Lithium battery testing with an SOH certificate

A lithium battery test measures how much capacity the battery has left compared with when it was new, its state of health (SOH), and detects BMS, insulation and cell faults. EcoBaterías tests packs from electric cars and buses, BESS, machinery, micromobility and power tools in 30 minutes to 6 hours per pack, and issues an SOH certificate with the measured values and the recommended route: repair, refurbishment, second life or recycling.

Source: EcoBaterías test protocol · 2026-09-26

What is SOH and why measure it?

State of health (SOH) is the measure of a battery’s general condition and of its ability to deliver the specified performance, compared with its initial state. That is how EU Battery Regulation 2023/1542 defines it in Article 3. In practice it is expressed as a percentage: a battery at 80% SOH delivers 80% of the capacity it had when new.

It is not the same as state of charge (SOC), which tells you how much energy is left right now, like a car’s fuel gauge. SOC says how much is in the tank; SOH, how big the tank still is.

The BMS (battery management system) is the electronics that measures and protects the cells and stores the usage history. The BMS estimates SOH with its own model, and that estimate can drift in a battery that sat idle, changed owners or had a thermal event. That is why we read the BMS and also measure. In the European Union, since August 18, 2024, the BMS of electric vehicle, light means of transport and storage batteries must give independent operators read-only access to that data.

SOH sets the value of a used electric car, the remaining life of a BESS and whether a pack is worth repairing or moving to another use. As a reference, electric car batteries are usually retired with 70% to 80% of their original capacity, and according to Recurrent, manufacturers typically replace them under warranty when they drop below 70%. More terms in the glossary.

Sources: Regulation (EU) 2023/1542, Articles 3 and 14 (opens in a new tab) · Zhang et al., arXiv, 2025 (opens in a new tab) · Recurrent, 2025 (opens in a new tab)

Who is the test for?

• Electric bus fleets and transport operators. Fleet testing to decide, pack by pack, whether to extend life, refurbish or retire. See the electric bus battery service.
• BESS owners and integrators. Failure analysis of modules under warranty and grading of modules withdrawn in expansions and decommissioning. See BESS end-of-life management.
• Dealers and buyers of used electric cars. An SOH certificate independent of the manufacturer: real usable energy and the weakest cell.
• Insurers and leasing companies. Technical appraisal of damaged batteries and a repair-or-replace decision.
• Mining and industry. Batteries from electric equipment, forklifts and backup systems (UPS).
• Micromobility and power tools. BMS and cell-group testing before deciding on a repair.

What do we measure in the test?

Each test answers a different question. None is enough on its own: the inspection rules out unsafe batteries, the BMS gives the history and the electrical tests give the real SOH.

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The letter C expresses current relative to capacity: 1C discharges the full battery in one hour and 0.2C in five. A resistance test takes seconds; a capacity test, hours.

Sources: UL Solutions, UL 1974:2023 overview (opens in a new tab) · UN R100 (opens in a new tab) · Battery Design, DCIR and ACIR (opens in a new tab) · EU battery ecodesign study, 2019 (opens in a new tab)

How we test: the five-stage protocol

1. Intake and quarantine (24 h)Registration with a unique code, weighing, visual inspection, thermography and gas detection. Any battery with mechanical damage, swelling or a thermal event is isolated in a quarantine container.
2. BMS readoutCAN or UDS connection to the battery management system: declared SOH, fault codes, cycles, cell spread, thermal and insulation history. Multi-brand tools and our own model-by-model database.
3. Fast electrical test (30–60 min)Insulation at 500 or 1,000 V DC (rejected below 100 Ω/V), open-circuit voltage per cell, internal resistance in DC and at 1 kHz, spread between cells and modules.
4. Capacity and advanced diagnostics (2–6 h)Charge and discharge with regenerative equipment that returns energy to the grid; incremental capacity analysis (ICA) to identify the degradation mode; impedance spectroscopy (EIS) to grade modules in minutes; thermography during the cycle and 24-hour self-discharge.
5. Route decision and certificateClassification into routes A, B, C or D; per-module report, SOH certificate with a 5% band, label and entry in the batch traceability record. If the battery needs repair or refurbishment, the work starts from this test.

What does the SOH certificate include?

The SOH certificate is an EcoBaterías document that summarizes the test of a battery identified by its serial number. It is not a product certification: it does not replace UN 38.3 testing or the IEC or UL standards each use requires. It lets you decide with data and back that decision in front of a buyer, an insurer or a client.

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When a batch is tested, every battery gets its own certificate and the batch gets a consolidated report with the number of packs in each route.

What happens after the test? The four routes

Source: EcoBaterías test protocol · in-house thresholds, not a standard · 2026-09-26

Repair, refurbish or second life?

The test tells you what is wrong with the battery. The work that follows depends on the result, and each job has its own page.

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A pack failure usually sits in one part, not in every cell. According to Autocraft EV Solutions, across 559 electric car pack repairs carried out in 2024, 92% of the modules were still fit and replacing 1.1 modules per pack on average was enough. That is why we test module by module: the pack average hides the module that is failing.

In the European Union, “remanufacturing” has a measured threshold: at least 90% of the original capacity and cells whose state of health differs by no more than 3% (Regulation (EU) 2023/1542, Article 3(32)). We only use that word when the output test proves it. UL 1974 treats “remanufactured”, “reconditioned” and “rebuilt” as equivalent terms.

Sources: Autocraft EV Solutions, May 6, 2025 (opens in a new tab) · Regulation (EU) 2023/1542 (opens in a new tab) · UL Solutions, UL 1974:2023 overview (opens in a new tab)

Which batteries are not tested for reuse?

A battery that is swollen, leaking, has melted areas, gets hot while switched off or is flagged as faulty by the BMS is considered damaged. It is not tested for reuse: it is isolated in quarantine, packed as a damaged battery and sent to recycling.

We also do not recover cells at 0 V or over-discharged cells for reuse. According to the EU Battery Regulation, even a minor over-discharge can grow dendrites and end in an internal short circuit.

A damaged battery can reignite hours or days later: the NTSB, the US National Transportation Safety Board, documented a case five days after the crash. If you have one, keep it at least 15 m (50 ft) from buildings and combustible materials, call the fire department (Bomberos, 132 in Chile) and, if it heats up, cool it with plenty of water. An ABC extinguisher does not stop thermal runaway.

In the laboratory we discharge below 2.5 V per cell before opening any module and work with 1,000 V insulated tools, quarantine with gas detection and a thermal camera, fire-rated cabinets, vermiculite containers and high-voltage qualified staff.

For transport, we coordinate pickup with licensed hazardous-waste carriers. Lithium-ion batteries travel as class 9, under UN 3480 (or UN 3481 when they are inside equipment): intact batteries going to recycling under special provision 377 with packing instruction P909; damaged ones under special provision 376 with P908, or P911 if they could react dangerously in transit. Details in battery and solar panel collection and transport.

Sources: ETH Zürich, damaged lithium-ion accumulator (opens in a new tab) · Regulation (EU) 2023/1542, Annex V (opens in a new tab) · NTSB, SR-20/01 (opens in a new tab) · RID 2025, special provisions 376 and 377 (opens in a new tab)

Coverage: Santiago and the regions

The laboratory is in Santiago. From there we serve all of Chile and coordinate pickup with licensed hazardous-waste carriers. For sites in other regions, we do the testing at our facilities or coordinate it on site, case by case.

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We reply within 48 business hours. Testing and pickup lead times are confirmed in the quote.

Reference standards and regulations

• Chile’s Extended Producer Responsibility law (Ley REP, Law No. 20,920): lists batteries among the priority products (Article 10) and defines valorization, which covers preparation for reuse and recycling (Article 3 No. 30). The draft battery decree (Res. Ex. 821/2026) proposes lithium-ion targets from 15% in the third year to 50% from the tenth, with at least 30% met through preparation for reuse. It is a text under consultation: the Ministry of the Environment’s deadline to propose the decree is January 29, 2027.
• Supreme Decree (DS) 148/2003: a discarded battery is handled as hazardous waste unless characterization shows otherwise. Anyone generating more than 12 kg of acutely toxic waste or more than 12 t of other hazardous waste a year needs a management plan (Article 25), storage lasts six months at most, extendable once for the same period with a technical report (Article 31) and transport requires a health permit (Article 36) and a declaration in SIDREP, Chile’s national hazardous-waste declaration and tracking system. What to require from an authorized waste manager.
• Test standards: ISO 12405-4:2018 (vehicle packs), IEC 62660-1 (traction cells), IEC 62620 and IEC 62619:2022 (industrial batteries) and IEC 61960 (internal resistance).
• Second life and remanufacturing: IEC 63330-1:2024, Repurposing of secondary batteries – Part 1: General requirements, and ANSI/CAN/UL 1974:2023, Evaluation for Repurposing or Remanufacturing Batteries (2nd edition). They are reference standards for our method, not certifications we hold.
• Transport: UN 38.3, the eight tests a new battery type must pass to be shipped, and the UN Model Regulations, which Chile’s DS 298/1994 of the Ministry of Transport adopted for classification and labeling in 2022.

Sources: Law 20,920, BCN (opens in a new tab) · Res. Ex. 821/2026, Ministry of the Environment (opens in a new tab) · DS 148/2003, BCN (opens in a new tab) · DS 298/1994, BCN (opens in a new tab) · 2026-09-26

Frequently asked questions

What is the SOH of a lithium battery?

It is the state of health: how the battery performs today compared with when it was new, expressed as a percentage of its original capacity. A battery at 80% SOH holds 80% of the energy it held when new. SOH sets the value of a used electric car, the remaining life of a BESS and whether the battery is worth repairing or moving to another use.

How do you know whether a lithium battery is still good?

With a test, not by looking at it. First we check that it is not swollen, leaking or warm while switched off. Then we read the BMS, measure insulation, voltage per cell and internal resistance, and run a charge and discharge cycle to measure the real capacity. The result is the SOH and the recommended route.

Can you trust the SOH shown by the car or the BMS?

It is a starting point, but it is the BMS’s own estimate and it can drift in a battery that sat idle, changed owners or had a thermal event. The certificate shows the SOH the BMS declares next to the SOH we measure.

How long does the test take?

The fast test (BMS readout, insulation and internal resistance) takes 30 to 60 minutes per pack. The capacity test takes 2 to 6 hours. Self-discharge is checked after 24 hours. The delivery date of the certificate is confirmed in the quote.

How much does a lithium battery test cost?

It depends on the format, the number of packs, the test level and whether it runs at our facilities or is coordinated on site. The price is confirmed in the quote. We reply within 48 business hours.

Do you test e-bike, scooter and power tool batteries?

Yes, if they are lithium-ion. We read the BMS and measure the voltage of each cell group, the internal resistance and the capacity. We do not work on nickel-metal hydride (NiMH) or lead-acid batteries: their recycling is quoted separately.

What happens if the battery cannot be fixed?

It goes to recycling. We manage its valorization with authorized receiving facilities, in Chile or in OECD countries where applicable; the authorized receiving facility closes the SIDREP declaration and issues the valorization certificate.

Does the SOH certificate count for Chile’s EPR law?

The SOH certificate is a technical test report. What is reported under Law 20,920 is how the waste was managed: when a battery goes to recycling or to preparation for reuse, we issue the technical testing report for each batch; if it goes to recycling, the valorization certificate is issued by the authorized receiving facility.

Sources

Updated October 9, 2026 · Reviewed by the EcoBaterías technical team