Joule Thief

[kb24]

I am no expert but, if your eb has exceeded 1.5 volts, which many of us have run the Fuji from, Then my guess would be your mA's are too low, or not flowing enough to keep up with the demand.  So, this is where the b-caps or supercaps come in.  In reality, if you looked at you eb's output on a scope, you might see the same high spikes that I have seen on mine.  These spikes will charge a supercap...and pretty quickly too....then you can use this a real power to drive the Fuji...or whatever you want.

Bill

So how am i supposed to charge the caps? do i have to manually charge the caps 1st before connect to my JT or i just connect the empty caps into my JT and it will charge on its own?

Thanks

[dasimpson]

So how am i supposed to charge the caps? do i have to manually charge the caps 1st before connect to my JT or i just connect the empty caps into my JT and it will charge on its own?

Thanks

you connect wires from the earth battery to the supercap then connect the joule thief to the super cap

[Pirate88179]

you connect wires from the earth battery to the supercap then connect the joule thief to the super cap

Exactly right.

Bill

[gadgetmall]

Why the puzzlement? ENERGY is the important parameter for longevity, not "Amps" or mA-H.

The energy stored in a capacitor in Joules is given by (C * V * V)/2, where C is capacity in Farads and V is the voltage it's charged to. NOT the rated voltage of the cap, but the charge that is ACTUALLY on the capacitor.

The energy in a battery, if the battery's capacity is given in Amp-hours, is
(V * Capacity) = Watt-hours
Watt-hours * 60 * 60 = Watt-seconds or Joules.

So a 1.3 volt rechargeable battery of 2500 mA-H capacity has
1.3 * 2.5 * 60 * 60 = about 12000 Joules, assuming a relatively flat discharge curve.

And a 650 Farad supercapacitor charged to that same 1.3 volts has
650 * 1.3 * 1.3 * 0.5 = about 550 Joules.

The capacitor charged to the same voltage as the battery contains less than 1/20 the energy of the battery.

The capacitor has much lower internal resistance than the battery and so can deliver its ENERGY much faster: that is, in a pulse that has greater amperage. In fact the cap can deliver essentially ALL the stored energy in one very quick pulse. The battery, with an internal resistance of several tenths of an ohm, can't come close to the current delivery capability of a capacitor. But it takes a BIG capacitor to store anything like the total energy in a decent battery at the same voltage.



Note well: you get more "bang for your buck" by increasing the voltage on the capacitor. The energy on the cap goes up as the square of the voltage but only linearly with capacitance. Double the voltage, you get 4 times the energy, at a given capacitance. Double the capacitance and you only double the potential energy storage at a given voltage.

For your amusement:
http://www.youtube.com/watch?v=cj5T0zRALKc

Nice machine . More explanations on ultracaps verse battery s .  Actually you cant discharge a large ultra cap "instantly" as demonstrated here . and if you try this with a battery it might explode .  http://www.youtube.com/atch?v=EoWMF3VkI6U  these  actually do have more power compared to batteries with the SAME Volts. we are talking KILO Joules Batteries heat up from internal resistance thus limiting the power it produces and Ultras  well are killers.  I am broke but could not pass up 5200 farads(a pair of 2600farads in parallel) for 35 bucks . they still have plenty . BTW for those wondering what happens when you charge them up over there rated volts  650 f 2.7 volt caps to 3.9 volts  they don't blow up just will eventually shorten the life .. The other thing that is not well understood (puzzelment)or recognized is that they take a very high current charger (constant current ) to charge but yet we can charge them with V-Spikes from earthbatteries   or a jt with  very little current faster than the calculations say . So by experiments done with them by some of us  it's possible to charge them up with just electrostatic volts with virtually no current similar to experiments done with batteries that appear charged (fluffy charge) except ultras charged this way have the power to back them up and this is not conventional 101 electronics.bet a tesla could charge em up fast .

Albert

[freepow]

I have charged my 50F cap on my Earth battery also, however it would not charge beyond what the Earth battery puts out, which is 0.95v.

My cap only charged to 0.951v over about 8 hours, why did it not charge up to the full 2.5v with all those spikes ?

I have a  400F 2.7v cap, I have not tried this as yet !