ElectroCat lithium battery powered motorcycle

[NeilBlanchard]

Hi,

I just recently read about this (A123) lithium battery powered electric motorcycle, and it looks freakin' awesome!

Eva Håkansson - with passion for electric drive

Voltage: Nominal 53 V, fully charged 60 V

Weight battery pack: 48 kg (106 lbs)

Capacity: nominal about 4.8 kWh

Total weight: about 165 kg (363 lbs)

Top speed: The bike is geared for 100 km/h (60 mph) at the moment. Because it has a PMDC (permanent magnet direct current) motor, max RPM is decided by the voltage (this is characteristic for PMDC motors). With a PMDC motor, you therefore have to choose acceleration or top speed. There is enough power for higher top speed, but because it bike is slightly under-motorized, gearing for a higher top speed would cost too much acceleration and also give lower efficiency. 100 km/h is an acceptable compromise at the moment.

A new battery pack with higher voltage is waiting to be installed. The new battery pack will hopefully give a top speed of 100 mph.

Range: About 80 km (50 miles) per charge at 70 km/h (44 mph).

[dcb]

Cool, I'm expecting one of those brushless eteks soon, though the lipos are gonna have to wait I'm afraid.

[ldjessee00]

What is it about electric vehicles that makes people not want gears?

Seems like a transmission will give you the ability to trade between speed and acceleration. I think that is why gas/diesel engines do it. I am just curious why (besides extra weight and mechanical loses) that most of the EVs seem to forgo any transmission.

I also think I have read where an advanced motor that is wound in such a way that the windings can be switched around, basically changing the way the motor works (effectively getting a transmission built into the electric motor)?

If this above is all true, then with the small size and compactness of motorcycle transmissions, why not keep it?

[MadisonMPG]

Originally Posted by ldjessee00

What is it about electric vehicles that makes people not want gears?

Most of the time, an electric motor doesn't need gears. Their usable RPM range is HUGE compared to a gas/diesel. That is assuming the motor is the correct size for the application.

A couple guys on this site use 2nd and 3rd for their EV's because they motors are underpowered.

[dcb]

I think the mechanical simplicity is very appealing, there are losses in a transmission, but just a chain to motor can be very efficient. But a gear or two would come in handy if it were efficient and inexpensive and not too bulky for a motorcycle.

I've been wrestling with some two speed ideas, hoping to avoid bulk/expense/losses. It gets a little complicated when you add those parameters in.

A motorcycle trans is not compact, after you shoehorn batteries and motor and whatnot on the bike. It is also overkill, the torque curve of an electric motor doesn't benefit from all those gears, only a couple are needed, and the extra gears are just spinning and turning your electrons into heat.

What I was thinking of was a motor with a through shaft, a bike with two sets of sprockets and chains (different ratio on each side), and a clutch on each end of the motor to engage that side, and maybe a one way sprag on the low speed rear sprocket so that you don't have to turn both chains while cruising in exchange for a loss of low speed regen performance.

EDIT, my ETEK showed up today

[MadisonMPG]

Originally Posted by dcb

What I was thinking of was a motor with a through shaft, a bike with two sets of sprockets and chains (different ratio on each side), and a clutch on each end of the motor to engage that side, and maybe a one way sprag on the low speed rear sprocket so that you don't have to turn both chains while cruising in exchange for a loss of low speed regen performance.

EDIT, my ETEK showed up today

I like that idea, what kind of difference in gear ratios are you thinking?

[dcb]

dunno, maybe 2:3 or 1:2? It should be easy enough to try different combos of sprockets and find something that works the best, depends on taste to some degree I'm sure.

But if it takes, say 18 seconds to reach 60mph with a single gear, an additional lower gear that is 2:3 the ratio should be able to top out at 40mph and give 50% better acceleration up to 40mph, which would ideally knock 4 seconds off the 0-60 time, maybe.

a low gear that is 1:2 the ratio would top out at 30mph and knock off maybe 4.5 seconds, kinda sorta.

[ldjessee00]

Thanks!

I didn't think you needed the 6 gears that some bikes have, but was thinking 2 or 3.