The commuter/mountain e-bike build project

[velovelo]

I´m going to convert a bike in the new year as a winter project and I wanted to collect my thoughts and research in this thread because I would like to know your thoughts as I´m new to this. Also, looking around the web there weren´t many places that showed peoples thought process from start to finish when converting a bike so it would be a good tool for people to see the thought process and build.

Here´s my build criteria:- :?

-Speed 40km/hr top speed motor only
-Have throttle and pedel assist, pedel assist when I´m mountain biking and throttle when I´m cycling to work in 40 degrees
-Have different assist settings
-Be able to get up 5% slopes at 20km/h unassisted and steeper gradients like 25-30% when assisted.
-Full suspension
-Good for trail riding at the weekends
-Commuter bike during the week
-The odd bit of tour cycling in the summer
-As stealthy as possible
-Range 15km unassisted (flat) (this is for the commute to and from work)
-Range 100km assisted

I will update the list as I find out more about what the build entails.

I have been reading the forums for a few months and have seen some interesting articles about home builds and I have used e bikes from my friends and family but it was being able to use the public e-bikes that made me want to get back into it. I live close to the mountains and there´s some good trail riding in Madrid. It gets very hot in the summer so that´s why I´m not so keen on exerting energy during the day on the ride to work and need the range.

Does anyone have any suggestions for bikes that fit the criteria to base my conversion on?

I was thinking at full suspension 29er or 27.5er.

Here´s my original build criteria:-

-Speed 50km/hr top speed motor only
-Have throttle and pedel assist, pedel assist when I´m mountain biking and throttle when I´m cycling to work in 40 degrees
-Have different assist settings
-Be able to get up 5% slopes without losing speed unassisted and much more assisted like 25-30%.
-Full suspension
-Good for trail riding at the weekends
-Commuter bike during the week
-The odd bit of tour cycling in the summer
-As stealthy as possible
-Range 45km unassisted (flat) (this is for the commute to and from work)
-Range 100km assisted

 

[rider95]

you are not going to achieve 45km with a rang e of 45km your asking for too much .

 

[velovelo]

What sort of range would be possible if going at 45kmh?

 

[dogman dan]

At 45 kph, ( about 30 mph) you will see your watthours per mile be around 35-40 wh/mi. (sorry about the miles, but it won't matter when the calculation reaches battery size)

So assuming a 48v battery, you'd need about 40 wh x 30 miles. 1200 watthours. 1200 wh divided by 48v is about 25 amp hours of 48v.

So you will need an abnormally large battery to do the commute. 48v 15 ah is more typical, because the cost, size and weight of a bigger battery adds up fast. Handling off road will suck packing such a large battery compared to off road riding with half that.

My advice, start with a very good 48v battery that fits in the triangle of the bike. 48v 13-48v 15 ah size. That's for off road. When on the commute, add a second battery about the same size, 48v 15 ah or so.

Any chance you can charge at work, and need only 48v 15 ah?


Now to pop a few more bubbles. You will not be going up hills at 45kph. But you will go up hills twice as fast as if you just pedaled with no motor. You will pedal moderately hard up the steeper hills, just to go 20 kph.

Range will not increase by 30% because you pedal when going 45kph. At that speed, you bike will be geared too low, and even if geared very high, your pedaling will at 5-10% more range at best.

For really long range on a tour, ride very slow. At 20kph, you can contribute as much as 50% of the total wattage needed if you pedal hard. At 20 kph, a 48v 15 ah battery can go as far as 65 k.

 

[velovelo]

Thanks for the advice. Really useful for a novice like me. I guess I was just pushing my luck with those speeds and distance. I have time to charge in between rides, basically I work in various clients throughout the city for periods of about 2 hours at a time so I could charge the pack at various intervals, my longest day would look like this.

11km ride in the morning so not hot and I can peddle and I spend 1,5 hours there.
then
9km ride, it´s the middle of the day and hot and I spend 2 hours.
then
15km ride, it´s about 1pm and really hot then and I spend 5 hours in this place.
then
6km ride home and by that time I can cycle home

total = 41km with time to change in between

So really the maximum I need to go is 15km and it´s all flat. So going by your calculation that would mean 30h x 10miles = 300 wh divided by 48v is 6/7 amp hours, that should see me through if it can charge up enough in between cycles.

I think I´ll go for somewhere around 10 amp hour battery based on 48v or equivalent for my set up then.

I´ll make an edit in the specs to reduce the milage.

 

[velovelo]

Now to pop a few more bubbles. You will not be going up hills at 45kph. But you will go up hills twice as fast as if you just pedaled with no motor. You will pedal moderately hard up the steeper hills, just to go 20 kph.

Range will not increase by 30% because you pedal when going 45kph. At that speed, you bike will be geared too low, and even if geared very high, your pedaling will at 5-10% more range at best.

For really long range on a tour, ride very slow. At 20kph, you can contribute as much as 50% of the total wattage needed if you pedal hard. At 20 kph, a 48v 15 ah battery can go as far as 65 k.

Well when I say without losing too much speed I mean have enough power to get me up the hill. I´ll edit that part as well. I was using the public bikes that are rated at 250W and they are bafang geared front hub motors and they could´t get me up a 2º slope . So I wanted a motor that wouldn´t stall when it came to a hill.

This was how far I got before it stalled. I wasn´t peddling. I even had a run up at 20mph but it was a 100m slope.

 

[wesnewell]

48V 1000W rear motor kit. Look on ebay for best deal. 10ah of 12s lipo will get you more than enough to go 15km at 45kph.
http://www.ebikes.ca/tools/simulator.html

 

[arkmundi]

I suggest you research until comfortable with your choice set. Look at a variety of options. You may want to consult my Top 10 eBike Conversion Kits & Where to Buy list. I'm doing a second build on its basis and decided on the new MAC from http://em3ev.com/store/, 10T and with the 12fet IRFB4110 Infineon Controller, running with a 48V A123 battery. This kit would be quite adequate for your purposes. FYI, my battery is 4x 8S1P 24V sections resulting in 48V 40ah. Sections are back rack mounted pannier style. I ride with 20ah most of the time, but if going the distance, double that for 40ah. My recommendation is buy from one of the vendors on my list, like Grin or EM3ev, rather than eBay. Another option is to goLocal and find a vendor near where you live. Best on your build!

 

[velovelo]

Great forum thanks for posting that. I am interested in the mid drive that you have posted there rather than the hub drive because of the unsprung weight and I want this to be as capable as possible. Also I´m thinking of swapping out the mountain bike tires for some slicks for the commute which would be easier if it was a mid drive machine.

However, I do like the idea of hub drives more as I´d prefer it to be quiet and stealthy.

I thought I should start searching for the bike as I´ve spent lots of time researching drive trains and motors but not too much about the bike. I´m thinking of getting an all terrain bike and perhaps changing the stem so I get a lower riding stance for the commute or an XC bike but they tend to have less travel. I´ll test some bikes out this weekend and see. I´m going to make a decision about 29 wheels because I´ve never ridden a mountain bike with 29s but I hear good things about them.

 

[velovelo]

48V 1000W rear motor kit. Look on ebay for best deal. 10ah of 12s lipo will get you more than enough to go 15km at 45kph.
http://www.ebikes.ca/tools/simulator.html

I´ve been deciding between the bafang mid drive and the rear hub motor that kepler used in his super commuter and the mid drive mountain bike. I liked the stealth and simplicity of the hub gear but it lacked a bit of power I´d want for my set up and with the mid drive I´d need to include gear shifting solutions and it´s a little less stealthy.



However, I think I might have come up with a solution in the BMC V4 geared motor which can be run at 1000W no problem and at 170mm is a little bigger than the Bafung at 134mm diameter but i think i can get away with hiding it with a 180mm disc brake. I´ve had no experience with riding full suspension e-bikes to know if the extra weight in the wheel will affect the performance of the suspension significantly. The BMC is 4.5kgs and the Bafang is under 3kgs.



You can read the review here

https://www.electricbike.com/bmc-hub-motor-review/

 

[dogman dan]

Whatever you choose, if you have 700-1000w of power, you won't have any difficulty getting up a steeper hill.

250w sounds like a lot, but heating losses in the motor and controller mean less than 250w reaches the road. If you have 500-750w or more actually getting to the tire, then you have lots of power to get up steep hills.

Even though you can charge along the way, 48v 13 or 48v 15 ah will give you more freedom from the charger.

 

[velovelo]

Thanks, I´ll choose between that range of Watts then and try to keep it as stealthy as possible. I´m still undecided on mid drive or hub drive.

About the battery, I was thinking about fixing a pannier to the back, bar bag or even a saddle bag (if I can get away with it) to house a small capacity battery and create a socket that plugs it in by means of the bag clicking into place. I´ve used a Brompton that has a font pannier which houses the battery, charger and controller and you just slide it in and that effectively plugs the battery in so I´m thinking of doing something similar as I would have to remove it and put it back many times a day.



I´d like to go with 10amp hrs max for the commutes and perhaps a more durable battery in the triangle with a proper connector for off road use so the bag doesn´t jump around and cause the connection to be interrupted and also a battery in the triangle would help to keep the weight down low.