Help needed with CAP ESR Values

Thread Starter

PhilipMiddleton

Joined Jul 31, 2018
4
Hello.
I'm new here, and to be honest I dont know a lot about electronics. More than most pedestrians, but much less than I need to know. Thats slowly changing as I'm currently schooling myself up.
I'm trying to diagnose an ECU fault in my 89 Celsior / Lexus. I'm told that the Electrolytic caps in that ECU are prone to fail and that they can be tested in circuit to see if they are failing. I have just purchased myself a cheap ESR meter but when looking for a chart to see what the ESR values should be I seem to be finding lots of different figures.
For example, one chart says that a 4.7uF 25V e-cap should be 6ohms and another says the same e-cap should be 2ohms
charts obtained via google search for "ESR Chart".
I'm confused. My understanding is the lower the value the better, but why the difference in charts? Is it dependant on manufacturer? I realised that some manufactures produce better quality caps than others... is that the reason for the difference?
Can someone point me to a reliable chart or do I need to go to the manufacturers for their charts (if they release them)?
e-caps I'm looking to test are apparently Nichicon's PF(M) type capacitors. These have very low ESR but contain quaternary ammonium compounds. Hence hey have a life span of about 10-15 years then fail and often leak potentially destroying the circuit board. Fortunately mine have not leaked (yet).
I'll be replaceing them with "United Chemi-con" e-caps. These are also apparently low ESR but dont contain the corrosive quaternary ammonium compounds.
Anyway, need a chart to see what my old caps and my new ones look like. I dont know enough to know whats right and wrong here and didnt even know that there was another value of consequence when it comes to caps (ESR).

Thanks for reading all this and giving a noob a chance.

Note: ECU = Engine Control Unit = Small computer that controls the Engine, has very tight electrical tolerances.
 

danadak

Joined Mar 10, 2018
3,726
I'm confused. My understanding is the lower the value the better, but why the difference in charts? Is it dependant on manufacturer? I realised that some manufactures produce better quality caps than others... is that the reason for the difference?
Can someone point me to a reliable chart or do I need to go to the manufacturers for their charts (if they release them)?
Not all designs want lower esr, some regulator designs want a min ESR to maintain
stability.

Same technology cap from different manufacturers will result in different characteristics.

You have to look at individual datasheets to see what performance looks like.

A generalized chart by technology -

upload_2018-7-31_6-26-25.jpeg

Regards, Dana.
 

Thread Starter

PhilipMiddleton

Joined Jul 31, 2018
4
Thank you Dana. I cant believe I missed your reply but thank you for your time.
I suspected as much regarding manufactures, depends on manufacturing technique I imagine.
I'll search as many different manufactures as I can and try and get as many different charts as I can find.
Thank you for your chart. It looks like it should be a good guideline.

Thanks, Philip.
 

JoeJester

Joined Apr 26, 2005
4,126
That Dick Smith's ESR meter uses approximately 100 kHz as it's test signal. Also the NOTE at the top states it's the approximate WORST ESR values for new capacitors at 20 degrees C.
 

ArakelTheDragon

Joined Nov 18, 2016
1,314
Hello.
I'm new here, and to be honest I dont know a lot about electronics. More than most pedestrians, but much less than I need to know. Thats slowly changing as I'm currently schooling myself up.
I'm trying to diagnose an ECU fault in my 89 Celsior / Lexus. I'm told that the Electrolytic caps in that ECU are prone to fail and that they can be tested in circuit to see if they are failing. I have just purchased myself a cheap ESR meter but when looking for a chart to see what the ESR values should be I seem to be finding lots of different figures.
For example, one chart says that a 4.7uF 25V e-cap should be 6ohms and another says the same e-cap should be 2ohms
charts obtained via google search for "ESR Chart".
I'm confused. My understanding is the lower the value the better, but why the difference in charts? Is it dependant on manufacturer? I realised that some manufactures produce better quality caps than others... is that the reason for the difference?
Can someone point me to a reliable chart or do I need to go to the manufacturers for their charts (if they release them)?
e-caps I'm looking to test are apparently Nichicon's PF(M) type capacitors. These have very low ESR but contain quaternary ammonium compounds. Hence hey have a life span of about 10-15 years then fail and often leak potentially destroying the circuit board. Fortunately mine have not leaked (yet).
I'll be replaceing them with "United Chemi-con" e-caps. These are also apparently low ESR but dont contain the corrosive quaternary ammonium compounds.
Anyway, need a chart to see what my old caps and my new ones look like. I dont know enough to know whats right and wrong here and didnt even know that there was another value of consequence when it comes to caps (ESR).

Thanks for reading all this and giving a noob a chance.

Note: ECU = Engine Control Unit = Small computer that controls the Engine, has very tight electrical tolerances.
Noone knows everything. We all have things that we do not know and we are still learning.

You might be better off using google and typing "my cap name/part number" equivalent or how to replace.
 

Thread Starter

PhilipMiddleton

Joined Jul 31, 2018
4
Thanks guys.
This is helping round out my fledgling knowledge.
So, next quick question. What percent past speck would you normally consider failed?
ie if a 2.2uF 100V cap that is meant to be better than 10ohms ESR, at what point would you consider it Failed?
Is there a rule of thumb that can be followed?

Thanks.
 

danadak

Joined Mar 10, 2018
3,726

MrChips

Joined Oct 2, 2009
19,778
Thanks guys.
This is helping round out my fledgling knowledge.
So, next quick question. What percent past speck would you normally consider failed?
ie if a 2.2uF 100V cap that is meant to be better than 10ohms ESR, at what point would you consider it Failed?
Is there a rule of thumb that can be followed?

Thanks.
No, there is no rule of thumb. It depends on the circuit application.

If ESR is non-critical, then 100% change would not matter much. More importantly, a drop of capacitance value of 50% would call for replacement. Note that brand new high value capacitances (>10μF) could be 20% above the nominal value.

If the circuit requires low ESR specs, then a rise of 100% above ESR spec would be concerning.
 
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