The Cost of Battery Power - will rechargeables replace the
primary battery?
Isidor Buchmann
Cadex Electronics Inc.
isidor.buchmann@cadex.com
www.buchmann.ca
December 2001
Compared with other power
sources, electrical energy from non-rechargeable (primary)
batteries is very expensive. To reduce cost, many organizations
are switching to rechargeable (secondary) batteries. This
article examines the advantages, limitations and economics
of primary and secondary batteries.
In Figure 1 we compare the energy cost delivered by commercial
alkaline cells. The right column shows an ultra-high density
lithium sulfur dioxide battery for military use. An increase
in cost per kWh can be observed with smaller cell sizes.
|
|
AAA Cell
1.5V
|
AA Cell
1.5V
|
C Cell
1.5V
|
D Cell
1.5V
|
9 Volt
|
BA-5590
for military
|
|
Capacity
|
1.1 Ah
Alkaline
|
2.5 Ah
Alkaline
|
7.1 Ah
Alkaline
|
14.3 Ah
Alkaline
|
0.6 Ah
Alkaline
|
7AhLithium
sulfur dioxide
|
|
Energy
|
1.4 Wh
per cell
|
3Wh
per cell
|
9Wh
per cell
|
18 Wh
per cell
|
4.2 Wh
per pack
|
168Wh
per pack
|
|
Battery Cost
(estimated US$)
|
$1.25
|
$1.00
|
$1.60
|
$1.60
|
$3.10
|
$60.00
|
|
Cost per kWh
|
$890
|
$330
|
$180
|
$90
|
$730
|
$357
|
Figure
1: Cost of energy obtained by primary batteries. Compared
to other energy sources, the energy cost from primary batteries
is very high. The cost increases with smaller battery sizes.
Primary
batteries have their advantages. Operational readiness, high
energy density, long storage and instant readiness are just
a few. But advancements in rechargeable batteries have put power
densities on par with primaries. Some work will still be needed
to obtain longer storage times and improve cycle life, issues
that plague the ultra-high density rechargeable battery.
Figure 2 reveals the much lower energy cost rechargeable batteries
provide. The analysis is based on the purchase price of a commercial
battery pack and the number of discharge-charge cycles it can
endure before replacement is necessary. The cost does not include
the electricity needed for charging, nor does it account for
the cost of purchasing and maintaining the charging equipment.
The comparison applies to batteries for commercial products
such as cell phones two-way radios, laptops and video cameras.
The extreme right column evaluates the cost of the BB-390, a
military NiMH pack, which is used in lieu of primary lithium
sulfur dioxide. The cycle life of all batteries is calculated
at best cases.
|
|
NiCdAA
Cell
|
NiMHAA
Cell
|
Lead
Acid
(plastic)
|
Li-ion
18650 Cell
|
BB-390
for military
|
|
Energy per discharge
|
4.5Wh
|
7.5Wh
|
24Wh
|
8.6Wh
|
130Wh
|
|
Cycle life (best cases)
|
1500
|
500
|
250
|
500
|
250
|
|
Cost per battery
(ref. only)
|
$50
|
$70
|
$50
|
$100
|
$260
|
|
Cost per kWh ($US)
|
$7.50
|
$18.50
|
$8.50
|
$24.00
|
$8.00
|
Figure
2: Energy and cost comparison using rechargeable cells.
Older battery technologies offer lower energy costs compared
to new systems. Larger cells are more cost-effective than smaller
packages. The prices of the battery packs are estimated.
|
