Advice on full e-bike build for someone new to the field

[TriggerGee]

Hi I've been reading through some topics already but I'm getting quite over loaded with info especially after spending the last two weeks trying to work out how to build a 18650 pack out of old laptop batteries...

My brief story is I enjoy mountain biking and fast motorbikes but I've got a degenerative muscle condition which means I can't ride my mountain bike the way I want to if at all in the future so I started looking into E-bikes and was led here.
I want to convert my bike so I can ride about 15-20 miles including most importantly some steep hills and rough ground which I just can't do any more. My bike is a 29 speed, hydro disk brake, front suspension, 26" wheel "boardman comp".
Speed isn't as important to me as hill climbing and range as most of the time I've got my dogs with me and although thy can run at 30 mph it's not really fair

I've been looking at 1000w rear hub motors from various places but don't know if that's what I should get and when from, I don't know what the pro's and con's of geared or gearless, rear hub or mid placed crank type, what brushless means and most other important things I should know.
I also need help building my battery or advise on buying, for instance do I need a bms in a li-ion pack?

I know I've asked a lot but there is a lot to know, any help would be very much appreciated!

 

[nutnspecial]

Welcome Trigger!

I may not be the most experienced as I've only been on this site for a month or two, but have a little advice.

If money isn't that important, I'd go with a mac. em3ev-com has the specs of each model to help decide whether you'd want 6,8,10,12 turn. I'd recommend buying for your max speed, keeping in mind torque and low speed performance suffer the faster you spec the motor. I think the 10t will give 25ish mph @48v, so that might be a good choice. They are also 30-40% lighter than non-geared hubs, with the main trade off being limited in speed compared to their counterparts.

The same reasoning holds tru for non-geared/directdrive (probably what you were considering), and because most of them come set at faster speeds for even 36/48v they just don't have the same power at lower rpms. (plus DDmotor rpm=wheel rpm, whereas gearedmotor rpm=5x wheel rpm, so mac is gonna do so much better at low speeds 20mph or less) If you want simplest and cheapest, try the amazon/ebay directdrive kits. It's still gonna be a huge power supplement, and half the cost of a mac.

Middrives are best for offroad because they center weight on the bike, and the ability to choose what gear you want the motor to work in. Probably more expensive than the other two, a little harder to setup, and you can't 'hotrod' them as much. They have much appeal as 'best of both worlds'

You'll find alot on the stickys and the wiki to help yourself decide. On batteries too.

I went with lipo for it's power, versitility in formfactor, best price, and voltage selectability/changing.
They are most dangerous and not anywhere near the userfriendliness of a store bought pack.
I can't offer much more than that on your batt question.

Have fun with it, looking forward to see what you end up with!

 

[Triketech]

Bafang BBS02 mid drive.

If you're handy with tools and smart enough to figure things out, and don't mind charging in a metal can get cheap LiPo batteries. Otherwise look at LiM batteries.

If you really want safe charging, go with LiFePo batteries.

Not much else to really consider.

 

[Russell]

First, start reading the WIKI;

http://www.endless-sphere.com/w/index.php/Main_Page

...also determine how much it is you want to spend.

-R

 

[TriggerGee]

Thanks guys, that's a ton of info to get me started, many of the terms used I still don't understand so that wiki link is going to be very useful. I am relatively competent with tools and such as I do all my own motorbike repairs but looking at some of the work on this forum I'm amazed! Some truly superior builds.

For this project money is a concern, I can probably stretch to close to £500 for the conversation not including the battery which I know is not much and I need it to be discrete as UK laws only allow for a puny 250w motor for road use, although most of my riding is off road I have to travel a short way on the road to get there. I forgot to say I only weigh 140lbs/ 10 stone/ 64kg so hopefully that makes things easier. 25mph is probably enough on the flat if I can tackle steep rough climbs or grass at lower speeds. Also any way I can escape downgrading my gears would be a bonus!

 

[dogman dan]

You will get the most out of a puny 250w limited motor by going with a mid drive, such as the bafang mentioned above.

But if you are willing to run 1000w, very simple to install a larger rear, geared hubmotor such as the Mac 10t, or similar size bafangs. This type of motor can be ridden on pretty steep singletrack, if you can just pedal some from time to time on the steepest bits.

I have a health issue too, but I can still ride single tracks very fast with my geared, 48v, hubmotor. Here is a picture of my dirt ride.

Unfortunately, you might need to increase the budget.

 

[ziltoid81]

Offroad=middrive......sometimes solutions are this simple. :wink:

Measure your bike, you need a 68 to 73mm BB and some room around it, then the Bafang BBS01/02
will fit on nearly every bike.

You also needsome kind of chain guide with the BBS......

 

[TriggerGee]

Ideally I think I would have 1000w or over rear hub with the ability to use cassette type gears, still not sure on what the geared and ungeared is. The bafang mid drive motor is only 750w and it looks like I'd loose two of my three front gears?.

 

[dogman dan]

Yes, with the bafang bb mid drive, you only get one front cog.

Mid drive can be badass, no doubt about it. But I have not experienced a more powerful one. 250w the one I've had. Above about 750-1000w, it's going to be real hard on regular bike chain, but you will get a lot of torque with just 750w. So you won't really need the tiny front chain rings at all. Just get a cassette with a large inside cog.

A geared hubmotor is a compromise, but works pretty well. Not so heavy as a monster direct drive hub motor, so you get used to the heavier wheel quickly with a geared hub motor. The nice thing about a hubbie is you can have 1500w on the geared ones, or 3000w on up on the big direct drives.

 

[TriggerGee]

How do you think the torque compares on a 750w mid drive to a 1000w geared hub? Am I right in thinking that the mid drive motor powers the actual bike chain and there for I can use the rear gears with the motor, thus giving more speed on flats in a high gear and better hill climbing in a low gear... Also would I be able to keep and use my 9 speed cassette? I suppose I only really use my middle cog on the front anyway....how easy is the bafang mid drive to fit?

 

[beast775]

Building a battery is a valuable learning experience that can never be rep[laced :wink: ,but dont rely on laptop batteries to get you very far on a first build.

 

[nutnspecial]

Am I right in thinking that the mid drive motor powers the actual bike chain and there for I can use the rear gears with the motor, thus giving more speed on flats in a high gear and better hill climbing in a low gear

Yessir.

I never have, but I don't think it's very hard to install. Yes you can use same cassette/chain/ 1 chainring.
Torque would have to be more for mid on similar wattages if you're running the motor through the lower gears on the cassette- only difference is having to shift thru the gears to accelerate fully.
Find some utube vids of the different systems? thats what helped me alot.

I wonder if there's a way to scavenge this site just for utube links?

 

[TriggerGee]

I've spent the whole evening researching the bafang bbs02 mid drive system and I think I might be sold on that one. It's a little less power than I wanted but the ability to use the gears should really help but I guess I won't know if it'll do the hill I want until I try it. I like the low wieght and wieght distribution being central plus installation looks really simple so it's ticking many boxes. Bmsbattery.com sell the kit as well as various battery packs, does anyone know if they are a trust worthy supplier and if the batteries are any good because I am getting fed up of testing these old laptop batteries which so far aren't that good (less than 2,000mAh) should I be wary of buying a restricted kit? I don't want that but I'm in the UK so they might try to sell me one

 

[nutnspecial]

I think that's a popular kit. Try to find different user vids of different middrive kits for comparison? I don't too much about them other than a little power goes a long way when you apply it thru the crank. And you're right, they are the most bike-like.
I don't think they'll sell you a limited version just because of your address, but whatthehey, just make sure with them.

Bmsbat is prob as good as any other batt supplier? I was about to buy from halomotor on ebay b4 I realized I'd need a huge battery to deliver 4500 watts if I didn't use hk lipo. So that's what I went with-forbetterorworse lol.

 

[Lurkin]

Em3ev is considered better, but more expensive.

Check your bb width before buying. Must be max 73mm, min 68mm, ideal being 68mm.

Still possible > 73mm but requires extra kit and gets more expensive than your budget.

If > 73mm, your looking at a rear hub motor. Would be time to consider drop out width and torque arm requirements. Do these thing before buying a motor to avoid buying motors that will not fit your frame.

It would be helpful to post a pic and description of your bike....

Its likely the mid drive will be more suitable for you given you can make use of rear gears.

 

[TriggerGee]

My bottom bracket is 68mm and the bike is a boardman hit comp, 27 speed mountain bike.
Is it possible to turn the power on the mid drive motors to 250w using the lcd controller on the handle bars or something like that? So I could stay legal on the road then once off road switch it back up to full power?...

 

[nutnspecial]

Nice bike! I went from a 24spd down to 5spd and miss those gears when pedaling with no motor. The bht motor doesn't need/use any bike gears, but inversely I had a hard time keeping even 5 gears to retain 'bikeness' with the motor sprocket and freewheel back there.
I'd really love to try a middrive kit someday.

The cycle analyst has fairly stealthy modes. x3 and you can switch very easy, but it's not obvious to someone inspecting the bike. I am currently only using mine for speedohmeter/mileage, amp/voltmeter, and power source for headlight. Everything else is through the controller, but suprisingly the ca did limit power when it hit the low volt setting yesterday. Not sure how it did that. It's not the simplest to figure out imo, but if you do it offers the most options for control in it's class.

There's prob other optionsfor speed or power limiting, even the 3 spd switch with the infineon controller can be programmed to whatever settings you want for power.

Then there's custom hidden electronics with hidden sensors or rfid's, there's prob some good threads on the subject come to think about it!
All depends on how tricky you want to be, and how custom to go?

 

[d8veh]

Only the 250w BBS01 is legal, but you can reprogram it to 18A (350w), which is still legal as far as I can see. There's nothing you can do to make a BBS02 legal because it's not a nominal power of 250w, which is the max allowed in UK.

 

[TriggerGee]

Thanks d8veh, that's what I thought really. Oh well I'll just have to break another stupid law, 250w isn't going to get me up the hills I come across and I'm not giving up cycling when the tech is out there...

I've been quite surprised by how simple the bbs02 is to fit and it's fairly low weight, it's also quite descrete so hopefully know one will notice. It would take a mean copper to do me for it but they're out there

 

[arkmundi]

Speed isn't as important to me as hill climbing and range as most of the time I've got my dogs with me and although thy can run at 30 mph it's not really fair

I've been looking at 1000w rear hub motors from various places but don't know if that's what I should get and when from, I don't know what the pro's and con's of geared or gearless, rear hub or mid placed crank type, what brushless means and most other important things I should know.

Geared motors do provide more torque. Love my MAC 8T... see more options on my Top 10 eBike Conversion Kits & Where to Buy thread.

I also need help building my battery or advise on buying, for instance do I need a bms in a li-ion pack?

Certainly the way I'd go if I were so inclined (and am, as my packs are made by myself. Read up on the ins & outs - there are lots of threads here. There's an on-going debate about BMS or not-to-BMS. I'm in the latter camp. But I use very high end & robust A123 AMP20 cells that stay well balanced without and do active monitoring on my pack's state of balance & health.

 

[TriggerGee]

The kits you suggested look good and I'm sure they are better than the bbs02 but they're also much more money and a lot more conspicuous which is an issue for me as I should only really have a 250w to stay legal but I'm going for a larger wattage than that. What is it that fails on the bbs? Why are they not good? I should say I'm not doing hard core off road riding just some bumpy tracks and steep hills.

The cells I'm trying to use are all reclaimed laptop cells so not the best anymore, would I be better off with a bms in this instance and where do I buy them from, how do I fit it? Lol I know so much.......

 

[docnjoj]

There is a member here, Drkangel, who has written a lot on using laptop used batteries. It is a lot of work. Read his stuff. Your battery is the most important piece of equipment on your bike. I would bite the bullet and spend the money for a good one as your first. Then you have baseline for comparison. You can't go wrong with a good battery no matter what motor you use.
otherDoc

 

[TriggerGee]

I'm starting to realise how much work they are to put together to create a useful pack, I've spent a couple weeks charging, testing, re-charging and so on and still am nowhere near knowing which cells to use lol. At best I'm getting 2,000mAh from a cell but mostly they are below that.

I've been looking at the packs from Em3Ev more specifically the 50v 19Ah one for around £450....lot of money but I agree that I should start with a good one whilst I (hopefully) build the other one. Are their batteries good? The cells if genuine are good I think and the 14s instead of 13s most others like bmsbattery use should really help no?

 

[d8veh]

The 48v 11.6Ah 09 bottle battery with Panasonic cells from BMSBattery is pretty good. It'll give 20A continuous, it's cheap, easy to install and looks good too. If you need more range, you can carry a spare as they only weigh about 3.5kg.

 

[TriggerGee]

I'm just concerned 11Ah won't be enough but to be honest I've got no idea, if anyone can give an estimation that s accurate that would be good. Like I said in my first post I'm looking to go about 15-20 miles maximum with some pretty good sized hills and grass to get over and I'm looking at a 1000w or so motor, most likely the bbs02 and I weigh 10 stone/ 64kg