Heltec Active Balance BMS User Manual

1. Introduction

The Heltec Active Balance Battery Management System (BMS) is designed to provide comprehensive protection and management for various battery chemistries, including LiFePO4, Li-Ion, and LTO. This smart BMS features active balancing, robust protection mechanisms, and versatile communication options, ensuring optimal performance and longevity for your battery packs. This manual provides detailed instructions for the proper installation, operation, and maintenance of your Heltec Active Balance BMS.

Heltec Active Balance BMS unit connected to a smartphone displaying battery data.

Heltec Active Balance BMS in retail packaging with included cables.

Video showcasing the Heltec BMS production facility and assembly process.

2. Safety Information

Please read and understand all safety instructions before installing or operating the BMS. Failure to follow these instructions may result in electric shock, fire, serious injury, or property damage.

Always wear appropriate personal protective equipment (PPE), including safety glasses and insulated gloves, when working with batteries and electrical systems.
Ensure the battery pack is disconnected from any power sources before beginning installation or maintenance.
Verify all wiring connections are correct and secure to prevent short circuits or improper operation.
Do not attempt to disassemble or modify the BMS unit. Refer all servicing to qualified personnel.
Keep the BMS away from water, moisture, and flammable materials.
Ensure adequate ventilation around the battery pack and BMS to prevent overheating.

3. Product Overview

The Heltec Active Balance BMS is a sophisticated battery management system designed for various battery configurations. It offers advanced features to protect and optimize your battery pack.

3.1 Key Features

Active Balance: Efficiently balances individual cell voltages to maximize battery life and performance.
Comprehensive Protection: Includes overcharge, short circuit, over-discharge, over-current, all-in (cable drop/poor contact), and over-temperature protection.
Wide String Compatibility: Supports various cell counts (e.g., 4S-24S).
High Current Handling: Available in multiple current ratings (e.g., 40A-200A).
Smart Connectivity: Bluetooth functionality for real-time monitoring and parameter adjustment via a dedicated mobile application (Android, iOS, HarmonyOS).
Communication Interfaces: Equipped with CAN and RS485 (by default) for integration with other systems.
Temperature Monitoring: Includes temperature sensor interfaces for critical thermal management.

Diagram illustrating six security protection features of the BMS: Over charge, Short circuit, Over discharge, Over current, All-in, Over temp protection. — Six Security Protection features of the Heltec BMS.

3.2 Components

Heltec Active Balance BMS Unit
Balance Wiring Harness
Temperature Sensor (if included with model)
Main Power Cables (7AWG Silicone wire with copper nose, approx. 25cm length)
Optional: External Switch, Relays, Shunt (depending on model and configuration)

Heltec BMS unit with main power cables and balance wires.

7AWG cable with copper nose, approximately 25cm in length.

4. Specifications

The following table details the general specifications for various Heltec Active Balance BMS models. Please refer to your specific product's packaging for exact model details.

Feature	HT-25S2ARP	HT-25S2AXP
Product Model	HT-25S2ARP	HT-25S2AXP
Size	234mm x 144mm x 32mm
Balanced Method	Energy-transfer active equalization
Suitable Number of Battery Strings	NCM(6-25S) / LFP(6-25S) / LTO(6-25S)	NCM(11-25S) / LFP(12-25S) / LTO(20-25S)
Active Balance Current	2A	5A
Connection Mode	Split port
Working Temperature	-20°C ~ 70°C
Voltage Requirements	10V-100V	30V-100V
Interface	Reserved charge/discharge switch control interface (12V), Reserved current acquisition interface of shunt (500A, 75MV), Three thermal sensor interfaces are reserved
Communication Interface	RS485/CAN/GPS/Display
Bluetooth Function	Support Android, iOS, HarmonyOS
Power Waste	The maximum power consumption is 1W, and the shutdown power consumption is 0.2MW

Table of product parameters for HT-25S2ARP and HT-25S2AXP models. — Product parameters for HT-25S2ARP and HT-25S2AXP models.

4.1 General Properties

Brand Name: Heltecbms
Accessory Type: Battery Accessories
Certification: CE
Electronic: No (refers to charger/battery inclusion)
Charger Included: No
Battery Included: No
High-concerned chemical: None

5. Setup Instructions

5.1 Hardware Connection

Important Note on Wiring Labels:

For 4-8S, 8-20S, and 8-24S BMS models, there may be a wiring error in the string number printing. During production, B1+, B2+ to B17+ are unified. Please refer to the labels on the outer packaging box and the product itself for the correct string count.

Image showing a note about BMS wiring label discrepancy. — Note regarding potential wiring label discrepancies.

Follow the wiring diagrams carefully for your specific BMS model and battery configuration. Incorrect wiring can damage the BMS, battery, or connected equipment.

Connect Balance Wires: Connect the balance wires from your battery pack to the corresponding ports on the BMS. Ensure that the last power cord (B+) is connected to the main positive pole of the battery pack.
Connect Main Power Cables: Connect the main negative (B-) and positive (P-) terminals of the BMS to your battery pack and load/charger as per the diagram.
Connect Temperature Sensors: If your model includes temperature sensors, connect them to the designated interfaces on the BMS.
Connect Communication Interfaces: If using CAN, RS485, or GPS, connect the respective cables to the BMS.
Connect Optional Components: If using an external switch, LCD, or heat function (if customized), connect them to their respective ports.

Detailed wiring diagram for the protection board connection method, showing connections for charge contactor, discharge contactor, charger, load, shunt, temperature sensor, RS485, and battery pack balance wires. — Protection Board Connection Method (General Wiring Diagram).

Image showing the protection board function acquisition interface area, including charging switch, power-on detection, CAN/RS485, and CNT temperature sensor interfaces. It also details the connection socket for the battery pack balance wires. — Protection board function acquisition interface area and battery pack connection socket details.

Diagram showing port labels for HT-817S04A40 and HT-820S06A60/HT-824S06A60/HT-817S06A80/HT-820S06A80/HT-824S06A80 models, including Temperature sensor, RS485, and LCD ports. — Port labels for HT-817S04A40 and HT-820S06A60/HT-824S06A60/HT-817S06A80/HT-820S06A80/HT-824S06A80 models.

Diagram showing port labels for HT-8S1A200/HT-8S2A200 models, including Temperature sensor, RS485, LCD, and Heat Function ports. — Port labels for HT-8S1A200/HT-8S2A200 models.

Diagram showing port labels for HT-820S06A100/HT-824S06A100/HT-820S1A150/HT-824S1A150/HT-824S2A150/HT-824S2A200 models, including CAN/RS485, GPS, LCD, and Heat Function ports. — Port labels for HT-820S06A100/HT-824S06A100/HT-820S1A150/HT-824S1A150/HT-824S2A150/HT-824S2A200 models.

Wiring diagrams for various cell counts: C-24s, C-20s, C-17s, C-16s, C-14s, C-13s, C-8s, C-7s (for Li-ion). — Connection modes for various cell counts (C-24s, C-20s, C-17s, C-16s, C-14s, C-13s, C-8s, C-7s).

5.2 App Connection

The Heltec BMS can be monitored and configured via a mobile application. Ensure all hardware connections are complete and the battery pack voltage is greater than 20V before proceeding.

Download App and Manual: Scan the QR codes provided below to download the official app, detailed instructions, and videos.
Startup: Activate the BMS using the display activation button or an additional switch.
Enable Bluetooth: Ensure Bluetooth is turned on on your mobile device.
Connect Device: Open the app, click on the top left corner to search for devices, and select your BMS from the list. The default password is 1234.
Set Parameters: For the first start-up, you will need to set parameters. The default password for parameter settings is 123456. Simply set the number of units (cells) and battery type.
Check Battery Status: After setting parameters, go back to the real-time status page to check the battery status. Ensure no error messages are displayed. In the app, blue indicates the highest voltage, and red indicates the lowest voltage.

Screenshots of the Heltec BMS mobile application interface, showing device list, real-time status, and parameter settings. Includes QR codes for app download. — Heltec BMS mobile application interface and QR codes for download.

6. Operating Instructions

6.1 Smart Energy Working Modes

The BMS features intelligent working modes to optimize power consumption and battery longevity:

Storage Mode: In transportation, storage offline, or wireless transmission off mode, the BMS does not consume battery pack current.
Normal Working Mode: When the charger is inserted in storage mode and off mode, the BMS will immediately return to normal working mode, and all protection, equalization, and communication functions will resume.
Shutdown Mode: To prevent power wastage during long periods of disuse and to protect the battery pack, the BMS has an automatic shutdown voltage. It will automatically shut down when a cell voltage falls below this threshold.
Standby Mode: When the battery pack is in a static state (no charge and discharge current, no equilibrium current), the BMS will automatically enter standby mode after a set time (1-30 days, configurable).

Flowchart illustrating the smart energy working mode switching: Storage Mode, Normal Working Mode, Shutdown Mode, and Standby Mode. — Smart energy working mode switching diagram.

6.2 App Monitoring

Once connected via Bluetooth, the app provides real-time data and control:

Monitor individual cell voltages, total pack voltage, and current.
View battery capacity, state of charge (SOC), and cycle count.
Check temperature readings from connected sensors.
Adjust protection parameters (e.g., over-voltage, under-voltage thresholds) as needed (requires password).

7. Maintenance

Regular Inspection: Periodically inspect all wiring connections for tightness and signs of corrosion or damage.
Cleanliness: Keep the BMS unit clean and free from dust and debris. Use a dry, soft cloth for cleaning.
Software Updates: Check the app regularly for firmware updates for your BMS to ensure optimal performance and access to new features.
Battery Health: Monitor battery health parameters via the app. Address any abnormal readings promptly.
Storage: If storing the battery pack for an extended period, ensure the BMS enters Storage Mode or Shutdown Mode to minimize self-discharge and protect the cells.

8. Troubleshooting

This section provides solutions to common issues you might encounter with your Heltec Active Balance BMS.

8.1 General Fault Analysis

BMS Not Activating/No Power:
1. Ensure that the last "B+" line of the balance cable has been correctly connected to the positive pole of the battery pack.
2. Start up after charging and ensure that the charger voltage is greater than 4V above the battery pack voltage.
3. Check whether the charger has voltage output.
Inaccurate Voltage Readings:
1. Measure the actual total pressure of the battery pack with a multimeter.
2. Fill the actual total pressure into the "voltage calibration" field on the parameter setting page in the app.
Inaccurate Current Readings:
1. The B- and P- terminals of the protection board typically use two 7AWG wires. Both must be connected in parallel; otherwise, it will lead to current measurement errors.
2. Measure the actual current of the battery pack with a clamp meter.
3. Fill the actual current into the "current calibration" field on the parameter setting page in the app. A larger actual current during calibration generally leads to higher accuracy.
Inaccurate Capacity Readings:
1. An initial capacity estimated based on monomer voltage when the protection board is first powered on may be inaccurate.
2. After the protection board is discharged to the cut-off voltage and then fully charged, the capacity will be calibrated. Ensure the charging process is not interrupted during this calibration cycle.
Incorrect String Number:
1. Check whether the "unit quantity" in the parameter setting is set correctly to match your battery pack's string count.
2. If there is no voltage in two or more strings in the middle, check whether the acquisition cable has fallen off or is damaged.

9. User Tips

Understanding Current Ratings: For models like '4-8S, 2A, 200A', the '2A' refers to the active balance current, which is the maximum current the BMS can use to balance cells. The '200A' refers to the maximum continuous discharge current the BMS can handle.
Bluetooth Connectivity: All smart BMS models (e.g., 8-20S 60A) come with Bluetooth for app connectivity. Ensure your phone's Bluetooth is enabled and the app is updated for best performance.
App Compatibility: The Heltec BMS uses its dedicated mobile application. While some BMS systems might share similar interfaces, it's recommended to use the official Heltec app for full compatibility and functionality.
Physical Size: When selecting a BMS, always check the board dimensions (e.g., 234mm x 144mm x 32mm for HT-25S2ARP/HT-25S2AXP) to ensure it fits your enclosure.

10. Warranty and Support

Heltec BMS products are manufactured to high-quality standards. For specific warranty details, please refer to the product documentation provided at the time of purchase or contact Heltecbms Official Store directly. Technical support is available through the official channels provided by the manufacturer.

Heltecbms Heltec Active Balance BMS