If an electric motor has a rating of 300 amps, is that usually at full load at continuous use? We are looking at building an electric vehicle and most of the motors we are looking at range in the 300-600 amp ranges and need to plan on the size of battery pack.
Suggest you read the data sheet for the motor. But typically that is the full load current. And the battery pack size is more determined by the vehicle range desired, then the motor current.
300A would be the RATED load current. there is also a short term overload rating, and a number that is not usually found beyond which you demag the magnets effectively destroying the motor.
for instance our customers use a 3HP 90VDC motor with a nameplate rating of 32A, magnetic destruction occurs at 100A. Short term overload says you can run it for say 10 minutes at 125% before it overheats.
I must disagree with crutschow though... your battery needs to be able to supply 400-500A to run a 300A motor and the AHr rating determines range. a typical crap car battery would be 500CCA (Cold Cranking Amps - the current rating) but only 50AHr ( the "range" of your vehicle ) but that is as good as a lie since lead acid cells ONLY deliver HALF their AHr rating at high drain rates!
Some hybrid electric cars use a modern (very expensive) Lithium battery. It can provide a lot of current to the motor when it starts running (to overrcome inertia) and when it works hard pulling a load up a hill or accellerating quickly.
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I must disagree with crutschow though... your battery needs to be able to supply 400-500A to run a 300A motor and the AHr rating determines range. a typical crap car battery would be 500CCA (Cold Cranking Amps - the current rating) but only 50AHr ( the "range" of your vehicle ) but that is as good as a lie since lead acid cells ONLY deliver HALF their AHr rating at high drain rates!
But you rather made my point. That car battery may provide the high current needed by the motor but only for a very short time. So it's likely the AHr rating of the battery (at the operating current) is the factor that determines the battery size, not whether it can provide the maximum current.
But you rather made my point. That car battery may provide the high current needed by the motor but only for a very short time. So it's likely the AHr rating of the battery (at the operating current) is the factor that determines the battery size, not whether it can provide the maximum current.
Lead acid is a bit cheaper to build but we are looking at Lithium for the weight savings amother other advantages. Right now we are just trying to set a target amp/hr requirment.
Does anyone have any experiance making a lead acid battery?
Some motors are rated for continuous use and others are not.
Some of the rating are for open air, meaning you would have to derate the ratings if the motor is run in a box without ventilation.
One thing that should be considered is the resistance of the motor and the internal resistance of the battery.
Does anyone have any experiance making a lead acid battery?
Lead acid is a bit cheaper to build but we are looking at Lithium for the weight savings amother other advantages. Right now we are just trying to set a target amp/hr requirment.
Does anyone have any experiance making a lead acid battery?
you are very scant on info. expected usage profile? a subcompact conversion would take 10HP continuous and 100HP peak. a golf cart is probably 10HP peak.
a full electric ground up can be made with a 10HP AC motor rewired to 60V and running off a 280V rail (60HZ geared down and run at 240Hz for 60MPH and no gear shift)
We are talking about manufacturing lead acid batteries in house so we can save costs and be able to custom fit cells-->packs to the vehicle being converted. This is going to be more than just a hobby one time deal.
The components such as lead and lead oxide are much cheaper to manufacture but I still would rather go Lithium if we can bring the total $/mile capacity within range. Lithium packs will end up running as much as the body, interior, and drivetrain combined.
I'm not fully explaining the need only because we are still deciding on what they will be. One side wants to develope a performance vehicle while the other wants to do a compact or crossover.
A Korean car manufacturer (Hyundai or Kia) and the Chevy Volt use Lithium batteries in hybrid cars.
All the other car manufacturers are using Ni-MH batteries.
Wheel chairs use old fashioned Lead-Acid batteries.
While far from a guru at this stuff I have noticed that those manufacturing electric cars have moved to the lithium family of batteries. While this does not hold true for the millions of golf carts and tow motors running around out there it seems a rule in the automobile industry globally. I figure these people did their homework when it came to cost and bang for the buck with all things considered. I can't imagine a small model helicopter flying with a lead acid battery but see no shortage of them with lithium batteries. I guess it is the weight thing.
I would think another consideration would be motor voltage. The DC motor that draws 100 amps at 12 volts to do its job would draw about 1/10th that or about 10 amps running and designed for 120 volts. Less current is smaller wire gauge and less current to switch.
We are talking about manufacturing lead acid batteries in house so we can save costs and be able to custom fit cells-->packs to the vehicle being converted. This is going to be more than just a hobby one time deal.
The battery makers have spent years and many dollars to get good performance out of there battery's.
Do you have years and lots of money to develop a battery thats even close to the performance of whats already out there?
Hey where did you get the picture of our design so fast? Kidding, but point taken. If we had it figured out, I wouldn't be asking you guys for answers and opinions.
Lithium is of course our desire but we are trying to come up with a lower cost option.
Hey where did you get the picture of our design so fast? Kidding, but point taken. If we had it figured out, I wouldn't be asking you guys for answers and opinions.
Lithium is of course our desire but we are trying to come up with a lower cost option.
Something I have always seen as important during any design phase is looking at what is out there. Fortunately I work with people who seem to think like I do. Would it be easier to design and build a battery from scratch to fit into a custom built battery compartment or would it be easier to find an existing battery with all the design work done and make my compartment to accommodate the existing battery? This is where you have a sharp pencil and calculator at hand.
I am currently involved with to some extent with a project that involves the development of a sort of stepper motor. With thousands of stepper motors out there you would think we could find an off the shelf model and use it for our needs. The biggest problem was this motor would need to run 24 hours a day in various hold and run positions. It also needed to run many years sans maintenance in a 800 degree plus F. environment. Slightly toasty. We discovered that Texas A&M University was developing such motors as experimental units. Currently we are working in collaboration with them during the development. Thus far in the technology exchange the marriage is working out well. This could have just as easily been a battery being designed at the University of Michigan for a US made battery powered vehicle. Get the idea here? While I hate the old business clique of "work smarter not harder" it does make some sense.
I am totally with you on working smarter not harder but we are looking at it as having to work harder now to possibly make it easier later. Again this is still all ideas on paper and we have not made that decision whether to build old tech inhouse or buy new tech.
Production cost is a major factor and run cost is second. However, with the major differences in specific power and energy density between lithium and lead it might not be worth it.
Right now we are looking at greater then $15,000 in lithium packs though...
I think that hybrid cars are expensive because their warranty must replace the original battery.
The average "Joe" dosn't know about the different kinds of batteries, he simply buys a Name Brand that he trusts.