# Mate X battery 52V 15Ah – diy with 21700 cells

> DIY 52 V 15 Ah e-bike battery for the Mate X: 42 × 21700 cells (14S3P) in the original enclosure, no BMS, two 7S blocks, 3D-printed cell holders (STL).

- URL: https://guillaumeplayground.net/mate-x-battery-52v-15ah-tesla-21700-cells-diy/
- Author: Guillaume (https://guillaumeplayground.net/about/)
- Published: 2021-12-23
- Updated: 2022-06-17
- Section: RC & builds
- Topics: battery pack, electric bike
- Source: Guillaume playground

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.

![Mate X battery 52V 15Ah – photo 1](https://guillaumeplayground.net/wp-content/uploads/2021/12/IMG_20211223_192555_6.jpg)

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.

📎 [cell-holder](https://guillaumeplayground.net/wp-content/uploads/2021/12/cell-holder.stl)

📎 [cell-end](https://guillaumeplayground.net/wp-content/uploads/2021/12/cell-end.stl)

The cell holder features 11 slots allowing 4 stacks: 11 | 10 | 10 | 11 cells like this:

![Mate X battery 52V 15Ah – photo 2](https://guillaumeplayground.net/wp-content/uploads/2021/12/IMG_20211218_205135_3.jpg)

![Mate X battery 52V 15Ah – photo 3](https://guillaumeplayground.net/wp-content/uploads/2021/12/IMG_20211218_205233_6-1.jpg)

![Mate X battery 52V 15Ah – photo 4](https://guillaumeplayground.net/wp-content/uploads/2021/12/IMG_20211218_205433_2.jpg)

The assembly (very ugly picture 😉 sorry)

![Mate X battery 52V 15Ah – photo 5](https://guillaumeplayground.net/wp-content/uploads/2021/12/IMG_20211218_205433_2-2.jpg)

![Mate X battery 52V 15Ah – photo 6](https://guillaumeplayground.net/wp-content/uploads/2021/12/IMG_20211219_121715_4.jpg)

Operational: >50 Volts

![Mate X battery 52V 15Ah – photo 7](https://guillaumeplayground.net/wp-content/uploads/2021/12/IMG_20211219_200547_4.jpg)

Balancing cables: 2 x 7s

![Mate X battery 52V 15Ah – photo 8](https://guillaumeplayground.net/wp-content/uploads/2021/12/IMG_20211219_220339_3.jpg)

Packing and isolation: epoxy plates and isolation foam which allows to compress make the packs tight and secured:

![Mate X battery 52V 15Ah – photo 9](https://guillaumeplayground.net/wp-content/uploads/2021/12/IMG_20211219_222421_1.jpg)

One half:

![Mate X battery 52V 15Ah – photo 10](https://guillaumeplayground.net/wp-content/uploads/2021/12/IMG_20211223_192846_9.jpg)

Charging, some time later… of course you can charge both half with two charger and upgrade the PSU to allow fast charging (I am limiting at 2Amps because I have a poor 65w psu in front of my 1000w ISDT T8)

![Mate X battery 52V 15Ah – photo 11](https://guillaumeplayground.net/wp-content/uploads/2021/12/IMG_20211223_201347_3.jpg)