How to build a 72Volt electric motorcycle

Step 4 Wiring

If I tried to explain where to connect every single wire I would get writers cramp. View the wiring diagram that I put together and let me know if you have any questions. This diagram should be pretty accurate to how I built mine, but obviously you are responsible for your project.

Comments

[zeroemission]

so THAT'S how you hid the "extra batteries", you stacked them high and hid them in the gas tank! very clever. i imagine it makes the cycle a little top heavy, but it looks so much more finished like that.

have you ever thought about making side panels for "the engine compartment" to hide the batteries altogether? some carbon fiber would look slick there.

[wraithsqaud]

is there an advantage to wiring the batteries in series and converting the voltage for the bike systems down instead of wiring them in parallel and converting the voltage up for the motor

[DabeAltis]

Wraithsquad, since nobody ever really answered your question, I'll put in my two cents. There is indeed a tremendous advantage. The power that is downconverted to 12 volts to power the control system, lights, etc., is a very small percentage of the total power of the batteries, and therefore a relatively small and inexpensive DC to DC converter will do the job. If you went the other direction the converter would have to be much larger and much more expensive. It would have to handle the lion's share of the load and battery power. This conversion is not 100% efficient, therefore the power lost in conversion would much higher. The current from the battery pack would be at least six times as high, therefore would require larger conductors and would be much more susceptible to resistance losses. I realize your question is almost a year old, but I am new to Instructables. Hope you get a chance to read this reply, and I hope it helps to answer your question.

[knikol]

I think some of you may have missed one of the points regarding the voltage converter. Only the motor is operated directly from the 72-Volts through the controller. The voltage converter is only there to operate the 12-Volt lights, turn-signals and such. The author's approach is probably the best trade-off in efficiency vs. weight, as opposed to a separate 12-Volt battery for the accessories.

[wraithsqaud]

Thanks. That makes it make a lot more sense now.  I was not thinking about the inefficiency of the converter

[dillweed2]

The batteries are connected in series, (pos to neg) to increase the voltage. Voltage is electrical pressure, comparable to PSI in a hydraulic system. The higher the voltage, the better efficiency and performance of a product. That's why you saw cordless tools go from 3V to 7V to 14V and now 18Volts. Wiring in parallel ( pos to pos and neg to neg) is how you jump a car battery. Parallel increases the amperage or capacity of the system while keeping the voltage the same. Flashlight batteries are connected in series (a 5 cell would be 7 1/2 volts). That's why electrical companies transfer power in thousands of volts, less resistance is greater efficiency.

[Stryker]

I don't understand what you mean. But I'm no electrical engineer so I doubt I could answer it if I did understand.

[msee]

Assume 12V deep cycle batteries.

Series Connection
6 x 12 = 72 V
72V x 100A = 7.2kW (or ~10 HP)

Designing a motor/controller combination to handle this voltage and current range is pretty easy and relatively inexpensive. There are MANY currently available.

Parallel Connection
1 x 12 = 12 V
12V X 600A = 7.2kW (or ~10 HP)

Although a DC-DC converter can be designed to convert 12V 600A to 72V 100A, it will add significant cost and weight, and will reduce efficiency of the overall system.

A motor could be designed to use 12V 600A, but it too would be less efficient because...

Resistive losses are a function of I*I*R, so as current increases resistive losses go up FAST. The lower you can keep the current, the better. That is one reason why AC power is transmitted over the grid at very high voltages and then stepped down locally.

[Edvahass]

Hi,

How's this thing doing in the cold (like -20 degrees celsius)?
What batteries would you reccomend for a vehicle that should be able to drive in such temperatures?

Thanks in advance!

[Stryker]

It's doing fine sitting in my garage...... I would never ride a bike in that weather and I wouldn't know what batteries to use for that application.  Sorry but you better check with a battery dealer.

[malangjata]

Hello Star,
       I am just beginner in this research to build electric motorcycle and a self rechargeable if support met our our aims and ambition.My Malang Jatta a Gambian.I find it very difficult to my mine till now searching for fund and additional research i made through library and in internet.I need your advance and support.
From Malang Jatta (Dipl.Electrical Engineer)
I hope to hear from you.

[gwean]

Hi guys.....I'm very new to this EV thing but just curious - where is the clutch or transmission ? I guess that the power from this system is much less compare to the one people use in electric car ..... so a plain controller is just fine . Thanks in advance ...

[kagenin]

A transmission is required if you want different gear ratios. A clutch is used to transition between different gear ratios. This bike only has, and really only needs, one gear. You could conceivably add a gearbox to this sort of project, which could a) play with the acceleration curve (although many charge controllers can do this directly with the throttle) b) increase (or fine tune) the maximum cruising speed (at the expense of range) It's not impossible to add a simple 2 or 3 gear system into an electric vehicle - maybe have high torque/low speed gear for off-road, a normal cruising gear, and max-speed gear for freeway driving - but it certainly isn't easy, and can introduce a lot of complications to a design.

[Stryker]

I still think a CVT would help, but I'm no engineer.

[kagenin]

I'm no engineer either, but I've always been fascinated with Continually Variable Transmissions. It seems like pairing a CVT with an electric motor would help smooth out low-end acceleration while still providing you with a good balance between top speed and max range. The main issues I'd see would be any added weight to the design, as well as cost. Compared to the cost (and weight) of an extra battery, I'm not sure what's more economical.

[Squeezmo]

Don't diss parallel battery ops. Parallel is good when you need quick current flows.... ie acceleration.... but wastes a lot of chemical energy becauase all cells are at the same pot... when one fails they all reverse or whatever. There's more energy to use in other cells but it's not available. Series helps suck the cells dry (ie: range). I was on an electric vehicle that wired both ways. Electric Submarine with two motors. We'd flip the armatures between series for acceleration and parallel for efficiency.

[darchole]

first of all when i got to this step it was like i was looking at my own version that i made up on windows lol, of how the wiring and all that went but i dont think i had the stuff in the right places ,since ive seen your s and now know i have a little more knowledge but my i dea isn't for a motor bike , I have some ideas i think the right person with the now how "unlike myself" lol could make my idea " the big one" and get paid large for it thanks for the little know how my email is [e-mail] let me know lol, have a good one

[depayton]

You should build another one and see how much you can get for it on ebay. If you can get the mileage up I bet you would'nt have a problem selling them for around 5,000.00 since electric powered vehicles are in high demand and the demand is only going to get higher.