Summary of "Embedded Systems and Design & Development - Feb 10, 2026 | Morning | VisionAstraa EV Academy"
Overview
The instructor reviewed EV power/connectors and charging architecture, then introduced charging calculations, C‑rating constraints, fast (DC) charging behavior and pulse‑charging. The session closed with a practical homework: download LFP cell datasheets for an evening follow‑up.
Main topics and key points
1) Connectors — types and identification
- Anderson SB series (SB50, SB75, SB125, SB175)
- DC power connectors marked with polarity.
- SB number denotes size/current rating.
- Housings are genderless (same mating part both sides).
- “Chagori” connector (presented as 2 + 4)
- 2 power pins (positive/negative) + 4 CAN/communication pins.
- Available as male and female mating halves.
- Three‑pin connectors
- Used for AC and sometimes DC; standard male/female arrangement.
- DT / D‑type connector
- D‑shaped body, polarity marked; used where physical thickness requires it.
- Brand-specific charger plugs
- Ola charger (“type six”): 2 (power) + 4 (CAN) configuration (2+4).
- Ather charger (“type seven”): 5 (power) + 4 (communication) configuration (5+4).
- Type‑2 (IEC) socket (common AC EV inlet)
- Terminals: L1, L2, L3 (line/phase), N (neutral), PE (protective earth), plus CP and PP.
- CP = Control Pilot (control signaling between vehicle and EVSE).
- PP = Proximity Pilot (often used to sense plug presence / cable rating). Note: transcript used “protective pilot” but industry term is “proximity pilot.”
- Single‑phase vs three‑phase: presence of only L and N indicates single‑phase (typical up to ~7.2 kW); L1/L2/L3 enables three‑phase and higher power.
2) Charger architecture — onboard vs offboard (and DC fast charging)
- Offboard charger
- External unit that converts AC → DC and supplies DC to the battery pack.
- Common in two‑wheelers and for portable car chargers.
- Onboard charger
- Installed inside the vehicle; receives AC input and converts AC → DC inside the vehicle.
- Limited by its designed maximum current (e.g., 50 A).
- DC fast charging (offboard DC)
- Large public stations convert AC → DC externally and supply high‑current DC directly to the vehicle battery (bypassing onboard AC→DC).
- These chargers are bulky and mounted offboard.
3) Why charger size and placement matter
- Higher current rating → physically larger charger and heavier thermal management.
- For very high currents (car/bus), either integrate large chargers onboard or use offboard DC fast charging to avoid excessively large portable chargers.
4) Charging time and basic calculations
- Approximate time under constant current:
- Time (hours) = Battery capacity (Ah) / Charging current (A)
- Example:
- Battery = 200 Ah; Charger current = 50 A → Time = 200 / 50 = 4 hours.
- Practical charging is often slower due to charge profiles, inefficiencies, and tapering near full SoC.
5) C‑rate and safety checks
- C‑rate = Charging (or discharging) current divided by nominal capacity (I / Ah).
- Example: 200 Ah pack charged at 200 A = 1C.
- Session examples:
- For 200 Ah pack, recommended maximum continuous charging current quoted = 0.2C → 0.2 × 200 Ah = 40 A. Charging at 50 A would exceed that continuous limit.
- Fast charging example: 300 A into 200 Ah → 1.5C.
- Always cross‑check with cell/pack datasheet continuous max charging current limits.
6) Charging methods / profiles
- CC‑CV (Constant Current → Constant Voltage)
- Charger holds constant current until voltage threshold, then holds voltage while current tapers.
- Constant voltage (variable current)
- Voltage fixed, current varies.
- Pulse charging
- Short bursts (pulses) of high current for brief periods, interleaved with lower base current or pauses to allow relaxation/redistribution.
- Example pattern discussed: base ~50 A, short pulses up to ~300 A for ~10 s, then back to base; repeat periodically.
- Verify allowable pulse currents and duty cycles from the cell datasheet.
7) Practical / engineering observations
- Know connector pinouts and pilot signals (CP/PP) to design the charging interface and embedded control logic.
- Charger selection must account for battery C‑rating, pack voltage, and intended use (onboard vs offboard, AC vs DC).
- Continuous vs intermittent (pulse) currents have different allowable limits per datasheet — do not assume high currents are safe without datasheet backing.
Practical homework / tasks assigned
- Download and bring 2–3 datasheets for LFP cells (example requested: LFP 3.2 V, 100 Ah cell — preferably pouch).
- For each datasheet, extract and compare:
- Maximum charging current (and continuous charging rating)
- Maximum and minimum cell voltages (charge/discharge limits)
- Continuous C ratings (charging/discharging limits)
- Any specified pulse/intermittent charging limits
- Physical dimensions (cell form factor)
- Prepare screenshots or links to the datasheets for the evening session; instructor will review how to read and compare datasheets.
Methodologies / step‑by‑step procedures presented
A) How to identify connectors and their pins
- Look for markings on the connector housing (e.g., SB50 / SB125 / SB175 → size/current rating).
- Locate polarity markings (+ / −) on DC power connectors.
- For Chagori/2+4 type: count 2 large power pins and 4 smaller CAN pins.
- For Type‑2/IEC inlet: identify L1/L2/L3, N, PE, CP and PP; note which power pins have metal contacts (determines single‑phase vs three‑phase).
B) How to compute charge time (approximate)
- Given battery capacity (Ah) and charger current (A):
- Time (hrs) = Ah / A
- Example: 200 Ah / 50 A = 4 hours.
C) How to check if charging current is safe using C‑rate
- Given battery capacity (Ah) and charging current (I):
- C‑rate = I / Ah
- Compare computed C‑rate to datasheet maximum continuous charge C (e.g., 0.2C). If computed C > specified limit → unsafe for continuous charging.
- Example: For 200 Ah, 0.2C = 40 A. A 50 A charger exceeds this for continuous charging.
D) Pulse charging concept
- Use a low base current for most of the charging time.
- Insert short, controlled high‑current pulses (amplitude/duration limited by the cell datasheet) to increase effective charge rate without continuous stress.
- Allow rest/recovery periods between pulses so voltage/temperature settle.
- Verify allowed pulse amplitude/duration from manufacturer data.
Terms and items planned for later coverage
- CCS2 connector (to be shown in the evening session).
- Reading and interpreting real cell datasheets; comparing LFP and NMC examples.
- Practical evaluation of whether datasheet limits match real charge strategies.
Speakers / sources featured
- Session instructor / facilitator — VisionAstraa EV Academy (single speaker).
- Mentions of connector manufacturers/brands and vehicle brands in examples: Anderson (Anderson SB series), Ola, Ather.
Note about transcript accuracy
- Subtitles were auto‑generated and contain some inconsistent spellings and terminology (e.g., “Chagori” connector, “protective pilot” vs. the industry term “proximity pilot” for PP). The summary clarifies commonly used industry terms where appropriate (CP = Control Pilot; PP typically = Proximity Pilot).
Category
Educational
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