Ammeter Wiring
- Thread starter wufibugs
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Try looking at it this way:
you can use a one horse power motor for an hour or
a sixty horse power motor for one minute or
a 3600 horse power motor for one second and consume the same amount of energy and do the same amount of work.
As you go through an exercise like this it is important to remember what one is looking for. In this case what we are looking for is:
How many amps were consumed in starting the motor?
The answer tells us how many amps need to be replenished.
Charles
How many amps were consumed in starting the motor?
The answer tells us how many amps need to be replenished.
Charles
This is precisely why I said "we don't reference removing amps per-SE". Amps is the unit of power just like watts or kilowatts but Ah's or watt hours or kWh/kilowatt hours are not the unit of power but what results from time at a given amperage, wattage etc... Of course you responded before I had a chance to clarify that statement, and make it clearer, while you were responding.
For now we are stuck with Ah's as a point of reference because that is how all deep cycle batteries are rated, in Ah's, and how all battery monitors display what has been used, in Ah's. The count amps and translate that into Ah's consumed. In other words we don't say I removed 4A from my battery bank you'd convert it to a time based unit and say we removed 4 Ah's... This is why my original statement used Ah's a the measure of capacity removed not amperes.
This is why from the beginning of this hair splitting event I have said .5Ah, not .5A, and at 286A for .75 seconds it removes peanuts in Ah's..
I am fully aware of that and have been saying that from the very beginning.
If you don't burn the 1A load for 1 hour, and burn it for less than an hour, then you've not used 1Ah. Please show me the math where this is an incorrect statement. I've shown you the math..
Yep simple stuff...
I am not using Ah's as a unit of energy, though you've certainly tried to twist it as such, I am using it as a unit of measurement.
Yes....Simple stuff..
Now you're getting it. Now try doing fractions of an hour...
1A for 30 minutes = .5Ah
286A for .75 seconds = 0.06Ah's
Here's another example: in your house, you have an electric meter (in many jurisdictions they are now "Smart Meters"). They measure kilowatt hours. How many kilowatts used for HOW LONG.
Indeed, if you get "into" the algorithms for all of the battery monitors, they actually use kwhrs and simply convert it to amp hours. That's what the manual for my Link 2000 says, in English, but in the fine print.
Hope this example helps you to understand.
Indeed, if you get "into" the algorithms for all of the battery monitors, they actually use kwhrs and simply convert it to amp hours. That's what the manual for my Link 2000 says, in English, but in the fine print.
Hope this example helps you to understand.
The engineer in me has to say that AH is technically not a unit of energy. You will remember from electrical engineering that Power is volts times amps and energy is power times time so energy is also volts times amps times time (E=V*A*t) But since we are always only talking about 12 volt systems it has become convention to just drop the "times 12" from all the equations where we use batteries. Makes it a lot easier to not have to specify a fully charged or partially charged ....... battery voltage. And the simplification is not that inaccurate since the difference between a fully charged and half charged battery is only around 1 volt
So to be clear 1 AH for a 12 volt battery = 1/2 AH for a 24 volt battery
same amount of energy in each amp hour but a materially different voltage so you have to account for it.
FWIW
So to be clear 1 AH for a 12 volt battery = 1/2 AH for a 24 volt battery
same amount of energy in each amp hour but a materially different voltage so you have to account for it.
FWIW
The Link 2000 manual includes this:
"One amp hour is (1) amp for one hour, or 2 amps for 1/2 hour, or 4 amps for 1/4 hour and so on."
This is simply a measurement compared to the battery storage quantity of the USE of power over a period of time.
Seems something this simple shouldn't be rocket science. Werner, Werner, vere iss Herr Von Braun when we need him???
"One amp hour is (1) amp for one hour, or 2 amps for 1/2 hour, or 4 amps for 1/4 hour and so on."
This is simply a measurement compared to the battery storage quantity of the USE of power over a period of time.
Seems something this simple shouldn't be rocket science. Werner, Werner, vere iss Herr Von Braun when we need him???
Leave it to wikipeida to make it misleading:
1 Ah = 3600 seconds * 1 amp = 60 minutes * 1 amp = 1 hour * 1 amp
to calculate the Ah if you are given seconds of time you do not multiply by 3600 you divide by 3600.
That is to say that since there are 3600 seconds/hour if you have 1 second you express that at 1/3600 hours NOT 3600 hours like wikipeida would lead you to believe upon a casual glance at the equation they quote. The equation is not incorrect it is just stating what an Ah is in seconds (which is TOTALLY dumb if you ask me).
1 Ah = 3600 seconds * 1 amp = 60 minutes * 1 amp = 1 hour * 1 amp
to calculate the Ah if you are given seconds of time you do not multiply by 3600 you divide by 3600.
That is to say that since there are 3600 seconds/hour if you have 1 second you express that at 1/3600 hours NOT 3600 hours like wikipeida would lead you to believe upon a casual glance at the equation they quote. The equation is not incorrect it is just stating what an Ah is in seconds (which is TOTALLY dumb if you ask me).
Nigel Calder Boatowners Mechanical & Electrical Manual Second Edition
Page 9 - Explains it well
Page 45 - Calder comes to the identical math I do in discussing high load battery testing using the starter motor:
Nigel Calder
"To avoid over heating of the stater motor during when simulating a high-load test, cranking should in no circumstances be continued for more than 30 seconds...............
High-load testing takes very little out of a battery. As I pointed out in chapter 1, even if the starter motor is pulling 400 amps, at 15 seconds this amounts to a total of only 1.66 amp-hours. 400 / (4 X 60) = 1.66 amp-hours"
400 X 0.00416 (15 seconds) = 1.66 Ah
or
400 X 0.00055 (2 seconds) = 0.2 Ah
that would be a good way to watch your power useage......but pricey on a boat i suspect....
regards
woody
To continue to beat this deceased equine thingie.. Bill and Stu are exactly right! It may be easier to convert to watt hours which is really a measure of how much energy is stored in the black box we call a battery. A 100 ampere hour battery at 12 volts has the capability to produce 1200 watt hours.. (10 amperes at 12V for 10 hours)
286 amperes at 12 V is 3432 watts.. so if it takes 5 seconds to crank, you've used :
5/3600hr X 3432watts = 4.9 watt hours out of the 1200 you had in the box. That is 0.41% of the stored power that you had in the box (battery) to start with. To replace it you have to generate 4.9 watt hours.. (plus a little for inefficiencies) so if your alternator puts out say 20 amperes at 14 volts, that is 280 watts.. so it can replace the 4.9 watt hours by running 0.0175 hours (4.9watt hours/280watts) or 63 seconds .. At 40 amperes output, the alternator would take 31.5 seconds.. to make 4.9 watt hours.
Maine's math is correct since it all hangs on a fixed conversion number ..
286 amperes at 12 V is 3432 watts.. so if it takes 5 seconds to crank, you've used :
5/3600hr X 3432watts = 4.9 watt hours out of the 1200 you had in the box. That is 0.41% of the stored power that you had in the box (battery) to start with. To replace it you have to generate 4.9 watt hours.. (plus a little for inefficiencies) so if your alternator puts out say 20 amperes at 14 volts, that is 280 watts.. so it can replace the 4.9 watt hours by running 0.0175 hours (4.9watt hours/280watts) or 63 seconds .. At 40 amperes output, the alternator would take 31.5 seconds.. to make 4.9 watt hours.
Maine's math is correct since it all hangs on a fixed conversion number ..
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Watt hours would be easier, IMHO, but the battery manufacturers, and battery monitor makers have clung to Ah's...
Certainly, but it sounded to me like Wayne was hung up on the fact that ampere hours is not a real term for power .. and indeed, my old EE prof friend would always cringe when I used ah as a power term.. but because of the 12 v constant (almost) it is the convention from which we work. Just trying another angle to get the terms across. Your videos of the cranking current and the battery monitor are great !
What time is it? Well, you start by making a metal case, get some gears and a spring or two and you build a watch.....
Unfortunately the use of watt hours is not more helpful as you HAVE to account for the voltage which is now a variable.
so if I use a pressure water pump for 1 minute (=1/60 hours) and it consumes 5 amps at 13.6 volts or 4.7 amps at 14.4 volts you get either:
13.6*5.0*1/60 = 1.13 watt hours
or
14.4*4.7*1/60 = 1.13 watt hours
just as you would expect since the power used is the same.
But the assumption of a standard voltage will give incorrect watt hours in all cases as a 12.0 volt battery is pretty discharged and not a very common voltage to operate at when using lead acid batteries. So you need to specify a more accurate "operating voltage" (probably a time averaged one).
So the situation is the same, you get an easier to use formula but it has the same errors. And since everybody else used AH to include the battery manufacturers why change?
so if I use a pressure water pump for 1 minute (=1/60 hours) and it consumes 5 amps at 13.6 volts or 4.7 amps at 14.4 volts you get either:
13.6*5.0*1/60 = 1.13 watt hours
or
14.4*4.7*1/60 = 1.13 watt hours
just as you would expect since the power used is the same.
But the assumption of a standard voltage will give incorrect watt hours in all cases as a 12.0 volt battery is pretty discharged and not a very common voltage to operate at when using lead acid batteries. So you need to specify a more accurate "operating voltage" (probably a time averaged one).
So the situation is the same, you get an easier to use formula but it has the same errors. And since everybody else used AH to include the battery manufacturers why change?
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