Here are some pictures of my e-bike with the custom built LiFePo4 battery pack installed.  This machine cruises at speeds between 26-30mph.  I've got a range of 25-30miles.  I ride it to work 4-5times a week weather permitting.  So far I've put 2000 miles on it (since January 2008).  So far, including the bike, I've put about $1500 into the setup.  Figuring at current gas prices, I've saved at least $350 in fuel.

Photosynth (46 pictures)

Yesterday my bullet connectors failed.  I suppose I shouldn't be too surprised, since  they were perhaps the most under-rated part on the e-bike and they take daily abuse.  This connection is made and broken at least twice each day and each time I get a nice big spark as the controller's capacitor chargers. The connecting wires were only 12 gauge so they probably also represented a high resistance connection especially under load.  I suppose it was for all those reasons that I really didn't mind being force to upgrade  them when they broke. 

It seems e-biking upgrades always follow a common pattern.  First you buy cheap because you just want to get started and you're thinking it will save you money.  Then you start putting on the miles and you have something break.  That's when you realize that spending a little extra money up front will save you money and time in the long run and you go ahead and upgrade to the best you can find.  1000's miles later you are still very happy you did it right!   Each day I'm forced to drive my car vs. the e-bike cost me at least $10 in fuel.  So the $30 I spent on this upgrade was nothing compared to driving the car all week.

So, I upgraded both ends of my battery connection  with heavy duty 6-gauge wire and high power connectors.  I suppose it's only fitting since I'm carrying around a $1000 + battery that it should have a high quality load carrying connector.  Now I've got at least 50A of load handling capacity.  I'd recommend this type of setup to anyone with an E-bike once your initial setup fails. I found the connectors and wire at NAPA auto parts.  They had the parts in the back though, not out on the shelves.  Tell them you need connections for a high power battery setup.  These connectors are the kind used in 36V and 48V electric pallet jacks and light duty forklifts. Here's an online source for the connectors  http://www.allbatterysalesandservice.com/browse.cfm/4,642.html

BMI is known for producing the LiFePo4 battery packs of the highest quality.  They have recently started producing and shipping a line of very large, high current LiFePo4 packs built as drop in replacements for hybrid cars.  These packs are made in voltages up to 144V and with current ratings in bursts up to 200Amps per parallel cell!

144V 10Ah pack	3.3V 10AH Individual cells

Purchasing the individual cells instead of packs gives you the flexibility to configuring them into any physical arrangement deemed necessary.  This means however that you're also responsible for determining how to charge and balance your custom pack. 

There is a cell balancing VMS available for purchase.  Each of these circuits can manage the charging of 4 batteries.  They also have a serial output that can be used by external circuitry or a monitoring computer to turn off load when low voltage or over voltage is detected.

Right now the cost per unit on these batteries is among the highest cost of any other cells on the market, but if you are after high discharge current capacity, extremely high recharge current capacity and up to 7000 recharges, no other cells come close.

For an e-bike, one of the most essential choices you can make is to purchase the correct battery. For my e-bike, I've had 3 different battery setups. I started with lead acid and quickly found them to be lacking. I carried nearly 50lbs of lead acid with me and even with that they were dead in only 12-13 miles of use. The insane amount of weight meant that when they died before a large climb near my job, I ended up pushing the bike up the hill. Many times I regretted taking my bike when that happened!   Before long you learn quickly that the best batteries for the e-bike (and many other high current applications) are called LiFePo4.  That's the chemical abbreviation for Lithium Iron Phosphate.  Lithium is better than Lead because lithium is the lightest metal.  This particular chemistry is also extremely stable.  Some estimates are that these batteries should last 20 years.  In the lab, they've been cycled over 5000 times before starting to degrade in capacity.  That means they could last 20 times longer than lead acid.

From LIFEPO4

COST

Still, the cost per cell is about 5-8times what you'd pay for lead acid which means you'll be better off financially over time.  I've been able secure a source of these cells from overseas and built up a battery pack that I can use with my bike.  It can handle up to 200amps of discharge, and can give me a > 35 mile range at an average speed of 16mph. At 27mph I get about 22miles out of it.  The pack is encased in Lexan which is very strong and resistance to impact and scratching.  Some say it's bullet proof at the right thickness.  The power supply is included in the case and can recharge after my commute in about 3 hours.

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