Electrified Downhill bike - Page 6 - RC-Monster Forums

zeropointbug · 11:02 PM

Okay, gotcha. Are you sure it could do 20A? I see 12.5 amps on the spec sheet for the 40+40 model. EDIT: Oh, the transformer must be center tapped? That is why you would get effectively double the current, correct? I am really gonna consider this idea for charging it.. btw this is for my brother so he is gone to University in fall so he will need his own charger, but for now it's the 720i.

The battery will be easily detachable from the bike by means of rare earth magnets built into the enclosure, and on the bike.

zeropointbug · 05.06.2010, 11:07 PM

Wait, isn't Sine = 0.7x something, so how do you get more than the average voltage when rectified and filtered? Shouldn't the voltage be pretty close to the AC voltage? Or am I missing some current formula that has to be factored in?

zeropointbug · 05.07.2010, 06:37 PM

Here is the donor bike, a 2 year old mountain bike from GT Bikes. 24 speed, alum. frame, magnesium fork, fr and rr disv brakes, so it should be a decent electric converter.

That's where I thought the batt and controller could go? Although the battery could be moved up and controller could move down and further back?

Each cell is 6.8 x150 x210mm, I still don't know whether I want to go 14 or 16s pack.

BrianG · 05.07.2010, 08:07 PM

Quote:

Originally Posted by zeropointbug

Wait, isn't Sine = 0.7x something, so how do you get more than the average voltage when rectified and filtered? Shouldn't the voltage be pretty close to the AC voltage? Or am I missing some current formula that has to be factored in?

Transformers are rated in RMS voltage. But when you rectify and filter them, you get the peak value. 40v AC rms = 56.5v DC (with some ripple depending on capacitance used and current load). Minus around 1.4v for the bridge rectifier diodes gets you around 54v. Oh, and do use a bridge rectifier because instead of the 60Hz ripple, you actually get 120Hz which is easier to filter.

zeropointbug · 05.07.2010, 10:43 PM

0.71 = Sine Right, okay, I thought you still got the RMS voltage. Yeah, definitely would want bridge rectifier to get maximum power from it. Really gonna consider this as a charger setup for the bike, but later in the summer when he moves away and needs one. It would be nice to get a full charge from empty in less than an hour, and probably less than 1/2 hour regular use.

Was calculating some energy stuff, the bike will have a MPG equivalent of 1800mpg @~25mph. Also, with 16 cells, or ~750Wh, the battery will have nearly the same energy as 1 Cup of white rice, or ~650 Calories.

Metallover · 05.19.2010, 08:12 AM

Good deal. Looking forward to progress and pics!

zeropointbug · 05.25.2010, 05:37 PM

I am trying to find some large shrink wrap to cover ~520mm circumference around the pack. So ~260mm exact 'flat' shrink warp width would need to be maybe ~280mm wide to make it easy to get it on? Preferably something like 300mm?

Anyone know of a domestic place to purchase this at is all I want, I have found places that have it, but in China or UK, etc.

Thanks.

zeropointbug · 05.28.2010, 08:59 PM

bump

Metallover · 05.28.2010, 10:55 PM

You can get 20cm heat shrink at ebikes.ca. Go to the site, then the store, then search for "shrink".

Another idea is to use Cohesive Flexible Bandages.

http://www.jefferspet.com/ssc/produc...&pf_id=0029430

Wow that stuff looks pretty good.. I'll look for some locally for myself.

zeropointbug · 05.30.2010, 01:27 PM

Actually, I guess I am not going to use shrink, I was talking to cell_man and he said just use fiber glass tape, and also I am going to use lexan guard sheets all around the pack for protection, like what I recently did to my RC lipo packs

thanks anyways.

It seems to be taking forever for the cells to arrive.

It's been 2 weeks now, so I'll give it 3 more days before I get worried, as I shipped it standard service.

zeropointbug · 06.03.2010, 10:54 PM

Well, after ordering the ebike kit and battery cells 2.5 weeks apart, they arrived here on the same day! Hmmm, goodies. The cells have the A123 Systems logo, part #, bar code, etc. still printed on them, and I guess they are made by Enerland facility, in Korea.

The Nine Continent motors are supposed to be one of the lightest built units available, but looks very solid to me. It would be nice if they could make them lighter, adds quite a bit of mass in the wheel, I'm not sure about rotating mass though, I would guess a 1/3 of the total motor weight.

zeropointbug · 06.06.2010, 12:46 PM

So no one thinks this stack of 30C A123 15Ah cells looks sexy at all?

Metallover · 06.06.2010, 01:16 PM

That whole pile of parts looks sexy! You'll get some serious power from those cells!

That motor might look sexier with cooling holes and a fan tho,,, If you ever need them

Make sure you run a couple torque arms in the back.. I didn't see any in the picture. I did see what I think is a disc brake adapter tho! Very nice!

zeropointbug · 06.06.2010, 03:46 PM

Yeah man, the 720i HP is reporting them to be 1mOhm (probably the lowest it can go?) each. Cell_man did some discharge tests on endless sphere, can discharge 600amps @ 2.0v/cell IIRC. I am going to buy a 1200watt charger for it to get less than an hour 0-100% charge. If you calc the power density from the 26650 M1's, it should have a solid 17kW power capability, so obviously it's not going to break a sweat at ~2000watts peak.

Those holes look scary to me.

Oh, and do I need a torque arm for the rear?

Metallover · 03:58 PM

You definitely need a torque arm for the rear. I would recommend two torque arms. Make sure you have steel dropouts too.

Here's a good ES thread on torque arms - http://endless-sphere.com/forums/vie...lit=torque+arm