There is no honest universal number. How many chargers a line builds in a day is set by its slowest station — usually the end-of-line test — and by staffed hours, and it changes with the model. A factory quoting a daily figure should be able to show the calculation and records behind it; without those, the figure is marketing, not capacity.
Key Takeaways
- Daily output is arithmetic: staffed minutes divided by the bottleneck station’s cycle time.
- End-of-line testing is usually the bottleneck, because every unit is tested and the routine cannot be rushed.
- Verify a quoted figure with the takt calculation and one day’s serialised test records.
- Model mix, changeovers and first-pass yield pull real output below the ceiling.
The Maths: Takt Time Sets the Ceiling
Line capacity starts with takt time: the cycle time of the slowest station, in minutes per unit. Divide a shift’s staffed minutes by that cycle time and you get the line’s ceiling. Every other station queues in front of the slowest one.
One worked example, explicitly hypothetical: a line runs one 8-hour shift, so 480 minutes are staffed. If its slowest station needs 6 minutes per unit, the ceiling is 80 units for that shift. Real output lands below the ceiling once breaks, changeovers, failed tests and rework are counted — and that gap is what a buyer should ask about.
The model matters as much as the line. A compact portable and a dual-connector station differ in assembly steps and test-station time, so the same line honestly produces different daily numbers for different products. One figure quoted for “chargers” in general hides that.
| Factor | What it means | What to ask |
|---|---|---|
| Bottleneck station | The slowest step sets the whole line’s pace | Which station, and its cycle time for this model? |
| Shift pattern | Staffed hours per day; number of shifts | How many shifts run today, not at peak? |
| Parallel stations | Duplicating the bottleneck raises the ceiling | Is the test station single or duplicated? |
| End-of-line test time | Every unit is tested; the routine takes its time | How long is the per-unit routine for this model? |
| Changeovers | Switching models or variants stops the line | How long, and how often? |
| First-pass yield | Failed units loop back for rework | What share passes first time, and where is it logged? |
Why the Test Station Usually Sets the Pace
Assembly scales easily: add people, add benches, split a step in two. Safety testing does not. The end-of-line routine — dielectric strength, a functional charging test, protective-function checks — runs on every finished unit and takes the time it takes; hurried, it stops being the test. Our factory audit checklist for importers makes the same point: final testing on every unit, with results saved, is a checkpoint, not a detail.
That is why the sharpest question is how many test stations the line runs: duplicating it is the standard way to lift the ceiling, and one test station sets a hard daily limit. Quoted figures often quietly assume that station never queues and never goes down.
Questions That Reveal Real Capacity on an Audit
- Ask for the takt calculation for your model, in writing, with the bottleneck named.
- Ask to see one recent day’s serialised end-of-line records, and count the serial numbers — that count is a real day’s tested output.
- Ask what happens to output when one test station is down for a day.
- Ask how much of the line’s current capacity is already committed to other customers.
- Ask how changeovers between your variants are scheduled, and what they cost.
A credible factory talks about your order in terms of line time and test records, not factory size — the pattern our guide to how an OEM EV charger project works describes.
Capacity and Your EVDANCE Order
EVDANCE is a Shenzhen manufacturer founded in 2011, with its own factory, exports to more than 30 countries, private label from 100 units and a 3-year standard warranty. We would rather show the maths than quote a headline number: bring your forecast and model mix, and ask for the line calculation and a day’s test records. Start through the OEM and private-label programme or contact us; the range is on the products page.
Frequently Asked Questions
Can a factory double its output by adding a second shift?
Only if the bottleneck is staffed or duplicated on that shift too. A second assembly shift feeding one test station builds a queue, not more finished chargers.
Is a bigger factory automatically a higher-capacity one?
No. Floor space and headcount describe the building. Output is set by line design: station cycle times, test-station count and shift pattern.
Why do quoted capacities differ so much between factories?
Different models, test routines and shift patterns — and different honesty. Compare the calculation and one day’s test records, not the headline.
Related Reading
- EV Charger Factory Audit Checklist for Importers
- How an OEM EV Charger Project Works, Step by Step
- Pre-Shipment Inspection and AQL Sampling for EV Charger Orders
- Chinese EV Charger Manufacturers: Factory, Trading Company or Marketplace Seller?
