help me build my second e-bike

[audipiglet]

Hello everyone, I have been e-biking for two years now on my cheaply made e-bike and enjoyed every minute of it, but after nearly 2000 miles it is time for an upgrade, my bike at the minute has a 750 watt motor 22 amp controller off eBay and a very heavy 36v 20ah SLA battery which gives me a top speed of about 20mph on the flat and 20 mile range, it gets me up the little hills on my way to work fine without peddling but I do help it out,

These are the problems I would like to sort out for my next e-bike

The battery is far to heavy for my bike and the location is not great, I would like lifepo4 if possible not lipo because they last longer and safety, and to plug and play,
I have to adjust the v brakes and rear wheel often, mostly to do with weight of the battery and a cheap wheel
Acceleration is ok with peddling but could be better but more speed would be much better
The back roads I go on are bumpy so full suspension would be great
Brakes are not very good, my cheap back wheel is always buckled and it doesn't make it easy to set the brake up

I would like a commuter e-bike that can go about 30mph for 20 miles which requires less maintenance than my bike at the minute, I'd like to have a 48v lifepo4 battery because I can use it on my motor until I upgrade it to a better motor, I have been looking at lots of people's builds on here and I like the look of drunkskunk's monster build, looks very strong and as stealthy as can be, but a bit too powerful (and expensive) for me, I haven't seen any frames I like so I want to make my own, I am handy with a welder but not very knowledgeable with bike parts (suspension, brakes) or with batteries so any information on these areas would be great, I've rattled on enough but wanted to give you as much info I could, thanks for looking!

 

[samoloh]

Ok I just got my first e bike build this week, its a 9C hub motor from ebikes.ca, I have a 48volt 10ah pack from A123RC that get me to about 30 mph holding the throttle down for quite a bit (15-20 seconds) its was good for about 41 km before I ran out of battery (not doing full throttle, and across different terrains)

 

[audipiglet]

Sounds like your motor/battery combo would be perfect for me! I thought I would have to have a 48v 15ah battery to go that far, how long have you been using your bike? Not had any problems?

 

[samoloh]

Sounds like your motor/battery combo would be perfect for me! I thought I would have to have a 48v 15ah battery to go that far, how long have you been using your bike? Not had any problems?

Too early to tell barely had it for a week, but quite a no of people recommended the 9C motor

 

[deffx]

I think id start by switching to lithium in a frame triangle bag and a maybe a thudbuster

Should really wake that bike up, then at least you can use it until you build your frame and transfer the electronics over

I like the idea of a steel trellis frame too, not being able to weld sheet aluminium

 

[dogman dan]

You may or may not quite reach 30 mph by simply switching to a 48v battery. At the very least, you will see 27 mph. If you can go a solid 25 mph now, you will see more like 29 mph on 48v.

Get a 48v 15 ah lithium battery. 15 pounds or less, and it will go a solid 20 miles at 27 mph. It should fit in the triangle of that bike, greatly improving the handling. You should be fast enough at 27 mph. By 35 mph, cops will be looking at you like .

I see NO REASON to get another motor. If you insist on 35 mph, then get a different controller, and run 60v or 72v.

Re the frames, lots of stuff here to imitate, but you'll have to dig for them. Locate the battery along the bottom tube. A common good idea is to make that tube into two smaller tubes, about 5 inches apart, to support a battery container really well. Can be round stock, or square. A slightly longer wheelbase is nice too, making a behind the seat battery box an option.

 

[audipiglet]

I was thinking a 48v battery was next on my list, just wanted to get a long thin one from somewhere so when I build a frame it will fit nicely into the bottom tube. I will get some square steel tube, easier to cut all the angles, I only see 20mph on the flats at the minute so I guess I'll get 25ish with 48v.

 

[dogman dan]

That could be a good thing then, if you have a slower wound motor.
The slow motors are a delight at 72v.

Or, a faster wind motor would work fine with your existing controller and 48v 15 ah of lithium. You'd be easily able to design a bike to carry that on top of the down tube. There is appeal to completely hiding a battery in a fat down tube, but for me, it's an absolute must that batteries be able to be completely removed from a bike in a few seconds. It needs to be easy for convenient charging when the bike cannot come inside, or to look over the battery for physical damage.

Check out the frame design of the EV Global. You would be very hard pressed to find much better battery tray designs than they came up with. Copy them shamelessly I say. Or better, snag up a used one.

 

[audipiglet]

If I can get to 30mph on 48v I would prefer it to 72v, I think 72v is a lot of battery, I am thinking in the long run when I need to replace them it will get expensive about 30mph would be ok, like you say dogman I'll get noticed at more than 30mph and trying to hide a 75v 15ah battery would be hard going, taking out the battery quickly and easily is a must, those EV global bikes do look good, I'll have a good look at those and see what I can borrow from them!