Looking for Help Getting Started on DIY eBike Conversion

[Tylen Wanister]

Hello, first post and all.

I used to ride a 2-cycle engine bike, but I'm looking for something cleaner. A recent change in city bus policy now allows riders to load their ebikes onto the bike rack at the front of the bus. Before this change it prohibited both 2-cycle gas powered bikes and battery-powered bikes. I'm partially mobility disabled, 60yo, 250+ lbs. and the bike is necessary for me to do basic things like using the bus, going shopping, etc... I'm moving into a new apartment soon, and it's located in an area of town with some moderate hills, and so my legs may not be able to get me up the hills, and the nearest bus stop is about 1/2 mile from my new apartment and that's really too far for me to walk.

I'm certain I don't want a pre-made "factory" ebike, and am reasonably certain I want the kind with the motors in the wheels, but could be talked into the kind where the motor is mounted in the middle. 2nd to that, I wonder about front wheel drive vs. rear wheel drive, vs both, and from there I've read about voltages, amperages, etc... One post I read said 52 volt was the "sweet spot" in terms of power, battery longevity, etc... but I've also read some disparaging posts about the person that made this claim, so I wonder how true it is.

My preferred bike has been a 29" Huffy, but I'm thinking I'll probably need to go with the more commonly-used 26", so Yes, I'm willing to buy a new bike for the build, and overall the budget could be as high as $1,000 if the reasons are compelling, but I'd prefer to keep it down to about half that, at least for the 1st bike I build and use, i.e. "toeing the water".

Any help appreciated and thanks in advance.

 

[gromike]

Buy a quality good condition used bicycle for your conversion. They're out there. Figure out the motor you will use first, and have an idea how to fit a battery to any potential donor. Twenty year old bicycles have been a sweet spot for me to motorize, and they have disk brakes, and suspension too. Probably best to avoid a full suspension bike due limited space for a battery in the triangle.

 

[amberwolf]

I'm partially mobility disabled, 60yo, 250+ lbs. and the bike is necessary for me to do basic things like using the bus, going shopping, etc... I'm moving into a new apartment soon, and it's located in an area of town with some moderate hills, and so my legs may not be able to get me up the hills, and the nearest bus stop is about 1/2 mile from my new apartment and that's really too far for me to walk.

What are the actual slopes of the hills, how fast do you need to go, and what is the estimated total weight of rider and bike and any cargo? Knowing those, power required to do this can be estimated. If maximum desired range is also included, that can be used along with the power to guesstimate required battery capacity.

There's a simulator at ebikes.ca under Tools that can be used to do this if you want to play around with it.

I'm certain I don't want a pre-made "factory" ebike, and am reasonably certain I want the kind with the motors in the wheels, but could be talked into the kind where the motor is mounted in the middle.

If you want easy install and reliability, hubmotors generally make these better than middrives.

If you want greater efficiency and you are going to keep shifting gears to keep the middrive in it's efficient zone (whatever that is for the particular drive) then the MD generally would be more efficient.

HMs have less moving parts, so less to wear out, and less to fail. DD's (direct drive) have even less to go wrong than geared hubs (GH) but can be heavier and less efficient depending on usage and actual motor, and can require a bigger controller and battery to support higher torque / load demands, since the gears in the GHs allow for a smaller faster motor inside that takes less current to do that part of the job.

MDs will use your normal rear wheel, so there's less potential for problems with the usually-too-large spokes on most hubmotor kits.

But MDs will wear the chain and sprockets faster.

Lots of other details, but those are major points.

2nd to that, I wonder about front wheel drive vs. rear wheel drive, vs both, and from there I've read about voltages, amperages, etc...

Mostly that's a preference.

FWD will be easier to take the wheel off and put it on for maintenance, flats, etc. But if you have slick road conditions, or gravel, dirt, etc., there is a risk that the tire can be spun out and lose control of steering or even skid out from under you while cornering, because the motor will keep spinning with the traction loss making it harder to regain control, unlike if it was an unpowered wheel. There is less stress on a front wheel, so the potential for problems with spokes is less.

RWD is harder to access the wheel for maintenance, but is easier to deal with a loss of traction in those situations. Most of the weight is on a rear wheel, increasing the potential for problems with the spokes. Your pedal drivetrain feeds the rear wheel, so changing that wheel means changing other things, possibly including how the sprockets in the back line up with your shifter and chainline, forcing other modifications to the bike. Some motor axles are wider (or narrower) than the frame back there, forcing other changes.


Reliable torque arms are available for both locations, such as the ones from ebikes.ca , depending on the power levels you need. Without htem the potential for spinning out the motor axle in the dropouts and damaing the bike and motor/controller exists; in the rear that does'nt usually cause a severe crash but in front it can cause loss of the whole wheel and a faceplant.

One post I read said 52 volt was the "sweet spot" in terms of power, battery longevity, etc... but I've also read some disparaging posts about the person that made this claim, so I wonder how true it is.

Voltage depends on the system you want to use vs the speed you need, etc.

Longevity is about quality of build and of cells used, matching of those cells with each other, using appropriate cells for the purpose, having a battery that is more capable than you need by enough to still do what you want for as many years as you want to keep using the system, and how you care for the battery, environmental conditions, etc.

Power depends on voltage and current. If you are looking for a low power system then you can have low voltage and low current. If you needa high power system you can get it with either high voltage or high current, with the other being low; there are advantatges to each one, and disadvantages as well.

Realistically, some sets of specs (voltage, current, capacity) are much more common to find in prebuilt batteries, so you may find cheaper ones with some of these specs just because they're more commohly made.

My preferred bike has been a 29" Huffy, but I'm thinking I'll probably need to go with the more commonly-used 26",

29" will ride better over poor roads, if you don't have good suspension on the bike.

so Yes, I'm willing to buy a new bike for the build, and overall the budget could be as high as $1,000 if the reasons are compelling, but I'd prefer to keep it down to about half that, at least for the 1st bike I build and use, i.e. "toeing the water".

The major cost for good parts is a battery, which itself could cost as much as half your budget (more if you need greater capacity and/or performance).

Any help appreciated and thanks in advance.

There are also other threads about each of the points raised that discuss them in more detail, mostly with titles that indicate taht's what they're about, making them a bit easier to find.

 

[Tylen Wanister]

There's a simulator at ebikes.ca under Tools that can be used to do this if you want to play around with it.

First thanks for the ton of information. I'm thinking about all of it, and will be asking questions at some point, however I JUMPED on this suggestion.

A = my new, soon-to-be apartment
B = the nearest Walmart

There's another local grocery that might be closer and easier that I will also want to run the analysis on, plus a few other destinations like the major bus hub on the other side of the freeway, in case I can get there faster on the bike than what the local bus can do. There are a few other places that I might want to go, but the Walmart is the primary location for the vast majority of my needs (food and other stuff). Meaning, this will be my "main" trip each week or so. Everything else will be secondary in both importance and frequency.

Some of the data I can understand, but it there's a lot I don't; particularly questions on the right column about motors, etc... No clue. Figured I'd attach a (edited) screen shot first, and ask questions from there.

Again, thank you. This is exactly what I was hoping for.

 

[Chalo]

Hub motor, geared because you have to lift it onto a bus rack. 350-500W rated motor, 26" wheel and used would be the sweet spot for capability, weight, and cost. Front hub motor wheels in this category are generally cheaper and more widely available than years, so you'll get to keep the probably stronger and more reliable normal rear bike wheel under your own body weight. Use up to 48V x 25A in the above described motor as necessary.

Don't use a crappy department store bike. Get a basic steel framed 26" bike from a reputable manufacturer, that was originally sold and set up by a reputable bike shop. Rigid fork if you want to avoid needless trouble. Up to 40+ year old MTBs are good choices, but much more recent ones are also fine if they're simple and rugged, not gimmicky. Use fat tires at modest inflation pressure for comfort and traction.

Unfancy no-display 18A controllers are cheap as dirt if they'll do your job. I just sold a whole kit, minus battery and charger which she already had, to a student in one of my e-bike classes for $101 plus tax. That was $50 for a used hub motor wheel and $51 (very close to my cost) for cheap simple 18A eBay controller, throttle, motor cable, on/off switch, nuts and torque washers, plus a few plugs and solder sleeves. We put it all together during the one class.

A second life rental scooter battery is a cheap shortcut if it fits and you can get one that's tested to be working. New but very cheap batteries are often a bad deal because they're low quality and made out of random nonsense. Used but good quality is okay, but don't cut corners on a brand new pack. The risk isn't worth it.

 

[gromike]

I really like this front geared hub motor bike. It's so nimble. It's an old Cannondale Badboy, steel front forks.
I bought the motor and laced it into a rim, about $200. The battery was an about $40 from Battery Hookup. The controller about the same price, though with high shipping,

 

[2old]

My recommendation if you need to convert the bike yourself is to locate a "vintage" steel bike that fits you comfortably then go to the "review and testing" section and read about what others have DIY'd with 1000w rear hub motors (many used a kit from YESCOM ($200 - $250). Purchase a good battery (em3ev or ebikesca if something affordable is available, bicycle wheel warehouse if not). The cost of my bike was < $1000 (I've built a couple over the years) and it's powerful and reliable. Note: it happens to have an aluminum frame.

 

[E-HP]

My preferred bike has been a 29" Huffy, but I'm thinking I'll probably need to go with the more commonly-used 26", so Yes, I'm willing to buy a new bike for the build, and overall the budget could be as high as $1,000 if the reasons are compelling, but I'd prefer to keep it down to about half that, at least for the 1st bike I build and use, i.e. "toeing the water".

Any help appreciated and thanks in advance.

I would convert the Huffy. If your budget is $1000, don't waste your budget on finding the perfect platform, if you already have one that fits you. Put that money toward a better battery. I spent $650 or so dipping my toe in the water when I started, and have been tweaking and modifying my bike ever since. I do upgrades in waves, mainly holding off until the rainy season, but usually very well planned out to make adjustments that I find most important based on my riding conditions. No DIY ebike project is a one and done exercise. The sooner you're out there riding and having fun, the sooner you'll identify what works best for you, and what doesn't.
I describe a few things you may want to consider in my newbie FAQ thread:

DIY Newb FAQ?

I think I've read through all of the stickies in the ebike forums, which provide great guidance. Yet, I see a lot a new folks getting into ebikes and posting questions that are not in the stickies, or are embedded somewhere among the existing stickies. Another observation is there are...

endless-sphere.com

 

[Tylen Wanister]

Hub motor, geared because you have to lift it onto a bus rack. 350-500W rated motor, 26" wheel and used would be the sweet spot for capability, weight, and cost. Front hub motor wheels in this category are generally cheaper and more widely available than years, so you'll get to keep the probably stronger and more reliable normal rear bike wheel under your own body weight. Use up to 48V x 25A in the above described motor as necessary.

Does any of this pertain to the image of the "trip simulator" I attached above? Specifically the "350-500W" recommendation. I ran the tool, didn't understand any of the output, and half-expected it would tell me the wattage of the motor I would need. 500W seems light, based on what I've read, and I'm a fattie at 250+ lbs. Hills, etc... make me think 500W is too light. Also why is 48V the upper limit, particularly when I read somewhere that 52W was the sweet spot? Isn't more better? Since the battery is 50%+ of the build, doesn't it make sense to "overbuild" on the less expensive parts like motors?

 

[E-HP]

Use fat tires at modest inflation pressure for comfort and traction.

I’m pretty sure I must be dreaming when I see Chalo recommending fat tires. Start recommending regen, and that will confirm we’re in an alternate universe.

 

[Chalo]

I’m pretty sure I must be dreaming when I see Chalo recommending fat tires. Start recommending regen, and that will confirm we’re in an alternate universe.

By "fat", I mean like 2.1"-2.5". I should have specified. But MTBs don't generally accept tires that are fat enough to be a functional problem or to mark you as a clueless chump.

 

[Chalo]

Does any of this pertain to the image of the "trip simulator" I attached above? Specifically the "350-500W" recommendation.

No, that's not what I mean. I was suggesting a hub motor rated 350-500W, which actually doesn't really mean anything in terms of how much power you can use to drive it. I also suggested an 18 amp controller for best cost effectiveness. "36V" (actually 37V nominal) x 18A = 666W nominal. "48V" (actually 48.1V nominal) x 18A = 866W. That's gross electrical power, so you could expect peak power at the wheel to be in the neighborhood of about 500W and 650W respectively.

If you want more power than that, use a controller with more amps; they only cost a little bit more. I use 22 and 26 amp controllers on 250W rated motors all the time with no ill effects and no warning signs so far.

 

[E-HP]

.But MTBs don't generally accept tires that are fat enough to be a functional problem or to mark you as a clueless chump.

Ok, the universe is back to normal. Whew!!

 

[gromike]

From what I've I seen of a Huffy is that would be a definite no build platform for me. I had friend motorize his twenty year-old Huffy Mtb with a 1000w rear hub. When I saw the bike I recommended he find another horse. I haven't seen such a cheap bike in long, long time. Cheap everthing. Bike failed him two blocks later and he fell to ground. Never rode it since.
What I'm trying to say is don't cheap out on safety. At least in my world, good used bikes come cheap.

 

[Tylen Wanister]

No, that's not what I mean. I was suggesting a hub motor rated 350-500W, which actually doesn't really mean anything in terms of how much power you can use to drive it. I also suggested an 18 amp controller for best cost effectiveness. "36V" (actually 37V nominal) x 18A = 666W nominal. "48V" (actually 48.1V nominal) x 18A = 866W. That's gross electrical power, so you could expect peak power at the wheel to be in the neighborhood of about 500W and 650W respectively.

Okay so first I've got like 4 questions bundled into this answer, but before that I'm still wondering about the trip analyzer thing, what it says, and what useful information it has about the specific, primary trip I am going to be making from my soon-to-be-new apartment and the nearest Walmart. Letting that go for now, to ask:

So I ran the math and get the idea that volts times amps equals watts, meaning power, but after that it all becomes a meaningless haze. If the fact that motors are "rated" between 350 and 500W, and the "W" means watts, meaning power, then how is "how much power you can use to drive it" not relevant to it's rating? Can I shove 700 Watts into a motor that's only rated for 350? Or does the watt rating only become meaningful after you calculate voltage times amps, as long as it doesn't exceed the rating? That makes sense, sort of, and nothing else does, so... uh... I figure I should have some words here, but I don't.

Anyways, also I notice that you are talking about an "18 amp controller" and while I get the idea that the batter power needs to be regulated somehow by a controller, I would think that the "18 amps" comes from the battery, and not the controller. Right? 350 - 500 Watt isn't a minimum, is it? And I'm still wondering about "52 Volts" being the magic "sweet spot" (or not), and I've been reading around, saw the newbies FAQ post(s) and read through that once, and read all the good arguments in favor of building a DIY ebike vs. a "factory" bike (or whatever the term of art is in the article) and agree with the DIY arguments and one point provoked the question about buying a very large, and expensive battery as the "core" of the build, and rotating the other parts out as needed, while retaining the primary investment of battery as the centerpoint. Change out the bike, even, while re-using the high-quality and expensive battery. Good strategic thinking?

Finally I'm aware that cheap chinese batteries on eBay are not as good as name-brand batteries like panasonic (something I was aware of before even thinking of building an ebike), but I'd like to read some compare and contrast material/content, showing WHY the more expensive and better-quality batteries are better than the less-expensive and lower-quality chinese batteries. What's the difference in savings and how does that compare to the difference in performance. Does an extra 10% in cost give you an extra 30% in performance, or does an extra 50% in cost give you an extra 10% in performance? How is performance measured? Battery life? Charge/recharge cycles? Do lithium ion batteries lose their capacity like laptop nickel-cadmium batteries do? Should I start a completely different thread for my many questions about batteries? Is there a newbie FAQ on this site that covers these questions?

EDIT***

I just found and watched this, and it goes directly to the heart of the question I asked. Short video, very concise.

 

[E-HP]

The Motor rating is the amount of power the motor can run continuously, indefinitely, under a standard set of conditions (ambient temp, assuming air flow, etc). The motor is able to shed enough heat so the temps don’t rise above where motor damage will occur. You can put much more power through the motor, for a shorter period of time. Or a little more power for a longer period. If the actual conditions are different than used to determine the rating (like a higher ambient temp), the amount of time will increase/decrease depending on the actual conditions. Geared motors have additional limitations since too much power can strip the gears, but the sky is almost the limit for direct drive, until the heat melts it.

 

[Chalo]

If the fact that motors are "rated" between 350 and 500W, and the "W" means watts, meaning power, then how is "how much power you can use to drive it" not relevant to it's rating?

Sadly, no. The motor's rating has more to do with where (to comply with local regulations) and to whom the seller is trying to sell it.

Can I shove 700 Watts into a motor that's only rated for 350?

Yes. Actually that's what the industry would call a 350W bike. More often than not, the gross electric power is about twice the rated power. But most hub motors can tolerate quite a bit more yet than that without problems.

Or does the watt rating only become meaningful after you calculate voltage times amps, as long as it doesn't exceed the rating?

The motor really only objects to too many amps, and it's never a value that's even somewhat close to the motor's rating. The controller can trade off volts for more amps at high load and low RPM, but only up to a point, usually 2-3x the battery current.

Anyways, also I notice that you are talking about an "18 amp controller" and while I get the idea that the batter power needs to be regulated somehow by a controller, I would think that the "18 amps" comes from the battery, and not the controller. Right?

Current comes from the battery but it limited by the capacity of the controller (for the vast majority of controllers).

350 - 500 Watt isn't a minimum, is it?

No. It's an arbitrary number the manufacturer decided to put on the motor. Really. If I didn't feed "250A" motors 1000W of juice on a daily basis and never even get them warm, I would have more regard for the motor rating.

And I'm still wondering about "52 Volts" being the magic "sweet spot" (or not),

There is no general sweet spot for voltage, there's only the optimum for your application. Motors have an unloaded RPM per volt, which is sometimes abbreviated kV, and they work best and most efficiently at about 75% of their unloaded speed. So if you know things like the motor kV, your desired speed, and how much power you need to achieve that speed, you can derive the optimum battery voltage and minimum required amps to get there.

I use secondhand battery modules from automotive, data center, and medical applications so I can get better than e-bike quality for less than e-bike prices. If you want to use a pack made out of lots of lipstick cells, there are many better sources than me for such guidance. I didn't find the slightly better energy density of most e-bike packs to be worth the reduction in reliability, lifespan, and power capacity compared to second life packs.

 

[amberwolf]

Current comes from the battery but it limited by the capacity of the controller (for the vast majority of controllers).

I would use the word "capability" rather than "capacity" because the latter is directly associated with batteries in the context of ebikes, and can be confusing to readers.

 

[amberwolf]

Finally I'm aware that cheap chinese batteries on eBay are not as good as name-brand batteries like panasonic (something I was aware of before even thinking of building an ebike), but I'd like to read some compare and contrast material/content, showing WHY the more expensive and better-quality batteries are better than the less-expensive and lower-quality chinese batteries. What's the difference in savings and how does that compare to the difference in performance. Does an extra 10% in cost give you an extra 30% in performance, or does an extra 50% in cost give you an extra 10% in performance? How is performance measured? Battery life? Charge/recharge cycles? Do lithium ion batteries lose their capacity like laptop nickel-cadmium batteries do? Should I start a completely different thread for my many questions about batteries? Is there a newbie FAQ on this site that covers these questions?

I would recommend reading the many threads about the problems with the cheap ebay / aliexpress / amazon / etc batteries, including the fires, failures, scams, etc. There's plenty of detail in those, though it will take a while to read them all.

It's easier to just avoid the issue by not buying those, but if you really want to know the details, it's all around the forum in many troubleshooting, repair, and problem threads.

 

[Tylen Wanister]

I would recommend reading the many threads about the problems with the cheap ebay / aliexpress / amazon / etc batteries, including the fires, failures, scams, etc. There's plenty of detail in those, though it will take a while to read them all.

I haven't posted into this thread for a few days due to moving. I'm now in my new apartment and am now learning 1st hand what kind of difficulties I'm going to have getting around without a car. All I have is a standard bicycle. The bus, however, is much closer and much more convenient and useful than I thought it would be, so that's a plus.

However, I have been reading and have several questions.

First, I'm rethinking the mid-drive as an option. Is there a compelling reason to NOT do it this way, vs. having the motor in the hub?

Second, I found a pre-made ebike for $750 new, and am wondering if the DIY is worth it, since I estimate that when it's all said and done, I'm probably going to spend about $750. The most compelling argument against this option that I've heard so far, is that once you are locked into a proprietary system, you are completely dependent on the manufacturer to maintain the system with spare parts, upgrades, and of course the company can always go out of business, leaving you completely stranded.

Third, I'm re-thinking front wheel drive only for the hub motor option, one because I'm FAT and all my weight is on the back tire (mostly) and the front fork of the bike I am thinking of buying has a shock absorber thing in it, so I wonder about losing traction due to excessive power, and bumps, etc... Seems like having the drive in the rear wheel is better, but then I've read that, due to the existence of the gears and the derailleur, installing a read-wheel motor can be more problematic, and I'm trying to avoid problems.

If I build front-wheel only, can I add a rear-wheel later if I want?

Also the issue of "rim brakes" vs. "disk brakes". The low-cost bikes I'm looking at are all rim brakes and I think I remember reading somewhere that disk breaks are better for motor-driven bikes, and I've seen "conversion kits" where it looks like you can convert a rim-brake wheel to disk brakes, but I wonder 1) how difficult is that, 2) how reliable and durable is that, and 3) is it worth the expense and effort.

I can always change-out standard brake pads if they wear fast, if that's the only, or primary concern.

Also, strange question, I read something about a 'removeable battery", so that you can take it off the bike and it won't be stolen. I'm wondering if there isn't a system where you can have two batteries; one "light duty" and the other (more expensive) "heavy duty" for longer trips, etc... I like the idea of being able to "rotate" the batteries, having one on the charger while the other is in use. Also, while I'm predisposed to buy the biggest, most heavy duty battery that there is, maybe I can get by in the beginning with something smaller, and therefore cheaper?

 

[Chalo]

First, I'm rethinking the mid-drive as an option. Is there a compelling reason to NOT do it this way, vs. having the motor in the hub?

Orders of magnitude more wear and tear, show stoppers, and maintenance. If you're down for that, mid drives have some advantages. They make the most of a limited amount of power, and they allow the use of good proven bicycle wheels that are easy to remove and replace for flat fixes.

Second, I found a pre-made ebike for $750 new, and am wondering if the DIY is worth it, since I estimate that when it's all said and done, I'm probably going to spend about $750.

Know that a $750 new e-bike is the equivalent of a $250 new pedal bike, which is to say it's probably garbage and not worth messing with. Certainly it won't be built to hold up under a heavyweight rider. Corner cutting will limit its durability, serviceability, and function.

The most compelling argument against this option that I've heard so far, is that once you are locked into a proprietary system, you are completely dependent on the manufacturer to maintain the system with spare parts, upgrades, and of course the company can always go out of business, leaving you completely stranded.

Typically a sub $1000 e-bike is relatively generic and pretty easy to maintain going forward. On the other hand, it is so crappy that you will be maintaining it right out of the gate and continuously.

Third, I'm re-thinking front wheel drive only for the hub motor option, one because I'm FAT and all my weight is on the back tire (mostly)

Normal bike wheels are lots stronger and more dependable than hub motor wheels, like for like. That's a point in favor of a front hub motor, and one of the main reasons I have used them for most of my bikes.

and the front fork of the bike I am thinking of buying has a shock absorber thing in it,

You really don't want to put a hub motor in a suspension fork. The flatted axle will break the fork tips. Even if you come up with a massive complicated torque arm to prevent this, motor traction will lock out suspension movement when it's pulling, and it will prematurely slop out the fork bushings. To you even know whether the fork in question is tunable for your weight? You need to be able to change the spring rate as well as damping rates.

I advise against using suspension for a low budget build. It will let you down. That $750 number you've thrown out there? It might buy you a fork that could be set up to work well for you. The bike will cost you extra.

If I build front-wheel only, can I add a rear-wheel later if I want?

Yes.

Also the issue of "rim brakes" vs. "disk brakes". The low-cost bikes I'm looking at are all rim brakes and I think I remember reading somewhere that disk breaks are better for motor-driven bikes,

Your heard wrong. Budget discs are worse than similarly priced rim brakes in pretty much every way. Plan on $100+ per brake to get something that's even equal to a good rim brake.

The advantage of disc brakes is that they're independent of wheel diameter, tire size, and rim shape. If one of more of those things applies to your project, that's the reason to consider them.

and I've seen "conversion kits" where it looks like you can convert a rim-brake wheel to disk brakes, but I wonder 1) how difficult is that, 2) how reliable and durable is that, and 3) is it worth the expense and effort.

Just don't bother. If your bike and wheels aren't set up for discs, you're 100X better off using good rim brakes (which aren't the ones that come on crappy department store bikes, by the way).

Also, strange question, I read something about a 'removeable battery", so that you can take it off the bike and it won't be stolen. I'm wondering if there isn't a system where you can have two batteries; one "light duty" and the other (more expensive) "heavy duty" for longer trips, etc... I like the idea of being able to "rotate" the batteries, having one on the charger while the other is in use.

This can be done, but it isn't very common to have different capacities in low priced e-bike batteries. If you seek out one that uses the same case and connector, but higher energy cells, then that would work but at a substantial cost premium. You can get most of the same advantage by having two of the same pack, and carrying the extra one along or not, depending on how much range you want.

It's hard on your batteries to leave them fully charged, and especially constantly being topped up on the charger. If you keep multiple batteries in rotation, try to avoid keeping them full all the time.

Also, while I'm predisposed to buy the biggest, most heavy duty battery that there is, maybe I can get by in the beginning with something smaller, and therefore cheaper?

No e-bike batteries are "heavy duty" by battery standards. They're cheap consumer grade goods with predictably sketchy quality. I use secondhand battery modules from automotive, medical, or data center applications so I can get the good stuff at bargain prices.

 

[lnanek]

A $350 kit and a $350 used bike from a reputable brand would get you a way higher quality bike than a random relabeled junky bike shaped object (BSO) for $750 IMO.

For cheap eBikes I'm generally stuck replacing things like the brakes anyway. They often use garbage cable actuated disc brakes that make a racket and barely stop. For the crap Rattan BSO eBike I started with, for example, even $40 XTECH HB-100 cable actuated hydraulic brakes off amazon were an enormous improvement in every way. You'll find every component like that on a BSO.

Adapters for disc brakes also are not a good idea. The frame isn't designed to take the load. There's some old Trek bikes where the adapter actually bolts in to the old proprietary disc brake mounts - that's fine. But retrofitting a rim only frame to disc is just asking for an eventual dangerous accident IMO.

Range extender batteries do exist. Almost always better to just have two identical batteries so you can wire them in parallel when charged to the same voltage at the start of a trip or use them one by one and swap out on exhaustion when needed, however. Much less chance of a fire that way than playing with diodes that generate heat with voltage drop and risky situations where one battery will feed another.

 

[E-HP]

I haven't posted into this thread for a few days due to moving. I'm now in my new apartment and am now learning 1st hand what kind of difficulties I'm going to have getting around without a car. All I have is a standard bicycle. The bus, however, is much closer and much more convenient and useful than I thought it would be, so that's a plus.

However, I have been reading and have several questions.

First, I'm rethinking the mid-drive as an option. Is there a compelling reason to NOT do it this way, vs. having the motor in the hub?

Second, I found a pre-made ebike for $750 new, and am wondering if the DIY is worth it, since I estimate that when it's all said and done, I'm probably going to spend about $750. The most compelling argument against this option that I've heard so far, is that once you are locked into a proprietary system, you are completely dependent on the manufacturer to maintain the system with spare parts, upgrades, and of course the company can always go out of business, leaving you completely stranded.

Third, I'm re-thinking front wheel drive only for the hub motor option, one because I'm FAT and all my weight is on the back tire (mostly) and the front fork of the bike I am thinking of buying has a shock absorber thing in it, so I wonder about losing traction due to excessive power, and bumps, etc... Seems like having the drive in the rear wheel is better, but then I've read that, due to the existence of the gears and the derailleur, installing a read-wheel motor can be more problematic, and I'm trying to avoid problems.

If I build front-wheel only, can I add a rear-wheel later if I want?

Also the issue of "rim brakes" vs. "disk brakes". The low-cost bikes I'm looking at are all rim brakes and I think I remember reading somewhere that disk breaks are better for motor-driven bikes, and I've seen "conversion kits" where it looks like you can convert a rim-brake wheel to disk brakes, but I wonder 1) how difficult is that, 2) how reliable and durable is that, and 3) is it worth the expense and effort.

I can always change-out standard brake pads if they wear fast, if that's the only, or primary concern.

Also, strange question, I read something about a 'removeable battery", so that you can take it off the bike and it won't be stolen. I'm wondering if there isn't a system where you can have two batteries; one "light duty" and the other (more expensive) "heavy duty" for longer trips, etc... I like the idea of being able to "rotate" the batteries, having one on the charger while the other is in use. Also, while I'm predisposed to buy the biggest, most heavy duty battery that there is, maybe I can get by in the beginning with something smaller, and therefore cheaper?

You may not be cut out for DIY, yet. It’s easier to do DIY if you have desire and passion. If a factory ebike gets you going, you should do that and start enjoying Ebiking. After a while, whether you go factory built or DIY, you will naturally find things you like and don’t about your ebike and a better understanding of what works for you. At that point you can make another decision of going DIY, sell and replace, or upgrading your factory bike at a pretty high cost relative to the improvements you’d like. A lot of folks come here at that point, and where you will be welcome at that time. But it’s better not to return with the illusion that you can economically upgrade a factory ebike like the others that come here, but with a desire to DIY build the bike you want.
My guess is once you start riding, you’ll be riding a lot more places than the Walmart.

 

[fill]

IMHO A cheap bike will either have a cheap battery or cheap components elsewhere that will prove a false economy if the bike is used frequently. but if used once a week or so for the odd chore could be ideal. The chances are a cheap battery will perform ok-ish until any short term warranties expire before showing noticeable signs of degradation.

Best VFM is employing a conversion kit from a trusted supplier and fitting to a 2nd use bike chosen to suit your requirements and bought at a bargain price, it may take a week or 2 for a suitable local bargain to turn up, just keep checking..

Consider comfort too if anything like me preferring not to work too hard when aided by a motor, the need to get out of the saddle to maintain momentum will be significantly diminished, and as a consequence many more bumps in the road will transfer up through the bike and seatpost to you.. seatpost suspension is a thing

 

[MxusMick]

You need to realize how heavy ebikes are, and the effort to lift onto a bus, or up a flight of apartment stairs, and if you leave the ebike outside it will be missing a battery pack in short order. If you are out on a ride and run out of power, the bike will be twice as hard to pedal, and hills will always need pedal assistance. You can absolutely teach yourself to build ebikes and create what fits your needs, go with rearhub over front hub, and middrive for steep hills. Good luck