Questions about voltage, amps and watts

kmarcetjr

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Hi, I'm pretty sure I'm going to build my first e-bike within the next month or so. I am on somewhat of a limited budget and want the best bike I can build for the buck.
I already have a bike to build on, not much really just a beach cruiser style bike from a big box store,
So now my questions about volts, amps, amp hours, watt hours and watts.
E-bike motors are rated in watts and generally the higher the watts the more power and speed the e-bike will have?
Battery voltage the more volts the more power?
Ah=A little confused at this one. I've read that is you multiply ah x volts you come up with amp hours?
So if I understand the above correctly:
An 36 volt 10.4 ah battery connected to an 800 watt motor = 374 watt hours, which would power an 800 watt motor for just under 1/2 hour at maximum output, under ideal conditions?

Thanks for educating me.
 
i think you should state your approximate budget and also check the laws within your state regarding max power and registration (if needed).
 
i think you should state your approximate budget and also check the laws within your state regarding max power and registration (if needed).

I have a budget of $500 to $600. I live in Florida, the way I understand the laws, if the bike has pedals with an assist motor and the bike has an assisted top speed of under 30 mph no license or registration is needed.
 
A good lithium 36v battery pack can cost between $300-400. You may be able to add a 36v hub motor kit within your budget.
Most of the US has a 750w limit to remain street legal. I doubt that most lawmen can distinguish between a 250w and 1000w motor.
 
Hi, I'm pretty sure I'm going to build my first e-bike within the next month or so. I am on somewhat of a limited budget and want the best bike I can build for the buck.
I already have a bike to build on, not much really just a beach cruiser style bike from a big box store,
So now my questions about volts, amps, amp hours, watt hours and watts.
E-bike motors are rated in watts and generally the higher the watts the more power and speed the e-bike will have?
Battery voltage the more volts the more power?
Ah=A little confused at this one. I've read that is you multiply ah x volts you come up with amp hours?
So if I understand the above correctly:
An 36 volt 10.4 ah battery connected to an 800 watt motor = 374 watt hours, which would power an 800 watt motor for just under 1/2 hour at maximum output, under ideal conditions?

Thanks for educating me.
OK the voltage is what with the controller gives the motor kv, kv=rpm the norm is 7-11 kv per volt 7 for cheap motors 11 for the really good ones so if you are running a 36v system that's 252 rpm at 7kv!So yes higher voltage can yeild higher rpm's but then the motor needs to see enough amparage to get to the upper available rpm.It takes amps to support the voltage.A basic rule of thumb is that an electric motor needs to stay within 20% of it's free spin speed while loaded!So really the power comes from the amparage capable of passing through the controller to motor so again a 36v system whitch has a 40 amp limit thru the controller is a 1,440 watt system peak probably called a 1,500 watt system in real life but as a retail item and to fit in with restrictions from law makers they call it a 500-750 watt system because the motor only ever sees the full amps when under extrem load normal operating is generaly 1/3 the peak level!And then you can work out your actual wh available!
 
I like to keep things simple, my eBike has 350 watts (speed 25MPH) 36 volts 10ah (distance 20 miles) want to go farther use Batts with higher ah or buy a larger volt system. Watts is your speed, Volts and ah, is the distance to recharge. Ca. is 750 watts and 25 MPH, (remember hills and head winds) and no CDL required. I feel the best system would be 750 watts and 48 volts with 20-30 ah, lithium batts if you can afford them. So ask yourself, how fast do you want to go and how far do you want to go???
 
I like to keep things simple, my eBike has 350 watts (speed 25MPH) 36 volts 10ah (distance 20 miles) want to go farther use Batts with higher ah or buy a larger volt system. Watts is your speed, Volts and ah, is the distance to recharge. Ca. is 750 watts and 25 MPH, (remember hills and head winds) and no CDL required. I feel the best system would be 750 watts and 48 volts with 20-30 ah, lithium batts if you can afford them. So ask yourself, how fast do you want to go and how far do you want to go???

Thanks for the info, I've already ordered a bit and a battery.
I've got a 1000 watt, 48 volt kit, and now I am waiting on a 48 volt, 11.6 Ah battery to arrive.
 
Thanks for the info, I've already ordered a bit and a battery.
I've got a 1000 watt, 48 volt kit, and now I am waiting on a 48 volt, 11.6 Ah battery to arrive.
Sweet, you going to build something like this shifter?

2_SpecializedEpicDoneR-1280.jpg


Sweet way to get around ;-}
 
Sweet, you going to build something like this shifter?

2_SpecializedEpicDoneR-1280.jpg


Sweet way to get around ;-}

No I've got a front hub motor kit, should be more than I really need for around town, but that does look pretty sweet.
 
Hi, I'm pretty sure I'm going to build my first e-bike within the next month or so. I am on somewhat of a limited budget and want the best bike I can build for the buck.
I already have a bike to build on, not much really just a beach cruiser style bike from a big box store,
So now my questions about volts, amps, amp hours, watt hours and watts.
E-bike motors are rated in watts and generally the higher the watts the more power and speed the e-bike will have?
Battery voltage the more volts the more power?
Ah=A little confused at this one. I've read that is you multiply ah x volts you come up with amp hours?
So if I understand the above correctly:
An 36 volt 10.4 ah battery connected to an 800 watt motor = 374 watt hours, which would power an 800 watt motor for just under 1/2 hour at maximum output, under ideal conditions?

Thanks for educating me.
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The most important thing is to have fun, TomyJ
 
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