Some pointers below:
Hepgreg said:
Currently running some 12v 15ah batteries. Range is good, speed is not.
For the same battery, range will go down when speed goes up, because air resistance will increase at the higher speed.
With SLA batteries, you'll only get around half their capacity using them the way EVs do; the capacity is rated by a method using only a tiny amount of current, vs the large currents EVs use, and lead-acid's ability to deliver is affected by how much current is being drawn much more than other chemistries.
Just changing the battery (assuming the new is equal in rated capacity and voltage, and is at least equally capable in current-delivery vs voltage sag) could nearly double your range.
Increasing the voltage of the battery will increase your top speed, more or less proportional to the difference in voltage from what it is now. (for instance, if you get 15mph now with 36v, then with 48v you'd probably get about 20mph, assuming the controller and motor can handle the increase in voltage, and also the power required to go the faster speed--they probably can't do it for long though).
I put a 55T sprocket on the wheel, definitely gained top speed, but lost acceleration & it puts alot of strain on the stock motor. I will probably swap back to the stock wheel sprocket until i can upgrade my motor & controller.
The sprocket change is another way to increase speed, but as you found it will proportionally decrease torque at the same time. If you need to stay at the same voltage, then the sprocket change is one way to do that, while changing the battery, motor and controller to one that can handle the proportionally higher current draw required to keep the same torque.
Which battery, motor, and controller to change to will depend on your ultimate goals, and your riding style, terrain, wind, weight of you and anything you carry plus the scooter, etc.
I recommend going to the http://ebikes.ca/tools/simulator.html and reading the whole page, then setting up different systems to see how they behave under your specific riding conditions/etc., to get an idea of how much power, how much current at what voltage, will do what you want to do with the system under those conditions.
It takes a bit to learn what it all means to you, but it's helpful in seeing the relationships between different things, which will help you figure out the general power level you need, and guesstimates for current and voltage.
WHen picking the controller itself, you should think about the features you'd like it to have:
--display? what should it show you? what controls should it have?
--brushed or brushless? (brushed is more efficient, but may need a bigger size and setup to give you the same low-end torque from a stop, as what you have now probably doesn't actually limit current so it'll just do whatever it can physically do until it burns up--brushless won't, it usually has protections against that).
--regen braking? on/off, or variable?
--user-settable/programmable? what type of things would you like to be changeable?
--square or sinewave? (sine is quieter) There's also FOC which is also sinewave, but more complicated and requires specific info about the motor to set it up, unless the controller's autotune/autodetect routines are good.
--sensored or sensorless, or dual-mode? (sensorless/dual works even when hall sensors in motor aren't working..but sensored startup is almost always smoother/easier).
--single-voltage, or wide-range? single-voltage means it only works with the particular voltage battery you choose it for. wide-range means it can work with a variety of different batteries, should you choose a higher voltage later for more speed or simply more Wh, etc, but it can complicate LVC (low voltage cutoff) protection of the system for empty battery, if it is autodetecting vs manually setting this in the controller. (the BMS of a battery will have an LVC too, but you don't wnat to depend on that becuase it is a safety shutoff that works when battery is *really* dead, and it's much harder on the battery to do this).
--current limit? how much current do you need it to supply to the motor?
Battery questions:
--chemistry? (generally this is between LiFePO4 and "Li-Ion" (which comprises a bunch of chemistries that are not usually specified by the sellers, but are not typically that important)). Biggest difference is it's easier to find a small pack that can output higher current in "Li-Ion" than LFP.
--current delivery? how much current does it need to supply? (this is determined by what the controller has to pull from it, worst-case--get a battery that can do say 20-50% more than is needed, so as it ages it still works fine.
--capacity? how many Ah does it need to supply? (how much range do you need) This is determined by how many watts it takes to run the system vs how much time it must last; often defined as Wh/mile or Wh/km; guesstimates can be made for various EVs for how much this will be vs how fast it needs to go vs conditions it's ridden under.
Motor:
--will it fit in the space you have? (will it stick out too far?)
--will the sprocket you have fit on the new one? (if not can you get one the same size to work?)
--what k/V (winding, RPM/volt) do you need to make it spin the right speed to drive your wheel the speed you want, at the battery voltage you're going to use).
--how much power (watts) does it need to do the job you need it to do? Is the cooling it will get in the spot it will go enough for the heat it will generate?
--is it sensored (with standard UVW / 3-phase hall sensors)? Or sensorless?
there are other things to think about but those are a start.
