Summary of "Embedded Systems and Design & Development - Feb 9, 2026 | Afternoon | VisionAstraa EV Academy"
Embedded Systems & Design/Development — VisionAstraa EV Academy
Session: Feb 9, 2026 (afternoon)
Overview
This session continued the morning’s discussion on chargers and vehicle electrical architecture, with a focus on wiring harnesses, connectors and DC–DC converters. Practical guidance, examples and hands-on demonstrations were provided along with homework and next-session topics.
Main ideas and concepts
- Chargers are not universal: they differ by battery chemistry (LFP vs NMC) and pack voltage.
- Typical charge profile: CC (constant current) then CV (constant voltage). The charger switches from CC to CV near full state-of-charge (≈90%), reducing current.
- Afternoon focus: wiring harnesses, connectors and DC–DC converters (building on the morning’s introduction to connectors and harness needs).
Wiring harness: definition and purpose
- A wiring harness groups many individual wires (power, signal, communication) into an organized bundle to avoid a tangled mass of separate wires.
- Harnesses simplify vehicle integration and routing for components such as battery, MCU/controller, motor, throttle, DC–DC, lights, horn, wipers and displays.
- Harnesses include multiple breakout points and mating connectors to distribute power and signals to components.
12 V auxiliary architecture and DC–DC converters
- Most vehicle accessories run from a 12 V system (headlight, indicators, horn, tail light, wipers, display, audio).
- A DC–DC converter (switching “chopper”) steps the high-voltage battery (e.g., 48–72 V) down to a regulated 12 V.
- Choose DC–DC converters based on both voltage and current rating. Negative/ground is commonly shared (common negative bus).
- In vehicle integration, battery positive/negative connect to bus bars; bus bars feed the MCU, DC–DC and other high-current devices.
Connectors: AC vs DC and polarity
- AC connectors: phase / neutral / earth — polarity is not the same concern as for DC.
- DC connectors: polarity matters (positive/negative); mismating must be prevented.
- Male/female mating and keyed designs are used to prevent incorrect connections.
Common power/charging connectors and typical uses
- Anderson SB50: DC polarized connector rated ≈50 A — often used on smaller packs.
- Anderson SB175: larger Anderson connector rated ≈175 A for high-current applications.
- Standard 3‑pin AC mains connectors: phase, neutral, earth — for AC inputs/outputs.
- “Chagori” (2 + 4 style): 2 power pins (pos/neg) + multiple smaller pins for communication (CAN) and status — used when battery power plus CAN data are required.
- Type-6 connector: used by some two-wheelers (e.g., Ola) — power pins + CAN pins (large pins for power, smaller pins for comms).
- Type-7 connector: used by some two-wheelers (e.g., Ather) — top section for power (multiple large pins for fast/dual charging) and lower pins for CAN communication.
- Type-2 (car) AC charging connector: used for AC charging in cars; different form factor and pin layout from two-wheeler connectors.
- Charger housings commonly include larger holes/pins for power and smaller pins for communication — OEMs place CAN/power pins differently (varies by design/patent).
Charger selection guidance & practical rules
- Match charger full-charge voltage to pack full voltage (e.g., charger output ≈67.2 V for a 60 V nominal NMC pack).
- Match charger current to the acceptable charge C-rate for the battery:
- Use the manufacturer datasheet limits. Example: for a 60 V, 26 Ah pack, 0.2C = 5.2 A. A 10 A charger would exceed a 0.2C recommendation.
- A 10 A charger might be appropriate for a larger pack (e.g., 50 Ah at 0.2C).
- Some packs support higher C-rates (up to 1C or 2C) depending on chemistry — always follow manufacturer specs.
- Don’t rely only on charger amperage rating — calculate permitted charge current from battery Ah and allowed C-rate.
BMS and VCU considerations
- BMS current ratings (charge/discharge) are based on pack Ah × allowed C-rate (e.g., 40 Ah × 3C = 120 A discharge).
- BMS must match the pack series count (S count) and current requirements:
- Example S count rule: S = rated pack voltage ÷ nominal cell voltage (use 3.7 V nominal unless specified). E.g., 48 V nominal ≈ 13S.
- For CAN-enabled smart vehicles, battery packs provide both power and CAN/communication lines to the VCU. Simple non‑CAN vehicles have only power wires.
- If telemetry (SOC, voltages, temps) is needed, choose a connector with extra pins (e.g., chagori) rather than a two-pin Anderson.
Harness and connector selection rules (practical guidelines)
- Size connectors for the maximum expected current (do not use a 50 A connector for a 120 A discharge).
- Use keyed and polarized connectors to avoid reverse polarity and mismating.
- If CAN or other communications are required, use connectors that include dedicated communication pins.
- Use a harness to combine many wires and reduce field wiring complexity; plan breakout points and fuses/switches.
- Include switches or relays to control accessory loads — do not hard-wire accessories to be always on.
Practical/demo and course logistics
- Instructor demonstrated physical examples: battery packs, various connectors, chargers.
- Offline participants will get hands-on teardown of harnesses; online participants will receive design-focused instruction.
- Homework / tasks:
- Finish CCCV calculations for LFP packs similar to the morning’s NMC example.
- Bring a notebook to the next session (next session includes charger design and full EV architecture integration).
Upcoming material
- Deeper coverage of DC–DC converter inner workings.
- Why two-wheeler chargers can be heavier than car chargers despite smaller pack sizes (design and thermal considerations).
- Charger design and EV architecture design exercises.
Methodologies / stepwise instructions
Selecting a charger and checking compatibility (procedure)
- Identify battery pack nominal and full-charge voltages (from pack/spec).
- Choose a charger whose maximum output voltage matches the pack full-charge voltage (charger rated ≈ full pack voltage).
- Compute maximum safe charging current:
- I_max = Ah × charge C-rate (from manufacturer).
- Compare charger rated current to I_max:
- If charger current > I_max → not safe (risk to battery/warranty/safety).
- If charger current ≤ I_max → acceptable (verify BMS/pack supports that current).
- Verify connector and wiring current ratings; choose connector/harness rated above expected current (add margin).
- Confirm whether CAN/communications are required; if yes, choose a connector with comm pins (e.g., 2 + 4 / chagori, Type‑6/7).
Calculating BMS current and series cell count (steps)
- Series cell count: S = pack nominal voltage ÷ nominal cell voltage (use 3.7 V nominal unless specified).
- Discharge current rating = Ah × allowed discharge C-rate (e.g., 40 Ah × 3C = 120 A).
- Charge current rating = Ah × allowed charge C-rate (use manufacturer or conservative value — e.g., 0.2C or up to 1C depending on chemistry).
- Select a BMS whose continuous charge and discharge ratings meet or exceed these values.
Harness design checklist
- List all loads (lights, horn, wipers, display, MCU, motor controller, chargers, DC–DC).
- Group wires by function (power high-current, signals, CAN/data) and route into harness trunks with breakout connectors.
- Specify connector types per breakout depending on required current and whether comms are needed.
- Ensure proper fusing and switching for accessory circuits.
- Use bus bars for high-current distribution to MCU, motor controller, DC–DC input.
- Label and color-code wires or document pinouts to avoid confusion during assembly and maintenance.
Key cautions / takeaways
Never exceed the battery manufacturer’s recommended C-rate for charging or discharging.
- Match connector current rating to worst-case current (with margin).
- Use CAN-capable connectors if you need telemetry and control data routing.
- Harnesses simplify assembly but must be designed for current, shielding (for signals) and protection.
Speakers / sources featured
- Main instructor/trainer (unnamed) — lecture and demonstrations.
- VisionAstraa EV Academy (session host).
- Unidentified participants (brief interjections).
- Product/brand references (examples, not presenters):
- Anderson (SB50, SB175)
- “Chagori” connector (2 + 4)
- Ola (Type‑6 connector)
- Ather (Type‑7 connector)
- Generic Type‑2 (car AC charging connector)
Category
Educational
Share this summary
Is the summary off?
If you think the summary is inaccurate, you can reprocess it with the latest model.
Preparing reprocess...