This quick post aims to detail the build of a 52v 15000mAh battery fitting in the aluminium enclosure of the Mate X.
This battery pack features 42 x 21700 cells (5000mAh) x 3 (parallel) x 14 (series).
One choice I made was to trash the BMS: remove a SPoF (Single Point of Failure), my previous original battery pack was killed by the stupid BMS (fully drained cells) and you get pretty angry when you discover 65×18650 cells dead because of a 20$ board failure.
I simply split the 14 cells series in two blocks of 7s which will be easy to charge with a classic external RC lipo/liion battery charger. Simple and less parts will be exposed to the bike vibrations.
Total cost for components under 200 Euros ($240)
- 42 x BAK N21700CG 5000mAh: 3.90 Euros
- new aluminium enclosure (if you are not reusing the original Mate X): ~30Euros
- 2 x balancing 7s cable: 5 Euros
Material and tools if you don’t already have:
- Charger Li-Ion >=7S: ~50 Eur
- Spot welding machine: ~12 Eur
- Silicon cable and nickel sheet plate: 10 Eur
- 3d printer… and ABS filament.
BAK N21700CG cells rocks. 5000mAh is the top of the line and it’s a well-known high quality brand which aims to clone Samsung cells. Every cell I received where all precisely charged with a maximum difference of 5mV between them, impressive.
The 21700 cell holder I designed is a perfect fit. I used ABS for the printing material.