How to build a 96-Volt Electric Motorcycle

Step 4: Where to put those batteries!

4 of the 8 batteries went on the sides (replaced the mufflers). I hung them with Uni-Strut channels from where the old side-handles used to be). I'm starting off with the cheapest sealed AGMA lead-acid batteries I could buy. If I like the results I will upgrade them to some high-end lead-acid batteries. When the price is right I'll go NiMh or Li-Io.

Comments

[calibran]

I was wondering on the battery issue. Would it be possible to addapt the Makita 18v Lithium-Ion batteries linked in succession to create a better power source at a fraction of the weight and price?

[Disc Dog]

You could do that, but in order to get the amp-hr capacity you will need A LOT of batteries (probably about 10 sets of 5 each (for a 90-volt system) just to get an equivalent capacity. It may be lighter, but I doubt it's cheaper. Amp-hrs are Amp-hrs, and you need a lot of them to run a vehicle. Volts give you speed...amp-hrs give you range. Mike

[The Lightning Stalker]

Watt hours give you range.

[phephq]

watt hours give you power amp hours give you range volts give you speed

[Disc Dog]

Kinda...sorta... but not really. Watts are the product of volts times amps. Watt hours give you driving time, but at 10 mph an hour is still only 10 miles. You need volts to get you up to highway speed, not amps. Then you need amps to get you down the road a bit. I know it's symatics, but it's true. High watt hours at low volts won't get you very far compared the the same watt hours at higher voltage.

[timstandley]

if ahrs is what gives a electric motor its range then on a motor cycle why not pull a battery pack on a small trailer or a side car.

[Disc Dog]

Some people have done just that. But the bottom line is that motorcycles are not very aerodynamic. As a matter of fact they are some of the least efficient vehicles on the road. If range was your primary concern then it would be far more efficient to convert a small car (like a Metro) and use it to haul all those batteries around.

[The Lightning Stalker]

Coming from someone who has so much experience with motorcycles, I find that comment surprising. Not considering the size of the engine, motorcycles have only 2 wheels instead of 4. Moreover, they are much thinner than a car tire. Less rubber on the road means less rolling resistance. Need I go on?

[ProfessorJWN]

The largest factor affecting Cd is the rider.  IF you want a motorcycle to go REALLY fast, build a low Cg shell for the bike to slipstream the air around you.

The contact point of the tires on the road is only (max) of 1inch long by (2/3) the width of the wheel approximately.  You can double that or triple for some cars (with radial tires).

On the same token, the turbulence of the spokes are also a drag factor on bikes.  If possible to place disks inside the rims, that would reduce the rotational turbulence, but you then become a  "sail" in side winds.

Bottom line, wheel drag is negligible compared to the rider.  Fairings can only do so much.  To reduce drag to appreciable amounts requires an envelope around the entire bike (look at HPVs and how those are made) this is one of the ways they can reach higher speeds.  Again on a bicycle, the rider is one of the highest drag inducers.

Trouble is that you COULD create an air foil on the front of the bike to create a shockwave and "build a bubble" around the vehicle, but the bubble would only form at reasonably high speeds which would be unattainable with the induced drag of the rider.

When you are "raciong" with buddies, have you ever "leaned down" to get speed?  Well that illustrates it better than perhaps I have here.

When it comes to bikes and CG we are our own worst enemy!

[Disc Dog]

I know, it does sound counter-intuitive, but because 2-wheeled vehicles cannot take ground-effect into consideration their Cd (Coeff of drag) is very high compared to that of a car. And they need that high Cd because they need to force the air through them (for cooling) where cars get to suck the air through using ground effect (which lowers their Cd even more). With only two tires on the ground they do have much less rolling resistance, but it is not enough to make up for the massive difference in Cd. I will agree that some of the newer, water-cooled, tank-hugging crotch rockets have a pretty low Cd (of which this bike is definately not one!), but still I dare say it's 5 times more than a small, light aerodynamic car would have. Look to the Aptera to see what the perfect design for a electric car/motorcycle would be.

[miron721]

I saw these batteries on Sparkfun, and I figured they might be good. Since I have very little knowledge of batteries, I'm just going by amps, but they seem to be better space-wise than car type batteries. I want to try building one of these, but I need more information on like circuit breakers used, if any. Also, the circuit for charging the batteries. Also, how are the batteries wired? Series, parallel, some combination? I need more info, I don't know this stuff on my own, heh.

[miron721]

Wow. It would really help if I gave a link.
http://www.sparkfun.com/commerce/product_info.php?products_id=8484
Heh, this is what happens when I don't sleep.

[drummer4848]

I have a BMW which is shaft drive. Where did you get your jack shaft, drive belt set-up? I like you need a way to seal between the jack shaft and drive shaft since BMW's run a wet drive shaft.

[Disc Dog]

Drummer, Ooooh...you have a tough one. The shaft on my bike is dry so all I needed was a 'plug' (made out of a piece of ABS plastic) that had the same OD as the inside of the rubber boot and an ID just slightly larger than the OD of the splined coupling I took off the output of the motor. The coupling has a CV joint on it (probably like yours) whose OD could be turned smooth to accept a common size of seal. I suspect yours is the same. I'm also thinkin' that you have a rubber boot that you could use to seal against. If that's the case, then you will need to get a local machine shop to turn you out a disk that has the right OD for the rubber boot and the ID for a common, press-fit seal (both Motion Industries and Grainger sell seals, drive-belts, sprockets, as do most other industrial/commercial supply stores). If you can get it out, you might be able to use the mating shaft that comes out of the motor's tranny as a jack-shaft. Take it out of the tranny and it might be long enough to turn each end down to fit in a pillow-block bearing like I did. You can get those bearings at Grainger or MI too. If you can use it, then you can use the CV joint as is. If not, then you 'll have to do as I did and make a simple jack-shaft arrangement with a piece of bar steel and a couple of pillow-block bearings. If that's the case, have the machine shop bore out the spline (in the CV joint) to a common, keyed shaft and run the jack shaft like I did into the modified CV joint coupling. This may not make sense until you look at the parts I'm taking about. If you still have problems, get back to me as I am sure a couple of decent photos between us may get it done. Mike