Test/Review of Cooper 300F supercap

Thanks for the review!
What brought you to supercap testing?

People that say then can be used instead of batteries. I did know that capacitors was considerable less, but I wanted directly comparable result.

Here is one of the silly examples: https://www.kickstarter.com/projects/shawnpwest/30-second-charging-rechargeable-battery

He is using a better capacitor that the ones I have tested, but it is very far from being good enough (Probably 40F @ 3.8V).

thats nuts, though i want to understand how only a few Wh can start a car

What you need to start a car is lots of amps for a short time.

300A for 3 seconds at 12 volt is only 3Wh

Wh is measured over on hour and there is 3600 seconds in an hour, i.e. something that uses 300*12 -> 3600 watt, will only use 1 Wh each second.

It’s not the Wh that matters to start a car, it’s the Watts (i.e. current) the battery can deliver.

@HKJ: About that kickstarter project using supercaps:
I quite often hear people saying that one day we will have smartphones or electric cars that can be charged in 1-2 minutes.
Although the battery/capacitor technology may become available one day, what people don’t realize is that you would need an AC to DC transformer 10 times bigger than the smartphone or the car to achieve that.

thanks, that makes a lot of sense now
the unbalanced circuit that is used with 6 supercaps in series, would that reduce their life drastically?

Not necessary, you just have to equip the charger with a couple of supercaps too and keep it connected to mains.

But the charge connector, that might need to be rather solid. No small usb connector, but probably a docking station.

Did that circuit not use some leds to balance the caps?

To high voltage on a capacitor can destroy it.

no circuitry at all, just the caps in series, and the battery to recharge them with (though i suspect the car alternator charging the lipo battery won’t work well long term)
The car would charge with 14-14.4V to 6 supercaps in series (i would not use the lipo battery as the guy didn’t in the video i linked)

As I wrote above, over voltage might* damage them, people that are used to working with capacitors always add a balancing circuit to avoid any problems.

*If the voltage is high enough it WILL damage them.

is there circuitry that would work in an automotive environment on 6 caps in series? (i guess each would see about 2.5V so below their max voltage?)

Of course. It's just diodes, but you can buy it as a kit and spend more money if you'd like.

http://www.ebay.com/itm/301130956938 - balancer kit only

The complete bcap module kit includes the balancer stuff as well: http://www.ebay.com/itm/301128832966

I saw a circuit with a led and a diode in series for each capacitor. It is not the best circuit, but it is simple and will probably work as long as the capacitors has about same value (They change value with age).

cool, thanks

But this balancing circuits only discharge overcharged caps and don’t prevent overcharging them or am I wrong.
If somebody would charge a couple of caps with some Amperes the leaking of 30mA seems to be no ideal thing.
Or does short time overcharging don’t harm these caps?

that is a good point, i would want it to maintain charge for a few days or up to a week.

How do you overcharge them? You'd have to connect the 6S module to a voltage source higher than 16.2 volts. So don't do that.

I just followed the link to the battery starter with a lipo attached and I am wondering why not directly use a lipo pack? These are often rated for high currents…?

Maybe I have t understand how the balancing works… I will check it a bit further…
This video shows what I mean very good

So it doesn’t prevent overcharge in all conditions…but it works good enough for being so cheap…

The over charge is due to difference in capacity and different leakage current and will happen slowly.

'High current' is relative...