Page 199 - Battery Reference Book

Zinc-bromine secondary batteries 1413
14.6 Zinc-(chlorine secondary perimentally, it has been found that, with a 50 kW h,
batteries 363 kg battery system, the vehicle could accelerate
from 0 to 64M in 10s. This requires a minimum
The rechargeable zinc-chlorine battery currently under power density of 10Wkg. To maintain an average
development by Energy Development Associates, speed of 80.5 km/h on level ground requires 12kW,
Michigan is proposed as a new approach to energy- equivalent to an energy density of 23 W Wkg. At a
saving power systems for vehicles. This is an
interesting new concept in battery design, which may 4h discharge rate, this would yield a 322pUn range
prove to have (applications in the small-battery field. between charges.
The object that Energy Development Associates have As can be seen from Table 14.1 the lead-acid
in mind is to produce a battery capable of propelling a battery will accelerate the vehicle, but its low energy
1 tonne vehicle 322 km at a steady speed of 80.5 km/h density seriously limits the operating range. The
with 120 hdhi excursions. Comparative claimed zinc-chlorine battery, on the other hand, yields
performance characteristics for the zinc-chlorine an energy density of 154WWkg (well above the
battery with those of the conventional lead-acid 23 W h/kg required for a viable vehicle). Note also that
electric vehicle battery are given in Table 14.1. the zinc-chlorine battery offers better performance in
The performance figures become important when terms of rechargeability, cycle life md volume, in
measured against the needs of a 1 tonne car. Ex- addition to a significant cost advantage.

Table 14.1 Comparative performance data on zinc-chlorine and lead-acid electric vehicle
batteries
Zinc-chlorine Lend-acid

Delivered energy (4 h rate) (kW h) 50 50
Weight (kg) 32 137
Power output (1 rnin peak) (kW) 40 150
Minimum charge time (h) 4 2
Cycle life 500-5000 300- 1000
Volume (dm3) 285 570
Overall energy efficiency (%) 70 75
Energy density (W hkg) 154 35
Cost (estimated) ($) 500-750 1000-1500
Average power to load (kW) 12.5
Peak power for 30 s (kW) 40
Peak power for 2 s (KW) 50
Energy per unit weight at 41: rate (Whlkg) 154
Energy per unit volume at 4 h rate (W h/dm3) 177
Peak power density for 30 s (W hkg) 125
Peak power density for 2 s (W hkg) 154

Table 14.2 Characteristics of zinc bromine secondary battery
~~~
Open Volts Discharge Gravimetric Volumetric Gravimetric
circuit under voltage energy energy power
volts load projile density density density
(VI (V (Whlkg-l) (W h/dmP3) (Wkg-'1
1.75-1.80 1.5-1.6 Flat one step 15-85 10-50 50- 150

Volumetric Storage Operation Self Cycle Calendar Types
power temperature temperature discharge life life available
density (" C) ("C) rate
(W cm3)
40-90 0 to 50 15 -45 5% in two days 3000
then 1% per projected 1 OY Not available
month commercially