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impedance meter to test car battery

Started by Jamie M December 29, 2019
On 2019-12-30, Rick C <gnuarm.deletethisbit@gmail.com> wrote:
> On Monday, December 30, 2019 at 3:01:02 PM UTC-5, Jasen Betts wrote: >> On 2019-12-30, Rick C <gnuarm.deletethisbit@gmail.com> wrote: >> >> >
>> You seem to have forgotten that altenators are current sources, >> incapable of producing more than the rated current. > > If it is a current source, then it can be equated to a voltage > source with a high value series resistor.
I didn't say it was a Norton current source.
> What would the open circuit voltage be?
That depends on the engine speed and the strength of the field. typically could be 80V.
> What would the short circuit current be?
That depends mostly on the magnetic field strength, which is controlled by the armature current and has a hard limit when the rotor saturates. When the stator current is high enough to cancel the magnetic field that's your limit, more spin won't get you more current. -- Jasen.
On Wednesday, January 1, 2020 at 2:27:01 PM UTC-5, Tauno Voipio wrote:
> On 1.1.20 16:53, Whoey Louie wrote: > > On Tuesday, December 31, 2019 at 7:33:42 PM UTC-5, Rick C wrote: > >> On Tuesday, December 31, 2019 at 12:23:49 PM UTC-5, Whoey Louie wrote: > >>> On Monday, December 30, 2019 at 5:25:55 PM UTC-5, Rick C wrote: > >>>> On Monday, December 30, 2019 at 3:01:02 PM UTC-5, Jasen Betts wrote: > >>>>> On 2019-12-30, Rick C <gnuarm.deletethisbit@gmail.com> wrote: > >>>>>>>> > >>>>>>>> How much is a supercapacitor that will have a useful capacity at that voltage? > >>>>>> > >>>>>> Not sure how the battery and supercap will interact. On discharge, > >>>>>> the cap will supply current at a decreasing voltage, so the battery > >>>>>> won't supply much current until the voltage starts to drop. As the > >>>>>> battery voltage starts to drop the battery will drain down. Once the > >>>>>> cranking stops and the alternator starts to charge, the cap will still > >>>>>> be at a low voltage and will suck up all the current. Do you know if > >>>>>> the electronics in the alternator will prevent damage by charging a > >>>>>> very high current into a low voltage? Will the current be limited? > >>>>>> Will the alternator not try to raise the voltage immediately? I don't > >>>>>> really know how the electronics in the alternator is designed. > >>>>> > >>>>> You seem to have forgotten that altenators are current sources, > >>>>> incapable of producing more than the rated current. > >>>> > >>>> If it is a current source, then it can be equated to a voltage source with a high value series resistor. > >>> > >>> Say what? The current would then decline rapidly with any applied load. > >>> That isn't a current source. > >> > >> Ok, if you say so Always Wrong. > >> > >> -- > > > > > > And what exactly was that about? A current source most definitely does not > > look anything like a voltage source with a high value resistor is series. > > It's not clear exactly what the poster who said alternators are a > > current source meant. If he meant they behave similar to an ideal > > current source, that's wrong too. They look more like a voltage source, > > with the alternator/VR trying to maintain a constant voltage. A current > > source puts out a fixed current, regardless of the voltage or load. > > > You are mistaken. Please get an elementary textbook on basic electronic > theory and look up de Thevenin's and Norton's theorems. > > -- > > -TV
I'm totally familiar with Thevenin and Norton equivalents. Neither has anything to do with some power source behaving like a *current source*. Why would an alternator or any electric power source be considered a "current source", when it can be modeled using either voltage sources or current sources? Hello? An alternator is only a current source in the same sense that a battery, a capacitor, or a static spark is a "current source". They all deliver current, sure. But so, what? When one starts talking about something being a "current source' in the context of it's output characteristics, that implies that they are saying it's behaving like an ideal current source or similar to one. Which is one that delivers a constant current regardless of load. That most certainly is NOT a car alternator. Cars have VOLTAGE regulators, which is a clue. They behave more like an ideal voltage source, seeking to keep the VOLTAGE within a target rangd. Nor is it like a voltage source in series with a high value resistor, which the village idiot put forth. That is beyond stupid. So sad that we have people here commenting on electronics, when they don't even have a grasp of the very basics of electricity 101.
On Wednesday, January 1, 2020 at 2:23:49 PM UTC-5, Rick C wrote:
> On Wednesday, January 1, 2020 at 9:53:51 AM UTC-5, Whoey Louie wrote: > > On Tuesday, December 31, 2019 at 7:33:42 PM UTC-5, Rick C wrote: > > > On Tuesday, December 31, 2019 at 12:23:49 PM UTC-5, Whoey Louie wrote: > > > > On Monday, December 30, 2019 at 5:25:55 PM UTC-5, Rick C wrote: > > > > > On Monday, December 30, 2019 at 3:01:02 PM UTC-5, Jasen Betts wrote: > > > > > > On 2019-12-30, Rick C <gnuarm.deletethisbit@gmail.com> wrote: > > > > > > >> > > > > > > > >> > How much is a supercapacitor that will have a useful capacity at that voltage? > > > > > > > > > > > > > > Not sure how the battery and supercap will interact. On discharge, > > > > > > >the cap will supply current at a decreasing voltage, so the battery > > > > > > >won't supply much current until the voltage starts to drop. As the > > > > > > >battery voltage starts to drop the battery will drain down. Once the > > > > > > >cranking stops and the alternator starts to charge, the cap will still > > > > > > >be at a low voltage and will suck up all the current. Do you know if > > > > > > >the electronics in the alternator will prevent damage by charging a > > > > > > >very high current into a low voltage? Will the current be limited? > > > > > > >Will the alternator not try to raise the voltage immediately? I don't > > > > > > >really know how the electronics in the alternator is designed. > > > > > > > > > > > > You seem to have forgotten that altenators are current sources, > > > > > > incapable of producing more than the rated current. > > > > > > > > > > If it is a current source, then it can be equated to a voltage source with a high value series resistor. > > > > > > > > Say what? The current would then decline rapidly with any applied load. > > > > That isn't a current source. > > > > > > Ok, if you say so Always Wrong. > > > > > > -- > > > > > > And what exactly was that about? A current source most definitely does not > > look anything like a voltage source with a high value resistor is series. > > Do you need a LMGTFY link, Always Wrong? Try "Norton equivalent".
Try understanding that neither a Norton equivalent or a Thevenin equivalent is a CURRENT SOURCE, no more so than any battery, any generator, any voltage source is a current source. An ideal current source is one that delivers a specified, fixed, current regardless of the load. An alternator in a car is nothing like that. It behaves more like an ideal VOLTAGE SOURCE, maintaing a fixed VOLTAGE.
> This is the real problem with Always Wrong. Anyone can be wrong, but it takes a special person to be wrong and refuse to admit they are wrong when they only need to look it up and learn something. I'm guessing you know or knew this and had a brain cramp. Now you have dug in your heels and are refusing to acknowledge that you need to learn or relearn something.
You are the fuckwit that does not understand that a car alternator does not behave like a current source. Here's a clue. What does every alternator have? A VOLTAGE REGULATOR that tries to maintain a set, constant VOLTAGE, not a constant current. Does that sound like closer to an ideal current source or voltage source? You really have totally discredited yourself on anything to do with electricity at this point.
> > > > It's not clear exactly what the poster who said alternators are a > > current source meant. If he meant they behave similar to an ideal > > current source, that's wrong too. They look more like a voltage source, > > with the alternator/VR
trying to maintain a constant voltage. A current
> > source puts out a fixed current, regardless of the voltage or load. > > I know in the "old days" the generators/alternators would try to maintain a constant voltage output.
And that is still what they do stupid. But that's actually not ideal for batteries. I don't know if they have improved any or not. Yet here you are pontificating and telling us that an alternator behaves like a current source. Go figure. Certainly it would not be hard to do. I don't know You should just stop right there.
On 2020-01-01, Whoey Louie <trader4@optonline.net> wrote:

> And what exactly was that about? A current source most definitely does not > look anything like a voltage source with a high value resistor is series. > It's not clear exactly what the poster who said alternators are a > current source meant. If he meant they behave similar to an ideal > current source, that's wrong too. They look more like a voltage source, > with the alternator/VR trying to maintain a constant voltage. A current > source puts out a fixed current, regardless of the voltage or load.
The regulator limits the output, but we were taling about recovery. when the voltage is low it's operating at full power, in that region it's a current source. Once the regulator kicks in it starts to pretend to be a voltage source and the battery, which is a voltage source, does a fine job of covering up its flaws. -- Jasen.
On Wednesday, January 1, 2020 at 3:01:09 PM UTC-5, Jasen Betts wrote:
> On 2019-12-30, Rick C <gnuarm.deletethisbit@gmail.com> wrote: > > On Monday, December 30, 2019 at 3:01:02 PM UTC-5, Jasen Betts wrote: > >> On 2019-12-30, Rick C <gnuarm.deletethisbit@gmail.com> wrote: > >> >> > > > >> You seem to have forgotten that altenators are current sources, > >> incapable of producing more than the rated current. > > > > If it is a current source, then it can be equated to a voltage > > source with a high value series resistor. > > I didn't say it was a Norton current source.
A Norton equivalent is not a voltage source in series with a resistor. It's a current source in PARALLEL with a resistor. And an auto alternator doesn't behave like a current source in any way shape or form. One clue is that they use VOLTAGE regulators, which make it appear like an ideal voltage source, that tries to keep the VOLTAGE with a small range. A current source would seek to put out a constant current, the resulting voltage, be damned. If it's a current source putting out 1A, and the load was 12 ohms, it would be 12V, if the load was 1200 ohms it would be 1200 volts. Capiche? Doesn't work well for a car. And equating a current source to a voltage source with a high value resistor in series is just beyond stupid. The higher the resistance, the less like a current source it behaves.
On Wednesday, January 1, 2020 at 9:53:51 AM UTC-5, Whoey Louie wrote:
> On Tuesday, December 31, 2019 at 7:33:42 PM UTC-5, Rick C wrote: > > On Tuesday, December 31, 2019 at 12:23:49 PM UTC-5, Whoey Louie wrote: > > > On Monday, December 30, 2019 at 5:25:55 PM UTC-5, Rick C wrote: > > > > > > > > If it is a current source, then it can be equated to a voltage source with a high value series resistor. > > > > > > Say what? The current would then decline rapidly with any applied load. > > > That isn't a current source. > > > > Ok, if you say so Always Wrong. > > And what exactly was that about? A current source most definitely does not > look anything like a voltage source with a high value resistor is series.
Ok, so now rather than admit you were wrong and move on from there, you are retrenching by trying to ignore what you posted. You are so much like the Always Wrong who you love to scorn. -- Rick C. --- Get 1,000 miles of free Supercharging --- Tesla referral code - https://ts.la/richard11209
On Wednesday, January 1, 2020 at 3:01:09 PM UTC-5, Jasen Betts wrote:
> On 2019-12-30, Rick C <gnuarm.deletethisbit@gmail.com> wrote: > > On Monday, December 30, 2019 at 3:01:02 PM UTC-5, Jasen Betts wrote: > >> On 2019-12-30, Rick C <gnuarm.deletethisbit@gmail.com> wrote: > >> >> > > > >> You seem to have forgotten that altenators are current sources, > >> incapable of producing more than the rated current. > > > > If it is a current source, then it can be equated to a voltage > > source with a high value series resistor. > > I didn't say it was a Norton current source.
You seem to not understand the term. What exactly do you mean by "current source"???? Norton equated a current source to other circuits. He didn't define or invent the current source.
> > What would the open circuit voltage be? > > That depends on the engine speed and the strength of the field. > typically could be 80V. > > > What would the short circuit current be? > > That depends mostly on the magnetic field strength, which is controlled > by the armature current and has a hard limit when the rotor > saturates. > > When the stator current is high enough to cancel the magnetic field > that's your limit, more spin won't get you more current.
So is the alternator a current source or not? -- Rick C. --+ Get 1,000 miles of free Supercharging --+ Tesla referral code - https://ts.la/richard11209
On 2020-01-01 11:23 a.m., Rick C wrote:

> I know in the "old days" the generators/alternators would try to maintain a constant voltage output. But that's actually not ideal for batteries. I don't know if they have improved any or not. Certainly it would not be hard to do. I don't know if the alternator protects itself in event of an overload which would be likely if a huge supercap is drained down to 6 volts as the engine cranks. Then when the engine starts and spins up the alternator tries to drive 13 volts into a hugely capacitive load at 6 volts. Actually, in this case a current source would be preferred. >
Hi, Using an extra current limited charging terminal on the supercap/battery would probably be a good idea to limit the alternator load, but I am guessing at the typical low RPM of an engine that was just started, the alternator won't have enough internal current to damage itself before charging the supercap anyway. Also the field strength of the alternator stator is provided by the alternator output voltage, so it will be a weaker field if the supercap is at a lower voltage maybe. cheers, Jamie
On 2020-01-01, Whoey Louie <trader4@optonline.net> wrote:
> On Wednesday, January 1, 2020 at 3:01:09 PM UTC-5, Jasen Betts wrote: >> On 2019-12-30, Rick C <gnuarm.deletethisbit@gmail.com> wrote: >> > On Monday, December 30, 2019 at 3:01:02 PM UTC-5, Jasen Betts wrote: >> >> On 2019-12-30, Rick C <gnuarm.deletethisbit@gmail.com> wrote: >> >> >> > >> >> >> You seem to have forgotten that altenators are current sources, >> >> incapable of producing more than the rated current. >> > >> > If it is a current source, then it can be equated to a voltage >> > source with a high value series resistor. >> >> I didn't say it was a Norton current source. > > A Norton equivalent is not a voltage source in series with a resistor. > It's a current source in PARALLEL with a resistor.
Damn, I always get those two confused. I didn't say it was a Thevenin source either.
> And an auto alternator > doesn't behave like a current source in any way shape or form. One clue > is that they use VOLTAGE regulators, which make it appear like an ideal > voltage source, that tries to keep the VOLTAGE with a small range.
Tries and sometimes fails. See also "load dump"
> A current source would seek to put out a constant current, the resulting > voltage, be damned.
And that's what happens in a load dump.
> If it's a current source putting out 1A, and the > load was 12 ohms, it would be 12V, if the load was 1200 ohms it would be > 1200 volts. Capiche?
You don't.
> Doesn't work well for a car.
like I've been saying all along. -- Jasen.
On Wednesday, January 1, 2020 at 5:01:13 PM UTC-5, Jasen Betts wrote:
> On 2020-01-01, Rick C <gnuarm.deletethisbit@gmail.com> wrote: > > On Wednesday, January 1, 2020 at 3:01:09 PM UTC-5, Jasen Betts wrote: > >> On 2019-12-30, Rick C <gnuarm.deletethisbit@gmail.com> wrote: > >> > On Monday, December 30, 2019 at 3:01:02 PM UTC-5, Jasen Betts wrote: > >> >> On 2019-12-30, Rick C <gnuarm.deletethisbit@gmail.com> wrote: > >> >> >> > > >> > >> >> You seem to have forgotten that altenators are current sources, > >> >> incapable of producing more than the rated current. > >> > > >> > If it is a current source, then it can be equated to a voltage > >> > source with a high value series resistor. > >> > >> I didn't say it was a Norton current source. > > > > You seem to not understand the term. What exactly do you mean by > > "current source"???? Norton equated a current source to other > > circuits. He didn't define or invent the current source. > > is it important what claims I did not make? I used the wrong term.
Doesn't matter. Both Norton and Thevenin are wrong the way you want to use them. There is no such thing as a "Thevenin current source". Thevenin just said you could equate any given DC circuit to a voltage source and a resistor. Norton said you could equate any given DC circuit to a current source and a resistor. You seem to want to make a distinction between a current source and the Thevenin equivalent.
> >> > What would the open circuit voltage be? > >> > >> That depends on the engine speed and the strength of the field. > >> typically could be 80V. > >> > >> > What would the short circuit current be? > >> > >> That depends mostly on the magnetic field strength, which is controlled > >> by the armature current and has a hard limit when the rotor > >> saturates. > >> > >> When the stator current is high enough to cancel the magnetic field > >> that's your limit, more spin won't get you more current. > > > > So is the alternator a current source or not? > > It's more like a current source than like a voltage source, in that > when open circuit it produces harmful voltages, but when shorted nothing > bad happens.
I don't know that. I was simply saying that combining a rather large cap with the battery an alternator may produce excessive currents. If nothing else it may blow a fuse. I believe that is what happened in my truck when something shorted to ground. A wire fried burning up it's insulation but the repair shop never could explain what shorted. Meanwhile the 160 amp fuse blew. I think this could happen with the super cap as well. -- Rick C. -+- Get 1,000 miles of free Supercharging -+- Tesla referral code - https://ts.la/richard11209