Battery Health Monitor for Electric Rickshaws and E-Bikes on STM32 with FreeRTOS

The problem: batteries die early and nobody knows why

Electric rickshaws, loaders and e-bikes have become everyday transport in South Asia. Wikipedia's article on electric rickshaws notes that India registered around 300,000 of them in 2022 to 2023 alone, and that Pakistan has an estimated fleet of one to three million three-wheelers, of which electric models are a small but growing share. The same article notes that the batteries are typically lead-acid with a lifespan of only 6 to 12 months.

For a driver or a small fleet owner, the battery pack is the biggest running cost after the vehicle itself. Packs fail early for reasons that are hard to see: drivers run them almost flat to finish a shift, packs are left discharged overnight, one weak block drags the rest down, or the pack overheats in summer. Battery University's guidance on lead-acid batteries is clear that they should be recharged after each use and never stored on low charge, because staying discharged causes sulfation that permanently reduces capacity. Yet most vehicles only have a simple voltage gauge, so nobody knows how the pack was treated until it is too weak to use.

What already exists and the gap

• Victron SmartShunt and similar battery monitors measure voltage and current, estimate state of charge and keep a history in a phone app. They are built for solar and caravan systems and are sold as premium products.
• Lithium BMS boards from brands such as JK and Daly protect lithium packs and often have Bluetooth apps, but they do nothing for the lead-acid packs most low-cost vehicles still use, and each shows one pack at a time.
• Generic voltmeter displays fitted to many rickshaws show a number and nothing else: no history, no per-block view, no warning before damage.

The gap is a low-cost, rugged monitor built for these vehicles: it watches every block, warns the driver in the moment, and gives fleet owners a record of how each pack was used and how its health is changing.

Inspiration

Researchers have studied exactly this: for example, work on using the discharge voltage profile as a diagnostic signature of capacity fading in valve-regulated lead-acid packs for e-rickshaw applications, and studies of how lithium iron phosphate cells degrade in e-rickshaw use. Commercial fleet telematics and battery swapping companies track pack health at scale. This project brings the core of both to a single vehicle and a small fleet.

What you build

• On the vehicle: a sensing board on an STM32 that measures each block's voltage (safely isolated or divided), pack current through a shunt with a current-sense amplifier, and temperatures, with a small display and buzzer.
• Firmware: FreeRTOS tasks for fast sampling, charge estimation, logging, display and communication, passing data through queues.
• Connectivity: BLE to the driver's phone, or a GSM/4G module for fleets, uploading logs when a connection is available.
• Backend and dashboard: per-pack history of charge, deep discharge events, temperature and a health indicator, with simple reports for owners.

The technically interesting part

• Accurate measurement in a noisy environment. Motor controllers are electrically noisy. You will design dividers and filtering, choose where to place the shunt, and calibrate against a reference meter.
• State of charge. Coulomb counting (adding up current over time) drifts, and voltage-based estimates only work at rest. Combining them, and documenting the error, is a real estimation problem.
• State of health. Estimating capacity from full cycles, or internal resistance from the voltage drop under a known load, lets you show a pack getting weaker over weeks.
• RTOS design. Sampling must never be delayed by a slow modem, and logging must survive sudden power loss. This is exactly what tasks, priorities, queues and watchdogs are for.
• Power and safety. The device runs from the traction pack, so it needs a proper DC-DC supply, fusing and isolation. Get supervision from a lab engineer before connecting to a vehicle.

Deliverables and how to evaluate it

Report numbers, not impressions: voltage and current accuracy against a reference meter, state of charge error over full discharge cycles on a bench pack, logging with no gaps across deliberate power cuts, alert latency, and uptime over a multi-day field test. Compare your health indicator with a controlled capacity test on at least one pack.

Stretch goals

Support lithium packs by reading their BMS over CAN or UART, predict remaining useful life from the health trend, add OTA updates, or build a charging station view for fleets.

Path to a product

Fleet owners and battery dealers have a direct financial reason to know how packs are treated, because it affects warranty claims and replacement costs. A product version would focus on a low-cost, sealed unit that installs in minutes, a subscription dashboard for fleets, and data that battery sellers can use to handle warranty claims fairly. Start by interviewing a few drivers, fleet owners and battery shops to learn which alerts and reports they would actually pay for.

Want feedback on your scope before you start? Discuss this idea at /account/fyp-ideas/e-rickshaw-battery-health-monitor-on-stm32-with-freertos/, ask a specific question at /account/ask/, or book a session at /account/book/. New to Sefism? Create a free account.

Learn what you need on Sefism

• Embedded systems and IoT roadmap: C for hardware, sensors, protocols, RTOS, connectivity and debugging, stage by stage.
• Embedded systems and IoT cheat sheet: dividers, ADC maths, FreeRTOS tasks and queues, power budgets.
• STM32CubeIDE and the STM32 MCU Wiki for the toolchain and peripherals.
• FreeRTOS Documentation and the Introduction to RTOS video series for task design.
• Making Embedded Systems for architecture, power and debugging.
• All About Circuits Textbook for the measurement circuits.