On-Board Charger Lead Times: What Actually Moves Them, and How to Plan Around It
A quoted lead time of “8 to 10 weeks” usually means the sales team averaged last quarter. The number that matters is which of four constraints binds first: the magnetic components, the switching devices, the potting and cure process, or the test and certification slot. Each has a different recovery path, and only the last one is unaffected by how much money you can spend.
Key takeaways
- Custom magnetics are the longest pole on a non-catalogue charger — 10 to 16 weeks is normal for a new core and bobbin.
- SiC and GaN devices are allocated by design registration, not by purchase order. Register early even at low volume.
- Potting and cure is a batch process: it adds days, not weeks, but it is the step that cannot be rushed without voiding the thermal model.
- Certification is a calendar booking. European EMC slots in Q4 are the single most common cause of a slipped SOP.
The four constraints, in the order they usually bind
| Constraint | Typical adder | What shortens it | What cannot shorten it |
|---|---|---|---|
| Custom magnetics | 10–16 weeks for a new core, bobbin and qualification | Reusing an existing core from the supplier’s catalogue | Paying more. The winding slot is booked, not bought. |
| Switching devices | 4–20 weeks depending on allocation | Registering the design with the device maker early, even at prototype volume | Changing the part number late — that restarts allocation. |
| Potting and cure | 3–7 days per batch | Sizing the batch to your order instead of a full run | Rushing the cure. A short cure passes the visual check and fails the thermal cycle. |
| Test and certification | 2–6 weeks for R10 EMC, longer in Q4 | Booking the slot before the first prototype is fully built | Negotiating. The lab’s calendar is the constraint. |
The practical consequence is that a “standard” 6.6 kW charger on a shelf can ship in two weeks while the same 6.6 kW charger with a different inlet, a different coolant port and a custom enclosure takes four months — not because the factory is slow, but because you re-entered the magnetics and certification queues.
Why the factory cannot just tell you a date
On a repeat order the answer is easy: the constraint is the production slot, and a factory with an honest capacity model can commit a week. On a first order there are four queues and the supplier only controls two of them. A supplier who quotes a single number without naming which queue is critical is either quoting from a similar project or hoping. Ask a direct question: “which of the four is the critical path on this build, and what is the evidence for that date?” The answer will tell you more about the supplier than the number will.
Ask for the constraint, not the date. A supplier who says “magnetics are the long pole, our core is booked for week 6, potting follows in week 8, EMC slot is week 11” has told you something you can plan against. A supplier who says “10 weeks” has told you nothing you can act on when it slips.
Planning a launch around the calendar
Work backwards from the vehicle’s start of production rather than forwards from the purchase order. The sequence that holds up in practice is: register the switching device and book the EMC slot first, release the magnetics drawing second, and place the production order third. Buyers who place the production order first and book certification last are the ones who end up air-freighting pre-production units to a test house.
For a European launch, add the approval time to the plan rather than to the buffer: R10 EMC plus the national registration step is a fixed cost in calendar terms. The R10 document set explains what the lab will ask for, and the FAQ covers MOQ and sample lead times for the catalogue models.
What a realistic first order looks like
For a catalogue model with a standard enclosure and an existing inlet, 4 to 8 weeks from purchase order is achievable and is what we quote. For a variant that touches the magnetics, the enclosure or the inlet, 14 to 20 weeks is the honest range, and most of that is not assembly. The distinction is worth writing into the contract as two separate lead times, because a single blended number guarantees an argument at the first slip.
Frequently asked
Does a higher MOQ get me a shorter lead time?
Rarely on a first order. Volume buys a better production slot on repeat orders, but it does not move a magnetics queue or an EMC booking. On a variant build, a larger order can even lengthen the first delivery because the batch is sized to the run.
Can I pay for expedited magnetics?
Sometimes, if the supplier’s winding house has spare capacity and the core is a catalogue item. It is not a reliable planning assumption. The reliable move is to design around an existing core.
Why is Q4 slower for certification?
Test house calendars fill with programmes that must ship before the calendar year closes, and notified-body availability tightens at the same time. A slot booked in September for November is normal; a slot requested in November for December usually is not available.
How much buffer should a first launch carry?
Four weeks on a catalogue model and eight on a variant, held as components rather than as finished units where the shelf life allows it. Holding finished units protects the schedule but freezes cash in a product that may still change.
Specifying a platform?
Send the pack voltage and the target power.
We reply with a model, a derating curve and the compliance documents that go with it.
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Grapcharger designs and manufactures on-board chargers, DC-DC converters and integrated charging units from 700 W to 6.6 kW for low-speed EVs, commercial vehicles, marine and industrial platforms, and supplies vehicle manufacturers and distributors worldwide.