Battery range?

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deronmoped
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Joined: 12/25/2007
Points: 342

Why is it that if you go faster or climb hills it significantly reduces the range of a battery?

When you go faster air resistance increases, but I heard that it's not really that much of a factor under 25 MPH. So why would going faster (as long as the gearing is correct for efficient motor operation) on a bicycle significantly reduce the range of a battery.

And as far as climbing hills, you should recover that energy when you coast down the other side.

Deron.

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LinkOfHyrule
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Joined: 10/17/2007
Points: 730
Re: Battery range?

Resistive and fluidic friction losses, probably.

Actually, air resistance IS quite a bit of a factor at 25mph. Depending on your bike, it starts to become a bigger hindrance than the various rolling frictions on your bike at something like 15mph. It starts to become very difficult to pedal once you hit 25mph (assuming your fit enough to hit that at all).

To climb a hill faster, you're going to need more amperage. Naturally, more amperage = heat = inefficiencies. Wind resistance also has an impact, detracting from both the energy you used to go up the hill at speed, and keeping you from fully recovering that energy by coasting down the other side. If you roll down faster than the no-load speed of the motor down the hill, that also starts acting as a brake.

That's kinda a WAG, though.

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rmay635703
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Joined: 03/31/2007
Points: 12
Re: Battery range?

You also have to take into account the Peukert exponent which has more and more effects as amperage increases.

Also momentum quadruples each time speed doubles.

Both of these put together reduce your range.

Also Peukert's exponent effects all battery technologies, obviously lead acid is effected most but lithium and NMH are as well just to a lesser extent.

Good Luck

jbird
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Joined: 01/20/2007
Points: 73
Re: Battery range?

rmay635703 wrote:

Also momentum quadruples each time speed doubles.

I think you have confused momentum which is equal to mass times velocity (p=MV) with kinetic energy which is equal to one-half mass times velocity squared (1/2*M*V^2)

rmay635703
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Joined: 03/31/2007
Points: 12
Re: Battery range?

Oops, momentum is infinite at the speed of light.

vinnie
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Joined: 07/27/2007
Points: 161
Re: Battery range?

Quote:

Oops, momentum is infinite at the speed of light.

Just a sidebar clarification/question:
If the mass of electromagnetic energy is zero, and the speed of light is 300,000 km/s, doesn't this mean light has a momentum of zero using the aforementioned formula?

p=mv
p=(0)(300,000 km/s)
p=0

Sorry to be off topic...just curious.

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Vinnie
Broomfield, CO

PJD
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Joined: 11/22/2006
Points: 1411
Re: Battery range?

Vinnie,

From what I recall, because a photon is massless, it can _only_ move at exactly the speed of light when in a vacuum. So, classical mechanics - Newton or Einstein) doesn't apply. Instead, quantum mechanics governs, and the energy of a photon being E=h(nu), where h is Planks constant (6.626*10^-34 Joules/Hz) and nu is the wave-frequency of the photon (at tiny sizes, things are both particles and waves). So higher frequency photons have more energy - this is why UV light damages you skin and x and gamma rays can pass right through things.

By the way Vinnie, off topic but the charger you sent me lasted all of about 10 uses. It is quite different than the original e-max chargers - it uses fancy programming of pulse on and off at varying rates. I suspect the programmable microprocessor control chip in it went bad.

vinnie
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Joined: 07/27/2007
Points: 161
Re: Battery range?

Quote:

From what I recall, because a photon is massless, it can _only_ move at exactly the speed of light when in a vacuum. So, classical mechanics - Newton or Einstein) doesn't apply. Instead, quantum mechanics governs, and the energy of a photon being E=h(nu), where h is Planks constant (6.626*10^-34 Joules/Hz) and nu is the wave-frequency of the photon (at tiny sizes, things are both particles and waves). So higher frequency photons have more energy - this is why UV light damages you skin and x and gamma rays can pass right through things.

Right, I was forgetting completelty about the particle-wave duality. Thanks!

Quote:

By the way Vinnie, off topic but the charger you sent me lasted all of about 10 uses. It is quite different than the original e-max chargers - it uses fancy programming of pulse on and off at varying rates. I suspect the programmable microprocessor control chip in it went bad.

Man, I'm sorry! I only used it a few times before sending it to you. So, for others, this was a 48v stock charger from E-Moto, the E-Max clones.

Sorry for hijacking this thread! I promise to stop now:)

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Vinnie
Broomfield, CO

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