Electric Scooter Forum for Scooter Enthusiasts, Scooter Chargers, and Scooter Mechanics.

By admael
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#10391
TJSplash wrote:
Wed May 29, 2019 7:29 pm
The m365 battery is 36v (V) and the current is 7.8A (i)

To obtain the Watts (P) you must multiply the voltage by the current

P=V×i

280w = 36V×7.8A
The battery capacity is 7.8Ah, the output is closer to 15-20A
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By 365GUY
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#10436
Ok if that’s the case then what’s the point of changing the firmware to 800 or 1000 watts if the battery doesn’t have enough amperage to even come close to that ?

What am I missing here ?
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By LAskooter213
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#10621
Alright.....I need to cut the head off this shit before it gets out of hand. I got nothin but love for ya bro but youre a little off the mark. And thats ok. No one is born knowing this shit and electricity is particularly tough to understand because you cant see it. So allow me to break it down for you and make it as easy as possible to understand....
There are three characteristics that we need to consider to understand basic electrical fundamentals. Voltage ( electrical "pressure"), amps(or "current"....and it is the actual AMOUNT of electricity flowing in a circuit, and resistance (the obstruction of free current flow.)
Think of electricity sort of like the water in a garden hose. And your battery is a barrel of water that feeds it. The amount of water in your barrel is your capacity. Usually measured in MAh (milliamp hours)or Ah (amp hours) or Wh (watt hours). Ill explain more about that in a minute....anyways garden hose analogy......The hose is like the wire, the volume of water flowing through the hose is the current. The voltage is how much pressure you have forcing the water out of the hose, the resistance is the diameter of the hose causing a restriction on the amount of water that can flow. So an example of a high voltage low amperage circuit would be like a spark plug firing. Or to use the water analogy think of pressure washer or a water pick for cleaning your teeth. High pressure but low volume of water. Lots of resistance (in the air gap on the spark plug). Now on the flip side would be a high amp, low voltage circuit. Like a soldering iron for instance. Low resistance, low voltage, but a lot of amps to get it nice and hot. Think of a bath tub spout turned up halfway. Just puking out a lot of water but without much pressure behind it. Thinking of electricity like water allows our brains to visualize what is happening in different circuits. And since were talking about electric motors mostly on this forum, if you wanna go fast just think how you would configure your garden hose if you wanted to spray it at a pinwheel to make it turn as fast as possible. You would want as much pressure as possible, and a decent amount of volume...(but not too much or youll empty your supply barrel very quickly) and you will need decent resistance to hold that water so it doesnt flood out.... but not so much resistance that the water pressure blows the hose up. Do you get what Im saying? Thats why VOLTAGE IS SPEED in an electric motor, amps are kind of like torque and resistance is, well, it just is what it is. Now getting away from this water analogy you have to understand some basic laws of electricity here. Mainly Ohms Law. It states, among other things that the voltage and resistance in a circuit dictate its current flow. So in other words you dont choose current, it decides for itself. Its based on the voltage and the resistance of the load. If you plug a bulb into your battery....simple 2 wires...pos and neg....that bulb will illuminate. Your battery voltage is set.....it is what it is ( depending on what kind of battery youre running) and the resistance of the bulb is what it is (you cant really change that value...well yes temperature affects it, but for all intents and purposes the resistance of the bulb is a steady and predetermined value). So your current flow (amps) are decided by these two values. If you up the voltage then that added pressure can force more current into the load. The bulb will glow brighter. But you cant make it brighter or make more current flow through it by adding more batteries -in parallel- . Series, yes, parallel no. There is no way of making more current flow unless you increase voltage or decrease resistance. Voltage stays the same if you add an additional battery in parallel. *Capacity* increases. So your bulb will glow LONGER, but not brighter. Which brings me back to milli amp hours and battery capacity ratings. What these numbers mean is how many hours your specific battery (when fully charged) can flow 1 milliamp of current for, before the battery is dead. Its a measure of capacity...not discharge rate or current FLOW. So using the water analogy its like saying how long can your barrel spill water out of a 1" hole for before it is empty. It measures how much power your battery holds in total. Not how much it can deliver to a certain device at one time. In the case of motor controllers, the controller itself is what controls and limits the current flow. And it does this by modulating voltage and resistance in the circuit. Think about it. When you first take off the controller is LIMITING your voltage and increasing it as you give more throttle. Otherwise you would be stuck going full power all the time. Current is also limited by a fuse in the circuit, it will blow at whatever current its designed to blow at. This is to protect the circuit from too much heat. I think the m365 bms is fused with 2 15 amp fuses (I may be wrong but I think thats accurate) So that battery can flow 30 amps of current before the fuses blow. The battery is CAPABLE of flowing a lot more current than that, even if its just a few cells...thing is, it will get so hot it will self destruct. If you want to see what I mean just short the battery pos and neg together and watch the fireworks show. Thats a shit load of amps! The battery is CAPABLE of producing a shitload of current if there is no resistance in the circuit. But you cant push too much current or things get too hot and the battery takes damage or just drains itself way to fast.
The controllers CAN be programmed to let you use more current if you have a greater capacity. But the capacity in amp hours has nothing really to do with the power you can make. Its the voltage at a given capacity and the resistance in the circuit that ultimately governs current flow.

Hope this makes sense and helps you guys to understand the principles of electricity a little better. Thats how I was taught and it made a lot of sense to me. And dont worry if you still dont get it, with experience and experimentation you will learn all this shit and it will become very clear. I suggest that everyone make a test bench and buy a multi meter with an inductive amp probe.. Sacrifice one motor, one controller and one battery pack and it will pay dividends in the knowledge you will acquire. If you just fuck with things for a while and measure the different values on a circuit you will see exactly how it works and know how to manipulate things to better suit your needs. Remember ONE SOLID TEST IS BETTER THAN 1000 OPINIONS. Be the dude that can back his shit up. The term "science " was derived from Latin and roughly translated the word meant "prove me wrong" . If you have the data, you are in control. And electricity has and always will obey the laws of physics and thermal dynamics and is predictable and able to be manipulated into doing amazing things.
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hahaha couldnt help it
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By 365GUY
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#10626
Thank you for taking the time to do that very informative write up. You are very knowledgeable and have the ability to educate without coming across as a know it all which is rare. So I appreciate your posts, I always seem to gain some knowledge from them.
And yes +1 on having a test setup to experiment with.
I’m currently experimenting with my Brain Power 350 and 1000 watt controllers.
I am building up that 3 wheel scooter I got for my mom since she likes the other one I bought her better. It’s way safer and more comfortable for her, plus I didn’t feel confident about her safety on the trike.
So I ordered some different things for it like a knobby front tire and different handlebars and replaced the front down tube with a 365 setup. And I added a hub motor to the back of the scooter to keep it from flipping backwards.

I just have to design a battery compartment for the front and wire it up. I’m hoping it will go around 25mph.
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