How To Match Motor | Battery | ESC
- Thread starter Tony
- Start date
Hello,
it is an permanent magnet high torue direct drive motor ( Siemens 1FW6090-xxB05-0Fxx). actually, it is just an option. we need an electric motor to used in an small electric urban car. this car need about total 14 kW power. we try to put the motor inside each wheel (hub motor), since it is a three wheel vehicle, We need three motors. I really also appreciate any other option you suggest.
thank you very much
it is an permanent magnet high torue direct drive motor ( Siemens 1FW6090-xxB05-0Fxx). actually, it is just an option. we need an electric motor to used in an small electric urban car. this car need about total 14 kW power. we try to put the motor inside each wheel (hub motor), since it is a three wheel vehicle, We need three motors. I really also appreciate any other option you suggest.
thank you very much
Tony
Staff member
Ah, I see now.
Your battery should ALWAYS be larger than the motor and ESC. The ESC should ALWAYS be larger than the motor. Remember that the motor is PULLING the power, the battery doesn't push it. Because I know nothing about electric cars, and there is a MUCH HIGHER danger factor with dealing with that kind of voltage, this is all the help Rc-Help can provide on the matter because of safety reasons. But, the first line should get you going. Sorry I couldn't be of any more help.
Your battery should ALWAYS be larger than the motor and ESC. The ESC should ALWAYS be larger than the motor. Remember that the motor is PULLING the power, the battery doesn't push it. Because I know nothing about electric cars, and there is a MUCH HIGHER danger factor with dealing with that kind of voltage, this is all the help Rc-Help can provide on the matter because of safety reasons. But, the first line should get you going. Sorry I couldn't be of any more help.
THANKS
I see. But I would be grateful if you give me a general calculation process. What does you mean by larger?
I did some calculation. forexample if I want to use the battery charge to derive a 6550W motor with the maxumum current of 9.5A, the minimum rated capacity of the battery should be: 9.5amp*2h=19 Ah and if I want to used 80% of battery charge it sdhould be 9.5*2/0.8
another way is that calculate the minumum required battery capacity from: 6550W*2h/600V
I am wondering if these calculations are correct?
Thank you very much
I see. But I would be grateful if you give me a general calculation process. What does you mean by larger?
I did some calculation. forexample if I want to use the battery charge to derive a 6550W motor with the maxumum current of 9.5A, the minimum rated capacity of the battery should be: 9.5amp*2h=19 Ah and if I want to used 80% of battery charge it sdhould be 9.5*2/0.8
another way is that calculate the minumum required battery capacity from: 6550W*2h/600V
I am wondering if these calculations are correct?
Thank you very much
Tony
Staff member
I'm not quite sure where the "*2" is coming from in your calculation. It may be because I'm just that tired with dealing with what I'm dealing with, but I'm completely lost. The thing you need to calculate is that 1. the battery(s) and ESC(s) can handle not only the wattage of the motor, but also the amperage of the motor. As long as the two are over what the motor is pulling, you should be fine. I will let Gaba, our electrical engineer, comment on this further since I have to be missing something. And again, I'm sure it's just sleep deprivation.
Thanks Tony, I forgot to mentioned that the calculations are for 2 hour operations of the motor. the "2" comes from here
coolgabsi
Super Mod & DEAL KING!
John you are using 2 hours of operation pulling 9.5A each hour? If it says that motor can pull 9.5A's that means on peak load in an instant the motor is gonna pull 9.5A. That is on an instant. Only by running the motor will you find the actual usage of what the motor uses with an average load applied to it, for a unit of time. And then extrapolate from there how much current capacity is needed for that motor.
As far as larger battery like tony said, that means that you need the battery to be able to handle more than 9.5A of burst output at any instant if motor can pull that much.
So now, looking at your motor specs with a rated amperage of 5.6A... means average 5.6A of current is used by the motor .. (in an instant).. so your battery needs to be rated at over 5.6C with a rated burst of over 9C.
I might be wrong.. haha.. but I dont think so.. until and unless I am just missing something.
As far as larger battery like tony said, that means that you need the battery to be able to handle more than 9.5A of burst output at any instant if motor can pull that much.
So now, looking at your motor specs with a rated amperage of 5.6A... means average 5.6A of current is used by the motor .. (in an instant).. so your battery needs to be rated at over 5.6C with a rated burst of over 9C.
I might be wrong.. haha.. but I dont think so.. until and unless I am just missing something.
Thank you. very helpful. So the maximum motor current is related to rated burst. by 5.6C, do you mean the battery should rated over 5.6 Ah?for the time issue, my point is that for exapmle if we want to use this motor to derive the vehicle for let say 2 hours, the battery should be rated over 2*5.6C with a rated brust of over 2*9C?
coolgabsi
Super Mod & DEAL KING!
C rating is different that amp hour rating. C rating is the burst of current the battery can provide at an instant , nothing to do with the Ah capacity of the battery. usually Lipos are rated at say 5C rated - 10C burst. So at normal operation, the battery can provide load current 5A of continuous current and 10A of burst for startup or stall torque. This in no way relates to the Ah capacity of the battery. Its like battery is a tank and C rating is the hose coming out of the tank. How fast can the water flow out of the hose is derived by how big that hose is, but it has nothing to do with how much water is in the tank.
How much water you need to have in the tank is gonna be decided by how much water can the motor pull in unit time. which is determined by testing the motor on an average load. The load will probably be determined by the weight of the car you are trying to pull plus the passenger, and if there are three motors with equally distributed weight, all that divided by three.
I didnt mean to sound "smart" . if I in any way shape or form did. Just trying to help you understand.
How much water you need to have in the tank is gonna be decided by how much water can the motor pull in unit time. which is determined by testing the motor on an average load. The load will probably be determined by the weight of the car you are trying to pull plus the passenger, and if there are three motors with equally distributed weight, all that divided by three.
I didnt mean to sound "smart" . if I in any way shape or form did. Just trying to help you understand.
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coolgabsi
Super Mod & DEAL KING!
So adding to that .. in affect .. t make sure you have an adequate battery, the battery will have to be rated at 5.6C or higher. ..
Then how many AH will you need to run the car motor , will be from testing. In RC where we get values from of how many AH are good, is the manufacturer has done those preliminary tests on the motor, done test flights / runs whatever, and figured out how many AH's were used in those flights / test beds with the appplied load. They then put recommendations that for 2-3 minutes of say hard core high power flight or race.. you will need a battery that is atleast (X) Amp hours. ANy more than that, is good, you will run longer, but more weight, any less, you will run lesser time. Now the customer looks at that, decides the Ah they want, and then look at the peak rating of the motor to decide what C burst they want in the battery (Seperate from the AH rating) and buy / match a battery
So for example you might have (if you are into helis like I am) seen a rule of thumb that 450 helis fly with a 2200mah battery. Thats only 2.2Ah .. those usually get used up in 4-5 minutes. and the batteries are usually rated at 20C (to 45C continuous) and 40C (to 90C burst).. so these batteries can provide 35A of current continuously for the flight time, but total Ah they carry for a recommended flight is only 2.2 .. Now I can install 2.65 or even 4.4Ah batteries and double my flight time, but still, that is seperate from my C rating that is how much continous current can be provided by the battery .
Then how many AH will you need to run the car motor , will be from testing. In RC where we get values from of how many AH are good, is the manufacturer has done those preliminary tests on the motor, done test flights / runs whatever, and figured out how many AH's were used in those flights / test beds with the appplied load. They then put recommendations that for 2-3 minutes of say hard core high power flight or race.. you will need a battery that is atleast (X) Amp hours. ANy more than that, is good, you will run longer, but more weight, any less, you will run lesser time. Now the customer looks at that, decides the Ah they want, and then look at the peak rating of the motor to decide what C burst they want in the battery (Seperate from the AH rating) and buy / match a battery
So for example you might have (if you are into helis like I am) seen a rule of thumb that 450 helis fly with a 2200mah battery. Thats only 2.2Ah .. those usually get used up in 4-5 minutes. and the batteries are usually rated at 20C (to 45C continuous) and 40C (to 90C burst).. so these batteries can provide 35A of current continuously for the flight time, but total Ah they carry for a recommended flight is only 2.2 .. Now I can install 2.65 or even 4.4Ah batteries and double my flight time, but still, that is seperate from my C rating that is how much continous current can be provided by the battery .
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Thank you very much for your time and kind consideration. I really appreciate that
The fact you're asking these basic questions on a high power application makes me think you're in over your head on this and should seek some in-person professional guidance, perhaps from a local university electrical engineering dept.
DO NOT use anything I mention here (both in case I'm wrong somewhere and in case I am right):
5.6A is the continuous current rating. 9.5A is the burst/peak current.
If you want to drive this for 2 hours straight at max continuous current rating, then you're talking 12Ah drawn over 2 hours, .7 underrating for capacity discharge safety, yields roughly 17Ah pack capacity at 600V per motor, aka 10.2kWh. Remember this is 600V so you're going to have to have a bunch of packs in a series/parallel combination to pull it off. Bringing it back into the RC realm: twenty-four(24) 6S Lipo packs in series, and three of those banks of packs paralleled (to cover the power for three motors). I AM NOT SUGGESTING YOU DO THIS. In fact I ACTIVELY DISCOURAGE IT. It will be a mess to charge (cells getting out of balance, etc.), it is highly dangerous (short it by accident and you could have a multi-pack lipo fire or explosion on your hands, over discharge and you can have a breach of a pack and a fire, etc.) to the point of being highly lethal (lots of amps and volts make for stopped heart, fried brain, etc.).
You mentioned a target of 14kW as your total vehicle power. At continuous rated capacity of the motor (5.6A), times 3 motors, at 600V, you're at roughly 11kW, somewhat below your target. And that isn't taking into account inefficiency either.
Also, you in an urban environment with lots of stop and go, you will be bursting a lot (acceleration from stop) so you have to throw in some extra for bursts, maybe add 15-25% capacity? Also lots of braking, so you will want to consider a regenerative braking system (use the wheel motors as generators to recharge the packs a bit on deceleration).
DO DO THIS: Again, seek some local, in-person consultation. Hire someone who might know what they're doing, such as a local/regional electric dragster hobbyist.
DO NOT use anything I mention here (both in case I'm wrong somewhere and in case I am right):
5.6A is the continuous current rating. 9.5A is the burst/peak current.
If you want to drive this for 2 hours straight at max continuous current rating, then you're talking 12Ah drawn over 2 hours, .7 underrating for capacity discharge safety, yields roughly 17Ah pack capacity at 600V per motor, aka 10.2kWh. Remember this is 600V so you're going to have to have a bunch of packs in a series/parallel combination to pull it off. Bringing it back into the RC realm: twenty-four(24) 6S Lipo packs in series, and three of those banks of packs paralleled (to cover the power for three motors). I AM NOT SUGGESTING YOU DO THIS. In fact I ACTIVELY DISCOURAGE IT. It will be a mess to charge (cells getting out of balance, etc.), it is highly dangerous (short it by accident and you could have a multi-pack lipo fire or explosion on your hands, over discharge and you can have a breach of a pack and a fire, etc.) to the point of being highly lethal (lots of amps and volts make for stopped heart, fried brain, etc.).
You mentioned a target of 14kW as your total vehicle power. At continuous rated capacity of the motor (5.6A), times 3 motors, at 600V, you're at roughly 11kW, somewhat below your target. And that isn't taking into account inefficiency either.
Also, you in an urban environment with lots of stop and go, you will be bursting a lot (acceleration from stop) so you have to throw in some extra for bursts, maybe add 15-25% capacity? Also lots of braking, so you will want to consider a regenerative braking system (use the wheel motors as generators to recharge the packs a bit on deceleration).
DO DO THIS: Again, seek some local, in-person consultation. Hire someone who might know what they're doing, such as a local/regional electric dragster hobbyist.
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