Twizy Virtual BMS

This is an Arduino library providing an emulation of the CAN communication protocol of the BMS (battery management system) on a Renault Twizy.

The library provides an API to control power limits and charge current, so a wide range of batteries can be used. Even lead-acid is an option.

In the most simple case this can be used without any customization. The provided "SimpleBMS" example shows how to derive a very basic battery monitoring by using the Arduino analog ports to monitor the battery pack voltage and temperature.

If you'd like to contribute a specific BMS adaptation, please fork and add your code in the examples folder.

Installation

To download, click the DOWNLOADS button in the top right corner, download the ZIP file. Start the Arduino IDE, select menu Sketch → Include Library → Add .ZIP library, select the ZIP file and click OK. Try out the examples included.

You will also need these libraries:

• MCP_CAN_lib by Cory Fowler
• TimerOne by Paul Stoffregen

To get the smallest possible ROM & RAM footprint, set TWIZY_DEBUG_LEVEL to 0 and DEBUG_MODE of the MCP_CAN library to 0. This reduces the core memory usage of the VirtualBMS library to (currently) 7782 bytes ROM and 403 bytes RAM.

Hardware requirements

• Battery: you will need battery cells capable of producing enough voltage and current for the Twizy. You don't need to exactly match the original voltage and power range. The SEVCON G48 series can operate with input voltages from 19.3 to 69.6 V. The Twizy SEVCON is by default configured for a range of 39 to 65 V, but that can be modified (see SEVCON configuration). In standard configuration, the Twizy will draw up to ~330 A or 16 kW from the battery, and recuperate at up to ~70 A or 3.5 kW. If your battery cannot cope with this, you can either use the Virtual BMS to lower the limits or modify the SEVCON configuration.

  Pascal is using Nissan Leaf cells, which offer a very good combination of capacity, availability and price. Blazej is using cheap 120 Ah lead acid batteries (price ~400 Euro for a complete set). Klaus will use chinese prismatic cells adding up to ~12 kWh.

  Note: Klaus offers to organize a bulk order of high capacity prismatic cells priced at ~230 Euro/kWh. For details please contact him at klauszinser@posteo.eu.

• BMS: using a BMS is optional for lead acid batteries but strongly recommended for lithium based batteries. You may pick any BMS, but you should focus on those that can be connected to the Arduino to query the battery state. Our recommendation is picking a good BMS capable of early balancing, monitoring the coulomb (Ah) consumption and calculating the real SOC.

  Note: Pascal is developing a fully integrated BMS solution supporting various cell & chemistry configurations and containing the complete Twizy interface. The BMS should be available by the end of 2017. Pricing is expected to be around 350 Euro. Using this BMS will both simplify custom battery integration and reduce points of failure. You won't need an Arduino when using this BMS. For details please contact him at pascal@ripp.li.

• Arduino: to run the Twizy Virtual BMS you will need some Arduino and some MCP CAN interface. A wide range of hardware options is available. The code perfectly fits into an Arduino Nano leaving enough memory to implement quite complex custom logics. You should pick an MCP 2515 SPI CAN module with at least 16 MHz clock rate. IRQ connection is optional.

  Note: Michael Balzer offers to customize the Virtual BMS for individual applications and BMS integration. For details please contact him at dexter@dexters-web.de.

• Connection: see the part list for relais and connectors needed.

• Battery case: you can use the original Twizy battery case, available as a replacement part from Renault (see part list).

  Note: Lutz Schäfer offers to build individual custom battery cases offering more space. For details please contact him at aquillo@t-online.de.

Authors

This library has been created and is maintained by Michael Balzer (https://dexters-web.de/).

The CAN & hardware protocol decoding and reengineering has been done by a joint effort of (in reverse alphabetical order):

• Lutz Schäfer aquillo@t-online.de -- Hardware development
• Pascal Ripp pascal@ripp.li -- Hardware protocol decoding & implementation
• Bernd Eickhoff b.eickhoff@gmx.de -- CAN logging & testing
• Michael Balzer dexter@dexters-web.de -- CAN protocol decoding & implementation

Special thanks to Klaus Zinser klauszinser@posteo.eu for support and to Blazej Blaszczyk blazej.blaszczyk@pascal-engineering.com for prototype implementation and testing!

Documentation

• API reference

• History

• Twizy CAN object dictionary

• Twizy BMS protocol

• Battery connection scheme

• Battery connection part list

License

This library is free software; you can redistribute it and/or modify it under the terms of the GNU Lesser General Public License as published by the Free Software Foundation; either version 3 of the License, or (at your option) any later version.

This library is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more details.

You should have received a copy of the GNU Lesser General Public License along with this library; if not, write to the Free Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110- 1301 USA

Have fun!