hey.. i am building a gokart fr the frst time.. i am using a bldc motor 800w 48volt... should i use 48*12 volt battery or 1 48 volt battery? moreover how do i determine no load current, no load rpm, full load rpm, full load current... my battery can hav hav capacity between 20 to 40 ah
power train electric
- Thread starter rish
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Welcome to the forum Rish. Have you had a look at the Sticky thread on electric engines yet
I have also moved this thread over to the electric section
I have also moved this thread over to the electric section
I am not an electric guy, but someone will come and answer your questions soon. Just hold tight
Motors?
Never ever run electro motors in series!
That is either you run 4 motors in parallel (4x250W @ 48V) or you run ONE motor (1x1000W @ 48V)
it stays 48V (if thats the voltage you intend to use)
But choose motors that have the same performance map i.e rpm@voltage or you will have to gear each motor individually and may end up loosing performance.
Ideally use the exact same model for all motors.
If you talk about batteries (as in your first post), then 4x12V battieries in series is a far easier approach than to find a 48V battery;
If you build the battery yourself from single cells, you are pretty free to do whatever you like; even 8x6V or 2x24V or 1x36V plus 1x12V, as long as in series you end up with 48V...
but keep in mind that to level the load, you want each battery to have the same load capacity.
So that you will not "recharge" one of them by the others because it drains faster (is smaller)
So easiest way: get 4 times the exact same 12V battery.
'sid
Never ever run electro motors in series!
That is either you run 4 motors in parallel (4x250W @ 48V) or you run ONE motor (1x1000W @ 48V)
it stays 48V (if thats the voltage you intend to use)
But choose motors that have the same performance map i.e rpm@voltage or you will have to gear each motor individually and may end up loosing performance.
Ideally use the exact same model for all motors.
If you talk about batteries (as in your first post), then 4x12V battieries in series is a far easier approach than to find a 48V battery;
If you build the battery yourself from single cells, you are pretty free to do whatever you like; even 8x6V or 2x24V or 1x36V plus 1x12V, as long as in series you end up with 48V...
but keep in mind that to level the load, you want each battery to have the same load capacity.
So that you will not "recharge" one of them by the others because it drains faster (is smaller)
So easiest way: get 4 times the exact same 12V battery.
'sid
mckutzy
Well-known member
How much money to spend on this. Then there is the controller. Equally expensive.
Indeed a decent controller can be as expensive as the motor itself.
Based on the requirements of course
What batteries.. okay
How far should the what weight kart move what load on what surface in what angle at what speed (in what ambient temperature range...etc) ?
See.. difficult to say.
Okay, the basics:
You have an 800W motor rated at 48Volts.
So it draws at least 16.666667 Amps
(800W/48V=16.667Amps)
So a 20Ah battery-pack would power the engine for about 1.2hours
a 40Ah pack twice as long.
That is if the batteries are perfectly levelled and in the best possible condition.
I'd expect less.
That is if your motor DRAWS 800W not PROVIDES 800W!
electric motors generally have an efficiency of about 80-90%
extremly good ones up to ~96% extremely cheap ones as low as 60% some times.
Also the controller will draw a certain amount of power, and if you add lights they will too of course.
Some of it will get lost on the way from the batteries to the motor (cables have a resitance!)
I think it's fair to assume that a 20AH battery pack will provide about 45-50 minutes worth of movement.
So if it's an average motor providing 800W it can draw more than 20Amps drawing 960W from the batteries.
And keep in mind, that batteries in series will add up voltage NOT capacity!
so 4x 12V 20Ah could add up to either 1x 48V 20Ah(series) OR
1x 12V 80Ah (parallel)
IIRC the off the shelf e-bikes have a 250W motor around here powered by a 36V 10Ah batpack (which mathematically would be sufficient for 1.44 hours) and they're called to last about 70-80 minutes.
So yes..
you should have a battery, but what exact size you need you can only assume and test, then reconfigure and retest
I suggest get yourself a 20Ah pack, and see what it can do for you, then get another 20Ah set if that wasn't good enough.
'sid
Based on the requirements of course
What batteries.. okay
How far should the what weight kart move what load on what surface in what angle at what speed (in what ambient temperature range...etc) ?
See.. difficult to say.
Okay, the basics:
You have an 800W motor rated at 48Volts.
So it draws at least 16.666667 Amps
(800W/48V=16.667Amps)
So a 20Ah battery-pack would power the engine for about 1.2hours
a 40Ah pack twice as long.
That is if the batteries are perfectly levelled and in the best possible condition.
I'd expect less.
That is if your motor DRAWS 800W not PROVIDES 800W!
electric motors generally have an efficiency of about 80-90%
extremly good ones up to ~96% extremely cheap ones as low as 60% some times.
Also the controller will draw a certain amount of power, and if you add lights they will too of course.
Some of it will get lost on the way from the batteries to the motor (cables have a resitance!)
I think it's fair to assume that a 20AH battery pack will provide about 45-50 minutes worth of movement.
So if it's an average motor providing 800W it can draw more than 20Amps drawing 960W from the batteries.
And keep in mind, that batteries in series will add up voltage NOT capacity!
so 4x 12V 20Ah could add up to either 1x 48V 20Ah(series) OR
1x 12V 80Ah (parallel)
IIRC the off the shelf e-bikes have a 250W motor around here powered by a 36V 10Ah batpack (which mathematically would be sufficient for 1.44 hours) and they're called to last about 70-80 minutes.
So yes..
you should have a battery, but what exact size you need you can only assume and test, then reconfigure and retest
I suggest get yourself a 20Ah pack, and see what it can do for you, then get another 20Ah set if that wasn't good enough.
'sid
see my kart woud me moving ona flat concrete surface andi want it to run fr longer durations... how do i calculate te current drawn from the battery when laod is applied on the motor.. how do i calculate theoreticallly the rpm at full load.. i need to do calculations before buying the stuff
Well the current drawn from the batteries is easy;
its always
voltage * amps = watts
So if you have a motor that's rated 1000 Watts (drawing! power) @ 48V
you simply divide 1000 by 48 and end up with the amps (~21 Amps)
You cannot calculate the rpm, that number you have to read from the motor spec sheet.
So first make a choice about your motor;
then download it's spec sheet to see what rpm power draw, power output, efficiency etc. it has.
Then search for the ideal controller for that motor.
get the spec sheet of the controller and check what power it draws etc.
And work your way through the documents, it'll be quite a lot of reading gibberish,
but you need to have all the info you can on the items to make a wise decision.
Say your 800W motor (you talked about earlier) has a power output of 800W and an efficiency of 82%, then it'll draw 975Watts (@48V that is 20.3 Amps) and the controller you chose draws roughly 35Watts (about 0.7Amps)
So what you want is a battery pack that can provide 21 Amps for the time you need the kart to run.
Say you want it to run at least 60 miles at full speed (say 30mph) then you need at least 2hours the full 21Amps thus 42Ah (amps * hours = Ah) in your batterie pack for your first "try";
because of the reasons I talked about earlier you should target something more like 50Ah.
But I cannot tell you what loss you have to expect, I don't know!
What exact length and diameters have all of your cables, what current is running through these cables, have you sealed the connectors, do you use gold terminals or aluminium etc.
You cannot build such thing on paper, you must either copy a working set up, or test till your happy with the result.
'sid
its always
voltage * amps = watts
So if you have a motor that's rated 1000 Watts (drawing! power) @ 48V
you simply divide 1000 by 48 and end up with the amps (~21 Amps)
You cannot calculate the rpm, that number you have to read from the motor spec sheet.
So first make a choice about your motor;
then download it's spec sheet to see what rpm power draw, power output, efficiency etc. it has.
Then search for the ideal controller for that motor.
get the spec sheet of the controller and check what power it draws etc.
And work your way through the documents, it'll be quite a lot of reading gibberish,
but you need to have all the info you can on the items to make a wise decision.
Say your 800W motor (you talked about earlier) has a power output of 800W and an efficiency of 82%, then it'll draw 975Watts (@48V that is 20.3 Amps) and the controller you chose draws roughly 35Watts (about 0.7Amps)
So what you want is a battery pack that can provide 21 Amps for the time you need the kart to run.
Say you want it to run at least 60 miles at full speed (say 30mph) then you need at least 2hours the full 21Amps thus 42Ah (amps * hours = Ah) in your batterie pack for your first "try";
because of the reasons I talked about earlier you should target something more like 50Ah.
But I cannot tell you what loss you have to expect, I don't know!
What exact length and diameters have all of your cables, what current is running through these cables, have you sealed the connectors, do you use gold terminals or aluminium etc.
You cannot build such thing on paper, you must either copy a working set up, or test till your happy with the result.
'sid
see i need formulaes to find out whether a given motor can run my kart or not.. i have to frst calculate and then buy.. say i have a 800w 48volt dc motor at 1100 no load rpm... and i connect it to 48v 40ah battery.. how do i calculate the acceleration provided by the motor.. my kart specifications are following
WEIGHT-170 KG WITH DRIVER
LOAD ON DRIVING WHEEL-55KG
DRIVE BY CHAIN REAR WHEEL DRIVE...
now my question is
1) max rpm at full load
2) current drawn at full load
3) acceleration of the vehicle
WEIGHT-170 KG WITH DRIVER
LOAD ON DRIVING WHEEL-55KG
DRIVE BY CHAIN REAR WHEEL DRIVE...
now my question is
1) max rpm at full load
2) current drawn at full load
3) acceleration of the vehicle
WRONG!
You can'T just calculate how fast a motor will run under load just by knowing it could do 1100rpm
by just adding a few numbers like weight and such.
You need to exactly KNOW the motor specs.
Therefor you need to know what motor you have in mind.
(with a weight of 170kg, I'd suggest more like a 1500W motor btw)
Anyways, google around for a few different motors in your given range (36-48V, 800-100W) from different manufacturers,
so you end up with -let's just say- 12 different motors to choose from. (800,900 and 100W from 4 different manufacturers)
Then read ALL the 12 spec sheets and make a decision based on what you KNOW by then.
I can't tell you what you have to buy.
If it's not what you had in mind initially it's my fault in the end... nope, I won't go that route.
So say one motor is revving up twice as fast under a predefined load as the other, a second motor is revving up just as fast but drawing 50-80Watts less power, the fourth motor is slightly slower than your first, but will draw more than 100Watts less than any other.
One can provide slightly less torque but over a wider rpm band thus accelerating more quickly than the others but isn't performing as good on slight uphill terrain....
And then there's a price range one can be as cheap as say 200USD and the other can be as high as 800USD.
What do I know what you could accept or afford?
You have to do your research on the things you have in mind yourself.
And asking in a forum is NOT research!
Answers:
1) with an optimal gearing 1100 rpm!
2) is written in the spec sheet, for a guess 22-25Amps
3) should be written in the spec sheet, for a guess bad
fuzzy, right?
'sid
thanx everyone for your help.. specially itsid... i got ur point of being more practical than solving things on paper....
http://www.leafmotor.com/hub-motors/800w-bldc-motor.html
AFAIK the MY1020's are also brushless..
'sid
AFAIK the MY1020's are also brushless..
'sid
yeah i saw this link but i think they will cost a lot of import duty because i live in india delhi.. see on converting the cost of motor into rupees it costs around 9000 rs... and another 10000 rs just for the shipping.. too very costly.. this is a link for china based country.. i have to make my kart in net 50000rs... these are competition rules i.e in 900usd
ask unite motor for a retailer in india, they make the my1020
http://www.unitemotor.com/en/contactmin.htm
or check on indiamart if you find other options locally;
http://dir.indiamart.com/impcat/dc-motors.html
like
http://www.indiamart.com/vinayak-automation-products/battery-operated-dc-motor.html
'sid
http://www.unitemotor.com/en/contactmin.htm
or check on indiamart if you find other options locally;
http://dir.indiamart.com/impcat/dc-motors.html
like
http://www.indiamart.com/vinayak-automation-products/battery-operated-dc-motor.html
'sid
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