E-motorbike
- Thread starter Archie
- Start date
For us to provide any useful advice, you'd have to provide complete information about the bike itself, your usage scenario (range required at what speed, riding style, traffic vs open road, etc), terrain, wind, etc., because all of those affect how much battery you need, as well as what shape/size/weight it can be, and what type of cells you might want to use.Archie said:
For examples of why this matters, you can read the various build / conversion threads here in this subforum.
As noted previously, that's not enough information, nothing like "complete" and missing most of the things asked for.Archie said:
So to show you why this information is necessary, we'll make some possibly extreme assumptions based on wild guesses instead of the information you won't provide, just to make sure you get a pack big enough to do what you want, and aren't disappointed by lack of performance and range due to insufficient battery.
First guess, is you weigh 250lbs, and your motorcycle is 1000lbs, assuming it's a bigger bike, rather than a smaller sportier bike that might only weigh 500lbs, or a moped that might only be a couple of hundred.
Next guesses are that you have 20mph headwinds all the time and the hills are 15% slopes but since they're nothing big they're only a few hundred feet long, so average slope is about 1.5% uphill on all routes, including the flatter sections. We'll assume perfect paved roads so as not to get into drag at the tires and wheels and such, which will affect offroad riding anywhere from slightly to greatly depending on specific conditions, specific bike type/weight/tires/etc.
We'll also guess that you have a lot of stop and starts, and you like to gun the throttle all the way every time you startup and hold it wide open all the time, trying to reach 100mph speeds on the long road sections.
With all that, then at a guessitmate it's going to be at least 200wh/mile or more (about 150wh/mile on the flat roads, plus all the acclerations and hills adding more), and need a LOT of amps to accelerate and hillclimb (which your 2kw controller and motor cant' really provide), so for 20 miles you need at least 4000wh, or 4kwh. It will also overheat your motor very quickly, in just a few minutes it will be twice the boiling point of water, and be unable to attain anything close to the speed guessed at, with about a 10mph average speed even at full throttle.
This is a simulation that comes something close to the above conditions, but is only steady-state, so doesn't show the problems with the hills and accelration, just full throttle on average conditions. It also just uses system components that might provide something like the 2000w you said your system is (since we don't know what those parts are in your system, any guess is as good as any other).
https://www.ebikes.ca/tools/simulator.html?batt=cust_48_0.2_84&hp=0&mass=612&cont=cust_45_700_0.03_V&axis=mph&grade=1.5&wind=-32&motor=MCRO5004
It shows below the chart the power usage, temperatures, etc., for the components guessed at and used there; what yours will actually do is completely unknown but would likely be similar or worse. You'd perhaps get a 20 mile range at best out of the battery, but your motor wouldn't last the trip, having overheated and burned out a few minutes into the trip, at a max of around 11mph, so only getting you about a mile or so down the road before you're stranded.
At 48v, 4kwh is about a 84Ah battery, which is around the size of a human torso, and perhaps a hundred pounds added to your bike (already added into the simulation above). This weight increases power required for acceleration and hills, taking more space and increasing the need for extra battery to compensate. How much more depends on the actual hills, conditions, and total system weight, and acceleration rates required.
I'd recommend EV-grade cells for ease of pack building and longevity, as even the used cells from scrapped EVs like the Nissan Leaf will probably outlast this version of the bike (most likely you will not be happy with it so you'll build a new one, like most do, with more power, etc), and there are new cells available like the EIG NMC cells, as well. Those two are nice because tehy just bolt together, without a bunch of welding or soldering, and are available from trusted good vendors so you don't have to guess at what you are getting. Cheaper solutions are avialable from generic Chinese battery pack vendors, but you get what you pay for (maybe).
The battery has to not only be able to provide capacity for the range needed, it also has to be able to handle the continous and peak power demands of the system (as does your motor and controller), whcih is why all the information is necessary.
If you provide us with the necessary information, even close guesstimates, plus specifics on your existing components, we can help you find a realistically sized battery to do what you are after.
Without that information, we can only guess, which isn't likely all that helpful to you.
If you don't want to provide it, then I recommend you read up on all the conversion and build threads here in this subforum, to find the ones that have motorcycles similar to yours, with usage scenarios similar to yours. Then you can see what they used, and how successful that was (if they ever reported back), and try something similar.
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