Ten+ years ago I purchased my first DIY kit, a 36V front hub kit from Dillenger. Initially, there was a problem with the controller, but the company sent me a new one; and the first battery was exhausted after one year but was replaced under warranty (the second battery is still in use). I had a blast running errands and even riding the bike off road. The kit is on my daughter's cruiser for its fourth trip to Burning Man. Anyway, this kit cost $699 10 years ago, but is $100 off now. I have no affiliation with them.