So, you just got a electric scooter, but you're not the type of guy - or gal - who thinks that you ought to stick with that underpowered old stock motor and controller. Perhaps you want to take it out to a skate park and try doing tricks with it - or perhaps you just carry more books than the average student and you'd like it to make it to the top of the hill.. or maybe you want a insane 0-30 in a 2 seconds.. and you start looking at controllers and seeing all these terms that you know have something to do with electricity, but don't know what.. volts, amps, watts, amp-hours.. or, worse yet, just funny number-letter combinations like 210A, 500W, 30AH, 6 AWG.. well, if you've ever had that problem, then this article is for you.
Let's start out by thinking of electricity as being like water. (You experienced electrical people can just skip this part) Imagine that instead of electrons flowing around in a circuit, you have a water tower as the + on the battery, the water flows through hoses (wires), a controller (valve), a waterwheel (the motor), and into another tank.
By that standard, you can think of volts as being 'pressure' and amps as being 'flow'. The number of volts indicate how hard the water is pushing - how much it wants to turn the wheel - and the number of amps indicate how fast the water is moving in the pipes (wires).
If you think about it, a little bit of water moving very fast can spin something just as much as a lot of water moving very slow - and electricity works the same way.
The math for this (we promise, there's nothing hard about this) is volts * (times) amps = watts. And watts = power. watts = acceleration, watts = hill climing. In short, watts = good. Most people aren't used to thinking of power in terms of watts, so it might help of you to divide by 750 and think of horsepower instead - 750 watts is about one horsepower. The good news is that unlike gasoline engines, electric motors can make their maximum rated horsepower - or often considerably more - over a wide RPM band. So in fact a 1 HP electric scooter is going to beat a 1 HP gas scooter every time. [Look for a upcoming ESM article explaining some of the many advantages of electric drives over gas ones]
Now, just like a water wheel, a motor's top speed will be governed by the pressure of the electricity - that is to say, with a permanent magnet or series wound DC motor, the motor will reach a speed where it doesn't want to turn any faster, and that speed is controlled primarily by how many volts you're feeding it.
Thusly you can see, if you want the scooter to move fast, you'd better either give it a lot of pressure, a lot of flow, or both. [Ideally, for laying those nice fat tire tracks as you're pulling out, you probably want both.]
Another number you may see is AWG, or wire 'gauge'. For this, the lower the number, the less power will be lost in the wire. In other words, AWG, lower = better. Don't go too far, because there comes a point where the weight of the wire costs you more than the power output gains you. I like to use between 10 and 6 AWG for scooters.
The last number that comes up regularly is amp-hours. This is a measure of flow over time - X amps * (times) Y hours. Sounds complicated, but it's really not that bad. 1 amp for 1 hour is 1 amp hour. 2 amps for 30 minutes is one amp hours. And so on.
A real world example: If your scooter advertises as a 600 watt model and has a 24 volt battery pack, then it should be drawing 25 amps wide open. [600 / 24 = 25] Thusly, if your scooter had a 25AH, or 25 amp-hour battery pack, you could drive it for one hour. Theoretically. In a perfect world.
Unfortunately, this isn't a perfect world. A friend of mine likes to say, 'There are liars, damn liars, and battery salesmen'. And sadly, it's true. Most batteries, especially the lead-acid batteries commonly used in sanely priced electric scooters, are only rated for 17AH if you take the power out of them over a 20-hour period. Since most of us don't drive our scooters around at .01 mph, this rating is really more or less useless to us. In the real world, we're lucky to get 10AH out of a battery with a nameplate rating of 17AH. Especially if the battery is cold. [Look for a article on care and feeding of batteries in a future issue of ESM!]
Now we reveal a few dirty little secrets (ahh, the real reason you came). First of all, some of the lost power in your scooter - power that comes from the batteries, but never makes it to the wheels and thusly the pavement - goes into heating up wires, both outside and inside the motor. We won't get into the hairy math on this particular one - but if you're curious, search on www.google.com for 'ohm's law' - but here's where it gets cute: if there are more volts, then you need less amps to get the same number of watts. And, the wire doesn't care how much 'pressure' or voltage is in it [within reason!], only how much 'flow', or amperage. The motor cares at some point, but that point is usually well above the point they put on the nameplate - the result is, if you up the voltage, the motor and other wiring will actually run _cooler_ to do the same amount of work - your acceleration for nothing and your watts for free!
Now, a scooter is only as fast as it's weakest link, so you have to look at the scooter driveline and decide what that weakest link is. It might be that really cheesy friction drive that barely can transmit the amount of power the scooter already has, or it might be the scooter's controller, or it's motor, or it's battery pack. In our experience, it's most likely to be the controller and associated wiring that's holding you back - although adding a few volts almost always helps. Unfortunately, you can't just plug in more batteries and say 'whee, a upgraded scooter!'. There are several factors you have to take into consideration. First of all, the batteries have to physically fit somewhere on the scooter (or in your backpack if you're really going all out). Second of all, you can't have more voltage than your scooter controller is rated for - things will go *bang*, and the 'magic smoke' which makes the controller work will be let out. And third of all, if your scooter has a integrated fuel guage, you will have to do something creative to get it to work with the higher voltage. Hopefully we'll have a article on how to accomplish this in a future issue.
However, if you're trying to make your scooter take off like a bat out of hell, you probably need to upgrade the controller anyway. Most scooters have 30 or 40 amp controllers - something about staying ostensably street legal - and most of us really want at least 100 amps, especially when climing that gnarly 8% grade that every city seems to put between you and your favorite pizza joint.
You also can't forget about the charger - after all, you have to fill those batteries somehow! Make sure if you up the voltage, you up the charging system to go along with it. It might also be nice to upgrade to a charger with a bit more crunch, to speed the charging process up some. Chargers are usually measured in amps - indicating how many amps they can put into the battery. As you might have guessed, a 'empty' 17 amp-hour battery takes 17 amps for one hour to fill. Of course, it actually takes a little more than that - batteries aren't perfect, and alittle gets lost in the charging process.
There is of course such a thing as too much power. Not only because of safety reasons [look, fun as it might sound, please remember these are _scooters_! If your 6" wheel hits a big pothole at 60 mph, you're going to be road pizza!] but also because other parts of the scooter may not be built for it, and may break. The most popular canidate here is whatever moves the power from the motor to the wheels. [We'd call it a transmission, but calling a overpriced rubber band a transmission just feels pretentious]. Ultimately, you'd like a chain drive here, but if you have a fat, sprocketed belt you're also probably good to go a-hoppin' up.
It's worth mentioning that you should feel free to make any creative modificatins that occur to you - don't be afraid to try modifying a belt-drive plank to be chain-drive instead. Or even gear-drive, if you're really mechanically inclined. We've even joked about using bicycle transmission parts. And send ESM pictures of any really frankenstenien mods you do come up with, so we can share them with our other readers.
The other thing worth remembering is that when you up the voltage, you also up the top speed and the unloaded speed. You should be much more careful about going to wide-open throttle with the drive wheel slipping [i.e. in mud] or off the ground once your ride's voltage has been cranked. You could easily leave a few parts of your motor behind, and that's a really bad way to end a day's scooting.
On the other hand, when there is a load on the drive wheel - like, say, when you're driving on a flat surface - that extra voltage means a higher top speed. And we all know how we feel about speed..