Thursday, 29 November 2018

Observing a 170% conversion of battery energy into work

The circuit used in these tests is not particularly unusual - it's a simple blocking oscillator and it has a work-efficiency of approximately 85% (quantifiable-work performed for total energy supplied)

Fig 1. Circuit with current feedback to supply battery

Unquantified losses include resistive heat-loss in the switching transistor & diode, coil windings, and transistor biasing

The switching circuit operates at approx 67 kHz, in 2 half-cycles: a `Drain` step, followed by a `Recharge` step

Fig 2. Current paths in the system

The battery capacity can be characterised by discharging it using a resistor with a known value

Using a battery with 3 NiMH cells of 750mAh rated capacity, a fully charged battery supplied a 268 ohm (measured) resistor with an average power of 14.4mA x 3.86V for 42.5 hours, converting a total of 8504 Joules of energy

When the discharge resistor is replaced with the preliminary circuit (ie. the feedback diode is connected to a spare battery which is not the supply battery, but similar construction) the quantifiable work consists of two parts:- 
 - converting 3105 Joules to illuminate some LEDs
 - recharging the spare battery by using 4238 Joules of energy which is being temporarily stored in the circuit as a by-product of the oscillator operation

The circuit provides this quantifiable work for a total of 30.5 hours, drawing an average of 20.1mA at 3.86V to draw a total of 8603 Joules (approximately matching the total energy, 8504 Joules, converted by the nominal 270 ohm resistor)

In this mode, the circuit draws the total energy available and converts this to 7343 Joules of quantifiable work, giving a quantifiable-work efficiency of 85%

When the feedback diode is re-connected to the supply mode (see Fig. 1), the circuit will operate for almost twice the duration of the conventional, non-feedback mode - the circuit now operates for a total of 60.5 hours, whilst drawing the same real average power, 20.1mA at 3.86V,  (compared to 30.5 hours duration for the non-feedback mode) with the loads remaining the same values

[The circuit can operate at the same power drain for longer because it is constantly re-charging its supply with a proportion of the energy which has been input - the actual supply current drained is pulsed, with an average of 20.1mA, whilst 10mA av. is switched back into the battery, being interleaved each cycle similar to time-division-multiplexed operation (see Figs. 2 & 3), resulting in a 'virtual' current drain from the battery of (20.1mA - 10mA) = 10.1mA av.]

Fig 3. Bipolar current pulses in supply connection (blue trace)

The total energy drawn by the circuit is now 16898 Joules

The efficiency of the oscillator circuit compared to its total energy drawn hasn't changed essentially:
 the quantifiable work has increased to 14566 Joules, and these values give an efficiency of 14566 / 16898 = 86%

The overall system efficiency for quantifiable work from the original energy in the battery, however, is now 14566 / 8504 = 170%

The total system efficiency for conversion of energy in the whole system (battery + circuit) now becomes: 16898  / 8504 = 199%

The system is recycling its input energy by a factor of 1.99

The 'feedback to supply' mode has extended the duration for circuit operation and enabled the amount of useful energy available for the LEDs to be approximately doubled compared to the 'no feedback' arrangement

Although the total work converted by the switching circuit LEDs, on their own, remains less than the original supply of energy, and the energy converted by those circuit LEDs matches that of a passive resistor-driven LED arrangement (6159J vs. 6169J), the 'With-Feedback' current arrangement still enables the circuit to produce a level of light output slightly greater than the passive DC-drive arrangement (146 Ft-candles vs 140 approx.) but for approximately 34% longer duration (60.5 hours vs. 45 hours)

This resulting system behaviour provides a worthwhile gain, which has been enabled by the 200% conversion to system work (16898J) of the original store of energy in the battery (8504J)

Sunday, 13 March 2011

Charge Anomaly confirmed

The results below, from the switched-charge experiment (
12 May 2008), show that the total value of charge-separation in the isolated test circuit increased by approximately 25% from the initial state of the circuit, after the switched transfer of charge from the input capacitor to the output capacitor

0.299 Coulombs of charge-separation were removed from the input capacitor, C1  

0.913 Coulombs of charge-separation were added to the output capacitor, C3

(any charge on the only other two capacitors in the circuit - 500uF and 0.1uF - was small enough to ignore by comparison with that on C1 & C3)

 the final state of charge in the circuit was significantly different from that expected by conventional circuit analysis - the circuit had gained an anomalous excess of charge-separation!

Charge Results:
Input cap, C1: 0.299F
Start volts: 8.0V
Start charge: 2.392Coulombs

Final volts: 7.0V
Final charge: 2.093C

Output cap, C3: 0.342F
Output volts: 2.67V
Output charge: 0.913C

charge switched from input to output capacitor, then discharged by S2

Total start charge: 2.392C
Total end charge: 2.093 + 0.913 = 3.006C

(ignoring charge on switching cap, C2, 500uF)

Switched-charge test period: 45.8s
cycle period: 0.85ms
charge period: 0.17ms
charge/cycle duty: 0.17/0.85 = 20%

Stand-alone switched-charge experiment setup:-
(12 May 2008 )

the circuit was constructed to transfer charge from an input capacitor to an output capacitor, via a switching capacitor and inductor, using a number of repeated cycles to switch a small amount of charge in each cycle

the switching was achieved using MOSFET devices driven by a free-running oscillator constructed using NAND gates from a CMOS logic device

the entire circuit was powered solely by the initial charge in the input capacitor

the only external connection was to a DVM, used to monitor the voltage on the input capacitor

the test achieved the same results, regardless of whether the DVM was connected for the full duration of the test or if it was disconnected at the start and only reconnected a few seconds before the end

Open switch S1, close switch S2;
Monitor C1 volts with DVM;
Charge C1 to approx 9V;
When C1 voltage approaches 8V then open S2;
As Voltage on C1 measures 8V, start timer &
  Close S1, to connect C1 into circuit;
When voltage on C1 reaches 7V, stop timer &
open S1;
  measure voltage on C3 with DVM;

Switched-charge experiment schematic

Parts list:
R1: 12K 0.25W
R2: 100K 0.25W variable
R3: 100K 0.25W variable
C1: 0.299F (4x1F, 2.3V series)
C2: 500uF 16V
C3: 0.342F (4x1F, 2.3V series)
C4: 0.1uF ceramic
D1: OA93
D2: 1N914
D3: 1N914
Q1: FDN304P
Q2: IRF540N
L1: 2.5mH
U1-U4: 4093B Quad Schmitt NAND