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Anybody into Electric-Bicycles? Looking for a custom battery pack!

jimdt7

jimdt7

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Hello everybody,
I use my bicycle almost everyday to go to work and since my birthday was 2 weeks ago I managed to gather a good amount of money so I decided to convert my bike to an electric one probably using the Magic-Pie 3 kit. The only thing that is killing my pocket right now is the battery pack. Most seem to start at 200-300$. Any cheaper options? Do you think I could create my own using quality 18650 batts in series? :thinking:
Bottle shaped would be best
At least 36V
10AH
Preferably: LiFePO4

Thanks in advance,
Jim
 
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jimdt7 said:
Hello everybody,
I use my bicycle almost everyday to go to work and since my birthday was 2 weeks ago I managed to gather a good amount of money so I decided to convert my bike to an electric one probably using the Magic-Pie 3 kit. The only thing that is killing my pocket right now is the battery pack. Most seem to start at 200-300$. Any cheaper options? Do you think I could create my own using quality 18650 batts in series? :thinking:
Bottle shaped would be best
At least 36V

Thanks in advance,
Jim
Click to expand...



Well, the 18650 route works for the Tesla, so why not?

For 36 v minimum, you'd only need ~ 10 cells. (3.7 v each...)


I'm not sure of the amps you need though, and, that's probably the limiting factor rather than the voltage.

If you know the amps needed, you could then figure out how to wire it. In series multiples the volts but the amps stay the same, and if in parallel, the amps go up but the voltage stays the same, and so forth, so, you'd need to find a combined configuration that gave you BOTH the volts and amps needed.


(Some in series and some in parallel, etc..)


:D
 
Ebay is full of Electric BIKE / Scooter batteries and chargers. I myself have got a
Schwinn XCEL Long Range Electric Scooter. Got a electric wheel chair microprocessor
controlled charger at a Good Will for $2 buck!!!! Charger worth about $150.00.
Works perfectly with the little scooter. It is a 24vdc lead acid powered scooter with about
a 8 to 10 mile range. Top speed is a blistering 15mph with a good tail wind.


36V 20AH Portable LiFePO4 Li-ion Rechargeable Battery for Electric BIKE Scooter

36V 20AH Portable LiFePO4 Li ion Rechargeable Battery for Electric Bike Scooter | eBay
 

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First of all thank you guys for the replies but how the heck am I going to carry that battery-block? :p

Jim
 
jimdt7 said:
First of all thank you guys for the replies but how the heck am I going to carry that battery-block? :p

Jim
Click to expand...

electra-commuter-backpack-180299-1.jpg
 
I've contacted them via eb@y since they claim that they can build custom battery-packs! :beer:

Thanks again,
Jim
 
So what about the current rating of the controller ? GM never announced what it was, but I can reveal after testing under a few different conditions with hard starts and up steep hills that the max current is about 28 amps. For the most part it's hard to get it to draw more than about 22 amps and if I had to put a rating on on it I'd say 25a. That's not too bad for an integrated controller and infact that's all the old 12 fet GM controllers would do.

It's quite an 'economical' motor, only drawing about 5-10a for the most part bar hard acceleration. I did 2 quick test rides with a 10S lipo pack (~40v actual voltage) and a 15S lipo pack discharged a little so it'd operate under the 60v HVC. Actual running voltage with the 15S pack was about 58v. Peak power draw on 40v was 1000w, peak on 60 (58) was 1600w.
Click to expand...
Magic Pie - first taste

Looks like ~30A draw in some situations may be necessary. You'll need high power cells, or you'll have to make a series-parallel array, which might be complicated to charge properly. Yeah, a pack maker ought to be able to get you what you need. Just make sure they know how much current you require too
 
It the pack ends up being lithium polymer or lithium iron phosphate make sure to have a balancing connector and a decent charger with balancing function

I needed 40 volts for something and I made 2 , 6 Cell lithium iron phosphate packs as most good balancers/chargers are capable if 6 cells max .
 
Well you say nothing about capacity or power draw requirements, so it's hard to recommend anything. I assume you'll want at least a few dozen amps of draw. If so I think LiPo batteries would be best.

The cheapest option would be something like three of these in series: Turnigy 2200mAh 3S 20C Lipo Pack

But more practical is probably a single 10 cell battery, like one of these two:
Turnigy nano-tech A-SPEC 4000mah 10S 65~130C Lipo Pack
ZIPPY Compact 3700mAh 10S 35C Lipo Pack

As said, I have no idea if this is enough capacity. You can put them in parallell to get double the capacity, but then you start to approach the price range you didn't want anyway.
 
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jimdt7 said:
Hello everybody,
I use my bicycle almost everyday to go to work and since my birthday was 2 weeks ago I managed to gather a good amount of money so I decided to convert my bike to an electric one probably using the Magic-Pie 3 kit. The only thing that is killing my pocket right now is the battery pack. Most seem to start at 200-300$. Any cheaper options? Do you think I could create my own using quality 18650 batts in series? :thinking:
Bottle shaped would be best
At least 36V

Thanks in advance,
Jim
Click to expand...




You could also just buy a used motorcycle or moped and call it a day.

:D
 
The cheapest option used to be, and might still be cordless drill packs. If you can find a few identical
ones that are 36V, all you would have to do is remove the circuit boards and connect them in parallel.
This is pretty dangerous unless you know what you're doing. It would be a good idea to connect them
hrough resistors until they are in balance. Otherwise the pack with higher voltage will try to charge the
one with lower voltage through what is basically a dead short. Then the whole thing would have to be
housed in a protective box. Strapping them to your back is not a good idea. I would either attach them
to the bicycle frame somehow or even safer, put them in a child carrier behind the bike. Lithium cells
do not like to be dented. You have been warned.
 
You could strip down a drill pack and stuff the cells inside a thermos flask or a mini keg. Thick cardboard
or cut up cutting board could be used as an insulator.

mini-keg.jpg
 
Sadly ebay deal is off since they informed that they don't ship to Greece...! :/ Using Li-Po's is also off at the momment due to the fact that they can become very dangerous, especially for first-time users.

Jim
 
So while I was eating today, an idea came to mind. Is it possible to build a boost driver like the ones we use here but for higher voltage and amps in order to reach 48V using a 36V battery? :thinking:

Just my 2cents,
Jim
 
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