Are Supercapacitors the better Batteries?

often viewers ask in the comments why do you still use batteries and not super capacitors for your projects good question do you know the answer gritty youtubers here is the guy with the swiss accent with a new episode and fresh ideas around sensors and microcontrollers remember if you subscribe you will always sit in the first row super capacitors are super like superman or superwoman otherwise they would only be called capacitors right where are they super and where not where can we use them and how and the most important question are they better than batteries all questions which have to be answered in this video let's start with the first question what are supercapacitors capacitors have their name from the capacity to store energy in an electrical field the unit is farad and this is the formula i have no clue why they use kilograms and meters in this definition but i'm only a poor engineer who knows how to use capacitors not a physicist who knows how they work so let's get started usually we only use tiny capacitors from picofarad in radio frequency applications to a few thousand microfarad in power supplies the latter usually are called electrolytic capacitors today i do not want to go into the details on how they are built instead i leave you a link in the description if you are interested all capacitors have in common that they store the energy in an electrical field and do not change any chemical structure therefore they do not wear out with charging cycles standard capacitors have no polarity and last extremely long on the other hand electrolytic caps have two disadvantages they have a polarity and at least the non-solid ones dry out after a few years lose capacity and eventually have to be replaced if we go on the way towards higher capacities we need the super or ultra capacitors they still are capacitors and still store the energy in a field so they theoretically support an infinite number of charging cycles they also use electrolytes but differently from the electrolytic caps they have a membrane in the middle so their construction is similar to batteries and as electrolytic caps or batteries they also can leak they are also polarized and have much more capacity than electrolytic caps their capacitance is measured in farads my biggest ones have 100 farads which is quite a lot compared with electrolytic caps this electrolytic cap for example has 3300 microfarad or 3.3 millifarad and this supercap with the same size has 30 farads or 10 000 times more capacity a huge difference so the super or even ultra is well deserved however there is a caveat the minimum voltage of this supercap is only 2.7 volts this electrolytic cap supports 25 volts so we need 9 super caps in series to get up to the 25 volts this is the formula for capacitors in series and the result is that we only get nine times less capacity and need nine times more space so the density factor between the two is only 123 still something maybe still super but for sure no more ultra if you ask me what is then the difference between super capacitors and batteries as we saw capacitors store energy in a field that means they do not do any chemical reaction and do not lose capacity with the number of charging cycles batteries on the other hand store energy by chemically changing their materials this is why they wear out and lose capacity over the number of charging cycles let's check out how good supercaps are for powering our small projects we do not need 25 volts for that we only need 3.3 or maybe 5 volts let's concentrate on 3.3 for this video so we need two capacities in series to get up to 5.4 volts here i have two supercaps in series with a total capacity of 15 farad i charge them to 5.4 volts and discharge them with 100 milliampere a typical load of an esp32 for the test i use this simple electronic load because it has software to report the results 0.1 ampere is a very low current for this load this is why it fluctuates a little but the average is okay here is the voltage curve it starts at 5.4 volts and decreases constantly not what i was hoping for why is that this is the formula for capacitors v0 in our case is 5.4 volts c is 15 farad and i is minus 0.1 ampere so it is clear that the voltage will drop constantly not very good for our purpose to say the least our mcu's are built to work with constant voltages so what to do we would need a buck converter for this area and a boost converter for that area extremely complicated and my frequent viewers know that i do not like complicated things so what would be a better solution we could only use a buck converter and do without the energy delivered below 3.3 volts not very efficient fortunately there is a better solution we know from before that inside these 15 farad caps are two 30 farad 2.7 volt supercaps so if we connect them in parallel we have a maximum of 2.7 volts and we only need a boost converter here is my setup two 30 farad caps in parallel and this small boost converter and here is the voltage curve much better we get our more or less constant 3.3 volts and the current still is around 100 milliampere but how long will the setup feed in esp32 nearly 5 minutes if we trust this test not a long time the two supercapacitors have about the same volume as this battery with a capacity of 650 milliampere hours the battery would last about five hours not only five minutes not good but how is it if we sleep the esp32 to draw 10 microampere i connect a 330 kilo ohm resistor at the boost converter's output and measure the voltage across the supercap as we see it keeps its voltage much longer very good if we keep in mind that the supercapacitors have an internal leakage current and the boost converter also has some losses so we see why supercapacitors are used in computers as backup batteries for memory chips of course we could add capacity we get supercaps up to 3000 farad and we can buy them bundled in larger packs but this gets quickly big and expensive and because we must not overcharge them we have to add balancing and protection hardware if we connect them in series fortunately for our setup with a boost converter we can connect them in parallel and therefore do not need to care for the balancing we just have to protect them against over voltage but even if we use a 3 000 farad capacitor we get 100 times 5 minutes or around 8 hours of continuous operation similar to this small battery these tests clearly show that batteries are much better for standard projects however for sensors with long periods of deep sleep supercaps could be an option if we could reduce the current 100 times to 1 milliampere average we could get 8 hours from these 30 farad caps if we combine it with a solar cell we could nearly survive the night with a 3 000 farad capacitor and a solar panel we probably could survive the whole winter if it is not up north where we hardly get any sun during a few months a typical system looks like that a solar panel a buck converted to 2.7 volts a super capacitor a boost converter to 3.3 or 5 volts and the mcu board with sensors not simple but also not much more effort than with a solar charge battery but one question remains why is this hype around supercapacitors did i make a mistake in my measurements or calculations i hope not but anyway super capacitors are not made to replace batteries they are made for different purposes because they can be used for an infinite number of charging cycles they are ideal for short-term storage for example to store energy created from de-accelerating a car this energy can be used a few seconds later without bothering the battery so the battery will last much longer or in this bus which is charged at every station like that the stored capacity can be low but the number of charging cycles is high supercaps are usually also built to support very high charging and discharging currents even small capacitors can create large currents for a short time most of those advantages are not helpful for our small projects where we need energy for a long time even the ultra low power in ocean sensors use tiny batteries as we saw in video number 406. however there is one use case for small projects harsh environmental conditions lithium batteries should not be charged below zero degrees centigrade so if your device has to be charged at such low temperatures you might consider using supercaps but as we saw you probably need space and money at least if your device is not extremely low power so we found that all capacitors store energy in electrostatic fields they keep their chemical structure all the time supercapacitors can store much more energy than ordinary capacitors or even electrolytic capacitors most super capacitors can only be used up to 2.7 volts if we need higher voltages we have to connect them in series unfortunately the capacity in this configuration is reduced but they can store much less energy than batteries which change their chemical structure to store energy capacitors have a less than ideal discharge curve discharged with a constant current they drop the voltage linearly utterly different to batteries which have a much more stable voltage across a long time we can solve this issue if we use a low voltage capacitor and a boost converter tests show that the capacity of small super capacitors are too low for an always on esp-32 or arduino board so super capacitors are not a replacement for batteries they are good in scenarios with high currents and or heavy charging or discharging because they can also be charged at low temperatures they could be used in harsh environments and with solar panels will the capacity gap between supercapacitors and batteries become smaller i do not think so chemical reactions have more potential to store energy than electrical fields so the chance that the game-changing material will be discovered is small increasing the maximum voltage would help a lot of course that was all for today as always you find the relevant links in the description i hope this video was useful or at least interesting for you if true please consider supporting the channel to secure its future existence thank you bye

Channel: Andreas Spiess

Views: 60,294

Keywords: arduino, arduino project, beginners, diy, do-it-yourself, eevblog, electronics, esp32, esp32 datasheet, esp32 project, esp32 tutorial, esp32 weather station, esp8266, esp8266 datasheet, esp8266 project, greatscott, guide, hack, hobby, how to, iot, lorawan, nodemcu, project, simple, smart home, ttgo, wemos, wifi, supercapacitors

Id: Orf9segRLv0

Length: 13min 29sec (809 seconds)

Published: Sun Nov 28 2021