Page 381 - Battery Reference Book

32/8 Lead-acid secondary batteries
Table 32.4 Yardstick operating costs
30 cwt payload urban delivery vehicles Case I Case 2
Electric Diesel Electric Diesel

Capital costs (5)
Vehicle 4800 7690 6330 7300
Battery 3076 - 3076 -
-
Charger - - __ -
-
650
650
8526 7690 10056 7300
__ __ - __
Standing chargedyear (5)
Vehicle depreciation (years) 320 (15) 1098 (7) 422 (15) 730 (10)
Battery depreciation (years) 615 (5) - 615 (5) -
Charger depreciation (years) 43 (15) - 43 (15) -
Interest on capital 639 577 754 548
Licence - 101 - 101
Insurance - __ __ __
112
152
112
152
1729 1928 1946 1531
__ - __
Running costslmile (p)
Electricity 1.5kW Wmile @ 2pkW h 3.0 - 3.0 -
Derv 12/15mpg @ E1.15 - 9.6 - 7.7
Maintenance materials, labour and overheads
including tyres and lubricants - - - -
4.3
8.2
4.7
9.1
Total running costdmile 7.7 18.7 7.3 15.9
Add standing charge reduced to cost/mile
21.1
(9125/7500 miledyear) (p) 18.9 - 25.9 20.4
~ __ __
Total cost/mile 26.6 39.8 33.2 36.3
__ __ __
Index 100 150 100 109
Case 1: vehicle with open milk-float body used 365 daydyeax. Top speed 15 mph. Range capability is approximately 50miles laden. This analysis
is done on 25-mile range with 250 stops, which is comfortably within daily range of the electric with reducing load
Case 2: vehicle similar to case 1 but with aluminium box-van body with hinged rear doors. Driven less intensively than a milk-float, the vehicle
averages 30 miledday on general urban deliveries
Source: Electric Vehicle Association, 1980
between the minimum capacity recommended and the battery.) The needs of a fork lift truck can similarly,
maximum that can be fitted. although less exactly, be calculated. How heavy are
Experience shows that, over their lifetime, vehicles the loads to be lifted? What speed is it required to
are required to fulfil a number of duties differing from do? What travelling time must be allowed from the
their original application. So if a vehicle is to be flex- truck’s base to where it will work? Are there any steep
ible enough to be switched to a more demanding duty gradients involved?
it makes sound economics to fit the largest possible Each of these facets will demand a known amount
battery initially. This will also help to avoid overdis- of discharge current from the battery and this is the
charging the battery, which can cause it irreparable basis of the calculation. The discharge current obtained
damage. from the battery is multiplied by the time (in minutes)
Where intensive and continuous operation of a taken to perform each movement, giving a series of
vehicle is involved, and the largest battery that can figures in ampere minutes. These figures can be added
be accommodated is not capable of completing the together to give the total value of ampere minutes
vehicle’s duties between recharges, it is actually nec- required to complete a delivery round or working
essary to calculate the total capacity required. shift.
Every electric vehicle, whether on the road or in For example, a fork lift truck lifting 2 tonnes might
industry, has a predetermined pattern of use. A milk require a discharge current of 200A for 0.25 min or
float is needed to cover a certain route, with a known 50 A min. This truck travels 6 m at 1 ds, during which
number of stops, distance to be travelled, and the the discharge current is 80A, or 480As (8Amin).
terrain it is required to negotiate. (It is important to These calculations are continued for the whole series
know of any steep hills the vehicle must climb, for of operations. The ampere minutes are added together
instance, as this will demand extra energy from the and the total converted into ampere hours.