Spence /1/
1 mW
- Joined
- Dec 30, 2011
- Messages
- 17
Hi, I am going to make a ev bike soon and am wondering what types of LiFePo4 batteries people use so far I only see headways as my real option.
Lithium batteries of choice?
- Thread starter Spence /1/
- Start date
dogman dan
1 PW
Depends on lots of things. How many amps do you need? How long do you need such amps to flow?
I have six ebikes at the moment up and running. 3 are used primarily as a commuting vehicle for a 30 mile round trip with charging while I work. For those bikes I don't need or want lots of speed. So a 48v 15 ah pingbattery lifepo4 is perfect for that use. Mostly I pull 15 amps, so 1c discharge rate is comfy for the 2c rated pingbattery.
The other three bikes are intended either for high performance, or rides less than 5 miles. So I use Lipo packs sold at Hobby King for those bikes. The 20-30 c type I've bought provides all the amps I need for dirt riding, racing, or just a quick zip to the convenience store.
Obviously you haven't yet seen this vendors site. We trust him to have real A123's. Lotta fakes or rejects on the bay. http://www.emissions-free.com/
I have six ebikes at the moment up and running. 3 are used primarily as a commuting vehicle for a 30 mile round trip with charging while I work. For those bikes I don't need or want lots of speed. So a 48v 15 ah pingbattery lifepo4 is perfect for that use. Mostly I pull 15 amps, so 1c discharge rate is comfy for the 2c rated pingbattery.
The other three bikes are intended either for high performance, or rides less than 5 miles. So I use Lipo packs sold at Hobby King for those bikes. The 20-30 c type I've bought provides all the amps I need for dirt riding, racing, or just a quick zip to the convenience store.
Obviously you haven't yet seen this vendors site. We trust him to have real A123's. Lotta fakes or rejects on the bay. http://www.emissions-free.com/
dogman dan
1 PW
One of the very good choices out there, provided your bike isn't drawing 30 amps, and you don't need huge range. Ideal for about 15 miles with not too much uphill, at 20-25 mph.
Spence /1/
1 mW
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- Dec 30, 2011
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Well lets say I wanted to a 250lb mass (bike+me+batteries+motor+ect.) to do 0-40 mph in 2.5 secs so I would need 7.25 kW of energy base (not including other forces such as air friction and RR) so ill add 750 W (I'm not sure if I added enough power or if I will need more to overcome those forces) for those and now I need batteries that can put out 8 kW. I'm not sure yet if the motor will run @ low or high voltage yet so I can't determine the discharge rate of the batteries yet, but once I find the right motor I will do tests to find what the motor can take. The max amperage will most likely be determined by what BMS or controller I use.
I would also like 15 miles of range @ 25 mph (not sure how to calculate how many Ahrs I will need)
also, I am new to ev's and I don't really know the options I have for batteries and what can be used in an ebike application; if anyone has a list of batteries that are currently used that would be awesome.
Thanks.
I would also like 15 miles of range @ 25 mph (not sure how to calculate how many Ahrs I will need)
also, I am new to ev's and I don't really know the options I have for batteries and what can be used in an ebike application; if anyone has a list of batteries that are currently used that would be awesome.
Thanks.
Kin said:
Word.
Spence, it sounds like you have a lot to learn. I would consider a high output chemistry like A123 / RC lipo, nothing else
8kW is not going to happen on a hub motor unless you're talking about short bursts of power. Chain drive to the rear is where you'll want to head. See what Luke ( liveforphysics ) is doing ( as one example ) and expect to spend a crapload of $.
That's also very much scooter / motorcycle territory unless you get into custom frame building ( longer rear ) to prevent wheelies and perhaps improve the handling as well.
Spence /1/
1 mW
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neptronix said:Kin said:
Word.
Spence, it sounds like you have a lot to learn. I would consider a high output chemistry like A123 / RC lipo, nothing else
8kW is not going to happen on a hub motor unless you're talking about short bursts of power. Chain drive to the rear is where you'll want to head. See what Luke ( liveforphysics ) is doing ( as one example ) and expect to spend a crapload of $.
That's also very much scooter / motorcycle territory unless you get into custom frame building ( longer rear ) to prevent wheelies and perhaps improve the handling as well.
Yeah I should have clarified that this will be non-hub, but what are some things that I should learn?
Kin
10 kW
Without overstepping the fact that I don't know everything yet, I would say
Ask yourself, "why 8kw?" and try to parse out what brought you to that number.
learn more about batteries: (for instance, it's unlikely that you'll get the power you need from the low C LiPO4 if you're building a high power RC build. You would need a huge 4kw battery pack to feed an 8kw motor at 2c. So, you'll probably be looking a pretty big LiMn02 pack, a123, or LiPo pack. All three have their quirks and costs)
learn about what you'll need to controll the 8kw motor (that's a really powerful motor)
figure out your budget. <--- very important. An 8kw build, especially as a first build, will need a relatively big budget. [
Think about Kv and what kind of reduction you think you will need. That in part also determines whether you're looking at belts, or motorcycle chains. Actually, that's only vaguely related. But it's important to understand how kv, voltage, and current matter. And, of course, this is part of figuring out what motor you're using.
learn about motor controllers. I don't think there are any RC ESCS that can handle an 8kw motor reliably in Ebike conditions. You presumably will be running a high number beefy FET controller, but will need to know more about this. Read up a lot on Luke's thread (That's user "Liveforphysics"). Probably, read his entire build thread (I assume he includes build info on his thread)
(later stuff)
learn about halls sensors, or optical sensors.
-a million more tiny side things. Torque arms, shocks, wheel size, wiring, harnesses.
__________
So, hell, you could know a lot of things in that list. Possibly overall more than me. But it's not entirely clear from this thread, and thats the kind of stuff you'll need to understand well to make a 8kw RC build. RC builds especially aren't very "plug and play," at least not until you understand everything you're playing with.
Personally, I'm surprised you cite that number, and suggest figuring out why you want such a powerful motor for a first build. Maybe a lower power system will satisfy your needs, and it'll be much more feasible to build. Most people would be amazed to see how good 3kw even feels. 8kw strikes me as overkill until you're really addicted.
If you want more help from users on this forum you're probably going to want to supply
--> what budget you have to work with.
--> what fabrication skills you have
--> what electrical skills do you have
--> why you want to build an 8kw RC setup
--> your ebike experience
--> what frame you're thinking about.
Ask yourself, "why 8kw?" and try to parse out what brought you to that number.
learn more about batteries: (for instance, it's unlikely that you'll get the power you need from the low C LiPO4 if you're building a high power RC build. You would need a huge 4kw battery pack to feed an 8kw motor at 2c. So, you'll probably be looking a pretty big LiMn02 pack, a123, or LiPo pack. All three have their quirks and costs)
learn about what you'll need to controll the 8kw motor (that's a really powerful motor)
figure out your budget. <--- very important. An 8kw build, especially as a first build, will need a relatively big budget. [
Think about Kv and what kind of reduction you think you will need. That in part also determines whether you're looking at belts, or motorcycle chains. Actually, that's only vaguely related. But it's important to understand how kv, voltage, and current matter. And, of course, this is part of figuring out what motor you're using.
learn about motor controllers. I don't think there are any RC ESCS that can handle an 8kw motor reliably in Ebike conditions. You presumably will be running a high number beefy FET controller, but will need to know more about this. Read up a lot on Luke's thread (That's user "Liveforphysics"). Probably, read his entire build thread (I assume he includes build info on his thread)
(later stuff)
learn about halls sensors, or optical sensors.
-a million more tiny side things. Torque arms, shocks, wheel size, wiring, harnesses.
__________
So, hell, you could know a lot of things in that list. Possibly overall more than me. But it's not entirely clear from this thread, and thats the kind of stuff you'll need to understand well to make a 8kw RC build. RC builds especially aren't very "plug and play," at least not until you understand everything you're playing with.
Personally, I'm surprised you cite that number, and suggest figuring out why you want such a powerful motor for a first build. Maybe a lower power system will satisfy your needs, and it'll be much more feasible to build. Most people would be amazed to see how good 3kw even feels. 8kw strikes me as overkill until you're really addicted.
If you want more help from users on this forum you're probably going to want to supply
--> what budget you have to work with.
--> what fabrication skills you have
--> what electrical skills do you have
--> why you want to build an 8kw RC setup
--> your ebike experience
--> what frame you're thinking about.
dogman dan
1 PW
Sounds like Spence is going to need to do some reading in the lipo threads for 8kw that fits on a bike. A few hubmotors can do it, but perhaps not so efficiently. Motorcycle size stuff. Bike hubbies reach their limit much lower.
This going to be a drag bike? There is a bit of a racing scene developing, but it's for Kart track races. Seems odd you want so much power and yet aren't talking about going 50 mph.
40 mph "quick enough" is pretty easy. Direct drive hubmotor, 9c, muxus, conhis, etc etc. 72v 40 amp controller. 72v 10 ah battery capable of 40 amps, headway, A123, HK lipo. Bingo, you'll just get into the 40 mph club. About 3000w . Will beat all but the most powerfull gasoline powered bicycles in a drag race.
BTW, it will also have at least 15 mile range at 25 mph. Up to 20 miles depending on areodynamics, headwinds, hills.
This going to be a drag bike? There is a bit of a racing scene developing, but it's for Kart track races. Seems odd you want so much power and yet aren't talking about going 50 mph.
40 mph "quick enough" is pretty easy. Direct drive hubmotor, 9c, muxus, conhis, etc etc. 72v 40 amp controller. 72v 10 ah battery capable of 40 amps, headway, A123, HK lipo. Bingo, you'll just get into the 40 mph club. About 3000w . Will beat all but the most powerfull gasoline powered bicycles in a drag race.
BTW, it will also have at least 15 mile range at 25 mph. Up to 20 miles depending on areodynamics, headwinds, hills.
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DAND214
10 MW
HOLY CRAP, HOLD ON TIGHT!
Rhat's not the 40mph club at all. Maybe 60mph might be needed to get there that fast. Big motor with lots of gearing, Oh I forgot BIG BATTS too. A123, or 50c LiPo's I would guess.
Just a gues you know.
Dan
Spence /1/
1 mW
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I don't necessarily need an 8kW motor just a motor that can deliver 8kW of energy for 2.5 seconds (peak). The reason I need 8kW is based on the amount of kinetic energy it will take to propel a 250lb mass with an acceleration time of 0-40 mph in 2.5 seconds here is the calculation1/2 *113.63 kg*17.88 m/s)= 18163.43 J /2.5 s= 7.3 kW Then I added .7 W to compensate for RR and air friction.
I am actually thinking of toning this down to more like 0-30 mph in 2.0 sec, this would be a normal road bike so I wouldn't need a speed faster than 30 mph. At this then I would only need 5.5 kW of energy.
1/2 *113.63 kg*17.88 m/s)= 18163.43 J /2.5 s= 7.3 kW Then I added .7 W to compensate for RR and air friction. I am actually thinking of toning this down to more like 0-30 mph in 2.0 sec, this would be a normal road bike so I wouldn't need a speed faster than 30 mph. At this then I would only need 5.5 kW of energy.
Kin
10 kW
Ok, I see that rational making some sense, actually. Well, meaning, I see that you've thought a bit about what you want and how you'll get it. That said, I'm suspicious whether that's the right way to calculate things. Even if you can make constant power assumptions with electric motors (you can't with a ICE), I am a bit skeptical of the total energy calculation.
More important, perhaps, is theg fact that controllers tend to regulate how they deliver power in the first instances of acceleration to get around the issue of stalling. So I will wait for someone more knowledgeable to response.
Just also want to remind about the other issues with a high power non-hub build (budget, fabrication, motor control, etc).
More important, perhaps, is theg fact that controllers tend to regulate how they deliver power in the first instances of acceleration to get around the issue of stalling. So I will wait for someone more knowledgeable to response.
Just also want to remind about the other issues with a high power non-hub build (budget, fabrication, motor control, etc).
dogman dan
1 PW
Thought that sounded like a pretty quick takeoff from the stop sign for street. Seriously, you build for about 40 mph, and you should be happy enough with needing new tires pretty fast. No need to buy a tire a week to go faster in street use. You'll already be wearing out tires and such fast enough in the 40 mph club. You'll still leave everything but motorcycles behind at the light.
Plus, as I keep trying to remind people over and over, in much of the world a 40 mph ebike is pretty illegal. No need to make one so fast you garantee the cops notice you. Not for use as a daily transportation that is.
Bikes for fun are a different story. Half the thrill is knowing the cops may bust you, or you need REAL speed for the racetrack. But for a daily driver, fast enough, yet not so conspicuous may be a good route. IE, have 40 mph but actually ride closer to 30 most of the time.
I bet you will be pleased enough with 3000w. Hell, a 1000w ebike leaves the line fast compared to a stock gas bike motor kit.
Plus, as I keep trying to remind people over and over, in much of the world a 40 mph ebike is pretty illegal. No need to make one so fast you garantee the cops notice you. Not for use as a daily transportation that is.
Bikes for fun are a different story. Half the thrill is knowing the cops may bust you, or you need REAL speed for the racetrack. But for a daily driver, fast enough, yet not so conspicuous may be a good route. IE, have 40 mph but actually ride closer to 30 most of the time.
I bet you will be pleased enough with 3000w. Hell, a 1000w ebike leaves the line fast compared to a stock gas bike motor kit.
Rather like CrazyBike2--in theory I could get at least 30MPH out of it, probably 35, but 20MPH is the local limit, so unless I need the speed to get out of someone's way in a hurry, 20 is it.dogman said:
(and once I get one of the other better controllers fixed, and the RC LiPo set up to easily add in, I could series that in there for probably 45MPH+, though I REALLY doubt I would ever ride it that fast even on the track, even assuming the bike didn't come apart!)
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