What is battery grade “C”? Is it important for electric skateboards?1 week, 5 days ago | 0 Replies
I remember when I was building my first electric skateboard, there was a complete emphasis on what parts to buy, mainly because I didn’t have the money to make any mistakes. I want to make sure I buy all the right and most suitable parts for work the first time. I’m on a tight budget, but I don’t want to skimp on what’s important.
Here are some of my search queries for “What is the best battery” “Most powerful battery” “Best Battery chemistry” “Peak Power of electric skateboards”The problem is that when you start working on something like this, you end up with more questions than answers… Remarkably, after three years of reading and testing batteries, I’m still learning… So maybe I’m just a slow learner! But let me tell you, there’s a lot of crap to filter out.Anyway, after a few weeks of reading, I decided to buy Lipo because I learned that they have a very high discharge rate and high power density. That means they have a lot of power per gram. So they must be good!
So how do you determine the discharge rate of a battery?Fortunately, it’s clearly written on the label. The following batteries have a “C” rating of 20C. This means the battery can reach peak output at 20 times its capacity.So what is capacity? Thankfully, it’s also on the label of all batteries, the one below is 3000mAh or 3Ah. So this battery pack can output 20 x 3Ah, giving the battery a rated peak output of 60Ah. You can get Lipo batteries with higher C ratings as well as batteries with higher mAh.
My first electronic board battery was 8000mAh 30C Lipo, so 30Cx8Ah = 240A output! A: wow! A lot of… So my board will be much better, right? . Not necessarilySo now you know how to determine the output of any battery, but that information is useless unless you know how much power your electric skateboard needs to run.
So how much power does an electric skateboard actually need to move a person from a stationary position to top speed to rip the ball?The solution to this problem is to purchase a wattmeter and install it on your electronic board. It is connected in series between the battery and ESC, and it allows you to read out the power passing through it in real time.
It shows you peak amperes and watts, as well as voltage. So you connect it to your board and look around to see how much power you’re using.Build tips You really don’t need to permanently integrate any of these into your eSk8. The information it displays is well worth knowing at first, but once you know the performance of your board, the information really doesn’t change, so it adds weight and unnecessary wire volume, and it’s dangerous to look down at your feet while riding!You’ll notice that it peaks when you start at rest, it peaks when you go uphill, and basically it peaks when the motor has a load pushing it, but cruising on your board should only use 15-20A power. In fact, you want low numbers and not high amps.So don’t brag to your buddies about how awesome your 6KW (24V X 250AMPS) electric skateboard is!
I can assure you that if your electric skateboard pulls too many amps, you will not be able to use it for long, and your battery may be damaged by discharging too quickly and overheating. What you want to build is a skateboard that is energy efficient when moving mass and doesn’t get hot even when hitting large hills. Heat is wasted energy!
Using too much power on an electric skateboard is like bragging about how much black smoke your car’s muffler belches out. It’s not that you have a really powerful eSk8, it’s that you didn’t design the drivetrain correctly. My design philosophy is strong, efficient and robust. These features must be balanced or they will fail. Having power and using it effectively are two different things. Therefore, if your setup is underpowered to your load (read “weight”), it will not be very efficient.So yes, your motor may be rated at 2400 watts (2.4 kW), your Lipo may be able to output 240 amps, you may have a 150A continuous electrical tuner… But you really don’t want to peak… It’s way too hot & the heat is bad! .
The best electronic boards will have an over-engineered power system with built-in safety features to prevent disasters. Especially in the battery, if excessive discharge or discharge too fast, will greatly shorten the battery life. Therefore, you need to be able to limit the power of motor and ESC requests. You can do this either electronically or mechanically by reconfiguring the driveline ratio.Brushless Outrunner motors are hungry little monsters… If they continue to be fed juice without a reduction in a given load, they simply want more juice. This can happen if you try to ride a mountain on an underpowered setting. This appetite motor has more power, will quickly convert to heat, and your motor will melt. So how do you stop this?
There are two electronic ways to manage the amount of electricity a system uses
Batteries can have their own built-in battery management circuit, usually called a BMS or PCB or PCM.
Motor controller can be built – in current limiting function.
I recommend the above two. You might also consider using a fuse directly behind the battery in case the heat melts the insulation on the wires and shorts out the entire system and destroys everything in a spectacular fire.
So the moral of the story is that you really don’t need the highest “C” battery on the market. What you need is a specially designed battery that can easily provide enough power to the limit of what you need. Ideally, you also need a device that protects itself with built-in circuitry, so if you ask it to provide too much power, you limit the discharge. This will ensure that your ESC and motor are protected and that your battery lasts a long time.I suggest a peak of 60A is sufficient for electric skateboards. If you often need more current, then you should increase the battery voltage and increase the mechanical reduction to lighten the motor load. Or go on a diet!Higher voltage = lower current less load = lower current lower current = less heat. Less heat = longer life and higher reliability of electronics.