first ebike build

[gogreenpower]

Hi guys,

Well I'm about to embark on my first ebike build, I've spent weeks researching and using calculators and I'm more confused then before I began!

What I want to know is what setup will I need to acheive the following:

1. 45-50km (27-30 miles) minimum range with light pedaling.

2. 25-30kmh (15-19mph) while not attracting attention so a small rear hub motor would be preferable.

3. Cost less than $1000

Some other useful information, I weigh 80ish kg (177lbs) and I'll be riding on terrain that is virtually flat but with possible strong headwinds. The donor? bike is a 26" beach cruiser, and it already has front hydraulic disc brakes.

My limited knowledge has led me to the following site, conhismotor.com and before I purchase anything I wanted to know if they would meet the above requirements? I'm open to suggestions also.

48V 350W Mini Motor
48V 25Ah LiFePO4
BMS 60A (120A at peak)

Thanks

 

[wesnewell]

First thing you need to do is go to the User Control Panel, select Profile, and then enter your location into the Location field. Minimum entry would be just the country you are in. This will help people help you. Example: Wylie, TX, USA.

 

[gogreenpower]

ok my profile is updated, help away!

 

[AussieJester]

welcome to the Sphere, perhaps contact fellow Aussie member Hyena (or click link in my sig) and see what he can do for you kit wise, hes a reputable dealer with many happy customers

KiM

 

[dogman dan]

If you really keep the speed that low, 20 ah of 48v battery will be enough. Riding faster, you'd need more, but at the low end, 15 mph, you could reliably get 35 miles from a 48v 15 ah.

But I'd advise getting the 20 ah, so you can easly make your distance at 20 mph.

 

[gogreenpower]

welcome to the Sphere, perhaps contact fellow Aussie member Hyena (or click link in my sig) and see what he can do for you kit wise, hes a reputable dealer with many happy customers

KiM

thanks, i've sent him an email, just waiting for a reply.

If you really keep the speed that low, 20 ah of 48v battery will be enough. Riding faster, you'd need more, but at the low end, 15 mph, you could reliably get 35 miles from a 48v 15 ah.

But I'd advise getting the 20 ah, so you can easly make your distance at 20 mph.

does a 48V system use more battery power for a given distance than a 36v? some recommended a 36v 350w motor and 36v 12ah li-ion battery to meet my specs.

 

[dogman dan]

Only if you let it rip. Many do ride faster if they use 48v, so more voltage can use the battery up faster. 36v will get you going 20 mph for most hubmotor kits. As for the capacity, 30 miles at 20 mph out of 12 ah would require heroic pedaling. Not saying it can't be done, but it sure wouldn't be done by me. At 12 mph, you likely could go 30 miles on 400watthours of battery. 36v X 12 ah = 432 wh. At low speeds, your pedaling is a much higher percentage of the total energy needed.

Basicly, most of use use about 400w to go 20 mph no pedaling. This remains the same regardless of voltage. So 400w for one hour gets you about 20 miles down the road, if there are no stops at all. Because of stops, headwinds, hills, etc use more power, a 48v 15 ah battery or a 36v 20 ah battery is a good size for reliably going 20 miles at 20 mph. That includes a reserve for a really windy day, capacity drop for a really cold day and such.

48v 15 ah or 36v 20 ah has about 700 watthours. So 25 miles at 20 mph, including many stop signs, is quite possible if you discharge it 100%. Idealy you size the battery up enough to use more like 85% daily. Nothing wrong though, with dicharging lithium batteries 100% once in a while when you really need it.

 

[Drunkskunk]

..... some recommended a 36v 350w motor and 36v 12ah li-ion battery to meet my specs.

Someone may have mislead you.

To qualify that, to go 30 miles with a 36v 12ah battery, you would have to get 14.4 watts per mile and drain the battery 100%. That is possible, on flat ground with no head wind, few stops, and lots of pedaling. You might even get further. It might be fun to try it once in a while.
But for the real world, you'll need about double that size battery. You are going to have hills, stops, wind, low tires, bad days when you don't want to pedal as much, and the normal loss of capacity of a battery as it ages. You'll also need a reserve, as fully draining the battery every time will shorten it's like considerably.
You're also going to find you pedal a lot less than you think you will. It happens to nearly every one. Ride an Ebike a few times and it gets too easy to let the motor do the work, or maybe you keep doing the same amount of pedaling, but you let the motor carry you faster than before. Either way, you'll find you use more power than you planned because you can. And it's fun. And it's fine. just plan for it now and get the size battery you'll actually need, instead of some battery that would work in theory.

 

[gogreenpower]

The range I wanted was to and from work without a charge, but I recently saw a water kettle battery? 36v 12ah Li-ion, Looks like a drink bottle and its removable, so if I recharge at work, that leaves a 15 mile range required, (it's only 12.5 miles, 80ish % capacity)

Would that 12ah get me there doing 20mph with a lack of interest in pedaling?

 

[dogman dan]

Not likely. For 36v, I have a rule of thumb for range, that is 1 ah = 1 mile at 20-25 mph. This rule includes some reserve, but only a small one. So to reliably go the 15 miles, you'd still want about 15 ah. There will be those days when you have a headwind, and a cold day with a headwind, yer screwed since below 50F you will lose capacity from the battery.

12 ah of 36v would do it for a really energetic pedaler at 20 mph, or no pedaling at 15mph . Slowing to 18mph, you ought to just make it with some mild pedaling, but you'd be discharging it 100% every day, which often shortens the lifespan of a battery quite a bit.

 

[gogreenpower]

OK, so after weeks of mental anguish I ended up going for a 36v system with a 20ah li-ion removable battery, the donor bike has turned up, accessories are in the post, now waiting for it all to arrive.

I'll post some before and after pics once I have everything.

And thanks for all the help.

 

[gogreenpower]

here is a link to my efforts

http://endless-sphere.com/forums/viewtopic.php?f=6&t=46978&p=688078#p688078