Second life for lithium batteries

Thresholds and times: Ecobaterías testing protocol, published in lithium battery testing and repair · September 18, 2026.

What second life is, and what it is not

A lithium battery stops serving its original application long before it runs out of energy. An electric-vehicle pack is retired when it no longer delivers the promised range; a storage rack is retired when it no longer meets its power contract. In both cases usable energy remains, but under duty conditions that are harsher than those of a calm stationary application.

Second life is not repair. Repair means returning the pack to its original use by replacing the weak module, the BMS or a contactor: that applies while the state of health stays above 80%, and it is the work described in our lithium battery testing and repair protocol. Second life is not recycling either: recycling destroys the cell to recover its minerals, and that is what we do at the hydrometallurgical plant once no usable energy is left.

Second life sits in between and has rules of its own: the module changes owner, application and duty cycle, so it needs a new measurement, a new match and a new label. A module that arrives untested and is installed “as received” is not second life: it is an electrical and thermal risk moved to another site.

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State-of-health thresholds: Ecobaterías testing protocol · September 18, 2026.

When a module qualifies: the SOH thresholds

State of health (SOH) is the module’s current usable energy expressed as a percentage of its energy when new. We do not take the value reported by the BMS: we measure it with an instrumented charge and discharge cycle and cross-check it against internal resistance and 24-hour self-discharge.

Our second-life threshold is the 65–80% band, and it is our own threshold, not a standard. Above 80% the module still performs in its original application and is better repaired than downgraded. Below 65% the remaining energy stops paying for dismantling, testing, matching, structure, electronics and warranty: at that point the value is in the minerals, not in the electrons.

On top of the capacity measurement we apply three filters that reject modules regardless of their SOH: visible mechanical damage, a history of thermal event or swelling, and excessive cell-to-cell spread inside the same module. A module at 74% SOH with one lagging cell does not enter a second-life block; it goes to recycling.

How modules are matched

The life of a second-life block is set by its weakest module. Matching is therefore the step that determines the outcome, and it is done with measured data, not with serial numbers or vehicle model years.

1. Grouping by chemistry and formatLFP with LFP, NMC with NMC, same cell format and same module architecture. Chemistries are never mixed inside a block.
2. Capacity bandModules whose measured capacity falls inside a narrow band are grouped together; outliers are reassigned to another block or sent to recycling.
3. Internal resistanceDC and 1 kHz resistance are compared; a high-resistance module runs hotter and drags the rest down even when its capacity looks correct.
4. Self-dischargeVoltage drop at rest over 24 hours is measured. A module with abnormal self-discharge is rejected: it is the least visible defect and the one that causes the most trouble later.
5. Cycle and thermal historyCycle count, maximum recorded temperature and insulation events are read from the BMS and recorded in the block file.
6. Labeling and traceability fileEvery module keeps a unique code and every block carries its measured usable energy, its test date and its retest plan.

Reference standards: IEC 63330-1 and UL 1974

We work with two international references for preparing batteries for a use other than the original one:

• IEC 63330-1:2024, general requirements for the reuse of secondary batteries: it defines what information must accompany a reused battery and which tests support its fitness for service.
• ANSI/CAN/UL 1974, evaluation for repurposing batteries: it describes the grading, testing and documentation process for modules and packs destined for a second application.

We cite them as reference standards for our method. They are not an Ecobaterías certification and we do not present them as one: what we deliver is the test report with measured data, so that the design engineer or the auditor can verify it independently.

A second-life battery without a per-module test report is not a second-life battery: it is a used battery.

Grid connection and electrical declaration

A storage system connected to the grid or to an internal installation is, first of all, an electrical installation. Declaring that installation before the Superintendencia de Electricidad y Combustibles (SEC, Chile’s electricity and fuels regulator) and meeting the project requirements are the responsibility of the owner and its authorized installer; Ecobaterías does not take part in that procedure.

What we do provide is the technical information the designer needs: measured usable energy per block, maximum voltage and current, internal resistance, temperature limits, cycle history and recommended operating conditions. Without that data no engineer can size protections or calculate what the system contributes.

For self-consumption or off-grid backup projects the requirements differ, but the logic is the same: the block arrives with its file and the owner integrates and declares.

Realistic applications in Chile

Second life pays off where the required power is moderate, the cycles are predictable and space is not critical. In Chile, the cases that reach us most often are:

• Backup for remote sites and camps, where backup today is a diesel generator running a few hours a day.
• Solar self-consumption in industry and retail, shifting midday energy into the late-afternoon peak.
• Backup for low-power critical systems: telecommunications, control, emergency lighting, pumping.
• Fleet depots and workshops, to smooth the charging peak of electric vehicles without upgrading the grid connection.
• Community and rural electrification projects, where the cost of new storage is the main barrier.

We do not recommend second life for fast-response grid services or for applications that demand sustained high power: there degradation accelerates and the cost advantage disappears.

Service life, warranty and follow-up

We do not publish a service life in years, because it would depend on a duty cycle we do not control. We publish what we actually measure: usable energy at delivery, spread inside the block and the internal-resistance curve. The warranty is defined on that basis, by available energy and by period, together with a retest plan.

Retesting is part of the service, not an extra: a second-life block is measured again to confirm the match still holds. When the block falls below the agreed threshold it is collected and enters the recycling route with a valorization certificate, closing the loop without the owner having to find a new waste manager.

Whatever falls below the agreed threshold is processed at our hydrometallurgical plant in Santiago, authorized for the hydrometallurgical process by the Seremi de Salud (Chile’s regional health authority) of the Metropolitan Region (see compliance and permits). Among other products, that plant yields the recycled cobalt sulfate successfully tested at the Codelco El Teniente hydrometallurgy plant (trials from November 2023; results published in July 2024), with 22% lower cost and 40% lower consumption than imported sulfate.

Source: El Rancagüino, July 15, 2024. The press report does not name the supplier; the documentation identifying Ecobaterías is available under a confidentiality agreement.

How it counts toward Chile’s EPR law

Chile’s Extended Producer Responsibility law (Ley REP, Law No. 20,920) requires producers to collect and recover the priority products they place on the market. Batteries still have no targets decree of their own: the Ministry of the Environment published a draft under Res. Ex. 821/2026 and the deadline to propose the decree is 2027-01-29.

That draft matters for second life for one concrete reason: it proposes that at least 30% of the lithium-ion target be met through preparation for reuse rather than recycling. If the text holds, grading and reusing modules stops being a voluntary alternative and becomes part of compliance. Until then we write it for what it is: a proposal under consultation.

Source: Ministry of the Environment, draft supreme decree on batteries (Res. Ex. 821/2026) · September 18, 2026. Law in force: Law No. 20,920, Library of the National Congress of Chile.

Status of each service line

Status reviewed on September 18, 2026. The pilot program works with limited batches and case-by-case lead times: we do not commit industrial capacity on lines that are not yet in full operation.

The four routes of a battery

Second life is route C in a scheme we apply identically across our service pages, so that the same module always gets the same decision:

How to engage us

1. InventoryYou tell us chemistry, format, number of modules, commissioning year and location.
2. Sample testingWe measure a representative sample of the batch and estimate how many modules will fall into each route.
3. ProposalYou receive the result by route, with the destination of each group and the certificate that applies to it.
4. Collection and full testingWe arrange authorized transport and test the complete batch in the laboratory.
5. DeliveryMatched blocks with their file, and a valorization certificate for whatever goes to recycling.

If the batch includes complete storage racks or containers, the starting point changes and it is better to begin with end-of-life BESS systems, where testing happens on site before anything is moved.

Frequently asked questions

Does every used battery qualify for second life?

No. Only modules with no mechanical damage, no thermal event and a measured state of health between 65% and 80% qualify. Above 80% it is better to repair them and return them to their original use; below 65% the remaining usable energy no longer justifies the integration cost and the module goes to recycling at our hydrometallurgical plant in Santiago.

How long does a second-life battery last?

It depends on the starting point and on the duty cycle. That is why we hand over the usable energy measured at delivery, the internal-resistance curve and a retest plan, instead of a promise expressed in years. The warranty is defined by available energy and by period, not by time alone.

Can modules from different vehicles or manufacturers be mixed?

Not inside the same block. We match modules by chemistry, format, capacity, internal resistance and cycle count, and we keep blocks of different origin separate. A system can combine several blocks, each one homogeneous and with its own management.

Does second life count toward Chile’s EPR law?

The draft battery decree from the Ministry of the Environment proposes that at least 30% of the lithium-ion target be met through preparation for reuse. It is a text under public consultation, not a rule in force: the ministry’s deadline to propose the decree is 2027-01-29.

Who is liable if the system fails?

Ecobaterías is liable for the modules it delivers, for their testing and for their usable-energy label. The electrical installation, its declaration and its operation are the responsibility of the project owner or its installer.

What happens to the modules that do not qualify?

They are discharged, dismantled and processed at our hydrometallurgical plant in Santiago, which holds a health permit from the Seremi de Salud (Chile’s regional health authority) of the Metropolitan Region for the hydrometallurgical process. We recover cobalt and nickel sulfate, copper, aluminum and graphite, and we issue a valorization certificate.