How To Calculate The Range Of Electric Vehicles
The range of electric vehicles is difficult
to find but not so difficult to predict.
yes, we can predict the range of electric vehicles but for that, we need to consider lots of stuff, like how much load is on the vehicle, battery capacity, motor wattage, power to weight ratio, and many more in this article, we will solve the problem of finding the range of electric vehicles but we are not considering losses during the run like rolling resistance, friction, aerodynamics.
what we are going to calculate will provide
an answer, which is closer to the actual answer.
first,
why it is so much difficult to find out the
range of the electric vehicle.
the answer is pretty much simple but a
little bit unsatisfied. which is related to the one term. “a variable current
consumption”
you know in electric vehicles, the nature of
current flowing through a system is different. it shows variable
characteristics.
why?
because in the case of motor the load is
variable hence as a result “current consumption” also shows variation in
magnitude.
the motors, which are used in electric
vehicle applications goes under various conditions like climbing, acceleration,
deceleration, braking, and so on.
this kind of situation produces different
kinds of results. which will affects motor “current demand”.
now in the case of the battery,
for example:
the capacity of the battery is 10ah and the
load current demand is 1 ampere then we have to calculate how much time does
battery is required to drain completely?
the question is easy to answer because the
battery is draining a constant current or steady current
the answer is 10 hours or 600 minutes.
right!!
formulae :
but as we discussed the current demand for electric vehicles is variable in nature hence it becomes complicated to calculate the exact kilometer or mile range of the ev’s.
therefore, we have to calculate motor
current demand at various conditions.
types of “current demand” in electric
motors:
- rated current rating
- peak current rating
- load current rating
note: please be sure before doing a
calculation you must have all datasheets and specifications for motor and
battery.
now let’s start our calculation with an
example,
calculate the rated current demand for the
motor.
ex. motor voltage: 60v
motor wattage: 1000w
the motor rated current is 16.66a.
now, calculate peak current demand for motor
as given,
motor voltage: 60
peak motor power: 1500w
motor peak current demand is 25a.
thereafter, we need to calculate the load
current which will tell us motor current demand when the load is applied on it.
(assume, the load is vehicle plus driving
person and luggage weight)
now, calculate the power to weight ratio
requirement.
ex.
motor maximum loading capacity: 350 kg
peak power: 1500w
from calculation power to weight ratio : 4.28 w/kg
consider,
the bike load (including all-electric
accessories) is 150 kg and mr. musk is driving it and you know mr. musk
is a healthy person so maybe his weight is around 75kg. suppose mr. musk
doesn’t know how many miles his car can cover! therefore, let’s help him to
find out the range of his vehicle.
so the total weight of the vehicle will be
230 kg.
to find motor power consumption during load,
multiply p/w ratio with vehicle total
weight.
power consumption under load condition is
984.9 watt. now we need to find out the current demand under load condition as
given,
motor voltage: 60v
motor wattage: 984.9w
from the calculation,
the current demand under load condition is
16.40a
did you notice we got three nature of
current?
- rated current
- peak current
- load current
these three natures of current are nothing
but a result that came from different situations or circumstances.
“rated current” is flowing through a system
when the motor is working under its full efficiency.
“peak current” is flowing through a system when the motor is under acceleration
or initial pick-up.
“load current” is flowing through a system when the motor is working under load
conditions.
now, we have to find the value of the
average current.
average current demand will be 19.35a
this is it!
the above answer can help us to understand
the nominal current demand for vehicles.
this is an average current demand for
electric vehicle motors.
let’s assume you design a lithium-ion
battery pack of 60 volts with a capacity of 100ah.
also, read | how to calculate battery
capacity for an electric vehicle.
divide that batter capacity by average
current demand.
hence battery backup will be 5.17 hours.
consider, your electric vehicle average
speed is 45 km/h
then the range of the vehicle will be 232.65
kilometers or 144.78 miles!!
but this is not an exact answer. during the
run, there is an instantaneous rate of change of current consumption. hence 233
± 10 kilometers (145 ± 6.21 miles) is always better to assume.
this is one of the ways we can find out the
range of the electric vehicle. hopefully, you found your answer in the
article.
note: the range of the electric vehicle may
vary with surrounding situations or circumstances.