First Time E-bike Builder with questions.

barry donaldson

New Member
I intend building my first E-bike, from scratch. I have decided to use the Bafang Fun8 for power source.
But have questions!

Does the engine have to sit below the frame our can it be installed between the V bars?

I hear bad things about the chain ring and its weight, would you change it and if so what for and how easy is this?

Do you always go for smaller ring, less teeth?

I want to use a double battery set up, Has anyone done this, and if yes how.

Can I fit a immobilizer to the engine, as I wish to use the bike round town and do not want someone riding off on it.

I wish to fit power lights back and front. how do I rig this?

Thats it for the moment any help would be gratefully revived. Do not want to spend money, without knowning what i am doing
 

pxpaulx

Well-Known Member
You'll probably get much more detailed (and just more) responses over at the endless sphere forum, it caters to diy electric vehicles, including bike builds. I'm sure there are a few knowledgeable people here as well!
 

harryS

Well-Known Member
The thieves can easily ride away your bike without power, or they can toss it in a van/truck in 30 seconds.

I never changed my front gear. Easy to do, but it costs $80-100 USD for a different one. Too much for a hunk of metal. Mine is a 46T and suited for flat terrain.

If you must use a double battery, I suggest you just run them one at a time and switch connectors. Keep it simple and you won't get careless and screw up. When you put them in parallel, or use a switch to flip between them, the details are important. Higher voltages. Lots of power. Even switching connectors will toss sparks unless your batteries have on/off switches or you use anti-spark connectors. Many of us barely have room to mount one battery. Why have two? Just get a bigger one.

There are step thru frames where the lower bar comes out almost perpendicular to the seat tube that take a vertical mount, but none of my bikes had the room. If you can rest a DVD disk between the two bars, maybe a BBS will fit.

It's simpler to run lights that use their own batteries. A rear flasher doesn't take much power. A really bright front can use rechargeables. An ebike battery would need a DC-DC converter to power LED lights. The converter will draw power just sitting there, so you have to wire it so it doesn't. Where you going to put the converter? More wires running around? After you get some wiring skills, you can look at this.
 

barry donaldson

New Member
Harry thanks for information. The Chain Ring had me worried are you saying that the one supplied is good enough. I had intended having a professional do a wiring harness for me, light, horn, key start. so the battery info is useful. the idea behind the double battery, is to give a longer travel distance between re-charge. Harry is there a re-charger that can be mounted too the bike, so i do not have to remove battery's?.
I am trying to recreate a pre-1915 motorcycle look for the bike.

thanks for the info.
All the best

Barry
 

harryS

Well-Known Member
The thing about the chain ring is its alignment relative to the rear derailleur and the freewheel/cassette, which is called the chain line by the bike guys. Mine came out fine. No gear slip or shift. They designed this to fit the average bike, after all. Other users need to change its offset, or they beat their bikes to death. so they go with third party. For a show bike, you probably want something that looks better than the Bafang part, made for the masses in China. Five or six allen head bolts, and its easy to swap.

If you want looks, batteries are sure to ruin them, especially two, but a good artist could make it work. Put them in the fake 1913 vintage fuel tank.
 

barry donaldson

New Member
Harry Thanks for additional information. what do you suggest for chain ring if I am to change it out.
Yes that was always the intention with the battery's to have them side by side with a tank cover. I am trying to build a city cruiser type bike with very long ride range and 15.5 top speed. Little peddling as possible.
can battery's be charged on the bike or do they have to come off.

once again thank you
 

barry donaldson

New Member
Thanks Thomas.
I have been looking at sine wave controller units, to wire up front and rear lights, on and off key switch, throttle control.
Is it possible to run two battery's through one of these controller to the motor.
I had considered a flick switch between the two. But I want both battery's to work in tandem.
I had looked at both the Lekkie and Luna as you suggested. But I have been told that there is no need to change the chain ring, supplied by Bafang. The bike will just be a city cruiser.
So do you think it would benefit from a new chain ring or do you believe the one supplied would be ok.
Once again thank you
Barry
 

Thomas Jaszewski

Well-Known Member
The OEM chainring 46T is fine. As a matter of fact I put mine back on when a Wippermann Connex eBike chain wouldn't run on the upgrade chainrings. Many consider the 42T upgrades the sweet spot for gearing and on some bikes they give the builder a better chainline. For others it's esthetics. The OEM is heavy and ugly by comparison. If you have a good chainline and are happy with the supplied I say ride and enjoy. Yet other use an adapter and aftermarket chainrings of various sizes to meet specific requirements. I'm doing that on a one speed Fat Bike to get a 38T x 22T gearing. I believe 38T is as small as you can get with an adapter. BTW the 46T OEM can be a bit faster than a 42T aftermarket.

Running two batteries in parallel has some difficulties. Both should be absolute identical builds and ratings. They MUST be charged separately. They should always be charged to the same level. NKK has the only switch I've found with acceptable specs for a 48V battery. We've been running one of them with a 20A controller for over a year without a problem. We are a little out of spec with a 30A system now being built.
 
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harryS

Well-Known Member
Like Tom says, running two batteries in parallel makes things complicated. You always have to mount them fresh off the chargers at the same time, and you have to make sure they are at the same voltage initially. If you are in a hurry, and want to mix old and new batteries on the bike, well you cannot do that. Keep it simple.

If you have to have two, your guy can install a switch to flip between two separate batteries. I consider that needless effort. He will have to engineer parts and wires to handle all the current. Sure, it's doable, but why bother. Use a larger watt-hr battery and manage your riding so you don't run out.
 

Thomas Jaszewski

Well-Known Member
HarryS gives good advise. A switch will work and I have a fellow I did one for that's very happy. BUT the specs are, well, questionable. No problems but if you are having someone do the work I'd avoid it.
 

barry donaldson

New Member
Thanks Guys. all of this information is extremely useful.
Do any of you have views on using a Sine wave controllers, it seems to be the easiest way to connect F/R lights/throttle/off and on Key/horn.
I want to mount two batteries side by side along the crossbar, and I am having a fabricator, build me a battery mount to do this. Are there any other problems I should look out for, mounting two batteries in close proximity.
 

Thomas Jaszewski

Well-Known Member
I'd look at ebikes.ca for a controller. They have an incredible product. The C_Phaserunner. But there's only one left for now. With the CA3 an incredible performer. It's on my list for purchase when the new stock is in. Their Grinfineon controllers are among the best on the market. But not sinusoidal. The buzz is nearly inaudible.
C_PhaseRunner