Monthly Archives: April 2019

New battery for ebike, part 2

Main positive and negative conductors are made of copper strips cut from sheet. Strip ends go trough fiberglass part where end are folded back to secure the strips in place.

Detail of balance wires and connector. Output cable is already soldered on copper tabs.

Whole battery


Battery housing. Intelligent BMS and all the wiring in place.

Plywood separating battery and BMS space

Cushioning of battery compartment with foam. There is fiberglass “floor” (with blue foam).

Battery fits tightly and does not move with lid on.

New battery for ebike, part 1

This is the temporary battery. 12S / 7700mAh. Battery is a few years old but still can give 250Wh of energy. I did over 200km on this one. Range with this one is between 10km to 20km depending on speed and pedaling. It is made from two old 6S Li-Po donated by Vladimir L. Thank you!

New battery is Li-Ion 12S 8P made of Samsung INR18650-30Q cells. There is 96 of them. I used plastic trays and paper stickers for + pole as additional safety isolation as the included plastic spacer in battery can potentially melt during welding causing short.


Welding was done by my trusty Spot Welder.


Next step is to get amperes out of battery. There is always problem of getting output current from end of battery of this kind. Nickel strip is itself not enough to carry big currents. I got myself 0.5mm copper plate. I used my CNC to  mill copper comb which is soldered to ends of nickel strips. Negative pole is simple. The stub is for soldering thick cable. Positive side includes custom made fuse holder.


That’s it for today. Battery still needs all wires soldered and some basic isolation. Last step will be to replace temporary battery with this one and enjoy range between 30km to 90km depending on how hard I will be on throttle.