New Member building first bike

[greasypants]

Hi everyone ,
New to the forum and I have decided to do an electric conversion on my moutain bike ( Kona nunu ). I will be using the bike for commuting purposes from Port Moody to Vancouver . One way trip of about 15 Km. I would like something with lots of power ( so I don't have to pedal ) and lots of torque . On the end of my return commute I have a very steep hill to climb ( for you local people the north end of North Road by burnaby mountain where all the moutain bikers park their cars). I am thinking of installing a 5304 in the rear hub and running 72v 35a controller from ebikes. I will make my own torque bars for peace of mind.I am looking for input on battery selection . To keep weight down I was considering 2 x 36v 8ah nexcell packs from Justin .That would be about the max weight I would want to carry from the underground p/lot at work to our 3rd floor office for re-charging . My concern is I think they will struggle to put out anything over 25 amps and may be damaged trying to climb the steep hill on my ride home . My other idea is to use 2 x 36v 14ah nexcell 3c's and not charge up at work . They should be able to put out enough amperage and only need chargeing up once a day so they should last twice as long as using the 2 x 8ah packs. I would like to use lots of throttle and cruise at about 50kph for the increased fun factor during my commute. I figure with 14ah packs and 30km round trip commute that would give me about 33 watt-hrs / km which I think should be o.k. as long as I am not to crazy with the power. Also is there any benefit to having a series / parallel switch to run 36v 28ah on the flat sections and 72v 14ah on the big hill ?Either way you still have the same amount of watt / hrs in the packs so wouldn't think so . Also any local people know if this settup would be able to climb the north road hill? I have no idea what grade it is but it only takes me about 4 mintues to peddle up it in 1st gear so it isn't very long.
Thanks
Greg

 

[Lowell]

You're on the right track, but you should plan for extra battery capacity. At high drain rates, actual Ah capacity will be reduced, and some energy will go towards heating the battery packs. If you want to check out my X5303 bike let me know, I'm not too far from your location.

 

[jondoh]

You definately don't want to be drawing more amps that your batteries can handle. That's a recipe for spending more money on better batteries later.

I'm slowly learning that there isn't a substitute for amp hours. get the most that you feel comfortable with on the bike.

The 5304 is the cruiser. Even the racer (5303) can be useful on the steapest grades-- if you peddle.

 

[Lowell]

A high voltage 5303 will fly up any hills on your commute. I've never tried the North Road hill, but when I get back from my work trip I'll give it a try on video.

 

[greasypants]

Thanks for the input , maybe I would be better to go with 2 18Ah packs because I would also like to run my lights as well. I have a 20W 36 degree and 35 W 8 degree phillips energy saver bulbs overvolted @ 16.8V, very bright lights. Anyone know where I can get a 72v to 16 v dc converter good for 6 amps ? That would put battery weight at 46lbs, motor 24lbs, bike 33lbs , me 155lbs , other crap 10bs total - 268lbs . Would this be o.k. for my aluminum frame? I would try to mount one pack in the frame and one on a rear rack to help weight distribution .
Lowell , that would be fantastic if you did a video going up that hill .
Thanks again
Greg

 

[xyster]

I bought a rear 5304/24" wheel from Justin, installing it on a 7005-series aluminum, dual-suspension frame. My bike weighs about 100-110 lbs I think; I weigh 175 lbs. No probs at all with the frame at the 80 volts and 35 amps (2800 watts) I feed the motor. Without pedaling, it powers right up the steepest hills around here (15%) at 10-20mph; moderate hills (10%) at 20-30mph; and 5% hills at 30-40mph. Top speed is 44mph on the flats, riding in a normal upright position.

My dropouts are spaced 135mm, so there was only room for a 3 speed freewheel -- no room for disk brakes. Justin spent extra time and did a terrific job mounting the freewheel and dishing the wheel.

I'd definitely choose the best batteries you can afford and can stand the weight of.

There's also a 40 amp 72 volt crystalyte controller available. I'm happy with my 35 amp controller, but for only $15 dollars more, I wish this 40 amp was available back when I bought it:
http://www.poweridestore.com/Hub-Motor-Acces/Series-500-Controllers

I don't believe there's any benefit to a series/parallel switch except perhaps as an easy method to switch to a "legal power level", or if the throttle is too sensitive at high voltages and you'd like more throttle control at low speeds.

I don't know anything about where to find that voltage converter; I just wired my six 12v halogens in series so the whole battery pack powers the lights.

It sounds like you're really on top of the specific options and ebike fundamentals.