how to test super capacitors - energy storage companies

Did you buy it on Ebay?
In other words, "Super Deal" is "super dumb ".
Did you copy one? to-
Many rough videos of YouTube super capacitors?
Or maybe you have a capacitor bank that has been serving for a while, just wondering how it works.
Using limited test equipment and some simple tests, I will help you to find out some secrets from the super capacitor.
Okay, I admit it.
I changed some "magic beans" with cows ".
Created this structure because I am cheap.
I haven't played super capacitors for a while, so when I stumbled across a lot of things on eBay, I took a bite and they rolled me in, hook, line, and
Of course, the price is less than half the price sold by big companies, and it also includes free shipping from China.
I'm sure they just passed on a lot of things they scored.
What the hell am I thinking?
I should know by now that there is no free lunch.
Have you ever felt that sinking?
I did do it when I started testing my super duper trading capacitor.
The first one I grabbed, when I connected it to the bench power supply, it didn't even suck any current.
Well, well, maybe it's a dumb bullet and it happened.
The next one I grabbed seemed to be charged, but when I took it out of the supply it immediately dropped by 1. 2 Volts.
Not very good looking.
Then I want to know exactly how I tested these.
The commercial super capacitor tester is certainly not possible and the price tag is within the range of "You can't afford it if you ask.
Let's see what we can do with some common test equipment.
We will study three parameters of the super capacitor.
Equivalent series resistance (ESR)
And leakage current/self-discharge.
I will show you several ways to test each parameter to let you know what works well for me.
Why is ESR important?
When the super capacitor is first available, the ESR rating is within the low ohm range.
It doesn't seem like a big deal until you start calculating the voltage drop in the high current circuit.
Assuming you need to power 12 v for 6 seconds at 10A, your circuit will work to a voltage of 6 v.
You make calculations and make sure that a series of 6, 50 Farad capacitors will provide the power you need.
Until you calculate the voltage drop from the series resistance.
Let's say that the ESR of these earlier-generated capacitors is 0.
5 ohms, 6 series to produce a total ESR of 3 ohms.
So 10x3 = 30 v down.
Don't go to work.
In order to lower the ESR to the available level, you have to parallel a bunch of smaller value caps.
Now, if we want to run 100 mA of the load for a longer period of time, this is feasible. 0. 1 x 3 = 0. 3V, 12V-0. 3 V = 11. 7 V.
For high current applications like audio peak power boost caps, low ESR becomes very important, or for energy collection of starter battery replacement packs and regenerative braking systems.
Not important for memory backup and low power applications.
Fortunately, the ESR of modern super capacitors is in the low mOhm range, which makes it possible to get high current items.
Constant current, voltage measurement look at the simplified super capacitor schematic diagram above.
All capacitors are reduced to the three elements shown.
ESR is only a series resistance element of our capacitor, so it is very suitable for analysis using Ohm's law.
We need a constant current source for this test.
The Workbench power supply or constant current load with current limit can work.
What we have to do is apply the current source and sink of 1 amp to measure the instantaneous voltage change.
Imagine the capacitor part of our circuit as a perfect current source/sink.
The trick here is to measure in the middle of the voltage range (0. 0 V -2.
Single cap 7 v)
So you definitely have a real 1a current.
The classic instrument for this measurement is a digital storage oscilloscope (DSO)
With the measurement cursor, you can resolve to about 10 mV in a typical hobby range.
If you don't have a range, don't worry, you can still use a high quality digital multimeter to have a relative understanding of your capacitor ESR (DMM).
If you are lucky enough to have a Moody's watch, it works almost as well as DSO.
I'm assuming you have a variable current limiting Workbench power supply.
If you do not, I strongly recommend the next one on your purchase list. With decent 0-30V 0-
5A supplies between $50 and $60 and there is really no reason why not.
That said, if you have a power supply with no adjustable current limit, you can build the super simple constant current load I included for less than $10.
You can also use one of the low cost DC to DC boost/Buck power modules available on eBay for about $5 to $10.
Discharge the capacitor through the appropriate current limiting resistor and then short it directly for about 15 minutes to prepare for the capacitor.
This should get you close to 0.
If not, you may have a high ESR problem.
It is a good idea to check the calibration of the power ammeter.
These tend to be a bit cheaper on cheaper units.
Shorten the power lead and set the current limit to 1. 0 A.
Set the DMM to measure 2 A or more and verify the power calibration.
Set the power supply voltage to be less than or equal to the capacitor rating, and when you set the power supply voltage, the measured displayed voltage is the same as the voltage read by the meter (
Don't forget to move your thread, we 've all done it)!
Connect the DMM or scope lead to the capacitor under test.
Connect the power supply to the capacitor under test, but not yet to the power supply.
Set the measurement range on the monitoring device.
For 1A test current, ESR in ohms will be equal to the instantaneous voltage difference that occurs when the 1 amp test current is applied or removed. (I. E.
50 mVolt = 50 mOhm)
On the new hat you should see a change below 10 mV. (
You may not be able to measure less than 10 or 20 mV)
On old or bad hats you may see hats up to 1 v.
Measure the voltage on the lid and record it.
Connect the power supply and immediately press the hold button on the DMM.
The value stored minus the starting voltage of the capacitor will be your ESR.
Using DMM for this is more of an art than a science.
According to your meter, the best resolution you may get is through/fail.
Hopefully you have a good upper limit known to measure, which will give you a baseline measure that can be compared.
If you are running a test on a DSO or moshimeter, you can immediately stop or have it charged to the completion point, depending on your settings.
Before the capacitor starts charging, zoom in and measure the starting voltage spike.
This voltage change is your ESR.
If you want to measure ESR using a constant current load, set the load to 1A.
Charge the capacitor to the rated voltage and take it out of the power supply.
Measure the voltage on the capacitor.
Apply the load and immediately click the hold button on the DMM.
The voltage drop is equal to ESR (
Volts under 1A charge/discharge current = ohms)
Yes, you can use a capacitor ESR meter to measure your super capacitor ESR.
One thing you have to do before measuring is to discharge the capacitor as close to zero volts as possible.
Any considerable DC voltage stored in the capacitor will damage the meter.
These meters use a DC clamping circuit to ensure the discharge of the device under test.
They are not designed to handle the large amount of energy stored in the Super hat.
Another factor to consider is that the meter may use a sine wave of 100 kHz instead of the 1 kHz specified by most capacitor manufacturers for testing.
This may cause the reading to be slightly different from the 1 kHz ESR Bridge, both of which will be different from the DC value.
This is the easiest and most accurate way to measure the super capacitor.
The $50 unit I have can be measured to 0.
001 Ohm, can be used on a capacitor full of electricity.
I have never had a cheap unit that is completely zero, so my measurements have 2 mOhm errors.
Even so, the convenience and consistent measure that was obtained made this a huge investment.
This is the big Kahuna we measured three straight wins.
It's all about power baby!
Well, that's different than money, but it's a different statement.
I don't know about you, but if I order a beer and the Cup is only a little over 3/4, we have a problem.
But this is exactly what some capacitor manufacturers can do to you.
Before you put the hard-earned cash into the Super hat, check the datasheet on the manufacturer's website.
Find out what is the allowable deviation of the capacitance value and use the minimum value in the design calculation.
It might be more sensible to spend a few more dollars on a hat rated-
5%, +-10% than rated20%. A +-
20% 500 Farad cap could actually be 400 Farad cap, even before it starts to degrade with age and use.
Therefore, we know the acceptable value range of the capacitor.
In my case, I have six 100 Farad capacitors with a rated voltage-20%.
This gives me an acceptable range of values from 80 to 120 Farad.
But how we measure it.
If you try to measure anything in such a big place, your capacitor meter will burst into laughter.
I would like to get stuck with an indirect capacitor value based on the energy we can push in or extract from the capacitor.
OK, I don't want to do that, but I need to do a little math.
You know I made it. it-with-a-rock, poke-it-with-a-
So it hurts me more than you.
Average current in capacitor I = C (dV / dt )
Second Solution for C = Farads, V = Volts, t = C = I (dt / dV )
Since we will use the current of 1A to measure the time when the voltage changes 1 V, in other words, this makes our final equation c = dtSo, in order to determine the capacitance value of my capacitor, all I need to do is measure the time interval (in seconds) at 1A charge or discharge between 1 V and 2 v ). Or 1. 5 Volts and 2.
5 V, the differential of any 1 V should produce the same result. (
As long as my charging current is constant)
So my 100 Farah
The 20% capacitor takes 80 to 120 seconds from 1 to 2 volts.
Similarly, DSO is the preferred test instrument, but the normal old DMM and stopwatch can also work. Piece of cake!
So what if you're really lazy like me, or just don't believe in math and want to see the total energy stored in the capacitor?
So you and my friend need a Re: load Pro from the spider lab.
This open source constant current load runs only $125 and has a lot of features.
One of them is the ability to calculate total power consumption.
We know that the potential energy stored in the capacitor is wh = 0. 5 (C x V^2 )
/3600So our 100 Farad cap, Wh = 0. 5 (100 x 2. 7^2 )/ 3600Wh = 0.
10. 1 determine the capacitance value according to the measured dissipation power, and for CC = 2, it can be solved by simply rearranging (3600 x Wh / 2. 7^2 )
Keep in mind that your capacitor must be charged to 2.
7 v and discharge to 0.
0 V for accurate measurement.
What is easier?
One convenient thing to remember is for 2.
7 v capacitance 1 farad is roughly equal to 0.
001 Wh or 1 mWh for energy storage.
I think this is the easiest topic to discuss.
Leakage current is specified on all manufacturer data sheets.
The only trick is usually to specify that value after 72 hours of charging.
But like most things in life, nothing is as easy as it seems.
I have a few capacitors that meet the 72 hour leak specification, but when taken out of the charge, the discharge starts at a much higher rate than the one measuring the leakage current.
It turns out that in the real world, our simplified schematic of the capacitor is not actually enough to handle the leakage current.
It becomes very complex, and the actual model looks like multiple capacitors in parallel, with voltage variable resistors in series and parallel.
This is the so-called transmission line model. we won't go there. (
No, there's no way, no way, the chance to teach monkeys to fly a space shuttle is better than I thought. )
Dielectric absorption and charge redistribution are two factors that affect self-discharge, and if a short charging cycle is used, it will have a significant effect on the voltage, but as far as I know, it should be the smallest after charging for about 4 hours.
Why are some of my hats acting like they are? Not a clue.
Depending on your application, leaving the hospital on your own may not be a problem.
This may not be a problem if your circuit is a UPS that is constantly powered on, or just needs to provide a boost current.
If you are building a solar cell bank, it has to keep charging for a cloudy few days, which is a big problem.
Let's try a more realistic way to handle self-discharge or leakage current.
These are my "ballpark" tests and you may make a difference.
If your application is self-discharge tolerant and your capacitor has passed ESR and numerical tests;
Charge for 8 hours at rated voltage.
The leakage current should be less than or equal to 2 mA. (
Up to about 600 Farads or so, higher values may have more leaks)
If your app has a short charging cycle and/or you may have a free charge for a long time.
Determine the shortest possible charging duration.
Charge your capacitor during this time.
Disconnect the power supply and measure the capacitor voltage.
Start the 1 hour timer and measure the capacitor voltage at this time. i leakage = C (dV / dt )
This will be closer to a real-world leak than a 72-hour test.
So let's go through this.
Let's say we have 100 mV change in 1 hour with a cap of 100 Farad. i = 100 x (0. 1 / 3600)i = 0. 003 A (Not great)
For equivalent shunt resistance = 2. 65 / 0.
003R = 883 OhmsLets says you are running a load that is manually turned on and off, so it will not consume any power until it is turned on.
When the operating voltage is 1 v, its drop fails. t = -C x R x ln (V1 / V2)
Where V1 is the discharge voltage, V2 is the charging voltage =-Ln (100x883 x)1 / 2. 7)
T = 87,704 seconds or about 24 hours.
The good news is that most of the super capacitors produced today have leak ratings within the miniature amplifier range.
This is a quick and fun project that can be built on the fragments of the perf board.
Be sure to use the radiator.
The radiator I show in the picture is only suitable for about 5 Watts in a row, but it will handle 10 to 15 Watts in a short period of time.
There are a lot of designs but I like this one.
It uses LM10C op-
It contains its own 200 mV reference amplifier.
This enables it to work at different supply voltages and still maintains good current regulation.
The rated power consumption of the IRF510 mosfet is 43 watts, but even with a very good radiator I won't push it over about 25 watts.
You can replace the IRFP150 if you need more power.
The test results look at my capacitance test results.
Of the 7 units obtained on eBay (
Drum, please)
There is no product that meets the manufacturer's specifications.
They're too bad.
How bad are they? )
I have to write some cheesy jokes.
I can't imagine these are actually new units advertised by suppliers.
Counterfeit rescued from the waste pile, rejected by the manufacturer, or rejected by the OEM? Who knows.
I know it wastes me too much time, and from now on this is the product I will buy from a known supplier.
The Eaton brand capacitor I purchased from DigiKey went through all the tests and was brightly colored.
I have purchased 8 additional tests as if they were clones of the first two.
This consistency is very reassuring.
Samwha or Shamwha?
For Korean companies that may or may not be part of Samsung, there is not much love online.
Since the so-called capacitor disaster in the 2000 s, Taiwan's low ESR electrolytic capacitors have failed at an alarming rate.
Samwha received quite a bit of negative news.
Many may not be worth it.
I have achieved great results on Samwha products and you can be sure that bad product manufacturers will not last long in the global market competition.
I would like to compare some Samwha Super hats from real suppliers.
My guess is that it's a good product and I'm stuck in more than just a suspicious transaction.
EBay and one-time access to CodeeBay is a great company.
The service they offer can buy anything and their customer service is top notch.
They even refunded my money from the crapacitor gate.
But I started to worry.
They are now releasing you a one-time code to access humans.
How many times did I get my access before the soulless gate admin switched to endless Mobius with voice tips and canned recordings.
I hope to receive an email as I approach. Cyber-
Tracked by a Chinese businessman?
"Hello, big customer, I am very sad. I didn't make you very happy. Please change the feedback and have a good time "and four others like it.
This is very simple.
Stop selling defective products and force your customer to open the box on eBay for a refund. Make On!