Summer Ebike Build?

[blown240]

Im kicking around the idea of building a fat Ebike this summer. I have some time to think about it since I need to put some $$$ into my truck before I do another bike build.

I have this frame:

I would mount a rear wheel on the front of this bike, since it has 135mm front spacing. And I have this fork, the legs are 1.5" steel tubing, I have no doubt they could take the abuse of a 1000w motor:

This motor kit looks promising:

http://www.amazon.com/Aosom-Electri...456337215&sr=1-1&keywords=electric+bike+motor

And this battery? The batteries are clearly the most expensive part. Am I better off starting with 4 smaller 12v lead acid batteries?

http://www.amazon.com/Li-ion-Batter..._UL160_SR160,160_&refRID=0JVKV74AN48K51ZHPRBQ


What am I not thinking of??

 

[Fv2]

It keeps being said that the expense of an e bike is all upfront, I'd say if you're gonna do it you may as well spend the money. But do your research so the money is well spent.

I'd get the lithium battery, the 12v SLA's are cheaper but lithium is going to be a better choice in the long run.

 

[blown240]

Do you think that 1000w motor will be enough for a 100lb bike with a 240 lb rider?

And it will be on the front, since I am not aware of an electric hub for 190mm spacing.

 

[Fv2]

I'd say yes, if you're thinking 1000 watt 48 volt. I don't know what your max speed would be. 100# is a heavy bike, but my ebike probably weighs 50# and is 750 watt 36 volt and cruises about 15 mph with 200# rider.

 

[blown240]

The bike I would put it on is 50 pounds already. I'm not sure the weight of the electric kic, but I'm sure it's not at all light.

Looks like $700 ish would get me a decent setup.

 

[Fv2]

You're definitely headed in the right direction, hopefully some of the ebike folks here can help you out with the numbers and whatnot.

Should be an interesting build watch.

 

[blown240]

Thanks! The build won't start before April or May because I have to rebuilt the front end on my panel truck and I'm going to put power steering in while I am at it. Then I REALLY need tires.....

 

[Duchess]

That's a decent amount of power (EU law limits to 250W and I believe US is 750, but that may vary and who's checking, anyway?). What kind of range are you looking for? Of course, you're probably not going to run full power all the time, but if my math is right, running at max power with that battery gets you less than a half hour, or ~13 miles using their quoted top speed (1000W/48V=20.83A. 10Ah/20.83=0.48h). I personally hate SLA batteries—heavy and don't do well with deep discharges. Probably be about a quarter of the price of li ion, but their life spans are much more limited, so it's a matter of weighing that value and how much you think you'll use it. Also, all that shouldn't be another 50 pounds if you use the li ion batteries.

 

[blown240]

What would I need to get about 20-25 mile range? 20mph would be good too.

It doesn't have to be 1000w 48v, thats just the first one I looked at.

 

[Duchess]

Pedal more or use less of the potential power. Otherwise, it's a matter of a bigger battery.

Watts/Volts=Amps
Battery Amp hours/Amps=number of hours.
According to that ad, that 1000W motor will hit 28mph. Assuming that's correct, full power range=28 x number of hours.

Real world will vary, of course. You can also use this to figure out range at relative power. For quarter-power, say, just plug in 250W. That's assuming a single speed hub motor. If you went with a mid-mount motor and gears, that's a whole pantry of cans of math worms. More or less, the difference between a 1000W and a 500W motor is the greater potential of the 1000W—the 1000W would be about the same range and speed at half power as the 500W at full power.

 

[blown240]

Gotcha. That makes sense. So 1000 watt motor and the biggest battery I can afford.

 

[blown240]

It seems like a lot of the batteries that are 15-20 amp hours are only rated for 350-500 watt.....

 

[blown240]

I found 6 of these small 12v batteries in the garage. They are out of garage door openers. They are rated at 4.5 AH. I figure if I wire them series/parallel I can get 36v 9ah. And they are free, and I get more regularly from my bro in law....

They are about 3.5 lbs each though, so for sure heavy...

 

[Duchess]

Watts is a measurement of work and batteries store potential energy, so they shouldn't be measured in watts. Watt/hrs (potential work it can provide in a given period of time) as an alternative to Amp/hrs, but not watts. Picture it something like trying to measure gasoline in horsepower (one horsepower is actually about 745 watts, which is also a helpful reference when picking electric bicycle motors).

Those lead-acids are heavy, but you can't argue with free! For that price, it might be a good place to start and see if it's worth upgrading later.

 

[OCD]

You should consider spreading the weight of those batteries around the bike like I did with my first e-bike. Try to keep the weight as low as possible or it will really change the way your bike handles.

 

[blown240]

what are you running for batteries on that bike?

 

[OCD]

That bike is long gone, all that weight was too much for such a cheap frame and it handled poorly/was under braked. Likely had 40lbs of batteries running 4 x 12 volt for 48 volt 16amp/hr total. Lead acid batteries will only last a few months before you see the range drop off rapidly. I did not get mine for free and so for 2.5 times the price, went to 20 amp/hr LiFePo4 which were still heavy but lasted about 3 years of daily commuting use. I now use packs with Li Ion 18650 cells, only 16lbs for this 48 volt 30amp/hr pack.

 

[spinningmagnets]

Where did you get the heavy duty girder fork? Does it have mounts for a disc brake?