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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