Yokohama, Kanagawa cell grading plant
How Yokohama — Kanagawa Diagnostics Works decides reuse or refining for every module — test sequence, grade bands, outputs and the sites that feed it.
Throughput
21,000 TPA
Process stages
6
Feeder sites nearby
6
Operating since
2020
From intake to grade assignment
- 1
Intake & safety triage
Packs are logged, thermally imaged and screened for swelling, coolant ingress or venting before entering the bench area.
- 2
Controlled de-energising
Residual energy is discharged to a safe state of charge with regenerative load banks and recorded per serial number.
- 3
Module-level capacity test
Full charge-discharge cycling at C/3 establishes usable capacity, internal resistance and cell-to-cell balance.
- 4
EIS fingerprinting
1 mHz–10 kHz impedance sweeps separate SEI growth, lithium plating and contact resistance degradation modes.
- 5
AI optical inspection
Machine-vision inspection of busbars, welds and cell cans flags mechanical defects that block second-life reuse.
- 6
Grade assignment
Grade A (≥85% SOH), B (75–85%), C (65–75%) and D routes are assigned, with D-grade material released to refining.
Acceptance criteria
| Criterion | Requirement |
|---|---|
| Accepted feed | Whole packs and modules from intake yards and fleets |
| State of charge | Below 30% on arrival, recorded per serial |
| Condition | Damaged units declared and routed to quarantine |
| Documentation | Manifest with serials, chemistry and prior history |
Grade bands and routes
| Grade | Route |
|---|---|
| Grade A (85%+) | Grid-tied and commercial storage builds |
| Grade B (75–85%) | Telecom backup and solar buffering |
| Grade C (65–75%) | Low-duty backup, short warranty |
| Grade D (<65%) | Discharge and refining feed |
Why Yokohama, Kanagawa
Yokohama is a major port and industrial city in the Tokyo metropolitan region, home to vehicle maker headquarters and engineering centres. The diagnostics works opened on Daikoku Pier in 2020 to grade Japanese packs, including those from some of the earliest mass-market EVs, which have built up many years of real-world use. Its catchment covers the greater Tokyo region. It opened as those early fleets began retiring.
With 21,000 TPA of capacity, the works tests fleet, dealer and engineering packs as well as hybrid modules. The long service histories of Japanese EVs give the site unusually rich data on how packs age, which improves grading accuracy for older batteries and informs decisions about second-life use. Reusable modules are released for second-life builds, and the rest are sent for processing.
Permitting
Act on the Promotion of Effective Utilization of Resources and the End-of-Life Vehicle Recycling Act
The works operates under Japanese waste and recycling laws, including the rules for end-of-life vehicle recycling. Transport follows Japanese dangerous goods regulations.
Technical strengths
Long-life EV data
Experience with Japanese EV packs that have many years of service.
Port location
On Daikoku Pier with direct shipping access.
Engineering support
Handles test packs from Japanese developers.
Sites that feed Yokohama, Kanagawa
Packs and modules arrive from these intake sites.
Yokohama, Kanagawa plant: technical questions
How long does grading take?
Standard passenger modules are graded within about five working days of intake; large-format bus and truck packs take longer because of disassembly.
What tests are run on each module?
A full capacity cycle, DC internal resistance, impedance spectroscopy and optical inspection of busbars, welds and cans.
Does Yokohama grade older EV packs?
Yes, including batteries from early mass-market EVs.
Can packs be shipped from Yokohama?
Yes, subject to transport and waste rules.
Damaged or defective packs are handled under a separate quarantine protocol — flag them in the form and the team calls you back the same day.
Need modules graded?
Share pack counts, chemistry and condition for a grading slot and indicative value split.