My real foray into e-biking began last summer, although I had a wheel kit and silverfish battery in hand in 2017. My first worry- were batteries going to prove too pricey. I have bikes galore and two 2 cycle bikes all set up with baskets for local travel and shopping, and hadn't been on those much anymore. The silver fish 36v pack performed well last year and into the early Spring as I struggled to piece another wheel hub build together this one not a kit but all separately acquired pieces, and the vintage 60's Peugeot mixte frame I bought to support a battery didn't help with several odd quirks even an old mechanic found annoying..
I wrote a thread on another forum that I'd rather have HALF a battery, because I seldom pressed the silver fish, and it is a heavy item with 50 or 60 18650 cells inside at 6-plus pounds and lashed to a rear rack with 4 inch worm clamps. I've had it out for almost 20 miles of range and it hadn't run down but getting slower and only one of 4 LED indicators lit.
As an old road cyclist, I like to keep it lightweight and minimal, but start adding weight and you have to get into heavier wheels and tires and everything else. Most of my trips are in town and almost never more than 10 miles.
Anyway- over the past winter- I discovered Hover board packs. Only 2 lbs a piece they are 20 18650 cells and use T-60 connectors that are cheap and efficient from China- even preformed parallel connectors.
Maybe best is the price- Usually about $50 standard retail-I shopped around on e-bay and have found them usually for 35-40 dollars- even $33 DELIVERED. And so that's generally 2/3 of a larger silver battery - 40 cells compared to 60, for well under a hundred while the silver bike battery is usually close to or over $200..
Beyond being lightweight and cheap, we can now also tailor our number of cells by the number of hover packs- for each ride. I've so far only ever used one or two packs- one was just to test- but two packs get me around town- 6 miles plus to coffee and grocery area and I usually take the long scenic routes, so I get back with 3 of my 4 LED indicators still lit - on idle- after 8 miles or so. It suits my needs very well.
I could easy carry another pack or two if I needed more range and wire them up, or replace the first two on the road. They fit in a slightly bended water cage if you'd care to tie them there- or in the new mesh compartments on newer china bags.