Monday, 1 August 2011

New Cell - New Circuit (Sept. 21 update)

Cell #5 is another Zinc/Copper pair, again with a cotton separator impregnated with honey

the on-load terminal voltage (Blue data) decreased initially during the first 400 hours of continuous operation, and then in the following 300 hours it steadily increased again

it regained just over 100% of its early voltage discharge and is now sustaining at an average of this level, having supplied the LED flasher so far for 1800 hours
(2.5 months) continuous operation

                                      (click images to enlarge, use browser Back btn to return)

the circuit is contained in a mild steel enclosure to ensure that it is not influenced by local utility or radio signal energies:

Cell #5 was originally tested in a 2 Cell battery supplying my low-power LED flasher circuit, which requires a supply voltage greater than about 0.9V

one of the weak points of the '2 cells in series' arrangement has been that the battery has relied on a good contact between the Zinc of one cell and the Copper of the other - any oxidation of the copper surface has tended to increase the internal impedance of the 'battery' and reduce the total voltage supplied by the pair of cells

for this test i'm using one of my variants of Professor Jones' 'SJ1' circuit - a 'common collector' oscillator similar to the 'Joule Thief' circuit (which is usually 'common emitter')

i've inverted the circuit to use a PNP transistor and, as with with my original low-powered LED flash circuit, i've also connected the LED to feedback some of the energy stored in the coil each cycle into the supply (a 200uF capacitor in parallel with the voltage cell) and connected a piezo sounder in parallel with C1 to give an audible click when the LED flashes


  the benefit of this new circuit is that it can operate down to approx 0.4V and still flash the LED - so i only need to use 1 cell for this arrangement, therefore the internal impedance of the supply is lower and there is less likelihood of connectivity issues