Which of these two kits to purchase?

amp1

Just Joined
Jan 26, 2014
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Hi Folks,

Looking for some comments and input over which of these two kits I should go for, first a little background...

I generally commute a near daily 29 mile round trip on a carbon road bike (best time for 14.8 miles is 38 mins which is an average 24 mph constant) but am looking to convert a mountain bike which I already own for the days when the wind and rain is blowing exceptionally and it can take the time for a one way trip to 1hr 10mins which is exhausting against the wind - also there are days I just don't feel like riding the whole way and it just feels wrong taking the car!

I'd be converting a GT avalanche with hydraulic brakes (I'm wearing out road bike pads so quick in the bad weather and gritty road surface so discs are a must) and am thinking I would feel a bit slow at the 15mph limit but obviously I'd be putting a fair bit of input in. There are a few short but steep hills but nothing severe and I guess mostly i'll just be using a thumb throttle minimally to keep my average speed as high as possible.

Originally i was thinking that:-
http://www.8funbike.com/detail.asp/sku=8F26F36B

would be spot on but then thinking I could go faster for the same money brought me to:-

http://www.ebay.co.uk/itm/36-48V-250-500-800-1000W-Electric-Bicycle-E-Bike-26-Front-Rear-Wheel-Motor-Kit-/181237508447?pt=UK_SportGoods_CyclAcces_RL&var=&hash=item6fd307c85c#shId
(36V 800W Front wheel)

and for a battery in the ebay option:-
http://www.ebay.co.uk/itm/2014-New-Model-36v-10-4ah-water-bottle-mount-Lithium-ion-electric-bike-battery-/131096945244?pt=UK_Bikes_GL&hash=item1e85fca25c

I'm also toying with making my own batteries from the hobbyking radio control lipos to keep the cost down and mounting them in a water bottle - I could do two water bottles and charge at my work easily.

I've tinkered with various electric bikes over the years (izip, yamaha easy pas) and making my own "version" to make things fit and work shouldn't be an issue......:)

Thanks in advance....
Andrew
 

trex

Esteemed Pedelecer
May 15, 2011
7,703
2,669
both kits use hub motors, not my choice for fast commuting because you are restricted to the motor maximum RPM. The standard SWXK are wound for 201 RPM, 15mph on a 26" wheel. You can already pedal faster than that.
The other kits, 48V 1000RC seems to be a direct drive unit, plus a 48V is too heavy in my view for a commuting bike.
My recommendation is for a crank drive, 8-Fun has one BBS01 with two options on voltage 36V and 48V and two on Amps, 15A and 20A. I have the 36V 15A BBS01 and it does about 22mph with light pedalling. I guess you'd be better with a 48V 15A, capable of 30mph with light pedalling.
You can buy a 48V 10AH bottle type (in the same casing as the one you selected) direct from China for about $270 + courier cost.
 
D

Deleted member 4366

Guest
Your bike is nice and easy to convert with virtually any kit. The only difficult thing is to decide which one.

If you go for a hub-motor, you need to get one that spins at the right speed. The speed changes in direct relation to the battery voltage so a 24v motor will run 50% faster with a 36v motor , and a 48v motor will run 25% slower at 36v, so you can tune the speed by choosing the right voltage battery. The plug and play batteries are 24v, 36v and 48v. You can get an in-between speed with 12S lipos (R/C batteries, which give a handy 20% speed and power boost to a 36v system, and, conveniently, you can still use a 36v controller.

The seller should state the reference voltage and the RPM, so that you can calculate and plan your speed, but they don't. They nearly always give the voltage and power rating. the power rating doesn't mean too much. It's usually about half of what it can handle. That Ebay seller has conveniently given the speeds, but without qualification.

201 rpm is about 15 mph,so you can cruise at about 21 mph with a 270 rpm one. it will help you a bit above that speed, but power drops off as it approaches it's max rpm. You also have to bear in mind the power of the motor. As a strong pedaller, a 250w one will enable you to cruise fairly comfortably at 20mph. You could cruise at about 25mph with a 328 rpm 250w motor, but you'd have to pedal hard, especially on the hills, where it will rapidly heat up if you go too slow, Really, you need 500w if you want to go that fast.

The two motors you referred to are probably unsuitable, the bigger one is a direct drive motor, so needs battery power all the time. They're good for going at constant speed without many hills.They're also heavy, so a front one will spoil your suspension and a rear one will mess up your nice gears. If you want a rear motor, you need a cassette one (CST) for a nice bike like yours.

Now you can see that things are not so straight-forward. Everything ends up a compromise; however, there's still theoption that Trex suggested: The Bafang BSS01 crank-drive kit, which could well be suitable if you have a high cadence. I'm not sure what size chain-wheels you can get now, but check that the gearing wikk suit you before ordering, particularly if you want to go at speeds above 20mph. I think they give reasonable power up to about 80 rpm, but it starts to decrease from about 60 rpm. My guess is that the 350w one would suit you best.

One last thing: Batteries can only give a finite amount of power, so you have to match the controller, motor and battery to all be able to give the power you need. The frame battery that you indicated is rated at about 10amps, and would be able to go up to about 18 amps for short periods, so it's only suited to 250w systems. It wouldn't work with the 800w motor. it would, however be OK with the BSS01 250w and 350w, although I'd go for a 50 cell one instead of 40 for the 350w.

Sorry for making it rather complicated. If you had a Tesco bike and wanted to do 15mph, the first kit would be OK with that battery. If you wanted it to go faster, the 800w rear wheel one would be OK, but with a more powerful battery, i.e. lipos or a bigger one.
 
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amp1

Just Joined
Jan 26, 2014
4
0
51
Thanks chaps for both your replies - d8veh its so kind of you to explain this so clearly and make perfect sense.

I am toying with the bbs01 - ideally I don't want to loose the smaller two rings on the front as my wife may ride in a lower gear/ring on occasions but the speed aspect obviously appeals to me.

I could also accept that the easy 15mph option would be the 8fun link and just look at the view for a change - my whole point of doing this conversion is to battle a 20-30mph facing wind so if it tries to keep me at 15mph that's not bad. (I ride alongside the Exmouth-Exeter estuary and depending on the weather and tides can be horrendous particulary after a 8 hour day at work)
Obviously my mileage may vary if its working hard...

I came back to the whole idea of a electric bike after spotting the Burisch was able to do 18-20 with the pedelec sensor wire disconnected and 23+ mph with the better controller option - I'm lost as to how this bike can do this speed on a 250W motor - does it have a 350W peak and they exploit it?

I've had a good look around ebay and the uk ebike sites but can't seem to find a battery that will supply more higher constant current without importing one and paying high postage and import duty charges - this brings me back to making my own from RC batteries from hobbyking but i'm thinking I would also need some battery management/cutoff protection or would the correct controller monitor that?

Andrew
 

trex

Esteemed Pedelecer
May 15, 2011
7,703
2,669
if you have to buy from more than one supplier, there is little saving building it yourself and you could save yourself a lot of time and uncertainty by buying a ready built bike. Keep in mind that bikes with high mileage won't fetch much on ebay, I would recommend that you buy a cheapo Chinese with high capacity battery for the job.
 

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