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Old 08-07-2019, 03:02 PM   #1
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Default Side discussions moved from "What a battery monitor may not tell you"

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It's not that difficult now to gain an understanding of how to use an Ah counter type meter and what to use it for.
Its also easy to misuse it as the article makes clear. And the consequences are not obvious. If you draw your AGM batteries down to 15% when you think you are at 50% there is not going to be any immediate consequence and you are not likely to connect the dots when the battery fails after two or three years.

My car has an odometer and the manufacture tells me the size of its tank and its miles per gallon. I wouldn't use that information to determine how much gas I have left in the tank. Especially if my only way of knowing if the tank was full was that the pump stopped. But perhaps one of the great myths is the simplification of batteries as tanks of liquid where you put electricity in and take it out. Its a useful analogy, but they don't really work that way.
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Old 08-07-2019, 03:16 PM   #2
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Ross, you haven't answered any questions, and as you think monitors are so bad, what do you use? How is it better than a monitor? How did you test it? What is the actual current capacity of your batteries? Explain to us your understanding of how a monitor works and why it won't, including what settings are so terribly hard to get right.



You are just arguing for the sake of arguing, if you aren't willing to usefully contribute some good information.


Just because any product can fail if misused, should we disregard them completely? You have an Onan? Surely couldn't use them, etc etc.


As to your example, what you are essentially advocating is really disconnecting the odometer, speedometer, and gas gauge in the vehicle because they may not be perfect to your standard and would prefer no information.


I repeat, what do you use that is better, and why?


And while you are at it, why is it horrible that you abuse your batteries by being at 15% when you think 50% because your monitor is set wrong, but OK if you do the same or worse because you don't have a clue what the SOC is?
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Old 08-07-2019, 03:57 PM   #3
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…………………………. If you draw your AGM batteries down to 15% when you think you are at 50% there is not going to be any immediate consequence and you are not likely to connect the dots when the battery fails after two or three years…………………………
Good point indeed, what is your way to prevent this potential scenario in your system, connecting dots of uknowns?
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Old 08-07-2019, 04:00 PM   #4
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But perhaps one of the great myths is the simplification of batteries as tanks of liquid where you put electricity in and take it out. Its a useful analogy, but they don't really work that way.
Actually, this analogy is not a myth at all. For a great many purposes, it is extremely accurate and the novice would be well-advised to start with a deep understanding of the "water flow" analogy of electrical systems before moving on to esoterica like "Peukert's law".

OF COURSE it isn't perfect--a perfect analogy is not an analogy at all. Even when talking about water in tanks, there are edge-phenomena (e.g. air pressure effects, temperature effects...) that complicate the analysis when great precision is required. It is easy to cherry-pick the edge cases for polemical purposes, but I am not sure how constructive it is.

To call the water analogy a "myth" is a disservice to those trying to learn.
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Old 08-07-2019, 05:03 PM   #5
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I would guess we will never get any useful information about what is better, what is being used, or an explanation of why totally inaccurate is better than slight errors. The goal has already been reached and that is to argue for the sake of arguing, regardless of what the actual data says. Shouldn't surprise any of us.
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Old 08-07-2019, 09:04 PM   #6
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Actually, this analogy is not a myth at all. For a great many purposes, it is extremely accurate and the novice would be well-advised to start with a deep understanding of the "water flow" analogy of electrical systems before moving on to esoterica like "Peukert's law".

OF COURSE it isn't perfect--a perfect analogy is not an analogy at all. Even when talking about water in tanks, there are edge-phenomena (e.g. air pressure effects, temperature effects...) that complicate the analysis when great precision is required. It is easy to cherry-pick the edge cases for polemical purposes, but I am not sure how constructive it is.

To call the water analogy a "myth" is a disservice to those trying to learn.
For some analogy could be could be a myth if it is not fully understood.

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…………………….
In the water/electricity analogy, volts are the water pressure, amps are the size of the pipe and watts are the flow. You don't have 9 gallon pipes. That solar panel generates 170 watts at 9.4 amps and 18 volts. So if there is universal confusion here it is between watts and amps. ……..
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Old 08-07-2019, 09:22 PM   #7
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For some analogy could be could be a myth if it is not fully understood.
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Originally Posted by RossWilliams View Post
In the water/electricity analogy, volts are the water pressure, amps are the size of the pipe and watts are the flow. You don't have 9 gallon pipes. That solar panel generates 170 watts at 9.4 amps and 18 volts. So if there is universal confusion here it is between watts and amps.
Ouch! I missed that one.
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Old 08-07-2019, 09:27 PM   #8
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For anyone who is curious about the "water" analogy, I posted a quick overview on the list a long time ago:

http://www.classbforum.com/forums/f2...html#post35500
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Old 08-07-2019, 10:29 PM   #9
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Has anyone else noticed how quickly Ross has pivoted from the thread topic to new criticisms of other things, so he doesn't have to address the very valid questions asked of him about the original topic, but he can coninue to argue?


All contrary and no useful input given, even when asked. Another good topic destroyed for no good reason, like many others lately.


So how about answering the questions?
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Old 08-08-2019, 03:42 AM   #10
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The first thing to understand is that batteries don't store electricity, they store energy in chemical bonds. The appliances in our RV use energy to do stuff. Electricity is used to convey the energy stored in the battery to the appliance that uses it.

The battery (water pump) creates a current(stream), the amount of energy/watts(water) the appliance can use from that current(stream) depends on its voltage(water pressure) and amps(width of the stream). That is electric current as a stream of water where the amount of water coming out the end of the hose is determined by the water pressure and the size of the hose. That is useful analogy if what you care about is how much water/energy you are going to use.

The analogy of a battery to a tank of fluid is useful to the point that it makes clear you have to put energy in the battery to take energy out, the same way you have to put fluid in a tank to take fluid out of it. But unlike a tank, a battery is not an inert vessel. You will always have to put in more energy than you get out in electric current and the difference will vary quite substantially for any given battery depending on a variety of different conditions, including the size of the current it creates. Moreover, unlike a tank of fluid, how quickly the battery wears out will also vary substantially based on how it is used.

The analogy of a battery to a tank of fluid becomes a myth when you start to simply measure amps in and out to determine how much energy is remaining in the battery. That's the reason any decent battery monitor doesn't do that. But if your model is that battery as a tank of fluid its easy to be misled by the information it does provide.

As the article I linked above describes, there are lots of other ways a battery monitor can provide inaccurate or misleading information. And its not always going to be obvious when that is happening.
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