Have you ever wondered what all those numbers and letters mean when looking at an E-bike? The ones you read on a spec sheet or the ones printed on an itty-bitty font on a battery or electric motor. If you've ever wondered what all this information mean, don't worry you're not alone in this confusion. Definitions
Let's start by explaining what these letters mean. These letters are symbols used to represent a specific measurement of electrical energy. The three most common symbols when looking at bikes are “V” for Volts, “Ah” for Amp Hours, and “W” for Watts. Volt, or voltage, also referred to as electric pressure, is the measured strength of electricity flowing through a circuit. To understand amp hours let's first learn a little bit about amps. Amp, or ampere, is a measurement of how many electrons are flowing past a given point in one second. Amp houris a unit of electric charge measured over a period of time, or in simpler terms the potential charge capacity. Watt is the overall measurement of the potential power that can be generated or used. Performance
Understanding these definitions leads us to the question, “how do these numbers relate to the performance of my bike?” One analogy for understanding is with cars or any other gas-powered vehicle. Think of volts as horsepower, affecting speed and acceleration; amp hour as the gas tank, affecting the writing range of each full charge; and Watts as the engine size, affecting the engine's maximum power output. In general the bigger the number the better the performance. The higher volts increased torque and acceleration, helpful for easily reaching higher speeds. The higher watts increase the overall power of the engine, ideal for heavy loads and climbing hills.
With this newfound understanding let's look at some of the common options. there are three common volts when looking at batteries and engines. 24, 36, and 48 volts can easily be found, 36 volts being the most popular. If looking for a nice casual cruise around the neighborhood or at the beach, 24 volts is the perfect cruiser. If higher performance is more to your liking, 48 volts will have you speeding down the street in no time. Moving on to the engine size, if you're a bicycle purist looking for a little pedal assist, 250 watts is a great compact choice to give a boost to your biking experience. if you're really looking at climb hills or carry a large haul, larger engines like a 500 or even a 1,000 watt have all the power you need. In general the larger the amp hours the longer you'll be able to ride. Though, this usually means a bigger and heavier battery. For more visual learners, check out our video explaining volts, watts, and amp hours.
“Hi! Hope you can help me. I bought a 1000W 48v front hub motor for my DIY E-bike project and have four 12v 18Ah UB12180 SLA Batts wired in series to make 48v/18Ah pack. My question is: Could there be any damage to the motor if it can only draw 880 watts at peak? (I live in a city with lots of hills and weigh about 240 lbs and plan on using just the motor most of the time, minimal pedalling).
Also, the charger that came with the motor kit (it says it is for lead-acid batts) has ‘48v/20Ah’ on the box it came in, ‘2.5-3.0A Output’ on the bottom of the chrgr and ‘6v-250A’ on the plug going to batteries. ??? A little confusing ya think?
Anyway, assuming the charger is safe for my config, will it charge all 4 Batts simultaneously if wired to the same terminals that feed to the controller? Or do I have to charge each batt separately? And will current also go to controller? I assume (hope) the controller (which says is 48v 26A max on it) has one way diode or something to protect itself but could I fry the controller? (I also put in a 20A in-line fuse on the hot wire). This is my first e-bike build, so appreciate your comments and taking the time. I haven’t hooked up everything just yet, I’m really looking forward to testing it out, but just wanted to make sure I’m doing it properly. You have a great website here with so much knowledge, thanks again,