How To Calculate The Battery Capacity
to find “battery capacity for electric
vehicle”
first, you must need some basic information
about motor like how much load you can put on a vehicle
always remember, in the electric vehicle the
weight (kg) is an important aspect.
because if you want to design a vehicle in
such a way that can handle more people on the vehicle rather than accessories
then you must care about not taking any extra load on the vehicle except basic
components.
So, let’s begin our calculation
before calculation, we need the following
parameters
Ø Motor Voltage (v)
Ø Motor Power Rating (w)
Ø Motor Peak Power Rating
(w)
Ø Motor Maximum Loading Capacity
(kg)
on the other hand, your valuable wishes like
Wish 1 how much distance do you want to cover in a
single charge?
Wish 2 how much weight do you want to carry with
your vehicle?
Wish 3 what will be the speed of the vehicle when
the vehicle is “loaded”?
so first you have to put your extra
activities aside for the next only 10 minutes. it is really a simple
calculation.
let’s do our first calculation
we find our first answer that how much
current does the motor need to work at full efficiency. next, calculate motor
peak current rating. do the same calculation as above.
now, we got two parameters that will help us
to find the battery’s “current rating”. the third parameter will help us to
find how much “load current” does require to motor for performance.
to calculate max. power to weight
ratio, as we know what is the peak power rating of the motor and what is the
maximum loading capacity of the motor. both the parameters are important to
know the motor limitations.
therefore,
now multiply the max. P/W ratio with how
much weight you want to carry with your vehicle (Wish 2)
it will show, how much power does the motor
consume under load condition.
now from “motor power under load
condition” we can calculate motor “load current”.
if you observe that we have three nature of
current,
Ø Motor Rated Current
Ø Motor Peak Current
Ø Motor Load Current
always remember for ev’s the basic technical
statement is, “nature of current flowing through the system of the electric
vehicle under various circumstances is always show a variation in magnitude
during acceleration or deceleration”.
hence to calculate a precise value for battery capacity we have to calculate the “average value”. the “average current
for example,
if your vehicle consumes “average current”
18a (battery capacity 18ah) and you are getting an average speed of 45km/hr.
so theoretically, the vehicle can run only
45 km because it has a battery backup of 1 hour.
now let’s calculate the battery capacity as
per your wishes.
remember, you have two wishes left!!
now Wish 1: how much distance do you
want to cover in a single charge
example. say 1000 km or do you want to ride
to the one specific point? let’s hope this is not your wish because then
you have to make a battery that is bigger than the size of a battery!
so 1000km is enough for us.
how much distance do you want to cover in a
single charge: 1000km
next wish 3: what will be the speed
of the vehicle when the vehicle is “loaded”?
example 100km/hr and average current 50ah
