Hello all, this is my first post to your forum. I've been looking at getting an electric bike for a while and I'm considering buying a 48v 1000/1500w rear hub kit.

 

My (and probably a few other peoples) problem is price & location of the battery. I don't really like the look of a battery hanging over the back wheel and so would like one to fit within the triangle of the frame.

 

I'm considering this idea, unless you techy guys can see a problem

 

42 x 'C' 1.2v 10000mAh Mi-MH rechargeable batteries, wired in series to give 50.4v @ 10Ah which only costs £58.59

 

The advantage to me is I can build the battery shape to fit the frame and a reasonable price and possibly use a standard 48v battery charger.

 

Any thoughts?

You've made a mistake. It's not our forum, it's yours, where you is us, if you can understand that.

 

How much do the Nimhs weigh? How much current can they give because you'll need about 25A, which sound a bit high for a single cell? How will you join them, bearing in mind that the connections will have to carry 25A.

 

Why do you want a 1000w/1500w motor? Most of them are very heavy, which spoils the handling of a bicycle.

Can the NiMH batteries deliver 30amps? That's 3C if they are 10Ah.

That's what you need for 1.5Kw with 50 volts.

I doubt they realy can..

The lithium batteries normally used can give 3C comfortably. Standard is around 4 volts and 2.5Ah per battery. So four batteries in parallel times12 in series to give 48 volt 10 Ah.

Precise figures are available but this is back of envelope stuff.

See? This is why I'm still noob to this! All I saw was the Ah of the 'C' batteries! Originally I was going to put them packed side-by-side and solder wire them in series. here's the batteries:-

 

http://www.ebay.co.uk/itm/6-x-C-size-1-2V-10000mAh-Ni-MH-rechargeable-battery-Red-/390848436847?pt=LH_DefaultDomain_3&hash=item5b0061da6f

 

I saw this kid use old laptop batteries on youtube and he made a pack using several cells in parallel and then put several packs in series for his voltage and got quite good speed & distance.

 

Whats 3C?

 

The reason for the 1000w/1500w is the terrain I use mostly is off-road and quite hilly, plus I weigh around 16stone! I got a regular bike for exercise but I just want a quiet, non-petrol off road fun machine. You're very limited where I live for taking petrol bikes off road, with the electric bike as long as I behave, I'm pretty much free to go anywhere.

Rather than one of those motors, get yourself a 500w Bafang BPM. It'll have much better torque and efficiency. Those big DD motors are great for constant high speed, but no good for hills and stop-start riding. Also, for off-road riding, you need to go up you about 40A, which brings all sorts of problems and expense.

 

Don't try and make a battery out of recycled laptop cells. You need a lot of equipment and knowledge. That guy on the Youtube video (if it's the one I saw) makes a lot of dangerous mistakes. By now, he's probably given up with his home-made battery and bought a decent one, like the rest of us did.

cheers d8veh, 40A is some serious current! I've been doing some reading on various sites (I think I know what 3C means now.... 3x current rating, right?).

 

I'm coming to the conclusion that it may be best to save the pennies and buy a lithium pre-built battery with charger etc!

...I'm also undecided about whether to go 1000w rear or 2x500w, would 2 wheel drive be better off-road. I suppose then i would need a beefy controller or a pair of controllers & maybe 2 batteries

Before deciding on a particular power requirement I'd recommend trying out one or two ebikes. You might find you really don't need so much power and that the decision only brings disadvantages (significant weight penalty, motor inefficiency, expense to name but three).

 

I've just finished a 250W BBS01 conversion of a Cube road bike to use for my 20 mile each way commute. I can't imagine needing any more power. I am averaging 20mph for each leg using power level 3 of 5, using anywhere between 5.5Ah and 6.8Ah of the 36V battery. In fact I'm thinking I should actually drop the power more in some areas and take it a bit slower. Now that is not hilly and on road, and I'm about 12.5 stone and the bike is light, so your requirements will I'm sure be different, but I mention it as an illustration. Incidentally the 250W BBS01 peaks at over 500W and my assist level 3 is round about 300W.

 

Michael

...I'm also undecided about whether to go 1000w rear or 2x500w, would 2 wheel drive be better off-road. I suppose then i would need a beefy controller or a pair of controllers & maybe 2 batteries

One 500w geared motor is equivalent to one 1000w DD motor. 2WD is good if you're doing serious off-roading, where you need grip on slippery surfaces. Anything bigger than a 250w motor in the front can bring a lot of problems. I can't see any advantage of two 500w motors.I built a bike with two 500w motors and it was nearly unridable. The torque from the back one lifts the front wheel, so the front one skips for the first 10 meters whenever you open the throttle.

OK, what about this as a starting point...

 

http://www.ebay.co.uk/itm/230642061196?ru=http%3A%2F%2Fwww.ebay.co.uk%2Fsch%2Fi.html%3F_from%3DR40%26_sacat%3D0%26_nkw%3D230642061196%26_rdc%3D1

 

I've asked the seller if the battery holding area will take a 48v20Ah when I decide to upgrade in future, they haven't replied. The reason I ask is that there is another bike which looks like it has the same frame...

 

http://www.ebay.co.uk/itm/2014-New-White-Super-X8-Ebike-48V-1000W-Electric-Bike-48V-20Ah-Li-ion-Battery-/181566851332?pt=LH_DefaultDomain_3&hash=item2a463a4904

 

I like the clean look of this frame, not keen on basket batteries...just my personal preference.

 

Do you think that frame will be OK? I'm not doing anything extreme like ramps & jumps, just off-road, tree dodging!

I know it's not strictly the frame, but the bike doesn't have a front disk brake. The forks have disk brake mounts but you'd need to fit one.

That Prorider bike has all standard Chinese electrics, so everyyhing can be easily changed. A 48v battery requires a 48v controller too. A 48v upgrade would work on the road, but the motor woild be too fast for its power for off-road., so it woild run inefficiently and overheat.

That Prorider bike has all standard Chinese electrics, so everyyhing can be easily changed. A 48v battery requires a 48v controller too. A 48v upgrade would work on the road, but the motor woild be too fast for its power for off-road., so it woild run inefficiently and overheat.

 

I bought the 250w Pro-Rider bike yesterday with a 36v/10Ah battery. What I didn't realise is the wheel controller sits inside the frame underneath the battery, the cables run inside the frame which makes for a smart install. I left the charger on overnight as recommended by the seller and took it for a short 5 mile run using a mix of throttle only & assist....not bad.

Undecided if I may sell the whole bike (the neighbour seems very keen on it) and go for a custom larger set-up. Maybe 500w rear/250w front.