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10-14-12, 08:36 AM
#16
To further enlighten you python.
http://fentonrees.addr.com/pdf/c3.pdf
IV. EXPERIMENTAL RESULTS
Three different capacitors were tested under different conditions. Details are provided below in Table II. Results from the tests are also summarized in Table II.
IV.1 Test1 - 63V, 6800μF, 105oC Snap-ins for Continuous Duty Cycle Application :
Two capacitors were tested at the relatively modest ambient temperature of 70oC (representative of the worst case ambient temperature for the system - not underhood) at a ripple current equal to the capacitor’s rating for that temperature and frequency. The internal temperature of the capacitor was measured to be 85-90oC. The small (27%) increase in ESR over the 1500 hour duration of the test is consistent with results such as those by Harada et al [3], where the ESR had increased to failure point (2-3X) after 6000 hours of operation.
VII. CONCLUSIONS
Electrolytic capacitors used in a three phase pulse width modulated inverter have to carry a pseudo-square wave of current. A test fixture for the electrolytic capacitor that would inject square wave currents into them and operate them in continuous and intermittent mode was designed and built. In this paper, results from high temperature testing of electrolytic capacitors are presented. Using a physics based model reported in literature, based on the physical wear-out mechanism, the change in ESR with time for various operating temperatures was modeled. The experimental and modeling results were compared and analyzed. It was found that the model over estimated the life for the two cases when electrolyte leakage was the main cause of failure. The electrolyte leakage (dryout) and electrolyte deterioration (wearout) characteristics have to be further understood and models need to be changed or adjusted to properly account for these phenomena. Further models should account for continuous and intermittent operation of the component. These models are essential for designers to design and guarantee the reliability/life of the inverters and converters.
So at about 160k miles you are on borrowed time
http://fentonrees.addr.com/pdf/c3.pdf
IV. EXPERIMENTAL RESULTS
Three different capacitors were tested under different conditions. Details are provided below in Table II. Results from the tests are also summarized in Table II.
IV.1 Test1 - 63V, 6800μF, 105oC Snap-ins for Continuous Duty Cycle Application :
Two capacitors were tested at the relatively modest ambient temperature of 70oC (representative of the worst case ambient temperature for the system - not underhood) at a ripple current equal to the capacitor’s rating for that temperature and frequency. The internal temperature of the capacitor was measured to be 85-90oC. The small (27%) increase in ESR over the 1500 hour duration of the test is consistent with results such as those by Harada et al [3], where the ESR had increased to failure point (2-3X) after 6000 hours of operation.
VII. CONCLUSIONS
Electrolytic capacitors used in a three phase pulse width modulated inverter have to carry a pseudo-square wave of current. A test fixture for the electrolytic capacitor that would inject square wave currents into them and operate them in continuous and intermittent mode was designed and built. In this paper, results from high temperature testing of electrolytic capacitors are presented. Using a physics based model reported in literature, based on the physical wear-out mechanism, the change in ESR with time for various operating temperatures was modeled. The experimental and modeling results were compared and analyzed. It was found that the model over estimated the life for the two cases when electrolyte leakage was the main cause of failure. The electrolyte leakage (dryout) and electrolyte deterioration (wearout) characteristics have to be further understood and models need to be changed or adjusted to properly account for these phenomena. Further models should account for continuous and intermittent operation of the component. These models are essential for designers to design and guarantee the reliability/life of the inverters and converters.
So at about 160k miles you are on borrowed time
Last edited by sam12345; 10-14-12 at 08:52 AM.
10-14-12, 10:29 AM
#17
lmao..omg,nice copy and paste. i know of several people who have well over 300,000 miles on these cars who have never had a ecu replacement. ur barkin up the wrong tree here..ive been a service writer..mechanic and now work at napa auto parts and know what cars have what problems. so that being said im not saying caps are never the issue..in ur case it might very well be,just like i posted previously it might be ur ecu...but at no point does a shop start diagnosing a car at the ecu. good luck..let us know how ur ebay ecu purchase goes. u buying it from a junkyard on ebay or a company that deals solely in ecu's? why not just send it into ur local napa store and let them have cardone refurbish it?
10-14-12, 11:44 AM
#18
I am a mechanical engineer who designs car parts for multiple brands. I agree that a capacitor can last longer but since mine is giving me fits I might as well look into replacing the caps, especially when you can get an ecu for 70 bucks. I was just pointing out that there is some reasoning in changing your caps.
10-14-12, 06:07 PM
#22
Moderator
Good question. Depending on the capacitance, it varies. In case of 220uF, around 0.1 Ohm at the ambient is preferred.
To use ceramic capacitors is of course a good idea if the regulator circuits are designed to use them compensating the rotation of the phase angle and side effects such as a big capacitance change by the applied voltage and impedance ditches at different frequencies. Of course it would be nice if you could try to use them and inform us the results.
As long as you use what I have recommended, you don't need to worry about the oscillation problem. Because I actually have used those recommended types capacitors to fix ECUs at different shops as a volunteer.
To use ceramic capacitors is of course a good idea if the regulator circuits are designed to use them compensating the rotation of the phase angle and side effects such as a big capacitance change by the applied voltage and impedance ditches at different frequencies. Of course it would be nice if you could try to use them and inform us the results.
As long as you use what I have recommended, you don't need to worry about the oscillation problem. Because I actually have used those recommended types capacitors to fix ECUs at different shops as a volunteer.
10-14-12, 11:06 PM
#24
Moderator
According to the graph at 1.4.3, those values are within the range and you can use them if you don't mind to spend some extra money and to have some risk.
In my actual experience of a decade ago, the risk of the internal short which sometimes cause the smoke/fire problem was more than 1000ppm and it was very high in our standard but it's all up to you to use those tantalum capacitors.
In my actual experience of a decade ago, the risk of the internal short which sometimes cause the smoke/fire problem was more than 1000ppm and it was very high in our standard but it's all up to you to use those tantalum capacitors.
10-15-12, 02:00 AM
#25
python has valid point. Not all issues are going to be related to the capacitor problems that these cars are going to have. I think he is right to suggest following traditional diagnostic steps before pulling the ecu. Just an opinion.
10-15-12, 09:09 PM
#27
I did follow proper diagnostics, I spent 2 hours, I checked the fuel pressure, I checked for spark, I found there was no spark. I checked crank sensor, I checked timing belt. Then I found that the cel light did not blink when shorting the obd1 terminals and that this was intermittent, that is when the cel showed communication (by the blinking) the car ran perfect and when the cel did not blink (no communication) the car would not work. Then I checked the fuse and saw corrosion so I switched the fuse and cleaned the terminal block. The car is still working perfect since I did that. The point that yamasaki and cowboy are making is that it is a fact that these capacitors deteriorate with time and may leak, even if they do not leak since their capacitance goes out of the specified range that the circuitry was designed for the ecu will not work at its optimum so by changing them your ecu may work better and you may notice the car work better. Also to avoid the acid that may leak out from damaging the ecu traces. Notice the word MAY in all my statements. Since you can get a used ecu on eBay for 70 dollars you can just wait till catastrophic failure or you can do "preventive" maintenance . It is up to you. If they are saying to skip the diagnostic steps somewhere else in some other post I don't care I wish you would stick to the subject and take your feud with them to some other post. Why don't you make a post that says "not all evils are caused by the edu and take your argument with them there. Thank you.
By the way the actual cause may just have been the fuse not the ecu who knows.
By the way the actual cause may just have been the fuse not the ecu who knows.