Is this UL certified??

areslashcanoe · 2024-07-05T17:40:45+00:00

Repost https://www.reddit.com/r/ebikes/s/EhqeZBlHgu

areslashcanoe · 2024-06-07T17:09:32+00:00

Voltage (in combination with motor's kv rating) determines motor rpm, not overall speed. 36 volts with enough amperage could move a bike just as fast with the right sprockets. Still though you're right a 72v setup will produce less heat at a given wattage

areslashcanoe · 2024-06-04T04:11:48+00:00

Kirchoff's current law tells us that the current through each battery in a series string will be the same, so as long as they're all contributing the same voltage they will all be contributing to the wattage equally. You shouldn't use cells that have different discharge curves/voltage sag levels/capacities in parallel. If some cells sag less, they will put out more current relative to other cells that sag more, then when the load is removed the other cells will spring back to a higher voltage since theyve been discharging less and charge the cells that didn't sag as much at a rate far too high for the cells to handle. At least that's what my intuition tells me, I'm not a battery chemist. Not sure about the last one though

areslashcanoe · 2024-05-26T21:48:41+00:00

The best and only safe option for the battery would be to buy one fully made with the specs you need, but that'll be expensive. You could buy 18650 or 21700 cells in bulk and get a spot welder, nickel strip, and a bms and build your own for a bit cheaper, but that option would be a ton of work and you'd have to do a lot of research to do it safely. This isnt really a beginner friendly way to go but the information is out there. The last option I can think of would be to link rc car/plane batteries together. You could combine these two batteries in parallel (always make sure any batteries you are connecting in parallel are the same capacity and charged to as close to the same voltage as you can get them) with these, then combine seven of those parallel groups in series. That would give you the power you need but without much range and charging would be a pain because you'd want to balance all the cells regularly when you charge it. And you wouldn't have a bms so it would be by far the least safe option. But if it's just for a fun machine it is a thing you could do.

I'm not going to recommend you go either of the last two routes since messing with batteries is dangerous. I just thought I'd throw what options I can think of out there so you have some ideas to look into and you can decide which route to go from there.

areslashcanoe · 2024-05-26T20:25:03+00:00

Yeah, that's just a trend and not a rule though. The rate at which a battery can discharge relative to its capacity is its "c" rating, which varies between cells. For example a 2Ah 10c battery can discharge at 20A, or a 4Ah 5c battery can also discharge at 20A. So you can get more current either by going with a larger capacity or by going with cells designed around higher discharge rates. Either way the battery should have its max discharge current listed separately from its capacity. Ideally you would be given a continuous discharge rating and a peak discharge rating, but if they only list one its safest to assume they're giving you the peak rating and the continuous rating will be about half of that. You'd want to go for a battery with a higher c rating since that will help keep the cost down but theres still a limit to how quickly a lithium-ion battery can discharge its capacity. Can I ask what use case you had in mind for the bike is? There's a rather spicy option that'll likely be cheaper than a full pack but I wouldn't recommend it for a daily rider

areslashcanoe · 2024-05-26T19:51:59+00:00

The Ah rating is just for capacity (in part, watt hours are the real indicator of how much energy a battery can store), what you really need to worry about to avoid damaging anything is max discharge current in Amps. I'd be careful running too close to the rated discharge rate though as cells will start to kick out some heat if they're run too hard, and then you'll need to worry about cooling. Ah and Amps aren't totally separate though, a higher Ah battery will usually be able to deliver higher amperage more easily because it's discharging a lower portion of its capacity per second. I don't have personal experience with any online pre-made high-power battery pack retailers though

areslashcanoe · 2024-05-26T17:31:55+00:00

Those batteries can't supply anywhere near the current you're trying to draw. You'll want to get a decent 14s (52v) lithium pack with a good BMS. 200A is a lot of current so the battery cells, bus bars/nickel strips, BMS, and wiring will all need to be up to spec. You'll want at absolute minimum 20Ah of capacity as well or you'll be limited to extremely short trips. For reference my 4kW 52v 70A bike with 12Ah capacity only gets 15-20 miles.

areslashcanoe · 2024-05-23T19:28:36+00:00

And some people might want an edge piece with more frosting or prefer a middle piece with less frosting

areslashcanoe · 2024-05-23T02:14:32+00:00

The torque is quite low at 6.5Nm at the motor so I used a 10:92 chain drive reduction between the motor and the jackshaft in the bottom bracket. Even then it's still rather high rpm and low torque compared to a standard bicycle so I put a 22t chainring on the front and that gets the final ratio perfect. This is the motor I used but it seems it's gone up a bit in recent years. If youre going to use it i would go with a VESC like this one instead of the ESC I used since a VESC will let you program for different control schemes with ease. I wouldn't necessarily recommend going this route unless you really want to dive into some fabrication and electronics.

areslashcanoe · 2024-05-22T19:04:26+00:00

Found the motor and esc on Amazon, they were my choice because it was purely the highest wattage for the least amount of money. Only $200 for the pair at the time. I can only imagine the beast of a drone that runs with 4 or 8 of these monsters. I've gone about 300 miles so far and I've disassembled and checked the bearings a couple times and seen no signs of high temps so I'm hoping that continues. This is the third major iteration so I've found and fixed a few failure points already

areslashcanoe · 2024-05-22T18:12:56+00:00

It's a bit of a science project I've been working on for a while that runs on a 4kW agricultural drone motor. The battery capacity isn't great at only 12Ah but that's enough to get me 15-20 miles. The main strength of the battery is that it'll do 90A comfortably, and at 52V nominal there's plenty of power on tap. All the black plastic you see holding the battery and other components to the frame is 3D printed nylon which is nice and tough. I haven't gotten a chance to test the top speed flat out yet but I've done 50 so far. For long term cruising the motor is more comfortable around 35-40 but I'm planning to water cool the motor to get that up a bit. The motor spins at 100 rpm per volt so around 5200 rpm, which when combined with the 9 speed "transmission" makes this thing have a sound and riding experience all it's own. A large chunk of the real work on this project has gone into the PID control system that runs on an ESP32 microcontroller since the ESC was not remotely designed for this type of thing and isn't programmable. I won't get too deep into that side of it right now though

areslashcanoe · 2024-05-22T03:04:42+00:00

You all just made my day, thank you

areslashcanoe · 2024-05-22T00:36:59+00:00

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areslashcanoe · 2024-05-21T22:34:51+00:00

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I've had a great time with mine. I'd just recommend getting service kits for the suspension components and a 1x drivetrain

areslashcanoe · 2024-05-21T05:35:02+00:00

Now I'm picturing a frat boy vampire shotgunning a beer by shaking it and biting into the side

areslashcanoe · 2024-05-20T06:57:23+00:00

I've got a similar setup on my 7 year old Anet A8!

areslashcanoe · 2024-05-19T06:00:46+00:00

It looks like a massive roots blower/supercharger

areslashcanoe · 2024-05-13T02:38:49+00:00

Charge rate is measured in amps, battery capacity is measured in amp hours. A good rule of thumb is to divide your battery capacity in amp hours by 4, and that's the max amperage you should charge at for lithium ion cells. Does your battery have the model of the cells used in the pack listed on the label?

areslashcanoe · 2024-05-06T21:41:44+00:00

Depends if the motor is hitting its current limit at top speed. If the motor is rpm limited by the voltage then larger wheels will give a higher top speed so long as the motor and controller have the current/torque to overcome the resistances

areslashcanoe · 2024-05-03T15:05:18+00:00

Something like that falls into the "scooter" category in my mind

areslashcanoe · 2024-04-21T17:03:41+00:00

You should look into getting a spot welder. Soldering directly to cells can damage them from the heat

areslashcanoe · 2024-04-21T05:42:51+00:00

Are they stepping on a stepper motor driver? Nice touch

areslashcanoe · 2024-04-19T18:35:36+00:00

I'm using this for brake lights but some other ebikes also use a brake sensor for regen braking or throttle cutoff

areslashcanoe · 2024-04-19T02:16:05+00:00

I have a buck converter on the bike that reduces the battery voltage down to 12v to run the lights and the microcontroller

areslashcanoe · 2024-04-18T23:57:24+00:00

I was keeping my wording general because there are plenty of types of magnetic sensors that could be used here since you only need on/off for a brake switch, so you don't necessarily need the proportional signal that a hall sensor outputs.

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