Good questions but the answers get big. There are many variables, rider weight, health, terrain, bike type, size of electric system, etc. I will try to keep it simple.

You are halfway there, i would just rearrange your formula in order of general importance. Volts x Amps=Watts.

Volts = speed. 24v = 15mph, 36v = 20mph, 48v = 25mph. This is the average kit and average battery, on flat ground with the average 200lb new ebike rider, average old 26" mtb conversion, etc.

Amps= torque. Climbing and pulling power. Also called current. Amp draw is set by the controller. Most 48v kits come with a controller in the 20-30 max amp range. More amps = more heat. Too much heat and parts get fried.

Watts is just a number, a result of Amps and Volts. "Watts" is usually a label slapped on a motor by a vendor to sell it. How much it can handle depends on how much copper is inside and how fast it can shed heat. A name brand motor rated "750 Watts" can often handle 1500 watts+ for short bursts and not overheat.

So the rated wattage is helpful in general as a guideline, but it is more helpful to know the number of windings inside the motor. This will also determine the rpm of the motor. For a typical 200lb+ rider at 48v on an old mtb look for a lower rpm motor around 3-400 rpm for more torque to start from a stop, climb hills, etc.


Not sluggish. Sluggish means bad parts, hooked up wrong, weak battery. This is an efficiency question. For a typical 750 Watt geared hub motor max efficiency comes around 2/3 throttle, cruising speed around 18mph on the flats, with some pedaling, to get the least heat, most range from the battery, longest life from the system.

3000 watts is a really big direct drive (DD, no internal gears) motor that needs a 60 Volt+ system to get the most out of it. 40 amp+ controller and a big, expensive battery and will suck down a lot of juice for sustained speeds over 30mph that can be dangerous for a first-timer on an old beater in traffic. Yes it will run at 1200 watts but not to its full potential (speed) so why waste the money when a smaller motor would be fine. Better yet a geared motor for more torque at lower amp draw than DD.

Bafang is a good name brand that has been around for a long time in ebike terms. Chinese brands come and go, look for a proven name that is affordable. As for cyclone try a search on endless sphere for user input they test everything over there.

Controller. Most ebike kits with a decent name have the controller matched to the system. At 48 Volts and 200lbs+ you'd want a 9 fet controller at 25 amps, and a 12 fet at 30 amps. Fets are terminals inside the controller that shed heat. If you go higher than 30 amps you really need to start looking at fet brands, custom controllers, etc = more money. A 25 Amp controller is fine for a first time build at 200 + lbs.

As for the battery.

First is Amp Hours, also called capacity = range. Average is 1.2 to 1.5 miles of range per Amp Hour without straining it. More range if you can pedal, less range with hills, etc. Cell quality and type have a lot to do with battery performance. Also the bigger the battery the easier it can handle short bursts at full throttle without overheating the cells inside = longer battery life.

Lithium Ion. "Lithium Ion" is a marketing term that doesn't mean much other than some type of lithium instead of lead. Lithium batteries are now cheap enough that "lead is dead" for ebikes.

Types of Lithium ebike batteries.
Lithium Nickel Cobalt Manganese (NCM) or Lithium Nickel Cobalt Aluminum (NCA) are the two current popular chemistries. NCA is the top of the line also more expensive. These are usually "18650" batteries which refers to the size, slightly larger than a AA cell. Light weight, high power, easy to use, last a long time, sold in many pack shapes and sizes also hard cases, relatively safe.
18650 cells are spot-welded together with metal strips wired to a circuit board (BMS) for protection. They are not user-serviceable without welding equipment and a lot of time/patience/small parts so it is important to buy a well-built pack with good cells (Samsung, Panasonic, etc) from a good vendor if you want it to last.

LiCo (Lithium Cobalt) is an older chemistry replaced by NCM/NCA. Cell makers are constantly upgrading chemistries to make batteries lighter, more powerful, safer.

LiFePo4 is an older lithium chemistry with less power than NCM/NCA, heavier, cost almost the same, more stable chemistry. They are roughly the size of c-cell batteries. They are more user-serviceable because the ends are screw connected, not welded. Also have a BMS wired in, usually come in plastic shrink wrap. They have largely been replaced in the mass market by NCM/NCA.

LiPo or LiPoly was swiped from the electric toy market, RC helicopters, etc. They are light, powerful, cheap, unstable. No BMS and you have to build your own pack with a rat's nest of wires. They have burned down houses from overcharging... also can burn from over discharging, or from being punctured in a crash. A hidden expense is you have to buy a bunch of monitoring equipment so they don't overcharge/overdischarge and burn. You have to babysit them while charging, store them in a fireproof place, etc. More for the track racing crowd, not for the new ebiker unless you already own toy planes with the knowledge and spare time to handle them.


If you build an ebike you will know how to replace the parts, the physical replacement is easy. With a $15 digital volt meter (dvm) you can figure out which part is malfunctioning. With a good set of wire crimpers ($10) you can often repair a cheaper system by replacing cheap connectors with better quality ones from ebay or amazon, etc. Cheap connectors often fall apart so a dvm is a must. A dvm is also a good tool to keep an eye on the state of your battery.

It is more about quality. The ebike pros say "don't cheap out on the battery." It is the heart of a system and the most expensive part to replace.

If you stick with a known motor or even a cheap kit from a seller with good feedback you should be fine. Especially through ebay or amazon if you need to exchange in 30 days. if it lasts 30 days it will probably last a couple years or more as long as you take care of it. You can always upgrade the motor or controller down the road, even from china. Eventually you will probably want more power. Learn how to build a wheel and you will save a lot on shipping. On all kit wheels you will need a spoke wrench, often right out of the box on the cheap kits. Or stick with mid-drive.

DIY ebikes are are mostly cheap old mountain bikes, with experimental chinese wiring and parts so that a chinese battery can push 200lbs+ down the road, up hills, etc. They are expensive for what you get, but cheaper than a car, don't need registration like a motorcycle, etc.

About every 6 months a new ebike technology makes it to the mass market. There is usually a 2-year run of the new stuff so new/old are always overlapping. Not all the new stuff is an improvement or well built. Look for what people have been using for a while, a bonus is the price comes down after a year when the next big thing hits the market. Right now you can get a good beefed up 48v kit with 11.6ah NCA pack for under $1000 shipped. Or a usable ebay/amazon kit + battery for $500 or less.

If you buy from china "you are the quality control" especially on the battery, costs too much to ship it back and forth, language barrier, shipping delays, etc. If you can stick to a us vendor you might get some warranty service. On cheap ebay/amazon kits you can at least get a refund if it doesn't work. hope this helps