# Theoretical e bike idea I want to make happen.



## major (Apr 4, 2008)

Wreck said:


> I really want to make one of these vehicles, but it seems like the batteries seem to be quite bothersome (Expensive) from what I have read. It seems that making your own battery would be safer and simpler to do. I have found a pretty good deal on ebay on 40 single lithium cells, each at 3.7v 5000mah. Here in Canada my government only permit's a bike not exceeding 500 watt's and a top speed of 32 km per hour( legally without license ) . I'm thinking if i putting 10 3.7 cells in series to make one 37v 5000mah pack. Probably make another and hook them both in parallel to make a 10ah pack. This would allow me to get to work and back supposedly. Could a 36v kit run a 37v homemade battery or would it be fried? Was going use battery packs like this http://www.ebay.com/itm/290756558332?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1438.l2649 to construct. Was just going to use this charger http://www.ebay.com/itm/151076612645?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1438.l2649 for the 18680 cell to keep them proper, probably get 5 to do all simultaneously. Would love some incite from some seasoned ev users/tinkerers. Thank's -Wreck


Hi Wreck,

I know you're trying to do this for just a few bucks, but the equipment you show is far to wimpy for an ebike. And I suspect the cheap cells you speak about are also unsuitable. At best, a system using these parts will simply not motivate the bike but worse may overheat and cause fire. The cell holders (and I suspect the cells) appear to be suitable for low current appliances such as flashlights or toys. 

A 500W system will draw about 15A at 36V. The small gauge wire, contacts and springs on the battery holder will not support that level for any reasonable duty cycle. And that will equate to 3C on a 10S1P string of cells. Are those cells rated to do 3C? For how long? 

I don't recall many ebike builds on this board. Thanks for checking with us but you will find much more on ebikes here: http://endless-sphere.com/

Good luck,

major


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## Ziggythewiz (May 16, 2010)

I haven't heard of any 5000 mAH cells coming close to that. Most seem to be around 2 or 3.

I'd recommend looking for 10 or 20AH LiFePO4 prismatic cells instead. Will still be a small pack but much easier to assemble and manage.


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## Wreck (Aug 1, 2013)

These are the batteries on salehttp://www.ebay.com/itm/221245626773?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1438.l2649. It does state that they are low discharge, that means it's bad from what is said by the major. It does not state what discharge rate it is but the price is right under 70 dollars. This fire you speak of terrifies me, I can only imagine bursting into flames on a bike. Sale ends in 3 day's so i gotta make up my mind if i want to risk the cheap battery. I guess i would have to make some kind of custom battery holder and use thick gauge copper wire instead of these battery cases even though they are made for the cell. The discharge rate must be a big deal then I assume.Just looked on ebay for a high discharge rate LiFePo4 battery and it was like ridiculously priced at like a thousand dollars. I have this battery in my saved list of things on ebay. http://www.ebay.com/itm/121150775376?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1438.l2649 It say's the max discharge rate is 2c so that is also a bad battery? Another question i was wondering, is the round normal shape cell better or worse that these flat packed batteries? Thanks for the input I'm glad there are still people around willing to help you out with things like this. I will check this endless sphere site out, but it sounds like i will be amassed by trolls, this site seems more legitimate. Something about it saying endless scares me like they want you to never stop or finish something. S:


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## Wreck (Aug 1, 2013)

Ziggythewiz said:


> I haven't heard of any 5000 mAH cells coming close to that. Most seem to be around 2 or 3.
> 
> I'd recommend looking for 10 or 20AH LiFePO4 prismatic cells instead. Will still be a small pack but much easier to assemble and manage.


 Like this type of battery? http://www.ebay.com/itm/12-PCS-NEW-...US_Rechargeable_Batteries&hash=item2c7139fb25 Would have to get a charger too, dang. Just clicked on the link below your message, shocky is rad Dave. I think an old Westfalia would be the funniest, the top would be flat so u could mount so many solar panels! I've have never heard of prismatic cells before this, good thing i searched this forum!


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## Wreck (Aug 1, 2013)

http://www.ebay.com/itm/390638764883?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1438.l2649 This is the kit I have bought. Estimated to take 8 weeks to ship because I opted for the boat to bring it(100 dollars off). I got the option of an lcd screen and regenerative brakes, I hope this isn't too technical for me to install. The bike getting electrified has hydraulic disk brakes, i don't think the levers supplied with the kit are compatible.I was hoping that I could just install the one motor cut off lever on the back disk and take the hydraulic mechanism off and put a cable driven unit in. As for the low discharge rate battery dilemma I've heard that the headway cell is a suitable candidate. http://www.ebay.com/itm/36V-10AH-38...US_Rechargeable_Batteries&hash=item2c71270ea7 I most likely will get this, battery management systems are something I will have to do some reading on.


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