View Full Version : Electric Scooter Build

11-26-2012, 05:52 PM
Planning to build an battery powered scooter. :cool: I'm using 4 12v batteries & can get a 48v motor for a few dollars more than a 24v & they're both the same size. Which should I use & why? Thanks!

11-26-2012, 06:08 PM
Well, this is right down Evan's alley, so I'll be interested in his opinion. One advantage to the higher voltage would be lower current (smaller wire/controller, etc for the same power). One advantage to 4 X 12V set up as 24V series/parallel would be a greater current supply and perhaps slower voltage drop. Speaking of voltage drop, I assume you are using lead-acid batteries which will have a pretty early and consistant voltage drop with time in use. What are your early thoughts?

11-26-2012, 06:23 PM
Know zip about this really, but would 6volt golf cart batteries be of use?

11-26-2012, 06:39 PM
I plan to use 4 12v 18ah lead acid batteries.

11-26-2012, 07:17 PM
Better mount an engine crane on the rear for unloading machines, with of course a good counterweight on the front. Lol

11-26-2012, 08:39 PM
One consideration is that 48 volts is just getting into the range where some electric shock can be felt when you put your fingers where they don't belong. You won't feel 24 or 36 volts , unless you're disconnecting something with wire coils that create a field breakdown voltage. Still, the lower current with a 48 volt system is attractive.
Perhaps other factors such as available speed controllers will make your decision for you. High currents can also play havoc with solenoid contacts , creating an arc that's hard to stop unless you disconnect the batteries. I found that out the hard way, and almost burned down my electric car. But, I was running about 96 volts.

11-26-2012, 09:18 PM
Using the higher voltage usually means lower losses where there is any resistance in the circuit. This includes wiring, brushes, protective breakers or fuses, electronic speed controls, etc. Besides the potential shock hazard, the higher voltage might narrow the capability of finding a suitably rated speed control. You would probably want one rated for 150 volts at least if you're using a 48 volt supply.

As chipmaker said, the 48 volt source can be reconfigured as a 24 volt or a 12v source. In a sense it could be like having a transmission. All batteries in parallel would give 12v, or slowest speed, and might help you get home if you've run the batteries down fairly low. A series/parallel connection gives you 24 volts, and twice the A/H rating of an individual battery. This might be equivalent to second gear, and would also give some 'limp home' capability. All in series of course gives the full 48 volts, which in addition to giving the fastest performance also is the hardest on the batteries.

Being able to switch this configuration on the fly lets you have three speeds without needing a speed control at all, but you also don't have any control over what speed each setting would give you. I don't know how big a deal that would be- I thought of doing this with my electric, but I ended up with a 12v motor and two six volt batteries.

Another point which might be worthy of consideration is charging the batteries. If you switch them into parallel, you can charge them with a common 12v charger. In either 24 volt or 48 volt configuration you would need a custom charger.

11-26-2012, 09:31 PM
Great ideas! I like the changing voltage idea. The best of all worlds.

The Artful Bodger
11-26-2012, 09:47 PM
All solid state controls are probably the best technology but as I do not have much experience in them and any such vehicle I made would be a continuing 'work in progress' I would be planning for a series of relays. However as this is a 'home machinists' web site I should probably be considering a custom made contactor with a series of cams or contact patches on a single shaft controller, thats what they did in the dawn of electric vehicles.

If you do not have the motor you might consider a brushless route, maybe a Fisher and Paykel or similar washing machine motor, I think LG make the F&P motors too now. They are big stepper motors and if one wont drive your scooter two probably would. Stepper motors are considered to require complex electronic controller but not so. Porsche The Elder made an electric car more than a hundred years ago which had a form of stepper motor in each front wheel and a rotating contactor drum under the seat to control the motors.


BTW, the washing machine motors have three series of coils whereas most steppers have only two so any commercially available driver that would suit may be hard to find.

11-26-2012, 10:01 PM
Another adventure! :p

Mr Fixit
11-26-2012, 10:44 PM
Hello flylo,
You will find a lot of information here at this site http://www.diyelectriccar.com/ it is just for the DIY type of project you are considering. The most common type of control for electric power vehicles is power modulation control done with controllers like the curtis brand.http://www.curtisinstruments.com/. You will find that the key thing to batteries is the amp hours that they can put out, the higher the amp/hrs the more run time you get.

One of the reasons that I joined this site and got into machining was to produce an electric car, still on the mind but far away from becoming a reality.

EVguru on HSM might be a source of info, I think EVguru is a poster on the DIY electric car site (just a guess on this last idea) when you start reading posts his name shows up. Not connected with Curtis instruments just the most populor name brand used.

Keep us informed as to what you come up with this could be a interesting build.

Mr. fixit for the family :)

11-26-2012, 11:14 PM
Oh man, for a home shop guy this is a wide open field. You could even build your own motor, or make one motor out of two, etc. I did this last thing a couple of times with windshield wiper motors. I used both commutators, all the magnets, and all the laminations. Of course the shaft had to be longer, so the build required both motors to be completely disassembled, down to a pile of armature laminations. With a commutator at both ends of the lamination stack, you get the possibility of a series or a parallel connection. If both sets of windings use the same number of turns, you can directly parallel the connections. Or you can wire them in series- the effect is similar to the battery switching scheme. Wired in series, the motor runs slower. In parallel, it's faster and draws more current. If the windings are a different number of turns, you can drive the motor using the fewer turns comm, then use the other one to feed voltage back to the battery for braking. You could also use this higher turn winding to run the motor, in which case it would be slower turning. All this without the benefit of a speed control.

But, it's a lot of work re-building the armature, winding it twice, tying the windings, epoxying or otherwise fixing the windings in place, balancing it dynamically, etc.

The washing machine motors are interesting. Basically they are a 3 ph motor, but need to be timed to run properly. All the ones I've seen have had some form of electronic sensing circuit built into them. You would need to know the circuit to be able to make use of it. I think they're easily good for one horse, maybe more. If you were to replace the ferrite magnets with neodymium ones, you could easily get five horse or more from it. It would be an adventure in rewinding, cooling, power electronics, etc.

11-27-2012, 01:21 AM
The problem with using battery switching or relays to control it is a lot of jerky movement. It's especially vexing at low speeds.

Modern controllers are so cool, and do such a good job that it would be a shame to use a hillbilly solution.


11-27-2012, 02:04 AM
Go for 48 volts. The higher the voltage the better the efficiency, and it matters a lot. I presume you are looking at the Electric Scooter Parts website?


Good place to shop. I have bought various items there. Use a solid state controller. I built my own and it was worlds ahead of switching relays which I also experimented with. They are relatively cheap.

11-27-2012, 02:06 AM
Dan has a good point. Maybe battery switching doesn't have a place in the driving cycle, except perhaps for the limp home mode as I suggested earlier. There is one other advantage to being able to reconfigure the connection of several batteries through mechanical switching, and that is that it becomes possible to go through a complete disconnect of all batteries. This means that there is nowhere that a voltage higher than 12v can exist. A high voltage battery pack can be rendered fairly safe to work on or around, as there would be no shock hazard. You still don't drop a crescent wrench across the contacts though-

11-27-2012, 02:15 AM
You will find out real quick that when you are working with an electrical drive system of any voltage there are a lot of ways to make things let out smoke and fire in a big hurry. Use a master switch on the system so you can turn off the batteries quickly and easily before you do any fiddling.

Like this:

The Artful Bodger
11-27-2012, 03:31 AM
The washing machine motors are interesting. Basically they are a 3 ph motor, but need to be timed to run properly. All the ones I've seen have had some form of electronic sensing circuit built into them. You would need to know the circuit to be able to make use of it. I think they're easily good for one horse, maybe more. If you were to replace the ferrite magnets with neodymium ones, you could easily get five horse or more from it. It would be an adventure in rewinding, cooling, power electronics, etc.

They are only 3 phase motors in the same way that steppers are 2 phase motors. There are a variety available now but the original F&P motors had something like 42 poles and fourteen magnets (those figures may not be exact). One of the delights of these motors is that each of the poles is easily accessable and can be easily rewired (no need to rewind) into various combinations of series and parallel. It is an easy job to fit neodymium magnets to the rotor. There is a Hall effect (?) transducer that you need to time the pulses if you want to run at higher stepping speeds.

11-27-2012, 07:57 AM

11-27-2012, 04:20 PM

11-27-2012, 07:35 PM
Thanks for the great links, I will post some ideas & links when my computer is back & I get off this stupid tablet:mad:

Errol Groff
11-27-2012, 09:29 PM
There was a multi-part article back in 02/03 in HSM about building a "Vandy Electric Scooter". Might be worth check out.

12-01-2012, 08:32 PM
One electric car I built a number of years ago used, as drive motors, war surplus Jack & Heinz generators from aircraft . I wired them to use a separately excited field , and ran them at a maximum of about 96 volts. These generators used to be readily available in surplus catalogs, and were usually sold as welding generators. They were bullet proof, and would handle 400 amps with no problem. For a power controller, I wound up using a rather crude logic box of solenoids, diodes, and step voltages , but the power transistor controller I never finished would have been much better. Now days, superior controllers are readily available, as are more efficient motors. ( And by the way, outgassing acid fumes from lead acid batteries under load will eat holes in your pants. I know this for a fact ! If using lead acid batteries, provide for the removal of such fumes from your vehicle battery area.)

12-02-2012, 07:51 AM
Your projected voltage is right in the group that includes industrial trucks like taylor dunn and also golf carts, parts should be easily available off the shelf. If you like e-bay there are many that can be had for cheap. I own an old taylor dunn 1 ton 3 wheel flat bed with a 5 speed mechanical resistor controller. I like the mechanical over taylor dunn's IC controller, but again there should be a lot of equipment to choose from.

What I would really like to see someone build is an engine/gen set coupled to an electric drive like a locomotive only small.

12-02-2012, 08:48 AM
Just in case you have not seen it, this is a thread about a scooter I built for one of my sons a while back. While I suspect this is not quite what you are looking to build, there may be an idea or two here from my work or in the many insightful comments that were posted in the thread.


12-02-2012, 10:43 AM
Is it possible to take the output from a Curtis PWM controller that's rated for 24 -> 48 volts and drive some higher-voltage-rated transistors/mosfets/whatevertheyuse in order to utilize a battery pack of 120 (or more) volts? The reason I ask is I've found some of those Curtis controllers on electric pallet jacks and golf carts at the scrapyard. In fact, I've completely rewired an old Club Car golf cart from a solenoid/resistor speed control to a Curtis PWM outfit. It works great and has been lots of fun. Even used a solenoid reversing control from a pallet jack by inserting a 15 ohm resistor in the coil circuit. Pallet jacks seem to be mostly 24 volts, my golf cart is 36 volts.