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Views: 0 Author: Site Editor Publish Time: 2025-08-26 Origin: Site
On-board EV charging converts AC to DC inside the vehicle with a built-in on-board charger, ideal for AC Level 1–2 charging. Off-board charging performs AC/DC conversion in the external station, enabling high‑power DC fast charging (Level 3) delivered straight to the traction battery and bypassing the in‑vehicle converter.
This guide is engineered for vehicle manufacturers, platform architects, and powertrain integrators. It clarifies where an on-board charger (OBC) fits relative to off-board DC fast charging, outlines selection criteria (power, cooling, bidirectional capability, compliance, and integration level), and maps typical duty cycles to hardware decisions. It also shows how Landworld’s on-board charger portfolio across 3.3–40 kW and integrated 2‑in‑1/3‑in‑1 systems align with passenger, commercial, and off-road vehicle programs.To review product classes while reading, see Landworld’s on-board charger lineup.
Conversion location: On-board (AC→DC inside vehicle) vs off-board (AC→DC in the station).
Typical power: On-board ~3.3–22 kW (up to 40 kW on select platforms) vs off-board ~50–350 kW.
Charging levels: On-board supports AC Level 1–2; off-board enables DC fast charging (Level 3).
Integration trade-offs: On-board adds weight, thermal and EMC considerations; off-board shifts complexity to the site (grid capacity, cooling, controls).
Best use: On-board for predictable dwell windows; off-board for time-critical turnarounds and long-haul corridors.
| Attribute | On-board charging (AC via on-board charger) | Off-board charging (DC fast) |
|---|---|---|
| Conversion location | Inside vehicle (OBC) | External station |
| Typical power | ~3.3–22 kW (up to 40 kW) | ~50–350 kW |
| Charging levels | AC Level 1–2 | DC Level 3 |
| Infrastructure | Lower CapEx; uses facility circuits | High CapEx; utility coordination |
| Vehicle impact | Packaging, harnessing, thermal, EMC | No added in-vehicle weight |
| Duty cycle fit | Overnight depot/home, workplace | Quick en-route replenishment |
Only AC Levels 1–2 rely on the OBC; DC fast charging is handled by the station’s power stack.
| Item | Level 1 (AC) | Level 2 (AC) | Level 3 (DC fast) |
|---|---|---|---|
| AC/DC conversion | In-vehicle via OBC | In-vehicle via OBC | In station (off-board) |
| Typical voltage | ~120 V (region-dependent) | 208–240 V (single/three-phase by region) | High-voltage DC |
| Typical power | ~1–2 kW | ~7.4–22 kW | ~50–350 kW |
| Speed ceiling set by | OBC + circuit | OBC + circuit | Station + vehicle DC limits |
| OBC in power path? | Yes | Yes | No |
Implication: The on-board charger is the AC speed limit for the vehicle. To accelerate Level 2 sessions, OEMs increase OBC power—subject to thermal, packaging, and cost constraints.
An on-board charger rectifies AC to DC, shapes the charge profile under BMS supervision, and manages thermal performance. Key functions include AC rectification and power factor control, regulated DC output following CC/CV profiles, communications with the BMS and charge post, and thermal management via air or liquid cooling. In searches and specifications, you’ll see terms like ev onboard charger, on board charger electric vehicle, on board battery charger, and power on board charger; these typically refer to the same in‑vehicle converter in an automotive context.
Power rating (kW): Align with energy per dwell, pack capacity, and target turnaround. Common classes: 7.4–11 kW for mainstream passenger platforms; 11–22 kW for larger packs or fleet turnover; 22–40 kW for commercial/heavy-duty.
Cooling architecture: Air-cooled for mid‑power and temperate use; liquid-cooled for high power, hot climates, or intensive utilization where thermal stability and acoustic limits matter.
Bidirectional capability: Choose bidirectional if V2L/V2H/V2G features are on the roadmap or required for resilience and grid programs.
Integration level: 2‑in‑1 (OBC + DC/DC) to reduce harness length and volume; 3‑in‑1 (OBC + DC/DC + PDU) for centralized power management and platform modularity.
Compliance and robustness: ISO 26262 (functional safety) and IATF 16949 (automotive quality) as baselines; add ISO 9001/14001/45001 and ESD S20.20 for process rigor. Prioritize EMC immunity, IP ratings, vibration tolerance, and proven MTBF.
| Platform/duty cycle | Recommended OBC power | Cooling | Integration guidance |
|---|---|---|---|
| Compact passenger, predictable depot dwell | 7.4–11 kW | Air (liquid if hot) | Standalone OBC or 2‑in‑1 for packaging |
| Premium passenger, larger packs or multi-driver | 11–22 kW | Air or liquid | 2‑in‑1; 3‑in‑1 on centralized architectures |
| Light commercial fleets | 11–22 kW | Often liquid | 2‑in‑1 to cut harnessing and improve efficiency |
| Heavy-duty or depot-centric operations | 22–40 kW | Liquid | 3‑in‑1 for centralized power management |
| Off-road/special vehicles | 11–22 kW | Liquid | 3‑in‑1; emphasize ruggedization and high IP |
Note: OBC power shortens Level 2 dwell only if facility circuits and posts support the target amperage and phase configuration.
2‑in‑1 systems (OBC + DC/DC): Typical pairings include 3.3 kW OBC + 2 kW DC/DC; 6.6 kW OBC + 2.5–3 kW DC/DC; 11 kW or 22 kW OBC + 3 kW DC/DC. Benefits: reduced harness mass, smaller envelope, improved system efficiency.
3‑in‑1 systems (OBC + DC/DC + PDU): 3.3/6.6/11 kW with 2.5–3 kW DC/DC plus PDU, enabling centralized control and streamlined validation.
Landworld’s capabilities align with OEM validation and global sourcing requirements:
Certifications: ISO 26262, IATF 16949, ISO 9001, ISO 14001, ISO 45001, ESD S20.20.
Industrialization: 90%+ production automation, 800,000+ annual unit capacity.
Track record: 1,000,000+ cumulative shipments, 20+ countries served.
R&D strength: High power density, modular design, and contributions to national standards.
Confirm AC use case (Level 1/2) energy needs and allowable dwell per platform.
Match OBC power to facility constraints (phase, amperage, panel capacity).
Select cooling to meet duty cycle, climate, acoustic, and packaging targets.
Define bidirectional requirements early (interfaces, protections, compliance).
Choose integration level (standalone vs 2‑in‑1 vs 3‑in‑1) based on wiring complexity and modularity goals.
Validate EMC, IP, vibration, thermal derating, and efficiency across the duty envelope.
Q1: What is onboard and offboard charging?
A1: Onboard charging uses an in‑vehicle on-board charger to convert AC to DC for Level 1–2 sessions. Offboard charging places conversion in the external station and delivers regulated DC for Level 3 fast charging, bypassing the vehicle’s OBC power path.
Q2: What is an onboard EV charger?
A2: An onboard EV charger (OBC) is the AC→DC converter and charge controller integrated into the vehicle. It manages rectification, charge profiles, communications with the BMS and post, and thermal limits during AC charging.
Q3: What is the difference between on-board and off board?
A3: On-board centralizes conversion in the vehicle (impacting packaging, thermal, EMC); off-board externalizes conversion in the station, enabling higher power with site-side cooling and grid integration.
Q4: What are the three types of EV charging systems?
A4: AC Level 1 and Level 2 (both rely on the OBC) and DC Level 3 fast charging (conversion in the station; DC delivered directly to the pack).
Q5: How should OEMs choose OBC power?
A5: Size to energy-per-dwell, pack capacity, and facility limits: 7.4–11 kW for mainstream passenger, 11–22 kW for larger packs/fleets, 22–40 kW for commercial/heavy-duty.
Q6: When is bidirectional capability required?
A6: Specify a bidirectional ev onboard charger if V2L/V2H/V2G is on the product roadmap or mandated by customer programs or resilience objectives.
Q7: When to adopt 2‑in‑1 or 3‑in‑1 integration?
A7: Use 2‑in‑1 to reduce harnessing and volume; select 3‑in‑1 for centralized power management, especially in premium, commercial, or off-road platforms.
