Specialized demo 8 - 2007 team build

[T04D]

Hello All,

OK, So im new to e-bikes and this is my first ever build and its safe to say that hooked

iv ridden mountain bikes most of my life and would consider my self a fairly strong rider; I`m no athlete by any stretch of the imagination but relativity fit and due to this i had no interest in building an electric bike that would only propel me at the kinda speeds that i could pedal (18-30mph).

After doing the initial research online and comming across people like DoctorBass and the likes i realised this was going to be anything but straight forward and the MTB that it was based on was going to have to be fairly special.

Due to the speeds this bike would be capable of once complete i decided on a full-on Downhill Mountain Bike based on the epic Specialized Demo 8 frame with 8" of travel front and rear. i proceeded bidding on all of the best parts i could get my hands on within budget and have finally finished and have made a monster of push bike

So; onto the electrics.......

after many weeks of research and keeping in mind that i have NO experience in electronics i decided to go with http://www.electricrider.com as they seemed to have done the hardest work of matching components and wiring the system ensuring everything works before you receive the kit and this all sounded good to me. I decided to go for the Crystalite Phoenix 2 system @ 72v 40amp. this was all good and well and few weeks and lots of anticipation later the kit turned up however after speaking with the company they advised that they could NOT send the batteries; so here i am today - a 95% built electric monster with no power-source :|

Iv done alot more reading and research on the batteries i can get a hold of in this country and decided the cheapest way forward would be old laptop batteries!! i know a few people on here have done this and had mixed results. Im currently in the process of stripping batteries @ the moment, charging and testing all the cells individually im realising that im in over my head when it comes to constructing the pack and charging it as either a single 72v or 2 36v packs.

anyways - heres a couple of pics so far and thier will be plenty more to follow

 

[T04D]

Hears the first cells i have out of the old laptop batteries - i know im going to need a whole lot more, maybe 300 upwards to hit the C rating needed but iv got alot of these things but its really difficult to get the cells out of the cases...my hands are sore.

 

[thepronghorn]

It sounds like you want a high a pretty high performance bike. Your bike is definitely capable of high speeds. You probably do not want to carry around enough laptop batteries to get the high power you want, their discharge rate is pretty low. Unless you're really hurting for money, maybe take a look at some higher performance A123 lifepo4 or lipo batteries. Cellman on this forum (em3ev.com) sells good lifepo4 (contact him directly for some options not on his website), lipo usually comes from hobbyking.com. Lipo does need to be respected for its ability to fail catastrophically, so it is a bit more work with charging and balancing and does require some reading to learn to treat it correctly...

 

[T04D]

Cheers man - all advice is much appreciated

yeah. money is pretty tight at the mo; i didnt plan the build very well and spent almost all of the cash on the bike build and electrics leaving nxt to nothing for batteries - i almost bought SLA batteries until i came across the laptop solution. im starting to understand that the sheer quantity of batteries and time involved in testing and constructing the pack is anything but ideal........

i originally was looking at the lipo solution but due to the instability of the cells and the fact that they only have a cycle life of around 200 charges put me off them. Lifepo4 would be good but im just going to bide my time with the laptop batteries until i can afford these

http://www.ebay.co.uk/itm/171010752994?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649

2900mah with a 10A continuous discharge rate - thought these would be perfect for the job; but very expensive.

the other difficulty iv hit so far with batteries is getting them imported into the UK. no where seems to want to send them here and ordering from china and the likes just seems too risky - not to mention the import charges and duty costs

 

[MadRhino]

You will love the Demo 8. It is a very good frame to build with.
Here is mine with cro-motor in 24" wheel, 24s Lipo, 18 fet 4110 upgraded to 150A.
I've put over 20 000 miles on it already. It rides so nice at 50 Mph, you'd want double that speed.
Good luck with your build.

 

[T04D]

lovely build mate - how does it handle offraod, was guessing when i get it going it should be like a small KTM how do you go about upgrading the controller to handle more amps? heres me wanting to upgrade it and iv never even ridden it yet.lol. best hobby iv ever come across

what kinda range do you get? have you had any issues with the Lipo`s? from what iv read they a fairley dangerous tech to mess about with but was guessing they would be perfect to get this thing moving at the speeds im after

20,000 miles sounds re-assuring though for cycle life of them.....

 

[MadRhino]

Not 20 000 miles with the same Lipo pack, I used 24 Lipo bricks so far for this bike.
I usually carry only 24s 1P pack, my trail is about 10 miles, then charge in 15 minutes. I carry more packs when needed.
It rides very good off road, but not a good jumper. I jump 2 feet often, ride the stairs sometimes. 3 feet jumps are the extreme limit for a hub build.
Steveo does repair and upgrade on controllers. He is very good at it, and I don't trust myself playing with electronics.
You will need to have a shock custom valved, to be able to tune the rebound with a hub motor. This is by far the best improvement I have done since I have built this bike.

I have built a few more since this one, but still ride it almost everyday because it has the best handling. I was going to build a Demo 9 this year, but finally decided for a Trek Session 10.

 

[T04D]

ah right - makes sense

what torque arms are you using? iv not looked into these yet but know the will be needed. any pics of yours? what manufacturer of Lipo are you using? i was looking at the Turnigy nano tech packs.....

 

[MadRhino]

Dropouts are custom made. Cut an opening at the end of the upper swing arm tubing, then insert strong thick steel dropouts inside the tubing with epoxy. Bolt in the tubing and the actual forged alu dropout using chain ring bolts. It been a while, but I will try to find the pic.

I am using the Zippy flightmax 5800 mah