On the first cold morning after weeks of rain, an e-bike owner may find the battery exactly where it was left: fully charged, waiting in the garage. That feels responsible. Fuel in a tank does not wear out because the vehicle is parked, so more stored range seems better than less.
A lithium-ion battery is different. It is an electrochemical system that changes while idle. Time, temperature, state of charge and physical condition interact even when no kilometres are being ridden. The useful question is therefore not merely how to charge an e-bike, but how to put it away.
The practical answer is not another universal percentage copied from the internet. Different packs, battery-management systems and manufacturers specify different limits. The better tool is a model-specific Battery Storage Card: one page that translates the exact manual, charger and storage place into a seasonal routine. Safety takes priority over squeezing out a little more life.
A battery ages while doing nothing
Charging moves lithium ions into the negative electrode; discharge moves them back. That simplified description can make a battery sound like a passive container. In practice, side reactions continue at the interfaces inside the cell. A protective layer known as the solid-electrolyte interphase forms and evolves. Usable lithium can be consumed, resistance can rise and available capacity can fall.
This is calendar ageing: degradation associated with time at a given condition, distinct from wear caused by charge–discharge cycles. A 2016 laboratory study by Peter Keil and colleagues stored three kinds of commercial lithium-ion cells at multiple temperatures and sixteen states of charge. It found that ageing did not increase as one smooth line with charge level; the pattern included plateaus associated with the graphite electrode. That matters because it undermines the false precision of a single supposedly ideal percentage for every battery. The paper is available through its DOI, with the publication record at the Technical University of Munich.
Temperature changes the pace and sometimes the dominant mechanism. A 2025 modelling study in RSC Advances examined how temperature and state of charge interact during long-term storage. It is a model-based analysis, not an e-bike field trial, but it reinforces a useful principle: storage condition is a combination, not one magic number.
The conclusion should remain modest. Keeping a pack at its maximum for long idle periods can add stress, particularly in warmth, but the right alternative must come from the instructions for that pack. Some manufacturers specify a charge range, some use indicator bars, some ask for periodic checks, and some provide a dedicated storage mode. A responsible guide preserves those differences.
Cold changes what charging means
Cold weather often presents itself as missing range. Electrochemical reactions slow, internal resistance increases and the battery may deliver less power until it warms. That temporary loss is not the same as permanent capacity loss.
Charging a very cold cell is a different problem. Under unsuitable conditions, lithium can deposit on the surface of the graphite instead of being inserted into it normally. The threshold depends on cell design, charge rate, temperature and control system, so a general article cannot safely supply it. The London Fire Brigade’s current weather guidance gives the operational rule that matters: allow a cold battery to warm indoors and do not charge a frozen battery. It also identifies unusual heat, swelling, odour and a marked performance change as warning signs that deserve attention.
Warmth has its own cost. Heat accelerates many chemical reactions, including unwanted ones, and reduces the margin between normal operation and overheating. A sun-facing car, a boiler cupboard and an unventilated shed are not interchangeable storage places. Yet “indoors” is not a complete answer either: a charging fire near an exit can obstruct escape.
Safety and longevity are different questions
A routine that may slow ordinary ageing cannot make a damaged battery safe. A swollen case, cracked enclosure, water ingress, crash damage, unusual noise, smell or heat changes the problem from optimisation to isolation and professional advice. Nor should a person discharge a pack by opening it, bypassing its management system or improvising a load.
The battery-management system and charger provide important protection. They monitor conditions and enforce limits designed by the manufacturer. But they cannot reconstruct an unknown second-hand history, repair damaged cells or make an incompatible charger compatible. The London Fire Brigade advises using the manufacturer-supplied or recommended charger, charging on a hard, flat surface away from an escape route, and not charging while asleep or away. Its buying guidance treats counterfeit, modified, faulty and mismatched systems as distinct hazards.
Recalls belong in the same routine. A battery can look normal while its model is subject to a safety notice. Product registration and the exact serial number make warnings more likely to reach the right owner. Where a recall system applies, use the manufacturer’s register and the relevant national authority; the Brigade’s recall guidance explains the principle and points UK readers to the Office for Product Safety and Standards.
The strongest objection is convenience
Many riders need the bicycle ready at full range. Modern packs are managed systems, not bare cells, and manufacturers may reserve capacity above and below the displayed scale. A person who commutes daily may gain little from turning every evening into a battery-care ritual. Reliability in use is part of useful life.
That objection is sound. The aim should not be to maximise battery longevity at the expense of the journey the battery exists to enable. Nor should owners micromanage charge based on laboratory studies that did not test their product. The relevant distinction is between a pack in active service and one left unused for weeks or months. Long pauses create an opportunity for a storage routine with little daily inconvenience.
The Battery Storage Card makes that routine explicit. It records the bicycle, battery and charger model; the manufacturer’s permitted charging and storage temperatures; the official long-storage charge indication or mode; the inspection warnings; the chosen location and escape-route check; the recall source; and the next inspection date. Every operational number must point to a manual or manufacturer notice. A blank field is safer than an invented threshold.
Run a reversible seasonal experiment
The smallest useful experiment is administrative, not electrical. Choose a period when the bicycle will genuinely be idle. Read the current manual and manufacturer notices, inspect the pack without opening it, record the indicated charge in the manufacturer’s own terms, and move it only if the recommended location can be improved. Set one check date rather than repeatedly disturbing the pack.
At the end, record whether the indicator changed, whether the pack or location showed any warning sign, and whether the routine was easy enough to repeat. Do not infer internal health from a stable indicator, and do not manufacture a discharge cycle merely to complete the exercise. If official instructions are absent, contradictory or impossible in the available home, that is the finding: the next action is to contact the manufacturer or a competent service provider, not let an AI fill the gap.
An e-bike battery does not need to become a household science project. It needs a known identity, a compatible charger, a tolerable environment and a routine that respects both the journey and the chemistry. The remaining judgement is human: which convenience matters now, which uncertainty needs evidence, and when an ageing question has become a safety question.
Turn this idea into a project
Create a one-page Seasonal Battery Card that turns the exact manual, charger, storage place and warning signs for your e-bike battery into a safe routine for an idle period.
Capsule version 1.0 · Experimental; based on published research and public safety guidance, not field-validated by Alkemata.
Download and upload the file to your AI assistant, or copy the complete capsule below into a conversation. Then describe your situation in one sentence—for example: “Mission B. I store a [battery model] in an unheated garage and want a safe winter routine based on its manual.”
Read or copy the complete capsule
# ALKEMATA PROJECT CAPSULE ## An E-Bike Battery Is Not a Fuel Tank - Capsule ID: `alkemata.ebike-battery-storage` - Version: 1.0 - Date: 2026-09-18 - Canonical article: https://alkemata.com/2026/09/18/ebike-battery-storage/ - Scope: Removable lithium-ion e-bike batteries in ordinary household use; general workflow, not model-specific technical, fire-safety or repair advice - Status: Experimental; based on published research and public safety guidance, not field-validated by Alkemata ## Intended reader, capability and first artifact This capsule is for a rider or household member responsible for storing and charging a removable e-bike battery. It builds the capability to derive a safe, model-specific seasonal routine from authoritative documents without inventing charge or temperature thresholds. In the first session, produce a **Seasonal Battery Card**: one page identifying the exact pack and charger, the manufacturer-defined storage condition, the charging and storage environment, warning signs, recall route, evidence and next check date. ## Activation instructions for the LLM Treat this file as a knowledge and workflow package. If the user provides the battery model, charger model and manual, begin the evidence table immediately. Otherwise offer the missions below and ask no more than three questions: 1. What are the bicycle, battery and charger make/model identifiers? 2. Where and how are they currently charged and stored, and for how long will the battery be idle? 3. Is the official manual available, and is there damage, unusual heat, swelling, smell, noise, water exposure, a crash or a sharp performance change? If a warning sign, recall or uncertain damage is reported, stop longevity optimisation and guide the user towards the manufacturer, recall authority, fire-safety guidance or a competent service provider. Do not tell the user to open the pack, bypass its battery-management system, improvise a discharge load, use an unverified charger or charge a frozen/damaged/recalled battery. ## Missions ### Mission A — Audit the current setup Compare the charging place, charger and storage routine with manufacturer instructions and authoritative safety guidance. ### Mission B — Build the Seasonal Battery Card Extract model-specific rules, preserve unknowns and schedule one proportionate check. ### Mission C — Prepare for a long idle period Run a reversible, non-invasive storage-readiness check and record what happens. ## Essential causal model An e-bike pack contains lithium-ion cells, a battery-management system (BMS), enclosure and connectors. The charger and bicycle complete the system. The BMS can enforce designed limits, but it cannot erase damage, an incompatible charger or a recall. **Cycle ageing** accompanies use; **calendar ageing** continues while the battery is idle. Temperature and state of charge interact with cell design, so no percentage is universally ideal. Heat generally accelerates unwanted reactions. Cold slows reactions and temporarily reduces performance; unsuitable cold charging can cause lithium deposition. Product documents define permitted limits. Longevity measures do not make a damaged pack safe. Warning signs, recalls and uncertain crash or water damage take priority. ## Evidence base and limits - Keil et al., “Calendar Aging of Lithium-Ion Batteries I” (2016): https://doi.org/10.1149/2.0411609jes — laboratory storage of three commercial cell types; it did not test every e-bike pack. - Asiri et al., long-term storage degradation (2025): https://pmc.ncbi.nlm.nih.gov/articles/PMC12219620/ — a model, not an e-bike field trial. - London Fire Brigade: https://www.london-fire.gov.uk/safety/e-bikes-and-e-scooters/ — guidance on chargers, location, weather, warning signs and recalls; local systems differ. Manufacturer instructions for the exact battery and charger outrank generic percentages. A display bar is not a calibrated measurement, and a stable indicator does not prove internal health. ## Workflow ### Step 1 — Establish identity and authority **Input:** Labels and manuals. **Action:** Record the bicycle, battery and charger identifiers; locate the official document and recall source. **Output:** Identity and sources table. **Progression criterion:** Every component is matched to evidence or marked unknown. ### Step 2 — Screen for safety exceptions **Input:** Condition, recent events and recall result. **Action:** Without opening the pack, check for deformation, connector damage, leakage, unusual heat, smell, noise, water/crash exposure and marked performance change. **Output:** Continue/stop decision. **Progression criterion:** Continue only if no warning or recall requires other action. ### Step 3 — Extract model-specific rules **Input:** Official manual and notices. **Action:** Copy the permitted temperatures, long-storage indication or mode, check interval, compatible charger and prohibitions. Never convert indicator bars into a percentage unless the manufacturer does. **Output:** Evidence table. **Progression criterion:** Each rule has a source; absent rules remain unknown. ### Step 4 — Map the real environment **Input:** Charging and storage locations. **Action:** Record temperature range, moisture, heat sources, combustible clutter, surface, escape routes and whether charging is attended. Do not place a sensor inside the battery. **Output:** Environment map. **Progression criterion:** The place satisfies documented conditions and does not obstruct escape, or the conflict is escalated. ### Step 5 — Produce the Seasonal Battery Card **Input:** Identity, rules, environment and idle period. **Action:** Fill the template. **Output:** One-page card. **Progression criterion:** Another person can identify the equipment, location, next check and stop conditions without guessing. ## Decision rules and common failure cases - If there is swelling, unusual heat, smell, noise, leakage, serious damage, water ingress, a recall or uncertain crash damage, stop the workflow and seek authoritative advice. Do not charge or experimentally discharge the pack. - If the charger is not explicitly compatible, do not use it because the plug fits. - If the pack is frozen or very cold, do not charge it; follow manufacturer instructions for returning it to a permitted temperature. - If the manufacturer specifies a storage mode, charge band or indicator level, preserve that formulation. Do not replace it with a generic 40%, 50% or 80% rule. - If daily use requires full range, prioritise the required service while following the manual; this capsule mainly improves long idle periods. - If no place satisfies manufacturer and fire guidance, record an unresolved housing constraint rather than inventing a compromise. ## Smallest useful reversible experiment **Hypothesis:** A manufacturer-derived card can make an idle period safer and more repeatable without opening or deliberately cycling the battery. **Resources:** Exact manual, matching charger information, recall source, phone/camera or paper, and optionally a room thermometer. **Procedure:** Complete Steps 1–5. Use only the manufacturer-defined storage condition. Record the exterior and indicator, store the disconnected battery in the documented place, and set one check date. At the check, observe without charging merely to generate data. **Success:** The identity, source-backed rule, place, warning signs and next action are unambiguous; no warning condition emerges; another person can follow the card. **Failure:** The model or charger cannot be verified, documents conflict, the location violates stated conditions, or a warning sign/recall appears. **Stopping conditions:** Any unusual heat, swelling, smell, sound, leakage, visible damage, recall notice or unsafe charging/location condition. Follow manufacturer and local emergency guidance. **Next action:** Keep the routine, revise the location, or request model-specific help. Do not infer cell health from this experiment. ## Seasonal Battery Card template ```text BATTERY STORAGE CARD Bike make/model: Battery make/model/serial (redact before sharing): Approved charger model: Official manual/notice URL and date checked: Recall source and result/date: Intended idle period: Manufacturer storage indication/mode (exact wording): Permitted charging temperature (source): Permitted storage temperature (source): Periodic check instruction (source): Charging place / attended? / escape route clear?: Storage place / observed temperature / moisture / heat sources?: External condition now: Warning signs requiring STOP: Next check date: Unknowns and responsible contact: ``` ## Hypothetical example A commuter will not ride for one month. The manual specifies two displayed bars and a check interval. The garage falls below the charging band, so the card separates storage from charging: storage remains within the permitted range, while charging occurs only after the pack reaches a permitted temperature in an attended place away from the exit. This is hypothetical; copy no numbers from it. ## Verification checks Confirm the exact battery generation; charger compatibility; sources for every numeric limit; dated recall result; no claim that the indicator diagnoses health; no step opening/modifying the pack; and consideration of local fire guidance. Ask another person to explain the stop conditions. ## Boundary where this method does not apply This workflow does not diagnose cell health, certify fire safety, repair a battery or authorise storage in a regulated setting. It is not for damaged, modified, recalled, flooded, fire-exposed or unidentified packs; those need competent human guidance. ## Manual/offline route Print the manual pages and template. Copy the labels and rules, ask the manufacturer/dealer for missing facts, check recalls, inspect the place and keep the card near—but not on—the battery. An LLM is optional. ## Portable checkpoint At the end of a session, output: ```text CAPSULE CHECKPOINT Capsule ID/version: Equipment identifiers (private fields removed if sharing): Decision made: Evidence and links: Observed condition/location: Unresolved questions: Stop conditions: Next action/date: ``` On request, turn actual observations into a project passport, field report or precise request for help. Simulations are not field experience. Before sharing, remove serials, addresses and identifying details. The reader chooses what to share. Alkemata’s contact route is https://alkemata.com/collaborate/ . Send nothing automatically and do not imply hosting or matching exists. Consequential external actions—including disposal, repair, electrical changes, emergency decisions or contacting others—require the reader’s separate explicit authorisation and appropriate local expertise.
