Recently I had need to build a custom battery for a project, unfortunately I didn’t take many photos of the project, but I thought it worth discussing how construction went, and the issues I had. The design I went with was a 48V 13S5P1 design based around an off the shelf box. I managed to acquire a large amount of 186502 cells of which 65 were needed for this battery.

New Cells

This is not a clever way to store loose cells…

Whilst the battery box frames made construction of the internals super easy, especially with the excellent KSpot Welder which I borrowed from a friend3, not everything went quite so easily.

Battery Construction

Likewise soldering on the BMS which involved connecting the input and output terminals as well as balance leads to each set of parallel cells went well. The soldering was aided by the great ts80 and ts100 soldering irons from mini ware4.

Battery Soldering

The real issues arose when trying to solder on the output connector and close those box. The problem was mostly caused by the very small tolerances inside the box. Closing the box and fitting the assembled battery inside the case was eased by a liberal application of Kapton tape. In the end I resorted to ignoring the provided spade connectors and exposed the power leads via fly wires and an XT60 connector.

Shopping List

Whilst this is not an instructional post for those considering building there own battery I have included the components I used bellow. As previously stated I would not recommend the battery box I chose. Also ensure you understand the risks before taking on such a project, lithium cells need special handling, and are are fire hazard. The assembled (and partially assembled) battery contains a lot of energy and special care should be taken to prevent shorting and shocks.

  • Battery Box
  • Common Port BMS
  • Nickle Strips (These should not be plated nickle)
  • KSpot Welder
  • Kapton Tape
  • Silicone Wire
  • 65x18650 Lithium Ion Cells

Thanks

A special thanks goes to Simon and Elliot for all their help and advice in this project, and for making sure I didn’t do anything too stupid.

Addendum

Soldering XT60 connectors can sometimes be hard… Xt60 Fail

  1. This refers to the layout of the battery with cells grouped into sets of 5 in parallel, and this groups of 5 connected in a series 13 long. ↩︎

  2. 18650 refers to the size of the cell being 18mm diameter and 65 mm long. ↩︎

  3. The thanks are above… ↩︎

  4. I have owned a TS100 for a few years, but after using the TS80 I was convinced to buy myself a TS80P. ↩︎