Had to buy a battery today, but while researching I came on this...



... he's got some interesting ez 2 do experiments on his channel too.

I can't see any point of replacing your good old car battery 70 Ah with "toy" equivalent of 1 Ah,
(but practically 0.2Ah usable - as capacitor voltage drops linearly- not like battery that keep the same voltage range) .

300 Farads at 12V = 1Ah

Supercapacitor make sense only for electric cars to allow regenerative braking - doesn't do any good for petrol driven car.

Beside supercapacitor used by dummies will fry possibly everything later or sooner .
For two reasons ;
1) in case of accidental shortcut - the amperage will be unimaginable high and will fry all cables
2) when the voltage drops - will damage more device feeding low voltage but high amps = possibly will cook your radio and all electronics and motors....

Hi Macro

I had a look at the video, I don't consider the concept completely outrageous. A few points I would like to make:

The designer might want to check the "Absolute maximum ratings" on the datasheets of the capacitors he is using and do some measurements to make sure he is not exceeding temperature (ie: leaving them on a car seat during a 45C day) and current and voltage rates.

If I was the designer, I would like to know what happens when max ratings are exceeded ("blowing **** up" is always the fun bit ).

He isn't working with a big 350F cap. He has put the caps in series, therefore the summed capacitance is 58F.

For his application, voltage falls away exponentially... but yes, in the working area of the graph, it's pretty much linear.

I've done a basic calc (see below). To simplify the problem, I've made an incorrect assumption that the circuit is resistive (which it isn't), but I don't have enough info for a reactive calc (electric motors aren't my area). I've also assumed the load resistance (battery in parallel, wiring, motor) is about 0.5 Ohm. In a period of a few seconds, the voltage of the cap pack looks pretty good.



PS/ I only saw the first 5 minutes of the video as my internet is pretty bad here.

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jn1 said..
Hi Macro

the whole video looks like complete "amateurish"
-the guy is handling this potential " bomb" without any insulators on the positive and negative bolts - just imagine what would happen if he accidentally touch any motor parts and create shortcut - video becomes more like Myths Busters blow up epizode

- beside capacitors require:
a)cell balancing ( each capacitors is slightly different and after many cycles voltage will be different on each cell
and
b)cell voltage protection - any voltage above 2.7v and capacitor is damaged permanently

Anyway who want a car that you could try to start only once and battery is completely flat ? or leave a radio for 5 minutes or position lights and do the same ?

M

Cell balancing is used for batteries configured in parallel and once capacitors are charged, they don't dissipate heat (unlike a lead acid battery). That's the concept of balancing, because when particular battery chemistries gets hot they damage and lose their capacity.

Connecting any type of voltage sources in series is always going to have it's limitations.

Nothing wrong with exposed wires when prototyping . This only becomes a problem when you give the prototype to an end user to use.

The device could be made safer by having two modes of operation: charging and discharging. In charging mode (using a charging port), the designer could implement a microcontroller that measures voltages across the caps. If any cap is less than 4 time constants, a relay inserts a constant current source (ie: resistor) into the circuit to prevent over voltage condition. When fully charged, the micro detects lower than expected voltages across any of the caps, the device enters fault mode and is disabled (relay isolated). Discharging is done through the battery interface (thick cabling and clamps), a constant current source is put in series with the caps to prevent over current (exceeding cabling, clamps, capacitor Absolute Max Ratings). A power diode is put in series with the battery interface to prevent the boaster being charged via the battery adaptor. For Temperature: an alarm goes off if temperature of device exceeds say 70% of the maximum rating. At the same time, a bleeder resistor slowly discharges the caps. At 100%, device enters fault mode, and is disabled (relay isolated).

As you said at the start Macro, nothing beats a good old lead acid battery. They are proven, robust, and fail safe. You don't need complicated electronics to manage them.

I cant give you any details - but in the dark ages [pre-internet] there was a "shed built" electric Suzuki hatch running around the hills near Adelaide.

The 'zook didn't run lead-acid batteries, instead it had banks of capacitors packed in the engine bay and where the fuel tank used to be.

Range was a bit better than lead acid batteries - and recharging time was super quick.

Vague recollection it had electric motors on either the front or rear hubs.

IIRC, there was a write-up in either an electronics or car magazine with decent photos and specs of the capacitors motors and associated electrickery.


stephen

I looked into these about a year ago and for the cost involved, it was cheaper to buy an ordinary old battery.

The super cap arrangement has the disadvantage that if the car doesn't start within a few seconds, your super cap needs recharging.
A starter motor sucks about 200 amps cranking on a cold motor first compression, which equates to about .05 ohms, and drops to about 60 to 75 amps cranking a hot motor, still about .2 ohms. That sort of load drains a capacitor very fast.
That's the biggest disadvantage, and the cost of course.

The only advantage I could see was that it supposedly lasted forever and it was very much lighter. Also, it can be charged much faster.

I think they might eventually be viable as a battery replacement, but not yet.
To do this they will need to be cheaper, and higher capacity.

I also wondered about what sort of balance circuit would be needed when charging because the cells are wired in series to get the 12 volts.
If a cell went high impedance, most of the voltage would be dumped across that cell and it would be destroyed. Lithium batteries have the same problem and balance circuits have to be included in the charger to account for this. Multi cell computer batteries all have balance circuits built into the battery case.

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pweedas said..
If a cell went high impedance, most of the voltage would be dumped across that cell and it would be destroyed. Lithium batteries have the same problem and balance circuits have to

A cap going high resistance is a safe fail. The danger I see is when one of them shorts out. Under this condition during operation, the remaining good caps will see voltages that exceed their abs max rating. There again, with certain resistive values, the cap will start generating excessive heat... and, I don't know enough about these devices to say if that will be a danger.

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Macroscien said..
-the guy is handling this potential " bomb" without any insulators on the positive and negative bolts - just imagine what would happen if he accidentally touch any motor parts and create shortcut - video becomes more like Myths Busters blow up epizode

So how is the solar powered cat going Macro??

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jn1 said..

pweedas said..

If a cell went high impedance, most of the voltage would be dumped across that cell and it would be destroyed. Lithium batteries have the same problem and balance circuits have to

A cap going high resistance is a safe fail. The danger I see is when one of them shorts out. Under this condition during operation, the remaining good caps will see voltages that exceed their abs max rating. There again, with certain resistive values, the cap will start generating excessive heat... and, I don't know enough about these devices to say if that will be a danger.

It's not a 'safe fail' in recharge mode.
The high resistance cell allows an abnormally high voltage across it,.. and promptly blows up. (because they are wired in series, same current to all cells therefore, as voltage is proportional to resistance,.. high resistance,.. high voltage,.. the cells have a maximum voltage rating of 2.7 volts. which will be exceeded due to overall charge voltage being 14v)
An even distribution of the charge voltage requires all cells to be of a matched resistance. Since they rarely are as the cells age, a balance charger monitors the voltage across each cell and make sure if a cell does go high, then it is compensated for by external circuitry.

If a cell goes short circuit, it would also run the remaining cells into overvoltage as you have said, in which case the remaining three good cells would be in danger of blowing up.
Either way,.. you could get problems.

I think the flysufferer is a good candidate to try it all out though and get back to us with results.

I detect a conspiracy in the making.

I don't even have to do any research to know that's rubbish.

This, on the other hand, is real research. 450hp from a 4 cyl using triple turbos, the first being electrically powered.

www.motorauthority.com/news/1094807_volvo-reveals-450-hp-four-cylinder-with-electrically-driven-turbo-video

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kiteboy dave said..
I don't even have to do any research to know that's rubbish.

This, on the other hand, is real research. 450hp from a 4 cyl using triple turbos, the first being electrically powered.www.motorauthority.com/news/1094807_volvo-reveals-450-hp-four-cylinder-with-electrically-driven-turbo-video

About 40 or 50 years ago you could get an electrically driven turbo for yoiur v8 mustang.
They were something along the lines of a starter motor driving a vacuum cleaner turbine. Very basic and they only gave about a 1 or 2 psi boost, but that's enough to give a big boost in hp.
They only ran for short periods when it switched in on full throttle.

With todays neodium magnet motors and better turbine technology they could be made very much more efficient, but ultimately, the effectiveness is limited by how much power you can suck out of your alternator via the drive belt, because this is where the power has to come from.

They would still be good option for short term power bursts though, like 20 to 30 seconds, but not much good for a flat out run for a hundred kilometers.

Stun gun or tazer potential?

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FlySurfer said..
Stun gun or tazer potential?

CRTs made effective capacitors. One of my colleagues at one job years ago was telling me about making sure that you discharge the CRT properly before working on the monitor. He was telling me of how he didn't do it properly once, and that the HT lead was dangling at just on crotch height as he started working on the monitor. He doesn't recommend it

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pweedas said..

It's not a 'safe fail' in recharge mode.
The high resistance cell allows an abnormally high voltage across it,.. and promptly blows up. (because they are wired in series, same current to all cells therefore, as voltage is proportional to resistance,.. high resistance,.. high voltage,.. the cells have a maximum voltage rating of 2.7 volts. which will be exceeded due to overall charge voltage being 14v)
An even distribution of the charge voltage requires all cells to be of a matched resistance. Since they rarely are as the cells age, a balance charger monitors the voltage across each cell and make sure if a cell does go high, then it is compensated for by external circuitry.

When you say high resistance, how much are you talking about ? 1R ?, 1k ?, 1M ?

I'm going to bow out of this argument, as I don't have any knowledge/experience with super caps, however, something doesn't sound right with your argument. I can only think that the resistance you are talking about (ESR = Effective serial resistance) is generating enough heat to break down the cap's dielectic to make it thermal runaway ?, or cause it is become derated ?. My understanding of normal electrolytic caps is the maximum voltage rating is to do with the reactive part of the component (ie: how much energy the "D" field can have within the cap before the dielectic breaks down). What you are talking about seems to be the ESR of the cap ?

FN: Most modern TV's and computer monitors have a bleeder resistor inside the devices fly back transformer. This discharges the CRT when not powered. A zap from a charged CRT (25kV) gives you a scare, but not as bad as an electric fence

Every cell has an equivalent series resistance and on a good cell it it very low. For a cell pack capable of say 20 amps output, it will be less than a tenth of an ohm.
This same series resistance will also be in effect during the charge cycle.

The cell resistance does not have to change a lot to be relatively much higher than another cell in the pack, so if the normal equivalent series resistance is say 0.1 ohms, then a cell with an esr of 0.12 ohms will be sufficiently high to mess up the charging balance,.. unless,.. it has an external balance circuit fitted.

Also, in a series string of capacitors of nominally the same capacity, the capacity of each cell can vary by around 10%. It's quite difficult to make electrolytics with accurate values to within a few percent. If values are critical, they are usually made to approximate value and then matched to requirement after they are made.

This variation in capacitance will also have an effect on the voltage it is charged to, in a series string connection even if the esr's were identical,,.. which they will not be.

Thus in a series string of ultra caps, you could have a cell which has both a lower capacitance AND a slightly higher esr, resulting in it charging to a higher voltage faster. Since they have a very low maximum voltage rating, they are usually operated close to this maximum.
It gives little room for error as the cells age and so a balance circuit of some sort is highly advisable.

If the cells were not damaged due to overvoltage during the charge cycle, then the overvoltage would not matter.
However, since ultra caps have a very low maximum voltage, just 2.7 volts, then it is most probable that any significant variation in internal resistance would result in that limit being exceeded and the variant cell permanently damaged.

The usual damage is that the cell esr increases, thus making it more likely to be run into overvoltage at the next charge cycle, and more so on the next,. and more so the next,..etc.
Within a dozen charge cycles, the pack would be wrecked due to one cell being made such a high esr that the drain current of the whole pack is reduced.
One bad cell in a series string connection means the whole battery is ineffective.
Eventually, the wrecked cell would blow open during charge mode.

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pweedas said..

kiteboy dave said..
I don't even have to do any research to know that's rubbish.

This, on the other hand, is real research. 450hp from a 4 cyl using triple turbos, the first being electrically powered.www.motorauthority.com/news/1094807_volvo-reveals-450-hp-four-cylinder-with-electrically-driven-turbo-video

About 40 or 50 years ago you could get an electrically driven turbo for yoiur v8 mustang.
They were something along the lines of a starter motor driving a vacuum cleaner turbine. Very basic and they only gave about a 1 or 2 psi boost, but that's enough to give a big boost in hp.
They only ran for short periods when it switched in on full throttle.

With todays neodium magnet motors and better turbine technology they could be made very much more efficient, but ultimately, the effectiveness is limited by how much power you can suck out of your alternator via the drive belt, because this is where the power has to come from.

They would still be good option for short term power bursts though, like 20 to 30 seconds, but not much good for a flat out run for a hundred kilometers.

As per the linked article, in volvo's engine the electrical turbo is only used in short bursts to compress air which is used to spin up the other turbos al low rpm, allowing you to run much higher boost from them without any issues of turbo lag. After that there's plenty of wasted energy in your exhaust to be tapped.

Your system reminds me of the nutty guy in that aussie movie "metal skin" he was experimenting with a hair dryer or something..

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pweedas said..

Ok. Understood :)

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FormulaNova said..

FlySurfer said..
Stun gun or tazer potential?

CRTs made effective capacitors. One of my colleagues at one job years ago was telling me about making sure that you discharge the CRT properly before working on the monitor. He was telling me of how he didn't do it properly once, and that the HT lead was dangling at just on crotch height as he started working on the monitor. He doesn't recommend it

That's why u always stick a bread knife in the back of anything and wiggle it, before disassembly. Shorts out all the caps and stuff.

I'm still here.

You mean stuff like toasters ?