How to Choose the Right BMS Current for an E-Rickshaw in India

Guide Overview

If you are building an electric motorcycle battery for the Indian market, BMS selection should start with the battery system and controller requirements rather than the motor-power label alone. Confirm the battery chemistry and exact series-cell count, battery-side continuous and peak current, operating conditions, and any communication required with the controller or dashboard.

For projects within the scope of AIS-156, the BMS safety functions and the complete Rechargeable Electrical Energy Storage System (REESS) approval requirements must also be considered. Selecting a BMS alone does not make the complete battery system AIS-156 compliant.

1. Start with Battery Chemistry and Exact S Count

Before comparing BMS current ratings, confirm the battery chemistry, exact number of cells connected in series (S count), nominal pack voltage and charging limits. LiFePO4, NCM/Li-ion and other lithium chemistries use different cell-voltage ranges, so the BMS must match the actual battery design.

Do not infer the exact S count from a nominal pack-voltage label alone. Use the battery-pack design or cell specification as the final reference.

2. Size the BMS from Battery-Side Current, Not Motor Power Alone

Motor power is useful background information, but it does not uniquely determine the BMS current rating. The BMS sees battery-side current, which is also affected by pack voltage, the controller's battery-current limit, acceleration demand, vehicle mass, gradients, drivetrain conditions and operating temperature.

Before choosing a BMS current tier, confirm:

Expected continuous battery current
Controller maximum battery-side current
Maximum peak battery current
Peak-current duration and repetition frequency
Maximum regenerative charging current, if regenerative braking is used

3. Check Continuous and Peak Current Separately

Continuous current and short-duration peak current are different requirements. A BMS that meets the normal riding current still needs to be checked against acceleration, climbing and other short-duration peaks.

When requesting a recommendation, provide both the peak current and how long it lasts. Do not approve a BMS only because its continuous-current rating appears close to the expected load.

4. Confirm Controller and Dashboard Communication

If the BMS needs to communicate with the motorcycle controller, dashboard or another electronic control unit, provide the equipment model and required communication protocol.

Controller Area Network (CAN), RS485 and UART describe communication interfaces. Having the same interface does not automatically mean that two devices can exchange the required messages. The protocol and data mapping must also match the target equipment.

5. What AIS-156 Means for BMS Selection

AIS-156 sets safety requirements for Rechargeable Electrical Energy Storage Systems (REESS) used in L-category electric vehicles, including electric two-wheelers. The BMS is one part of the complete REESS evaluated within the vehicle approval process.

AIS-156 Amendment 3 specifies a microprocessor- or microcontroller-based BMS and identifies safety functions that are verified during REESS testing, including over-voltage, over-charge, over-discharge, over-temperature, overcurrent and short-circuit protection. Applicable electromagnetic compatibility (EMC) requirements also need to be considered.

Official source: Ministry of Road Transport & Highways (MoRTH) — Amendment 3 to AIS-156: Official PDF

AIS-156 compliance is evaluated at the REESS and vehicle level. Choosing a BMS with the required safety functions is only one part of the complete battery-system design and approval process.

6. Match the Verified Requirement to DALY A-Series Smart BMS

DALY A-Series Smart BMS provides several verified continuous-current tiers. Use these as candidate ranges only after the project requirements above have been confirmed. They are not fixed motorcycle-to-model recommendations.

DALY Smart BMS	Verified continuous current	Selection boundary
AH	40A / 60A	Evaluate only if the verified continuous-current requirement, peak profile, S count and project configuration fit this tier.
AK	80A / 100A	Evaluate when the verified current requirement falls within this range; confirm peak current, duration and thermal conditions separately.
AM	150A / 200A	Evaluate for higher-current projects only after controller limit, continuous current, peak current, duration and thermal conditions are confirmed.
AS	250A / 300A / 400A	Use only for a verified higher-current requirement; do not select it from a general “heavy-duty motorcycle” assumption.

Product boundary: current tier alone is not enough. Final selection still requires the exact battery chemistry, S count, continuous and peak current, thermal conditions, controller requirements and communication needs.

7. What to Send DALY for BMS Selection

To receive a project-specific BMS recommendation, send the following information:

Vehicle type and intended application
Battery chemistry and exact S count
Nominal pack voltage and capacity
Expected continuous battery current
Controller brand/model and maximum battery-side current
Peak current, duration and repetition frequency
Maximum regenerative charging current, if applicable
Maximum ambient temperature and battery-enclosure conditions
Controller/dashboard communication requirements
Prototype, pilot or production quantity

With these inputs, DALY can review suitable A-Series options, confirm the required current and communication configuration, and provide the relevant product specification and quotation.

Frequently Asked Questions

Q1Can I choose a BMS from motor power alone?

No. Motor power is only one input. Confirm the controller maximum battery current, expected continuous battery current, peak current and duration, pack voltage and operating conditions.

Q2Does a CAN interface guarantee compatibility with my motorcycle controller?

No. The interface and the communication protocol must both match the target equipment. Provide the controller or dashboard model and required protocol for confirmation.

Q3Does choosing a BMS with AIS-156 safety functions make the battery pack AIS-156 compliant?

No. AIS-156 compliance is evaluated as part of the complete REESS and vehicle approval process. The BMS safety functions are one part of that system-level assessment.

Q4What should I confirm when sourcing a BMS for an AIS-156 project?

Confirm the required BMS safety functions, battery configuration, current capability, temperature conditions, communication requirements and the documentation needed for the REESS or vehicle approval project.

About DALY

DALY designs and manufactures lithium battery management systems for OEMs, battery-pack manufacturers and system integrators. For electric two-wheeler projects, BMS selection can be reviewed according to the actual battery configuration, current profile, controller requirements, communication needs and project compliance requirements.

Need a BMS Recommendation for Your Electric Motorcycle Project?

Send the battery, controller, current, operating-condition and communication information listed above. DALY can review the project requirements and provide a suitable BMS selection recommendation, relevant product specification and quotation.