4-12 Cell Integrated Battery Management System


Download design files:


Files are provided under the open source MIT License.
A copy is included in the ZIP archive.


The ZEVA BMS12i was designed to address the need for a simple, reliable and easy to install Battery Management System for 12V to 44V lithium battery packs. It can be used for both storage battery applications (off-grid systems, backup batteries etc) or electric vehicle applications (golf carts, NEVs, motorbikes, mobility scooters, etc).

The BMS12i features dual solid state relay outputs capable of directly switching large contactors for protecting against under- and over-voltage conditions, a CAN bus interface (non-isolated) for communicating with a monitor, external current sensor and/or third party devices, a temperature sensor input for monitoring and protecting against under- and over-temperature conditions, and an isolated shunt interface for current measurement and battery state of charge calculation. It also handles pack balancing via internal shunt resistors to bleed a small amount of power from any cells above average voltage at any time.

The BMS12i uses a built-in switchmode DC/DC converter to power itself off the batteries it is connected to, to avoid the need for any separate power supply. To prevent the possibility of over-discharge caused by the BMS itself, it can switch its own power off if any cells get critically low. There is also a Sleep terminal which can be used to put the BMS into a low power mode when the battery is not in use, turning off the CAN bus and SSR outputs to greatly reduce quiescent current consumption.

For battery storage applications, the BMS12i uses programmable hysteresis bands for the high and low voltage thresholds, to allow for automatic operation (no need for manual resets) without rapidly cycling external devices. For example, the BMS12i may disable the charger when a cell hits 3.8V, then will automatically re-enable it some time later when the cell drops below 3.4V. In EV mode, outputs will stay off until the unit is power cycled, or wakes from sleep.

The BMS is normally configured using one of our V3 Monitors, however the BMS can work fine without a monitor attached. In this case the BMS can be preconfigured to suit your system before shipping - feel free to contact us after ordering with your requested settings.

The BMS12i is functionally very similar to the BMS16, except designed to handle fewer cells. The other significant difference is that the BMS12i's CAN bus is not isolated, so is not suitable for CAN bus integration with battery storage inverters (though they usually involve 14-16 cells anyway).

Related Products

EVMS Monitor V3   $165.00
View information from the EVMS3, BMS12 modules, ZEVA motor controllers, TC Chargers or BMS16 over CAN bus

Temperature sensor for EVMS3, BMS16 and BMS12   $6.00
100Kohm NTC thermistor for use with our BMS12, BMS16 and EVMS3 devices

Gigavac GV240 Contactor   $215.00
800V 400A+ DC contactor


Cells managed: 4 to 12 cells
Supported chemistries: LiFePO4, LiCo, LiPo, LiMn
Maximum total voltage: 51V
High, low and shunt voltage thresholds: Factory configurable between 2.00-4.50V
Accuracy: 0.002V
Dual solid state relay (SSR) isolated outputs, 60V 1A max
Built-in current measurement via isolated shunt interface
CAN bus interface for external monitor, hall effect current sensors, TC chargers, etc.
Status LED for visual feedback
Internal switchmode power supply
Internal shunt balancers (~80mA)
Dimensions: 104x78x18mm
Mounting holes: 2x 4mm, 98mm apart

Datasheets & Manuals:



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