Conversion kits?
Posted by No_Tomorrow3907@reddit | ebikes | View on Reddit | 25 comments
Is it worth buying a conversion kit online and if so which one. I’m just a bit concerned in the sense that a motor in the wheel would get damaged super easily on a trail. And a mid drive motor the same. I still can’t justify the price for a an emtb so just trying to figure out my options. Any tips would be much appreciated
born1999chica@reddit
Was looking at cheap conversion kits a few months ago because the branded stuff is insanely expensive. Ended up going down a rabbit hole about battery safety and honestly changed my mind completely.
The bikes themselves aren’t really the issue, it’s the random batteries/chargers people buy from sketchy sellers to save money. Some of the footage of fires is crazy.
This breakdown was actually one of the more balanced explanations I found because it doesn’t just go “e-bikes bad”:
https://www.youtube.com/watch?v=-ag9wkef0Zk
Made me way more careful about buying secondhand too.
Spirited_Peak_2531@reddit
trail riding on a hub wouldnt do it. a mid drive would work beter.
Spirited_Peak_2531@reddit
i got a 3kw 72v 30ah. good bike goes for ages and best power wheelies out too
o_Divine_o@reddit
It's nearly always best to get a good frame with full suspension and add mid drive so you have range of torque. Hubs are basically all negatives.
Bbshd with 52v battery is the ideal starting point.
52v is the advertised max voltage but I've seen people throw more at them consistently.
BoringBob84@reddit
OP should be aware that the BBSHD is a 1,000 Watt motor, so it is not legal in most countries / states. The aggressive cooling fins make it easy to visually identify from a long distance away. It also requires a huge / expensive battery and that much power is destructive to bicycle drive trains.
o_Divine_o@reddit
Laws everywhere I've seen in legislative documents say "maximum power output". Output is from the controller
Every motor can handle more wattage then it's listed for. A 750w rated motor can easily do 1,500w without extra cooling.
Cooling fins mean nothing. They're definitely not "aggressive". Fins are structural and assure that if you're in a hot climate it can still cool down.
Definitely doesn't. Hailong battery boxes are some of the most common on ebikes. They are the same length × width as a 36v, 48v, and the only time they're bigger is in vertical height when going for amp hour capacity that exceeds the box size.
If we calculate the cost per watt hour from this random Amazon seller (VEVOR Ebike Battery, 52V 20Ah) * 48v 20Ah with usb - 960Wh * 52v 20ah with usb - 1040Wh the 52v is 0.02 cents cheaper per watt hour (at time of posting this)
Watt hour is nominal voltage × amps hour.
The difference in price is $6.
However one could use a lower Ah battery with 52v and save more weight than you could with 48v. More voltage is more energy efficient since it doesn't require as many amps for the same output of wattage.
Yet serious cyclists or mountain bike riders that own ebikes will choose mid over hub.
Can you be destructive, sure, nearly has to be intentional. if you insist on starting out in top gear repeatedly. In a car you'll stall out, on a bike you run the risk of snapping the chain. Just down shift like any reasonable person.
If you consistently make mistakes like this, just bring an extra chain, chain pin tool, and some master links. Should be doing that regardlessof what you buy, along with tire spoons, patch kit, and enough tools to service the bike.
BoringBob84@reddit
I have never seen a controller mentioned in any ebike law. The law specifies the performance; not the design. It does not require an ebike motor to have a controller; only to limit power output that is provided to move the bike - no matter how the motor does that.
o_Divine_o@reddit
I'll use us law as it's more readily available to me. basing this in logic for controller output as i know more than those writing these laws, but that doesn't make me right or wrong. It's a lot like broken English, they're trying, and from context I can infer what they're trying to convey, regardless of their fumbling here.
There's two main ways to interpret the written law for this sentence. * "fully operable pedals and an electric motor of less than 750 watts (1 h.p.)"
Motors don't provide wattage. They receive voltage and amps resulting in wattage. This is all one really needs to know.
Can make a case for * ¹ nominal wattage is the rule * ² peak wattage is the rule * ³ output wattage to the motor is the rule * ⁴ dyno the tire for a wattage output is the rule
If it's 1, then long as there's a 750w stamp on the motor, it could receive any wattage from the controller. If it lets the smoke out, at least you were legal at 15,000w output.
Next * "whose maximum speed on a paved level surface, when powered solely by such a motor while ridden by an operator who weighs 170 pounds, is less than 20 mph."
ways to interpret; * ¹ if you aren't 170lbs 20mph doesn't apply to you * ² someone who's 170lbs must test the maximum speed it can go. * ³ no mention of head or tail wind. Head wind can drastically reduce speed. My 48v 20a bike at times had issues hitting 12mph due to head wind.
Additional information.
A motor nominal wattage and peak are determined by many factors. * temperature both ambient and uv * heat that amps will cause. * Insulation of the wire determines the nominal voltage it's rated for, but not limited to. * the metal composition of the wire defines what nominal amps it's rated for, but not limited to.
Not limited to, is based on wire length and heat. You can look up wire gauge calculators and see how that all changes.
Also bearings play a roll but I'll just gloss over the basics. Key factors include * bearing type * size (smaller = higher RPM) * lubrication type (oil > grease) * load, often defined by a "limiting speed" in manufacturer catalogs.
How the law defines things. * 15 USC § 2085(b) defines "low-speed electric bicycle" they do not use the term "ebike". * The term “low-speed electric bicycle” means a two- or three-wheeled vehicle with fully operable pedals and an electric motor of less than 750 watts (1 h.p.), whose maximum speed on a paved level surface, when powered solely by such a motor while ridden by an operator who weighs 170 pounds, is less than 20 mph. * Public Law 107-319, 107th Congress is the document states; low-speed electric bicycle (as defined in section 38(b) of the Con- sumer Product Safety Act) shall not be considered a motor vehicle as defined by section 30102(6) of title 49, United States Code. * Title 49 basically says the business/seller is considered to be the manufacturer of all items on a sold product. So your tires for instance are considered to be manufactured by the brand/seller you bought the bike from.
BoringBob84@reddit
That doesn't make sense to me. An electric motor is an energy conversion device. It receives electrical energy and converts it to mechanical energy. The mechanical energy at the output is what the law regulates.
I am not sure where you read that. California law says:
The speed restriction does not depend on weight, wind, incline, or any other factor. It is the same, regardless. This is a trivial problem in feedback control system electronics design: Measure the speed of the wheel and adjust the power output to keep the speed constant.
Federal law only defines ebikes for consumer product safety regulations. The federal government does not regulate the performance or the operation of ebikes. That is solely the responsibility of each state. Some states (like Utah) allow 1,000 Watts, for example.
o_Divine_o@reddit
I said "Motors don't provide wattage." Technically that's incorrect, I was simplifying. * almost all DC motors can generate electricity (act as a generator) if you mechanically spin their shaft, as they are essentially reversible electro-mechanical transducers. When spun, they produce voltage proportional to the RPM. * Without supplied energy it doesn't do anything. You still need some form of energy to spin the motor. This is how regen functions, but you apply energy to the windings to generate more braking force (magnetic drag).
In the case of using it like a generator, there's no limit to output wattage, other than failure due to heat generated that exceedsitsabilityto keep cool enoughto not fry.
So wattage isn't determined by the motor, technically. * Without active cooling, an ebike motor can generally achieve 1.5 to 2 times its rated (nominal) wattage for sustained periods, and up to 3 to 5 times its rated wattage for very short, intense bursts, such as quick acceleration or climbing short, steep hills. * with activate cooling
This means any motor over 375w could be illegal based on what their capabilities are.
Order of operation on capabilities of wattage are first based on battery capabilities (basically amps the cells can output, and resistancein of the battery) > BMS (battery management system) settings and capabilities > controller, in that order. While motor is mostly based on temperature limits.
If i was riding in freezing temps and you're riding in the blazing desert heat, I could do far more wattage on the same motor.
I used federal law as a blanket, as each state could be different. Partly why i didn't want to use different countries because things vary, just like our states.
So lets say we both buy the same 750w bike. If i reduce tire size by ½ i lose half of my speed. So in this instance would need to exceed 750w to maintain 20mph.
This is partly why wattage is moronic and clearly a law that shouldn't be. It doesn't factor in: * hub motors where your torque is based on Wattage only * rider weight * mountains and their grades * people's health related issues from lugs, joins, or appendages missing
If we were all stole and zero physical ailments + hub drive wasn't a thing, and the earth was flat as float glass, 750w is reasonable.
I'm in the appalachian mountains my first ebike was hub drive (I loved the frame but didn't want the hub drive). left me with a boat anchor that gives essentially zero assistance up these inclines. Just leaving my neighborhood is a suck fest because I'm in a very steep valley. Very few places around here are flat for a good distance, all up and down rolling hills.
Federal law is the base, local law is capable of making their own laws. Touched on that earlier, basically for sake of easier discussion.
I believe everything out there (global) is capped at 750w and down. Think one place is capped at either 20ish or 34v around the EU area but I could be wrong or they misinterpreted what was permitted.
I don't follow any of these laws. I ride a 72v Eride Pro S (not SS) that has 16" rims, Michelin Pilot Street tires. I do the speed limit up to 40mph (bike doesn't go faster than that). Only ride the roads, no bike trails or dirt, and no sidewalks. I have a pedal kit, but it doesn't function, so I took it off. It should limit speed to 20mph amd throttle based on pedal rotation, but the electronics don't work.
I do obey all traffic laws, don't weave in traffic, and never pull wheelies. Basically ride like a mature adult. I wave at the cops and they wave back. We have a mix of state police, and local riding around.
BoringBob84@reddit
I feel like I am interacting with AI. Much of that rambling is confidently nonsensical. I don't design ebikes, but I am an electrical engineer and I have particular expertise with motors, controllers, and feedback control systems.
California is currently looking at clarifying their law to specify that the 750 Watt limit is to continuous power; not to momentary overload.
I believe that limits on power are intended to limit the size of ebikes to keep weight under control for safety, and to limit the damage that irresponsible riders can do when they defeat the speed limiters. 750 Watts is far more power than a bicycle will ever need, so it is not really a restriction on anyone who isn't trying to get away with riding a motorcycle on non-motorized infrastructure.
China places limits on power, speed, and weight of ebikes. After visiting NYC and seeing the enormous cargo trailers and delivery vans in the bike lanes, I would like to see similar restrictions in the USA.
o_Divine_o@reddit
Well, we are the education for ai.
Such as my disregard for laws about power, me dumbing down the response so it's digestible for all potential readers, or the annoyance of wattage restrictions?
Sweet, it's rare to find people educated in electronics. I don't do a lot of that now. Raised in a tv and vcr repair shop. worked on anything electronic but the main business was those two, so been working on them since the 80s. I mostly stopped building and designing around 13 years ago.
I'd prefer a speed limit only.
My best guess is they based this off of someone that has a mid drive, possibly without mountains as a consideration. I know Cali has some steep hills but not sure how it is compared to s.w. pa. It's all rolling mountains here and not much flat ground.
My 48v 20a 30ah single hub was a constant workout around here. If it was speed limit only then you could do 2kw with hub and 5 turns, that should be good for our grades while restricting speed.
thriftstorehacker@reddit
I have about 4000mi on a 1000w 48v 26in hub motor kit. Purchased from eBay and love it. Running a 16ah 48v battery it will do about 26mph for at least 15mi. Only maintenance I've done is a little dust cleaning and spoke tightening.
FaithlessnessRich490@reddit
I have the 1500w kit, with about 500 miles on it. Its fun as hell.
BoringBob84@reddit
For an eMTB, I recommend a mid-drive motor, especially if local law restricts power to 250 Watts. A mid-drive motor is more efficient than a hub drive motor, because it can take advantage of the bicycle's gears. It also keeps the weight centered for better handling.
I have installed a Bafang BBS02 (750 Watts) and a battery for my ebike. It required considerable mechanic's skill and several special tools, but I am very happy with it.
The BBS01 is a lower-power version (250 or 350 Watts) that is cheaper and that requires a smaller battery. The Tongsheng TSDZ2 also seems like a good option. It is available in versions from 250 to 750 Watts, depending on your local laws.
Finally, be aware that it can be difficult to find a location for the battery on a full-suspension frame, so I recommend measuring carefully before buying the bike and the battery.
Duct_TapeOrWD40@reddit
Kits have the advantage of reversibility. If it fails after 7 years with no spares you just revert it or get an other complete kit...
BoringBob84@reddit
This was a major reason for me. In contrast, Bosch (and other brands) requires a proprietary mechanical interface on the frame and they have recently changed it so that newer motors will not fit on older frames. When they decide not to support those older motors anymore, the owners of those bikes could be stuck with an expensive pile of trash.
After many years, my frame cracked, so I just got another donor bike and swapped the kit over. I can decide at any time to remove the motor and have a good standard bike, or to upgrade to a different motor. I like this flexibility.
geekroick@reddit
Why would a kit motor be damaged when a pre installed one wouldn't? I don't understand the reasoning there.
No_Tomorrow3907@reddit (OP)
What I mean is because some bikes motors are internalised in the frame whereas a kit would be exposed so wouldn’t the components be more susceptible to damage?
geekroick@reddit
If you have a hub motor, there's just the same chance of damage. Frame mounted mid drives is a slightly different story I guess, but unless you're the kind of rider who regularly bottoms out their chainring or cranks, you're probably going to be okay.
joeroganfolks@reddit
What is your budget? A better question for the subreddit would be to list all your requirements including how you ride, budget, experience— otherwise there are too many variables with prebuilt and conversions. I’ve built 4 bikes and generally add about $1500-$3000 worth of parts and battery to get them competitive with top tier prebuilt bikes. This is not including bike cost (and yes I realize I’m not building bikes with bleeding edge tech, but tried and true components like King, white industries, Etc).
If you have a low budget I’d suggest finding the bike first— then budgeting around $1k for a bafang and an adequate battery.
MaxTrixLe@reddit
Most conversion kits on aliexpress are perfectly good. Just never buy a kit with the battery included, since they’re almost always the worst batteries imaginable
Latter-Ad-1523@reddit
Rear hub kits are easy and don't cost much. I built mine to be able to handle off road, which basically means start with a good frame and shocks imo
Hungry_Orange666@reddit
It's not economical to build eMTB, you can find them on sales for 1500€, or buy refurbs even cheaper.
Building middrive ebike with similiar quality components will not be cheaper.
It only make sense to build hub motor commuter ebikes, but it's still 1000€ minimum for something decent.
Zenigata@reddit
If you're converting with the intention of offroading go mid motor to keep the weight central and also allow the motor to use the gears. A hub motor messes with the handling.
if you're in the uk I recommend the woosh tsdz8 kit, loads of power, legal, torque sensing so it rides well and from a British firm with a presence here that has an incentive not to set your house on fire.