[Iain]

Hello there,

I am interested in creating an electric bike from a mountain bike frame, and would like help sizing the battery and and motor. I have found an article that would indicated a 15 hp peak and 7.5 hp cont. would be OK for 50 mph.

that would be this unit here
http://www.robotmarketplace.com/prod...ACDSBL450.html

Does anyone have any good prices on lifebatt? or know other LIFEPO4 batteries?

Now, is 70 mph ok on a bike like this, or would it get a bit scary?
15 mile radius

Ideally 150 miles but the pack would be too large yes?
What is the best voltage? 144 volts makes sense for lead acid but lithium is higher?

thanks

Iain

[Ziggythewiz]

So...is this a car, or a bike?

What is the intended use?

70 mph can be scary in a VW bug, on a bike?? And rather uncomfortable for 75 miles at a stretch.

Typical e-bikes run from 24-48V, 144 seems a bit much.

[Iain]

Hello, yes this is for an electric bike, wasnt sure if 70 was a safe idea or not, or even if the pack could be sized for such a job

so 48V@125A 250A peak for a 6kw pack, (100 kg?) which seems way to heavy

maybe an electric motorbike would be a better idea with stronger frame and aero parts?

thanks

Iain

[frodus]

do you mean 125Ah and 6kwh?

150 miles is going to require a HUGE pack. rethink your range requirements, or increase your budget and get a very large bike.

[njloof]

Or pedal. You can easily stretch the range of an electric bike by using a food-based energy source.

[Ziggythewiz]

Not at 70 mph...

[Iain]

LOL peddling at 70... Id love to see that..

ok yes, 50 miles range is better I think at 50-70 mph you guys think?
a 2.5 kw pack, or more pertinently: what is the largest size pack I could get away with

thanks

Iain

[njloof]

I'll be honest, I have a beefy chopper bicycle carrying about 1kW of lithium and it's a good chunk of weight to stabilize. Hang it off the top tube and your stability will suffer. I put mine just in front of the cranks.

Some folks build custom packs in triangles made to fit the frame, but I've never seen a 2.5kW one. Pick a battery and start looking at the geometry issues...

[frodus]

Originally Posted by Iain

LOL peddling at 70... Id love to see that..

ok yes, 50 miles range is better I think at 50-70 mph you guys think?
a 2.5 kw pack, or more pertinently: what is the largest size pack I could get away with

thanks

Iain

You won't be able to do that on a bicycle. And I wouldn't try, at those speeds, it's dangerous not only to you, but others on the road.

To be possible, you could go 50-70mph on a motorcycle, you're going to be using between 100 and 130wh/mile, so you'd need at least 5kwh, but it could need to be up to 6.5kwh, but you want a bit over that because you don't want to discharge to 100%, so maybe 5.5-7kwh. There's no way you'd get 50 miles range with 2.5kwh of battery. And you'd almost 100% have to go with lithium.

Above 5kwh the pack gets harder and harder to fit into a normal 600-700cc sized motorcycle.

And that motor might have trouble hitting 70mph. 48V is a bit low for a motorcycle. Start thinking 72-96V.

Also, try to use the correct units. You're speaking about energy (how many kilowatt hours) but using units for power (kw).

[mizlplix]

Reverse engineer this one.

What speed would you feel safe stopping from with those brakes?

Some early motorcycles (motorbikes) looked similar to a mountain bike, but they had some suspension and better brakes.

They only went 35mph or so too...

Miz