures probably three, maybe four parameters. Voltage, for certain. Time, for certain. Battery temperature, probably. And amphours in and out ( maybe, website isn't clear) It can't measure other factors such as battery inter connect length and dimensions. Well I know my battery voltage, I know the temperature, I've got a watch and know how to read it, and I have a good idea how many amps are being fed in and out of the battery at any one time. I know more then the smartgauge can sense. I don't know more about batteries then the guy who designed the smartgauge and embedded his knowledge within it as an algorithm. But if he achieved an accuracy of 1 per cent as regards to state of charge, I'm sure iI can get within plus or minus four to five hundred per cent of that number, and that's within five per cent. All I want to know is, does anyone have reliable numbers for how far a battery bank of a given size drops it's voltage under a given amp load? DaveGood

I'd love a smartgauge, But I can put together a 200 watt solar system for less money, Bimble solar sell 120 watt kits for less money. The smartgauge takes the battery voltage, does a bunch of clever maths and comes up with a figure. Well I know my battery voltage, I know my capacity, I know my draw in amps. All I need is reliable numbers on what voltage drop to expect from a given amp load to form a reasonably accurate guesstimate on battery SOC. DaveGood.

Does anyone have some accurate figures for this? The only thing I've seen is a voltage drop of 0.32 volts on a battery bank of 1440 Ah when placed under a 20 amp load. If we could cobble together some idea of what voltage drop to expect from a battery bank of known capacity when placed under a known load, us CC\liveboards, could have a rule of thumb for estimating state of charge. DaveGood

Good thinking Nicknorman, I'd overlooked shading out some of the panel as a means of controlling raw output. Have a greenie. DaveGood.

True, But not in my case, I have 250 watt 37 volt residential type panels. I'm not certain exactly what would happen if I tried to shove a 37 volt supply into a 12 volt battery, but I suspect it would keep the fire brigade entertained, the chandlers in profit and my insurance company despondent. DaveGood

Nicknorman, That'll work for panels connected directly to the batteries, but won't if it goes through a controller that restricts the voltage to well below 15 volts. DaveGood

Oarfish, I have mppt tracer controllers and don't seem to have a proper eq charge function on it. It doesn't hit a voltage higher then 14.8 volts which it describes as an eq voltage but is not. Does yours go up to 15.5 volts? DaveGood

All wet lead acid will benefit from an occasional eq charge, not just Trojans, it's not essential, but will increase battery life. Same goes for gel and sealed batteries but it is NOT SAFE, due to the way they are constructed, to do so.