my electric trike

[chinmay]

hello friends,
I m from India and new to the world of electric vehicles. As a college project we even decided to make a electric vehicle for the college campus. We worked out the following specification.
sitting capability: 3 adults
configuration: tadpole or revesed trike
single wheel drive
top speed : 20kmph
according to this we worked out the calculations
motor: 1000w continious rating, 12v
battery: 3*12v 100amphr SLA deep cycle battery
controllers: pwm with regenerative breaking

It is to be noted that the car cost has to be maintained as low as possible as it is a self financed college project and my group cant afford if the prices are above Rs-40000/- i.e. around 560 pounds or 750$.
i m not sure about the calculation. i am also not sure what type of controller to use and how i can built one.
so friends please help me out.
thanks

[AussieJester]

Welcome to the forum. There is another member on Endless Sphere who is from Pakistan, his nick here is 'Naeem' he has a thread titled 'low cost electric bike from Pakistan' It shows what can be made with a HEAP of ingenuity a lil skill and a great imagination, his bike was built entirely from 're-purposed' parts, its really quite amazing the parts he has used and the implementation of them, perhaps his thread would give you some ideas and inspiration for the build, will at least show you what can be achieved on a budget...not sure Naeem actually spent anything on his build IIRC.

Best of luck with the project...

KiM

[torker]

Welcome, Since you are doing a reverse trike I assume that 2 adults will be sitting up front and maybe the driver in back? Also most ebikes are at least 24 volts. Not that you can't do it with 12 though. If you can source a motor to run on 12 v and then run it through the gears it should work. Do you have some idea what kind of motor you might run.? Have you searched the forum for ideas?

[chinmay]

@AussieJester
yes sir i did see naeem's thread. he is a genious. thank you for telling me.
will try to complete my project by march.
@torker
yes u r positioning is right except the driver is in the front. actually my exams r going on hence will start the project by jan till then i will search the forum for ideas.
about the motors i have never studied electric motors in my life so to my best knowledge and whatever i could manage to understand i came up with a 12v PMDC.
u mention running motors on gears so please tell me what difference is there in choosing motor according to the voltage i.e.(12/24/36 etc)
please reply

[chinmay]

i am able to get three 250W DC motor from scrap dealers should i take them and make them run in parallel for the same required power?
please reply?

[Lessss]

See this topic on mutiple small watt dc motors

viewtopic.php?f=12&t=23353

[chinmay]

i have problems doing battery calculation,

i have 12V 18Ah C20 batteries on which i will have to run a 24V-750W motor for 2 hours. how many batteries will i need. Can someone please also tell me the calculations. it will be better if no links are posted and it is explained in this thread.

[SamTexas]

750W x 2hrs = 1500wh energy needed
12V, 18Ah = 216wh per battery
1500/216 = 6.94 batteries needed.

Since you're running a 24V motor, you will need a 24V battery, so 8 batteries are needed to make a 24V, 72Ah
24V, 72Ah = 1728wh
since these are lead acid batteries, they can only be discharged at C(apacity)/20 or 3.6A or 86.4W
but you need to draw 750W or 31.25A which is 8.68 times the rated discharge. So your battery will be empty before 2 hrs.

The Peukert constant for lead acid batteries is around 1.2
Your battery will be depleted after 1.50hrs (90 mins)
You need another pair.

Bottom line: 10(ten) 12V, 18AH batteries needed. This 24V 90Ah will run your 750W motor for 1.95hrs, 3 mins short of your goal.

[chinmay]

thanks buddy
solved my problem

[chinmay]

750W x 2hrs = 1500wh energy needed
12V, 18Ah = 216wh per battery
since these are lead acid batteries, they can only be discharged at C(apacity)/20 or 3.6A or 86.4W
but you need to draw 750W or 31.25A which is 8.68 times the rated discharge. So your battery will be empty before 2 hrs.

i was not able to understand the capacity calculations though

[SamTexas]

Lead acid batteries' capacity are rated at C/20. It means that you can utilize all the wh if you consume electricity at a slow rate.

So with 8 batts you can make one 24V 72Ah. The total energy of this big batt is 1728wh (more than your 1500wh requirement). To use ALL that energy you have to consume at a rate no higher than 3.6A (72Ah/20). But your motor consume 31.25A (750W/24V) so you can not retrieve all the energy in that big batt.

This is where the Peukert effect comes in. And the needed capacity is calculated based on that. If you want to understand this effect and the calculation involved you need to read this:

http://en.wikipedia.org/wiki/Peukert's_law

[chinmay]

Lead acid batteries' capacity are rated at C/20. It means that you can utilize all the wh if you consume electricity at a slow rate.

So with 8 batts you can make one 24V 72Ah. The total energy of this big batt is 1728wh (more than your 1500wh requirement). To use ALL that energy you have to consume at a rate no higher than 3.6A (72Ah/20). But your motor consume 31.25A (750W/24V) so you can not retrieve all the energy in that big batt.

This is where the Peukert effect comes in. And the needed capacity is calculated based on that. If you want to understand this effect and the calculation involved you need to read this:

http://en.wikipedia.org/wiki/Peukert's_law

pardon my dumb self but i am still not able to understand it will be better if u can tell the below:---
now if we take four 12V 18Ah C/10 capacity battery they how long will they run our 750 watt motors

[torker]

I'm not good with math in the morning What the problem is with lead batteries is you can only get about half their rated capacity when you start pulling 20 or 30 amps from an 18 ah lead battery. If you pulled 30 amps you may only get 10 miles or less on flat ground. That is why SamTexas showed calculations based on paralleling more batteries for more ah. Lithium is so much better for e-vehicles. If it is a 10 ah lithium battery you can get 10 ah from it at 20 amp draw easy and the weight is less than half.

[SamTexas]

chinmay, it's really not that complicated. Here's the time equation for the Peukert's law from the link I gave you earlier:


where:
H is the rated discharge time (hours)
C is the rated capacity at that discharge rate (Ah)
I is the actual discharge current (A)
k is the Peukert constant, dimensionless.
t is the actual time to discharge the battery (hours)

Let's walk through everything on the right side of the equation

H = 10.........................for C/10 rated battery. 20 for C/20 rated battery, 15 for C/15 rated battery
C = 36.........................4 x 12v 18ah batteries to form a 24V 36Ah battery bank
I = 750/24 = 31.25..........750 is the power of the motor, 24 is the voltage of battery bank
k = 1.2........................typical Peukert constant for lead acid battery

That's it. Plug those numbers into the equation and calculate the result t in hours.

Have fun and good luck

[chinmay]

thanks a ton

[chinmay]

can some one tell me what type of controller can i built for the 24V 45amp motor and 12V 18Ah c/20 batteries???
can u also give me information about the basic working principles of a controller?

[chinmay]

more than a week and no reply yet

[Lessss]

... and have you bothered to read any of the topics here in that week?

Looks at Stevo and Doc's threads

viewtopic.php?f=2&t=21722&p=370120&hilit=build+controller#p370120
viewtopic.php?f=2&t=78&p=26773&hilit=+build+controller+#p26773
viewtopic.php?f=2&t=23205&p=342192&hilit=+controller+build+#p342192
viewtopic.php?f=28&t=20766&p=335592&hilit=+controller+build+#p335592
viewtopic.php?f=2&t=22630&p=329350&hilit=+controller+build+#p329350
viewtopic.php?f=2&t=17680&p=258270&hilit=+controller+build+#p258270
+ 10 more pages on a 5 second search for "controller build"

You have asked such a tremendously open ended question. Try stating the performance characteristics you are looking for.

[chinmay]

sorry for the long absence
but i've completed my vehicle successfully
i have problems putting images
someoe help

[chinmay]

here are some videos of the trike
showing its working
http://www.youtube.com/user/tapil123#p/u/5/z5Ouw-eShjg
http://www.youtube.com/user/tapil123#p/u/4/BoRmOfINUCo
http://www.youtube.com/user/tapil123#p/u/3/BFIgEAFO2gk
showing its running
http://www.youtube.com/user/tapil123#p/u/2/0PsN1J00SQI
http://www.youtube.com/user/tapil123#p/u/1/UHkfBHMMwbk

thank you guys for helping couldnt have been possible without this forum.

[TylerDurden]

Nice!

Regarding pictures: viewtopic.php?f=1&t=14748