# I need help answering some battery questions...



## [email protected] (Jul 5, 2008)

OK for starters my name is Travis and I own a small business here in So-Cal building limited number custom motorcycles and bicycles and CNC parts. I'm planning to test the market with a custom built electric bicycle that I may build in small batches of the highest quality both in design and components.

I've been slowly building an adult sized low-rider stretch cruiser that will have a 36v 500w rear drive hub I salvaged from an E-Bike. I salvaged all of the electrical components from an E-Bike that my business partner had stored behind his garage. The SLA battery had long since rotted away. He told me it worked fine when he put it in storage over a year ago but he noticed the battery wouldn't hold a charge. 

I'm quite familiar with building my own battery packs as I've been involved with electric RC cars and planes for many years but this whole BMS thing is new to me. Can someone point me in the right direction? I'm planning on using (144) 1400mAh 18650 (LiFePo4) cells to build (12) 38.4v 12 cell packs run in parallel to create a 38.4v 16.8Ah battery.

My questions start with who sells a BMS that I can use and do I need 1 or 12 separate BMS's for this pack design?

Also how would I go about charging a pack such as this? Would I charge as a whole or each of the 12 packs separately? What kind of charger is specifically designed for LiFePO4 batteries?

The reason I chose the 18650's is that I needed to create a rather special shaped series of packs to fit in a well designed package to keep the weight of the batteries as low in the frame as possible for handling characteristics.
80% of the batteries will be stored in a sealed Alloy case mounted below the wheel axle centerlines making the bike "feel" much lighter while under motion than it truly is.

Once the prototype is finished and I have some time to do some testing I will figure out if the 36v system is ideal or a larger 48v or 72v system will be needed. So far it has been a real blast building this bike, sorry I don't have any pictures just yet but as things come together a bit more I will post some. 

I'm also in the process of writing a book detailing how to build a complete custom cruiser bicycle from concept to cruising. It will include chapters on basic bicycle theory and geometry; frame and fork design; frame building; molded fake gas tanks; spoked wheel building; paint, polish, and anodizing; and final assembly. Also included will be a whole multi chapter section on building your creation into an electric assisted cruiser. I'm hoping to have the book finished by sometime early next Spring and will be available through Amazon books.

Thanks in advance for everyones help. later Travis


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