[inertia8 (Australia)]

Just some thoughts on the batteries.

Many of the batteries at first glance seemed on the expensive side to me, but doing the math doesn't back this up.. From a quick search, many appear to use 18650 cells (often the Samsung 25R 2500mah high drain), the same type of cells as I use for my super bright torches that draw higher amps and that are found in power tool batteries, nominally cost around $4-$12ea depending on brand (some are not high drain and give higher mah values)..

If we are dealing with 18650 2500mah cells for a 48v 10ah pack (some packs are lower voltage).

13 cells in series gives 48.1v @ 3.7v/cell nominal or 54.6v @ 4.2v/cell fully charged.
Add 4 of these in parallel gives 10000mah.

So that's 52 cells if I'm correct with the above calcs and assumptions on configuration.

The prices I have seen appear to beat the individual cell prices by a fair margin, especially when considering the labour to assemble, the hard pack casing, waterproofing and any other electronics that may or may not be present.. such as low/high voltage protection cutoffs, status displays and usb port(s) for charging your phone or powering a light set.

I did see one manufacture Karmic was trying to offer a battery pack where you could replace the individual cells, for their kickstarter project, which is extremely appealing given the propensity for a couple of cells to get out of balance and die prematurely.. but seemingly they have failed to bring that to market and now offer a sealed 44v pack.

And it would also appear that there is some more compact Lithium (presumably LiFeP04?) battery packs available from some ebike retailers.

It could be perhaps DIY'd with cheaper cells and maybe some heatshrink but seems to be an aweful lot of soldering or the use of brackets or other chemistries.

I will be saving towards a conversion kit, but may bite the bullet and just buy a factory bike once the funds are available.