Happy BMS: a 9s-15s smart BMS for Xiaomi and Ninebot scooters

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  • Happy BMS: a 9s-15s smart BMS for Xiaomi and Ninebot scooters

Xiaomi and Ninebot electric scooters are of excellent quality, including their batteries. The batteries are well assembled and high-quality branded electronics equipped. On the one hand, this affords maximum safety and usability, but on the other hand, it’s not so easy to make a custom compatible battery using general purpose parts widely presented on the market .

Happy BMS is especially designed to be hardware and software compatible with Xiaomi and Ninebot e-scooters, so you can easily make custom batteries for it. A battery equipped with Happy BMS is recognized by Xiaomi and Ninebot electric scooters as original, keeping all the functionality of the scooter. 

The main Happy BMS feature is up to 15s battery support, which means you can equip your scooter with a 15s battery instead of the original 10s, reaching +50% to the maximum speed. You can also configure some parameters, such as capacity, discharge curve, serial number and maximum current, improving the performance of your scooter.

General view of the device

Happy BMS - Xiaomi edition

Happy BMS - Ninebot MAX edition

Key features

Happy BMS is the result of my many years of experience in making batteries for Xiaomi and Ninebot electric scooters. It can be said that this is a product from a battery manufacturer for battery manufacturers.

Classic general purpose BMS require a lot of extra work to solder wires and plugs, while Happy BMS is already equipped with all the necessary connectors, so you only need to solder two power wires and the balance cable:

Happy BMS vs a general purpose BMS: plugs and wires

Happy BMS - Xiaomi edition, pinout

Happy BMS - Ninebot edition, pinout

Happy BMS is efficiently assembled and made of expensive and high-quality parts, therefore, with dimensions similar to the smallest classic BMS, it provides much more power and functionality:

Happy BMS vs a general purpose BMS: dimensions and power

Typical application

The plugs and wires of the Happy BMS are placed optimal way, providing convenient internal wiring and sticking the plugs outside the battery:

Typical application: internal wiring

Typical application: packing

Typical application: a finished battery

Typical application: the finished battery inside the scooter

Basic specifications

The Happy BMS electronics are placed in a plastic case and equipped with an aluminum heatsink, which affords high power, protection from mechanical damage and moisture resistance. The key technical characteristics are presented in the table below:

Basic specifications

*The Xiaomi edition of the BMS requires the discharging plug reinforcement for 30A+ discharging, as the original plugs are 30A rated. The BMS and wires are strong enough for 44A discharging. The Ninebot edition is ready for 44A discharge out of the box.

**The Xiaomi edition of the BMS requires the charging plug reinforcement for 3A+ charging, as the original plugs are 3A rated. The BMS and wires are strong enough for 5A charging. The Ninebot edition is ready for 5A charging out of the box.


Happy BMS supports batteries from 9s to 15s. All available configurations are described in the user manual, but a few typical and most popular configurations are listed below:

15s battery wiring

13s battery wiring

10s battery wiring

Battery setting up and monitoring

Happy BMS is a typical smart BMS: it is controlled by a microprocessor, so it allows you to flexibly configure many parameters, such as battery capacity, maximum load current, temperature sensor thresholds, overcharge and overdischarge protection thresholds, balancing type, and much more. A smartphone app is used to set the battery:

Battery configuration

The app also displays the current battery status - voltages, current consumption, temperature and more:

Battery monitoring


Happy BMS is a great choice for those who want to make a battery for themselves or produce batteries for sale. Smart design saves production time, and full software and hardware compatibility simplifies installation.

Check the user manual for more technical information: http://public.embedden.com/Happy_BMS/Docs/English/happy_bms_manual_latest_en.pdf

Order Happy BMS at my website:



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Russian edition of this post: https://m365.embedden.com/blog_happy_bms_introduction_ru

Thanks for your attention!