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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:
>> > >> > 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. -- Jasen.
On Monday, December 30, 2019 at 11:39:38 AM UTC-5, Whoey Louie wrote:
> On Monday, December 30, 2019 at 12:21:37 AM UTC-5, Rick C wrote: > > On Sunday, December 29, 2019 at 11:13:59 PM UTC-5, Jamie M wrote: > > > On 2019-12-29 7:59 p.m., Rick C wrote: > > > > On Sunday, December 29, 2019 at 8:08:26 PM UTC-5, Jamie M wrote: > > > >> On 2019-12-29 4:46 p.m., Lasse Langwadt Christensen wrote: > > > >>> mandag den 30. december 2019 kl. 01.39.07 UTC+1 skrev Jamie M: > > > >>>> On 2019-12-29 4:29 p.m., Cursitor Doom wrote: > > > >>>>> On Sun, 29 Dec 2019 16:21:10 -0800, Jamie M <jmorken@shaw.ca> wrote: > > > >>>>> > > > >>>>>> Hi, > > > >>>>>> > > > >>>>>> For a 12V lead acid car battery, at 12.6V and a > > > >>>>>> measured internal impedance of 9mOhms, is that enough > > > >>>>>> info to accurately estimate the CCA of the battery, or should > > > >>>>>> a battery load tester be used? > > > >>>>> > > > >>>>> The latter. > > > >>>>> > > > >>>> > > > >>>> Thanks, > > > >>>> > > > >>>> Also when a car battery can no longer provide enough CCA to reliably > > > >>>> start the car but is in otherwise "good condition", are there any > > > >>>> disadvantages to putting a supercapacitor in parallel with the battery > > > >>>> rather than replacing the battery with a new one? > > > >>>> > > > >>>> https://www.ebay.com/itm/16V-83F-Farad-Capacitor-Super-Capacitor-2-7V-500F-With-Protection-Board-Module/223685920878 > > > >>>> > > > >>> > > > >>> why bother? just get new one > > > >>> > > > >>> https://youtu.be/h7rTcBanpMk > > > >>> > > > >>> > > > >> > > > >> I've actually seen that video (good youtuber), ironically his first > > > >> sentence gives the answer to your question! (lead acid batteries are a > > > >> waste of money) > > > > > > > > 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. > > > > Regardless, I don't see the point. A new battery isn't $100. I get mine at Costco for more like $70, which is more than $40, but not enough to make me want to try to make this work. > > > > -- > > > > Rick C. > > > > + Get 1,000 miles of free Supercharging > > + Tesla referral code - https://ts.la/richard11209 > > Price depends on the size of that battery. Larger batteries for SUVs, > for example, are over $100. But that doesn't change the rest, which > I agree with. A battery should last 5+ years. It's a small expense > in owning a vehicle. Many places even install them for free. > I would not be looking at screwing around with > band-aids that could have an undesirable effect on other parts of the > system.
So your SUV takes a larger battery than my V8, full size pickup??? Sure, you can pay more, or you can pay less for the same battery. Costco has a good price, but not as good as it used to be. One I bought had a 9 year warranty, pro-rated of course, but only after 3 years of replacement. I think someone lost a lot of money on that and the warranty is a lot shorter now. -- Rick C. -- Get 1,000 miles of free Supercharging -- Tesla referral code - https://ts.la/richard11209
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. What would the open circuit voltage be? What would the short circuit current be? -- Rick C. -+ Get 1,000 miles of free Supercharging -+ Tesla referral code - https://ts.la/richard11209
On 12/30/2019 10:39 AM, Whoey Louie wrote:
> On Monday, December 30, 2019 at 12:21:37 AM UTC-5, Rick C wrote: >> On Sunday, December 29, 2019 at 11:13:59 PM UTC-5, Jamie M wrote: >>> On 2019-12-29 7:59 p.m., Rick C wrote: >>>> On Sunday, December 29, 2019 at 8:08:26 PM UTC-5, Jamie M wrote: >>>>> On 2019-12-29 4:46 p.m., Lasse Langwadt Christensen wrote: >>>>>> mandag den 30. december 2019 kl. 01.39.07 UTC+1 skrev Jamie M: >>>>>>> On 2019-12-29 4:29 p.m., Cursitor Doom wrote: >>>>>>>> On Sun, 29 Dec 2019 16:21:10 -0800, Jamie M <jmorken@shaw.ca> wrote: >>>>>>>> >>>>>>>>> Hi, >>>>>>>>> >>>>>>>>> For a 12V lead acid car battery, at 12.6V and a >>>>>>>>> measured internal impedance of 9mOhms, is that enough >>>>>>>>> info to accurately estimate the CCA of the battery, or should >>>>>>>>> a battery load tester be used? >>>>>>>> >>>>>>>> The latter. >>>>>>>> >>>>>>> >>>>>>> Thanks, >>>>>>> >>>>>>> Also when a car battery can no longer provide enough CCA to reliably >>>>>>> start the car but is in otherwise "good condition", are there any >>>>>>> disadvantages to putting a supercapacitor in parallel with the battery >>>>>>> rather than replacing the battery with a new one? >>>>>>> >>>>>>> https://www.ebay.com/itm/16V-83F-Farad-Capacitor-Super-Capacitor-2-7V-500F-With-Protection-Board-Module/223685920878 >>>>>>> >>>>>> >>>>>> why bother? just get new one >>>>>> >>>>>> https://youtu.be/h7rTcBanpMk >>>>>> >>>>>> >>>>> >>>>> I've actually seen that video (good youtuber), ironically his first >>>>> sentence gives the answer to your question! (lead acid batteries are a >>>>> waste of money) >>>> >>>> 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. >> >> Regardless, I don't see the point. A new battery isn't $100. I get mine at Costco for more like $70, which is more than $40, but not enough to make me want to try to make this work. >> >> -- >> >> Rick C. >> >> + Get 1,000 miles of free Supercharging >> + Tesla referral code - https://ts.la/richard11209 > > Price depends on the size of that battery. Larger batteries for SUVs, > for example, are over $100. But that doesn't change the rest, which > I agree with. A battery should last 5+ years.
It's seems like it is rare to get 5 years here in North Florida. More than 3 years less than 5 years.
> It's a small expense > in owning a vehicle. Many places even install them for free. > I would not be looking at screwing around with > band-aids that could have an undesirable effect on other parts of the > system. >
Jamie M wrote:
> Hi, > > For a 12V lead acid car battery, at 12.6V and a > measured internal impedance of 9mOhms, is that enough > info to accurately estimate the CCA of the battery, or should > a battery load tester be used? > > cheers, > Jamie
One does NOT measure battery _impedance_; one _can_ derive internal resistance and thus CCA. Standard is to use an 0.01 ohm resistor (120A load) with a voltmeter; voltage must be greater than 10V (100A load) after ten seconds. Both gel (sealed) and standard batteries, if good, will easily pass this test.
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.
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. -- Rick C. +- Get 1,000 miles of free Supercharging +- Tesla referral code - https://ts.la/richard11209
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.
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". 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.
> 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. 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. -- Rick C. ++ Get 1,000 miles of free Supercharging ++ Tesla referral code - https://ts.la/richard11209
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