Battery grading for second-life, fleets, and insurers

Price the pack after you grade the plating.

CellGrader reads voltage, current, and capacity logs and returns a plating index, a health band, and a disposition for every cell: reuse, derate, recycle, or hold.

Request a pilot Inspect a sample lot
Signatures
7
Chemistries
LFP · NMC
Window
Cycles 10–100

Showing illustrative assay CG-1842, grade D, recycle.

CellGrader assay

Illustrative sample · not a certificate

Recycle

D

Recycle

0.86 Plating index SoH band 71–76%
Cell
CG-1842
Build
NMC/graphite · Pouch
History
Charged at 0°C
Window
Cycles 10–100

Confidence Standard

Stripping-window area grew sharply, and the capacity knee arrived early. Keep this cell out of a full-duty second-life pack.

Top signals · relative strength

Early kneeStrong
Stripping areaStrong
Resistance growthStrong

LFP and NMCGraphite-anode cells in the research base

7 signaturesRead from voltage, current, and capacity

Cycles 10–100The early-life window the assay uses

Four datasetsPublic and lab campaigns behind the method

01 — The miss

Capacity can look fine while the anode is plating.

Second-life packs are still priced on a capacity percent. Plating is a different failure: it brings the knee forward, raises resistance, and can end in an internal short. The log often already contains the evidence.

01

The percent hides the mode.

A cell can still show a high state of health and already carry metallic lithium on the anode. Buyers pay for the percent and inherit the knee.

02

The cycler queue is the cost.

A full capacity retest takes a channel and days of calendar time. It still does not name plating. Most of that queue is cells you could have sorted from the log.

03

A passport needs a reason.

Insurers, residual-value desks, and battery passports need a degradation mode. “84% SoH” does not say reuse, derate, or recycle.

02 — Method

From a CSV to a disposition.

No new sensor and no teardown. The assay uses the curves a cycler or a BMS history already stores, then asks for a capacity check only on the cells that need one.

  1. 01

    Drop the log.

    A CSV of voltage, current, and discharge capacity. Charge capacity and rest segments unlock the resistance and relaxation readings. We map your export with you.

  2. 02

    Read seven signatures.

    Curve shape, dQ/dV peak shift and height, resistance growth, rest-voltage drop, the early knee, and the stripping window. Each one is a physical reading, not an anonymous model weight.

  3. 03

    Sort the lot.

    Every cell comes back with a grade, a plating index from 0 to 1, a health band, and a disposition your buyer can price.

03 — Sample lot

Four cells. Four different decisions.

These rows are illustrative. Pick one and the assay card above updates. The short log is a hold: CellGrader does not invent a grade from an incomplete window.

CellBuildHistoryIndexGradeDisposition

04 — Customers

Who pays for a grade.

The buyer is the desk that currently prices a pack without knowing whether the anode has started to plate.

Second life

Graders and recyclers.

Sort an incoming lot before it occupies a cycler channel. Quote the module with plating risk on the page, and send only the ambiguous cells to a capacity test.

Fleets

Leasing and residual value.

Set the buyback from duty history, not from odometer alone. The same grade can be shown to the driver when a fast-charge habit is starting to plate.

Insurance

Underwriters.

Bind battery risk to a degradation mode. A plating index is a reason you can put next to a premium, a deductible, or a declined pack.

Warranty

Pack makers.

Grade returns and warranty cells in the lab you already run. The same index can later be called from a BMS on packs you track.

05 — Science

Seven readings. One index.

The index is a screen built from electrochemical signatures, developed in the Department of Chemical Engineering at IIT Delhi. A single feature tuned on one chemistry falls over when the cell type changes. These seven are read in a way that can be calibrated across LFP and NMC.

01

Curve distortion

How much the discharge curve changed shape. Plating is uneven, and the curve shows it.

02

Peak shift

Movement of the main dQ/dV peak as cyclable lithium is lost.

03

Peak height

A shorter peak means less active lithium is still taking part.

04

Resistance growth

Plated lithium and extra surface film push resistance up faster than ordinary aging.

05

Rest-voltage drop

After current stops, plated lithium can strip back into graphite and tug the voltage down.

06

Early knee

The cycle where fade stops being linear. Plating tends to bring that knee forward.

07 · Most direct

Stripping area

Growth of the dQ/dV window associated with lithium stripping. This is the signature the other six cannot fully replace.

06 — Workflow

Fits the lab you already run.

Start with a file. Move to an API when the lot sheet needs to land in a LIMS. A BMS call of the same index is a later step for packs you already grade.

  • CSV today. One lot in, a sheet of grades out. We map the columns in the pilot.
  • API next. Your lab software posts a log and stores the JSON against the cell record.
  • BMS later. The same index, called from the pack, for vehicles whose history you already trust.
POST /v1/grades 
POST /v1/grades
Content-Type: application/json

{
  "cell_id": "CG-3091",
  "chemistry": "NMC",
  "log_url": "https://files.example/cg-3091.csv"
}

200 OK
{
  "grade": "B",
  "plating_index": 0.47,
  "soh_band": [0.84, 0.88],
  "disposition": "derate",
  "confidence": "standard"
}

A short log returns disposition: hold and no index.

07 — Why grade first

Spend the cycler on the cells that need it.

The queue today

  • Full capacity retest on a channel
  • Days of calendar time per pack
  • A percent, with the mode unnamed
  • Cold-charged cells mixed in with quiet ones

With a CellGrader lot

  • Grade from logs you already store
  • Minutes once your export is mapped
  • Plating index plus a health band
  • Reuse, derate, recycle, or hold — before the channel is booked

08 — Pricing

Pilot rates, in the open.

Illustrative rates for a first deployment. A pilot on your chemistry can move them. Passport and House are quoted from a teardown set.

Screen

₹220 / cell

Any lot size. A PDF assay per cell. Useful when you are grading a handful of warranty returns.

Where most lots land

Batch

₹100 / cell

From 200 cells. A lot sheet, plus a PDF on every Hold and D. This is the rate the sketch below tends to pick for a grader.

Passport

Quoted

White-label report, audit fields for a battery passport, and a private instance. Priced after we see your teardown set.

Sketch a monthly bill

Compares Screen, Bench, Batch, and Floor at the rates above. Batch opens at 200 cells. Passport and House are not in this sketch.

09 — Questions

What buyers ask before a pilot.

Voltage, current, and discharge capacity, tied to a cycle index. Charge capacity and rest segments let us score resistance and relaxation. Temperature is welcome as metadata — a lot charged cold belongs on the report — and we map whatever export your cycler or BMS already writes.

10 — Pilot

Bring one lot. We’ll grade it with you.

A useful pilot is a few hundred cells from your line, your export format, and a handful of cells you have already opened or capacity-tested. We calibrate against those, then you compare the grades with the decision you would have made by hand.

  • Your chemistry, not a generic demo cell
  • A mapped CSV and a lot sheet you can audit
  • Grades marked as a screen, never as a teardown

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