Engineering guide
Power Electronics Development Guide: BMS, DC-DC, EV Chargers and Motor Control (2026)
Developing a power-electronics product — a battery management system, an isolated DC-DC converter, an EV charger or a motor controller — typically takes 5–15 months from specification to a pilot build and, as a planning range with an India-based team, $30,000–$250,000+ in engineering, depending on voltage class, power level and the safety standard it must meet. The cost is driven less by the schematic than by high-voltage isolation and safety design, magnetics and thermal iteration, and the test campaign: efficiency, EMC, abnormal-condition and certification testing.
Key facts
| Product | Typical architecture | Key standards | Time to pilot | Planning engineering cost |
|---|---|---|---|---|
| BMS, 16S LFP / 48 V class | Cell-monitor AFE, MCU, MOSFET or contactor switch, CAN | IEC 62619, UL 2580/1973, AIS-156, ISO 26262 (vehicles) | 5–9 months | $30,000–$100,000 |
| Isolated DC-DC, 800 V → 48 V, ~3 kW | SiC primary, LLC/PSFB/DAB, planar transformer, digital control | IEC 62477-1 or 62368-1, IEC 60664-1, CISPR 25/32 | 8–15 months | $80,000–$250,000+ |
| AC EV charger, 7.4 kW | Control pilot, contactor, RCD/DC fault detection, metering, OCPP | IEC 61851-1, IEC 62196, IEC 62955, OCPP | 6–10 months | $50,000–$150,000 |
| DC fast charger | PFC + isolated DC-DC modules, ISO 15118 communication | IEC 61851-23/-24, ISO 15118 | 12–24 months | $250,000+ |
| Motor controller, BLDC/PMSM 48–96 V | 3-phase inverter, gate drivers, current sensing, FOC firmware | IEC 61800-5-1, ISO 26262, AIS (vehicles) | 5–10 months | $40,000–$120,000 |
Architecture choices: 48 V, 400 V or 800 V, and GaN vs SiC
The bus voltage sets most of the design’s cost. Under IEC 62368-1, DC voltages up to 60 V in normal operation fall in the lowest electrical energy class (ES1), so 48 V systems can often avoid the heavy insulation needed at higher voltages. At 400 V and especially 800 V, every path from the high-voltage side to anything a person or a low-voltage circuit can touch needs basic, double or reinforced insulation sized by IEC 60664-1 for the working voltage, pollution degree and overvoltage category. That drives creepage slots in the PCB, transformer construction, isolated gate drivers and isolated sensing.
| Bus | Typical switch | Why | Watch out for |
|---|---|---|---|
| 12–48 V | Silicon MOSFETs or 100 V-class GaN | Low voltage; GaN for high frequency and density | Layout parasitics, gate-drive voltage margins |
| 400 V class | 650 V GaN, 650–750 V SiC | GaN for high frequency and small magnetics; SiC for robustness | GaN gate sensitivity; dv/dt immunity of drivers |
| 800 V class | 1,200 V SiC MOSFETs | Mainstream GaN is rated around 650 V | Negative gate bias, short-circuit withstand time, common-mode currents |
Topology follows from the application: LLC resonant converters for fixed-ratio isolated conversion, phase-shifted full bridges for wide load ranges, dual-active-bridge (DAB) for bidirectional power, and totem-pole PFC stages on the AC input of chargers. Our blog post on GaN bidirectional switches covers layout for wide-bandgap devices.
Battery management systems
A BMS measures every cell, protects the pack, estimates state of charge and health, and talks to the charger and the vehicle or inverter. The design decisions that matter:
- Cell-monitoring AFE: channel count, voltage accuracy (a few millivolts matters for LFP’s flat curve), balancing current and daisy-chain isolation for stacked packs.
- Protection path: MOSFET switch for low-voltage packs, contactors with pre-charge for high-voltage packs, a pack fuse, and independent secondary protection where the safety case needs it.
- State estimation: coulomb counting corrected with open-circuit-voltage models or a Kalman filter; LFP needs careful calibration.
- Temperature: enough sensors in the right places; AIS-156 sets minimums for Indian two- and three-wheelers.
- Isolation monitoring for high-voltage packs, and data logging for warranty and incident analysis.
- Communication: CAN (often J1939 or CANopen), with a defined protocol to the charger.
Standards: IEC 62619 for industrial lithium batteries (including stationary storage), UL 1973 for stationary and motive applications, UL 2580 for EV batteries, IEC 62133-2 for portable batteries, UN 38.3 for transport, and in India AIS-156 (L category) and AIS-038 Rev 2 (M and N), amended with additional safety requirements from 1 December 2022 and 31 March 2023 (PIB). See our India certification guide for the AIS-156 details.
DC-DC converters
Isolated DC-DC bricks for 800 V and 400 V platforms — feeding 48 V or 12 V auxiliary buses in vehicles, energy storage and industrial systems — are where magnetics, thermal design and EMI dominate the schedule:
- Magnetics: planar or custom-wound transformers, leakage inductance used deliberately in resonant or DAB designs, and insulation built into the winding structure.
- Control: digital control on a real-time MCU or DSC for soft-start, current sharing between paralleled modules, protections and telemetry.
- Thermal: cold-plate or forced-air design validated with thermocouples and thermal imaging at full load and maximum ambient.
- EMI: input filter designed against CISPR 25 (vehicle) or CISPR 11/32 limits, with common-mode currents from fast SiC edges as the usual problem.
- Protection: over-current, over-voltage, under-voltage lockout, over-temperature and short-circuit, verified by abnormal-condition tests.
Efficiency and power density are design targets until measured on a power analyser across the full input, load and temperature range. Ask any supplier to state which figures are measured and which are targets.
EV chargers: IEC 61851 and OCPP
AC chargers (Mode 3)
A wallbox or public AC charger follows IEC 61851-1: control-pilot PWM signalling and proximity detection with the vehicle, contactor control and welding detection, residual-current protection (a Type B RCD, or Type A with 6 mA DC fault detection per IEC 62955), and connectors to IEC 62196. Revenue metering, tamper detection and local display requirements vary by country. India has adopted the IEC 61851 framework through the IS 17017 series.
DC fast chargers
DC chargers add power-factor-correction and isolated DC-DC power modules, insulation monitoring, and high-level communication with the vehicle (IEC 61851-23/-24, ISO 15118 for Plug & Charge). They are system programmes rather than board designs.
Back-end connectivity
The Open Charge Point Protocol connects chargers to operators’ management systems. OCPP 1.6J remains widely deployed; OCPP 2.0.1 is published as IEC 63584:2024; OCPP 2.1, released in January 2025 and published by IEC as IEC 63584-210:2025 on 9 December 2025, adds bidirectional charging, distributed-energy-resource control and ISO 15118-20 support (Open Charge Alliance). Our cloud development team builds the back-end side when it is in scope.
Motor controllers
Controllers for BLDC and PMSM motors in e-mobility, robotics and industrial equipment combine a three-phase inverter with field-oriented control (FOC) firmware:
- Position sensing: Hall sensors, encoders or sensorless observers — sensorless start-up under load is the usual hard part.
- Current sensing: low-side or in-phase shunts with fast amplifiers, or Hall-effect sensors for isolation.
- Gate drivers with dead-time control, desaturation or over-current protection, and regenerative-braking handling.
- Thermal design of the power stage and derating logic in firmware.
- Safety: IEC 61800-5-1 for drives, Safe Torque Off (IEC 61800-5-2) where required, and ISO 26262 for road vehicles.
Development stages
| Stage | What happens | Key evidence |
|---|---|---|
| 1. Specification and safety concept | Ratings, efficiency and density targets, insulation scheme, protection strategy, applicable standards | Requirements, hazard analysis, insulation diagram |
| 2. Simulation and magnetics | Topology and control simulation, loss and thermal estimates, magnetics design | Simulation results, loss budget, first magnetics samples |
| 3. Low-voltage bring-up | Control, sensing and protections verified at reduced voltage | Protection trip tests, control-loop measurements |
| 4. High-voltage bring-up | Stepwise increase to full voltage and power with interlocks | Switching waveforms, double-pulse results, thermal map |
| 5. Characterisation | Efficiency across load, line and temperature; EMI pre-scans | Power-analyser data, conducted-emissions plots |
| 6. Abnormal conditions and reliability | Short circuits, overloads, component faults, thermal and power cycling | Fault-test report, reliability data |
| 7. Certification and pilot | Formal safety and EMC testing, pilot build with production test | Test reports, pilot yield |
Test equipment and lab safety
| Equipment | Used for |
|---|---|
| High-voltage differential probes; isolated probes | Switch-node and high-side gate waveforms without ground loops |
| Current probes and Rogowski coils | Switching currents, inrush and fault currents |
| Precision power analyser | Efficiency and loss measurements you can publish as measured |
| Programmable DC sources, regenerative loads, battery emulators | Full-power operation, bidirectional testing, BMS validation |
| Double-pulse test setup | Switching losses and gate-drive tuning for SiC/GaN |
| Thermal camera and thermocouples | Hot-spot mapping and thermal validation |
| LISN and spectrum analyser | Conducted-emissions pre-compliance |
| Hipot and insulation-resistance tester | Insulation verification during development and production |
| Climatic chamber | Operation and derating at temperature extremes |
| CAN analyser | BMS, charger and motor-controller communication |
High-voltage development also needs lab discipline: interlocked enclosures for HV tests, isolation transformers, bleeder and discharge procedures, and a two-person rule for live work above safe voltages.
Safety standards map
| Standard | Scope |
|---|---|
| IEC 62368-1 | Power supplies and power stages in ICT and audio/video equipment |
| IEC 61010-1 | Test, measurement, control and laboratory equipment |
| IEC 62477-1 | Power electronic converter systems and equipment |
| IEC 61800-5-1 | Adjustable-speed electrical power drive systems |
| IEC 61851 series, IEC 62196, IEC 62955 | EV charging equipment, connectors, DC fault detection |
| IEC 62619, UL 1973, UL 2580, UL 9540 | Industrial, stationary and EV batteries; energy storage systems |
| IEC 62133-2, UN 38.3 | Portable lithium batteries; transport testing |
| IEC 60664-1 | Insulation coordination: creepage and clearance |
| ISO 26262 | Functional safety for road vehicles (see our ISO 26262 explainer) |
| AIS-156, AIS-038 Rev 2 | Indian EV traction battery safety |
More on automotive functional safety in our ISO 26262 explainer.
What drives cost and schedule
- Voltage class: 800 V designs need reinforced insulation, more test effort and more careful layout than 48 V designs.
- Magnetics iterations: custom transformers often need two or three sample rounds.
- Destructive testing: abnormal-condition and short-circuit tests destroy boards; budget spare builds.
- Certification: high-power products need specialised labs with limited capacity; book early.
- Functional safety: an ISO 26262 or IEC 61508 work-product set can add a large share to engineering effort.
- Variants: each voltage or power variant needs its own verification.
How Rapid Circuitry works on power electronics
Rapid Circuitry designs power and battery electronics together with the firmware and connectivity around them — electronics design, embedded hardware, firmware and pre-compliance testing — for energy and automotive and EV clients. We state which performance figures are design targets and which are measured, and we scope high-voltage testing explicitly in every proposal. For hydrogen power, our hydrogen drone power system case study covers integrating a 5 kW fuel cell and its DC-DC stage into a drone powerpack, with thermal and mass analysis (design study; bench testing not yet done).
Frequently asked questions
How much does it cost to develop a BMS from scratch versus buying an off-the-shelf one?
As a planning range with an India-based team, a custom BMS for a low-voltage pack such as a 16S LFP battery with CAN costs about $30,000–$100,000 in engineering and takes 5–9 months to a pilot build, before certification testing. An off-the-shelf BMS costs nothing up front but more per unit, and you inherit its firmware, protections and communication protocol. A custom BMS usually pays off when volumes are in the thousands, when the pack needs specific state-of-charge accuracy, safety features or data logging (for example for AIS-156), or when the BMS must integrate tightly with a charger or vehicle controller.
GaN or SiC for a 3 kW DC-DC converter?
It depends mainly on the bus voltage. For an 800 V input, 1,200 V-class SiC MOSFETs are the usual choice for the primary side because mainstream GaN devices are rated around 650 V. For 400 V buses and below, 650 V GaN allows higher switching frequency and smaller magnetics, while SiC offers robustness and easier gate driving at moderate frequency. On a 48 V secondary, 100 V-class GaN or silicon MOSFETs are both common. Gate-drive design, layout loop inductance and thermal paths matter as much as the device choice.
What does it take to design an 800 V to 48 V isolated DC-DC converter of about 3 kW?
Typically a SiC primary stage in an LLC, phase-shifted full-bridge or dual-active-bridge topology, a planar or custom transformer providing reinforced insulation sized to IEC 60664-1, synchronous rectification on the 48 V side, digital control, and protection for over-current, over-voltage, over-temperature and short circuit. Plan roughly 8–15 months and, as a planning range, $80,000–$250,000+ in engineering to a pilot build, with most iteration spent on magnetics, thermal design and EMI filtering, and a test lab able to run high-voltage, efficiency and abnormal-condition tests safely.
OCPP 1.6 or OCPP 2.0.1 for a new 7.4 kW AC charger?
OCPP 1.6J is still the most widely deployed protocol, so many charge-point operators expect it. OCPP 2.0.1, published as the international standard IEC 63584:2024, adds better device management, security profiles and smart-charging features, and OCPP 2.1 (released January 2025, published by IEC as IEC 63584-210:2025) adds bidirectional charging and distributed-energy control. For a new product, design firmware to support 2.0.1 with 1.6J for compatibility, and confirm what your target operators require.
What test equipment does a power electronics development lab need?
At minimum: high-voltage differential probes and, for fast high-side gate measurements, isolated probes; current probes; a precision power analyser for efficiency; programmable DC sources, electronic or regenerative loads and battery emulators; a double-pulse test setup for switching characterisation; thermal imaging and thermocouples; a LISN and spectrum analyser for conducted-emissions pre-compliance; a hipot and insulation-resistance tester; and a climatic chamber. Just as important are HV lab safety practices: interlocks, isolation, discharge procedures and trained staff.
Can an outsourced team deliver an ISO 26262 ASIL-B safety case for a BMS?
Yes, provided the work is structured under your functional-safety management: the vehicle-level hazard analysis and safety goals normally come from the OEM or system owner, and the supplier delivers the hardware and software work products for its scope — technical safety concept, hardware metrics, software development to the required ASIL, verification and the supporting documentation — under a development interface agreement. Ask the supplier which ISO 26262 work products they have produced before and how they handle confirmation reviews.
Which safety standards apply to power electronics products?
It depends on the product: IEC 62368-1 for ICT and audio/video power supplies, IEC 61010-1 for test, measurement and laboratory equipment, IEC 62477-1 for power electronic converter systems, IEC 61800-5-1 for adjustable-speed drives, the IEC 61851 series for EV charging equipment, IEC 62619, UL 1973 and UL 2580 for industrial, stationary and EV batteries, IEC 62133-2 and UN 38.3 for portable batteries and transport, and in India AIS-156 or AIS-038 for EV traction batteries. IEC 60664-1 sets insulation coordination across most of them.
Sources
- IEC — IEC 62368-1:2023 — AV/ICT equipment safety, edition 4
- IEC — IEC 61010-1:2010 + AMD1:2016 — measurement, control and laboratory equipment safety
- IEC — IEC 62477-1:2022 — power electronic converter systems safety
- IEC — IEC 60664-1:2020 — insulation coordination (creepage and clearance)
- IEC — IEC 61851-1:2017 — EV conductive charging, general requirements
- IEC — IEC 62619:2022 — safety of secondary lithium cells and batteries for industrial applications
- UL Standards & Engagement — UL 2580 — batteries for use in electric vehicles
- Open Charge Alliance — OCPP — OCPP 1.6, 2.0.1 and 2.1 (checked September 2026)
- Open Charge Alliance — OCPP 2.1 published by IEC as IEC 63584-210:2025 — OCPP 2.1 released January 2025; IEC publication 9 December 2025
- PIB — AIS-156 and AIS-038 (Rev 2) amendments — 27 September 2022
Cost and timeline ranges are Rapid Circuitry planning estimates, stated with their assumptions above.