When developing lithium battery systems for e-bikes, e-scooters, AGVs, industrial machines, and light EVs, choosing the right communication protocol is one of the most important engineering decisions. That is why CANopen vs J1939 vs Custom CAN has become a common comparison among OEMs, integrators, and battery designers looking to balance interoperability, diagnostic depth, and system complexity.
CANopen vs J1939 vs Custom CAN differ in structure, data formatting, integration complexity, and application focus: CANopen is ideal for modular automation systems, J1939 is optimized for heavy-duty vehicle communications, and Custom CAN provides maximum flexibility for proprietary lithium battery applications.
Because the communication protocol directly affects safety signaling, VCU compatibility, charging behavior, remote diagnostics, and multi-battery management, choosing the correct one from the start can significantly reduce development time and integration cost. Below is a clear breakdown to help you identify the most suitable option for your lithium battery system.
What Is CANopen? The Industrial & European Favorite
CANopen is a standardized higher-layer protocol operating above the CAN physical and data link layers. It is built around a structured CANopen Object Dictionary and uses Process Data Objects (PDOs) for real-time data and Service Data Objects (SDOs) for on-demand access to requested data such as cell voltages, configuration limits, or calibration parameters.
Key Features
- Standardized data objects
- Good modularity for multi-device systems
- Supports advanced diagnostics
- Flexible mapping options
Typical Applications
- AGVs & AMRs
- Industrial electric vehicles and warehouse robots
- Warehouse automation
- Medical equipment
- Stationary battery energy storage systems (BESS) – almost every major European inverter/charger supports CANopen
- European and Asian passenger EVs (many Tier-1 suppliers use it)
Advantages for Lithium Batteries
- Easier integration with industrial controllers
- Strong diagnostic capabilities
- Reliable for multi-battery or energy-dense systems
Limitations
- More complex configuration
- Requires deeper engineering experience
When to Choose CANopen
Choose CANopen when your battery is part of a robotic, factory automation, or AGV/AMR platform requiring standardized communication and robust diagnostics.
What Is J1939? The North American Heavy-Duty Standard
J1939 is a high-level CAN protocol used in commercial and heavy-duty vehicles. It defines structured PGNs (Parameter Group Numbers) and SPNs (Suspect Parameter Numbers).
Key Features
- Highly standardized messaging
- Designed for vehicle powertrains
- Supports large networks and high-power systems
Typical Applications
- Heavy vehicle
- Utility vehicles
- Construction machinery
- Agricultural equipment
Advantages for Lithium Batteries
- Clear definitions for torque, speed, state-of-charge, temperature, etc.
- Widely supported in industrial controllers
- Excellent for large pack systems
- Address claiming handles dynamic node addition
Limitations
- More rigid message structure
- Slower to customize
When to Choose J1939
Choose J1939 when your battery is used in vehicles, utility platforms, or commercial machinery, especially when interoperability across multiple modules is required.
What Is Custom CAN? Full Control, Full Responsibility
Custom CAN refers to manufacturer-defined CAN frame structures tailored to their own BMS features.
Key Features
- Lightweight and fast
- Fully flexible message definitions
- Optimized for product-specific functions
Typical Applications
- Extremely cost-sensitive products (e-bikes, power tools, small home storage)
- You control the entire ecosystem (vehicle OEM + battery + charger)
- You need proprietary diagnostic or anti-counterfeit features
- Development speed is critical and you can’t wait for standards compliance
Advantages
- Fast time-to-market
- Ideal for unique battery features
- Reduced overhead for simple applications
- Tailored to your BMS’s internal logic
Limitations
- Limited interoperability
- Requires detailed documentation for OEM integration
- Diagnostic tools may be proprietary
When to Choose Custom CAN
Choose Custom CAN when you need maximum flexibility, application-specific functions, or fast integration, such as in e-bikes, e-scooters, smart chargers, or compact mobility devices.
CANopen vs J1939 vs Custom CAN – Feature-by-Feature Comparison
While all three run on the same Controller Area Network physical layer (differential pair, 120 Ω termination), they differ dramatically in how higher layer protocols are structured.
Feature | CANopen | J1939 | Custom CAN |
Structure | Object Dictionary, PDO/SDO | PGN/SPN | Free-form frames |
Bitrate (classic) | 125–1000 kbps | 250 kbps (500 kbps FD emerging) | Any |
Complexity | Medium–High | Medium | Low–High (flexible) |
Interoperability | Strong | Very strong | Limited |
Diagnostics | Advanced | Vehicle-grade | Depends on design |
Ideal Applications | Industrial automation, AGVs | Vehicles, utility machines | E-bikes, scooters, compact devices |
Flexibility | Medium | Low | Very high |
Multi-Battery Support | Good | Very good | Customizable |
Integration Speed | Medium | Medium | Fast |
The Future Is Already Here
- CAN FD adoption is accelerating
- J1939-22 (2021) brings multi-packet and CAN FD support
- CiA 1301 (CANopen FD) and CiA 443 updates are in progress
- 100BASE-T1 automotive Ethernet is taking over for > 10 Mbps needs, but CAN will stay for control
Conclusion: CANopen vs J1939 vs Custom CAN: Which One Is Right for You?
In summary:
- Choose CANopen for industrial, robotic, and automated environments.
- Choose J1939 for vehicle-grade systems, utility vehicles, and heavy-duty applications.
- Choose Custom CAN for fast integration, flexible design, and compact mobility products like e-bikes and e-scooters.
The right protocol depends on your system architecture, diagnostic needs, and interoperability requirements. Evaluating these factors early ensures your lithium battery system integrates smoothly with motor controllers, displays, chargers, VCUs, and parallel power systems.
FAQ
Do I have to pay royalties to use CANopen?
No. Implementation is free. CiA membership is optional and only required for creating new specifications.
Can I mix protocols on the same CAN bus?
Physically yes, multiple protocols can technically run on the same bus via standard CAN wiring, but logically no, because their message IDs and structures will conflict.
How does a new battery join an existing CAN network without conflicts?
In J1939, every transmitting node (including the battery) performs address claiming to get a unique source address. In CANopen, a CAN node can be assigned dynamically via LSS — both prevent collisions on the CAN network even with dozens of electronic control units.
Can I add advanced diagnostics to Custom CAN?
Yes. Most OEMs add Unified Diagnostic Services (UDS, ISO 14229) on top of their Custom CAN implementation using ISO-TP. This enables dealership-grade diagnostics, firmware flashing, OTA updates, and deeper service functions beyond normal CAN messaging.
Why does J1939 work so well for heavy-duty batteries?
Because J1939 includes a robust Transport Protocol for multi-packet messages, standardized PGNs/SPNs, and dynamic address-claiming. These features make it extremely reliable in noisy, large CAN-based systems found in heavy-duty trucks, agricultural equipment, and construction machinery.
