Impedance Battery Research
is a high impedance battery?
High Impedance Battery is an electrochemical cell with
a high internal resistance. It produces voltage but
very little current.
life exceeds that of low internal resistance cells by
factors of ten, since the cell dipole is maintained
for much longer by the low current drain.
class of High Impedance Batteries are ideally suited
for driving High Impedance Loads that require only very
small current, such as Electrostatic Motors.
the days when Vacuum Tubes or Valves were commonplace,
the "C" battery used to apply a potential to the grid
of the electron tube would last for as long as its shelf
life since it was only applying a voltage to the grid
- no current flowed from the battery.
combination of High Impedance Batteries with Electrostatic
Motors offers the possibility of greatly increased efficiency
for Electric Vehicle applications. The energy density
of conventional cells is now becoming high enough to
offer enough range for EVs to be psychologically competitive
with Internal Combustion Engine (ICE) vehicles, notwithstanding
the average trip length of 20 miles that motor cars
are generally used for. However, the High Impedance
Battery and Electrostatic Motor combination could offer
still greater efficiencies.
Sodium Nickel Chloride battery in production today has
an energy density of about 120Wh/kg, four times that
of lead acid. Lithium Ion batteries are also currently
able to provide about 120 Wh per kg weight in real world
conditions, though some development systems can go up
to 200Wh/kg; Zinc Air has demonstrated about 220 Wh/kg
and the Lithium Sulphur system in development may hold
400Wh per kg (but with restricted cycle life and volumetric
density not significantly better than LiIon).
has an energy density of about 13kWh per kg but 85%
of the energy in petrol is wasted as heat - only 15%
is converted into useful work in an Internal Combustion
Engine. A battery with 2000Wh per kg energy density
would therefore more or less equal the effective energy
density of petrol, taking into account the fact that
the Electric Motor - Battery system is also much more
efficient than the Petrol - ICE system; 90% conversion
efficiency of electrical power input into mechanical
output is normal in an AC or DC electric motor.
is no electrochemical battery on the market today that
can reach an energy density of 2000Wh/kg in the foreseeable
future. Only the Li Air or Li Water Fuel Cell has reached
1100Wh/kg and has a theoretical specific energy of 11,000
Wh/kg. This is a very interesting future candidate for
very high energy density batteries.
Finnish company Europositron claim to have developed
a rechargeable Aluminium Air battery with a specific
energy of 1300Wh/kg. This is also a very interesting
and potentially highly important development.
cars today average between 4 and 8 miles range per kWh
of stored electricity. At teh upper end, a mass
market appeal electric car would therefore ideally have
about 100kWh of battery storage. This would equate
to 100kg of Lithium Air fuel cell storage or only 80kg
of AlAir - outstanding figures. But with current technology
LiIon batteries, with a real world specific energy of
150Wh/kg at best, the weight would be over 650kg - prohibitively
heavy and expensive.
if we were to take a High Impedance Battery - Electrostatic
Motor approach, an even more efficient electrical motive
power system could be produced that could equal and
surpass the energy density of the petrol powered automobile.
electromagnetic motor requires a rotating magnetic field
to drive the armature. This is produced by energising
and de-energising in sequence the electromagnets of
the stator. Even though little energy is lost when a
current is applied to a solenoid - the energy applied
is stored in the magnetic field of the coil - that energy
is lost when the voltage is released and the back EMF
is produced. Certain EM Motor concepts capture that
back EMF and divert it to re-charge the battery, which
is certainly another approach to ultra efficient EM
Motors that would greatly extend the range and efficiency
of vehicles powered by conventional batteries or cells.
alternative approach is to use voltage only motors that
require very little current - Electrostatic
Motors can easily exceed the power per unit weight capabilities
of Electromagnetic Motors but up to now have taken up
more volume than the equivalent EM motor. However,
the higher the electrode density the smaller the volume
and the higher the power to weight ratio of an ES motor.
Research at the University of Tokyo into thin film pulsed
ES motors that will operate on less than 1000 Volts
could offer significant reduction in the size of ES
Motors. Very high mechanical power outputs are
also being achieved.
Impedance Batteries that Meridian International are
researching include Cu - Zn, Cu - Al and CuO - Al cells.
We are also researching improvements for a next generation
of ES Motors using optimised dielectrics, electrets,
differential electrode metals and new geometries.