Introduction: The Unique Challenges of Underwater Robotics

Pool cleaning robots represent one of the fastest-growing segments in marine and domestic service robotics. Unlike terrestrial vacuums, underwater cleaning robots operate in highly demanding environments involving direct water submersion, high static pressure, ambient chemical exposure (chlorine and salt water), and dynamic impeller load fluctuations.

At the heart of every cordless pool cleaner is its lithium battery system. The pack must not only power dual traction motors and high-flow filtration pumps, but also maintain precise weight-to-volume ratios for neutral buoyancy.

Choosing an improper battery design leads to short operational runtimes, seal failures, premature capacity fade in cold water, or false over-current shutdowns. This guide outlines how OEM/ODM engineering teams can specify the ultimate power system for pool cleaning robots.

Chemistry Comparison: NMC vs. LiFePO4 for Underwater Units

Selecting the optimal lithium-ion chemistry depends heavily on the robot’s form factor, weight constraints, and target deployment environment.

Essential Engineering Requirements for Pool Robot Batteries

IP68 Submersible Sealing & Thermal Dissipation

Standard IP67 ingress protection is insufficient for continuous submersion. Pool robot batteries require IP68 sealing structures (rated for 2 – 5 meters submersion).

• Double-O-Ring & Structural Potting: Utilizing custom aluminum or reinforced polycarbonate housings sealed with two-stage silicone potting to resist chlorine and salt corrosion.
• Underwater Thermal Management: Water is an excellent heat sink, but static air trapped inside sealed battery compartments acts as an insulator. Implementing high-conductive Thermal Interface Materials (TIM) transfers heat efficiently from cells/BMS to the outer shell.

High-Rate Anti-Overcurrent Protection Algorithm

Pool cleaner impellers frequently encounter sudden torque spikes caused by leaf blockages, suction pressure changes on wall-climbing modes, or debris jam.

• The Problem: Standard BMS hardware protection mistaking short motor torque surges for short circuits, causing the robot to stop unexpectedly in the middle of the pool.
• The Solution: Our proprietary Smart BMS Anti-Overcurrent Algorithm uses dynamic current-time integrals  to differentiate between motor stall surges 3C-5C for 2-5 seconds and real electrical short circuits, eliminating false trips while ensuring absolute safety.

Low-Temperature Self-Heating Technology

Early morning water temperatures or winter storage environments, severely restrict lithium-ion charge acceptance and reduce discharge capacity. Integrated PTC low-temperature heating elements inside the pack automatically warm the cells before charging or under heavy load, extending cell lifespan and restoring full runtime.

Precise SOC Estimation & Auto-Docking Reliability

To prevent a pool robot from dying at the deep end, precise State of Charge (SOC) tracking is vital. Combining Coulomb counting with dynamic impedance compensation, the Smart BMS maintains an SOC accuracy within 2%, triggering an auto-surface or auto-docking sequence before energy runs out.

Smart BMS Communication Interfaces

Modern smart pool robots require real-time system monitoring. The Smart BMS integrates CANbus 2.0B, RS485, or UART protocols to report cell voltages, state of health (SOH), temperature profiles, and fault logs back to the robot’s main controller or mobile app.

End-to-End MES Traceability & Quality Control

For OEM/ODM brand owners, product reliability and safety are paramount. Every battery pack we manufacture is integrated into our Manufacturing Execution System (MES), providing complete digital traceability:

1. Cell Matching: 100% automated grading and sorting by voltage, capacity, and internal resistance.
2. Process Tracking: Laser welding parameters, screw torque logs, and thermal compound application are recorded per unique battery serial number.
3. End-of-Line (EOL) Validation: Comprehensive automated testing including high-potential insulation, 100% charge-discharge aging, and pressurized air/water leak detection.

Global Certifications & European Battery Passport Readiness

Exporting pool robots to global markets demands full regulatory compliance:

• Transport & Air Safety: UN38.3, MSDS, and Drop-Test Certification.
• International Electrical Safety: IEC 62133-2, UL 2271 (Light Electric Vehicle/Robotics), UL 2054, CE, FCC.
• Environmental & EU Directives: Fully compliant with RoHS, REACH, and structured data tracking ready for the upcoming EU Digital Battery Passport under new EU battery regulations.

Frequently Asked Questions

Q1: How do you achieve IP68 waterproofing while maintaining heat dissipation in a pool battery?

A: We combine dual-seal O-rings with full silicone/epoxy potting inside a corrosion-resistant housing. Internal heat from the cells and Smart BMS MOSFETs is directed to the outer aluminum casing using high-thermal-conductivity interface pads, utilizing the surrounding pool water for passive cooling.

Q2: How does your Smart BMS handle motor stall currents from pool debris?

A: Our custom BMS firmware features an advanced anti-overcurrent algorithm. Instead of shutting down instantly during a sudden current spike, the system evaluates the duration and waveform of the surge. It allows temporary high-rate discharge (3C-5C for up to 5 seconds) to clear the block, while retaining instantaneous hardware protection for actual short circuits.

Q3: Can your battery packs be integrated into our factory MES for quality tracking?

A: Yes. Each battery pack carries a unique QR/barcode linked to our cloud-based MES database.

Partner with an Experienced OEM/ODM Battery Manufacturer

Engineering a custom underwater battery pack requires a balance of electrochemical selection, mechanical sealing, dynamic BMS programming, and industrial compliance.

Ready to power your next-generation pool cleaning robot?

Contact our engineering team today to receive a complete technical proposal and quotation within 48 hours.

The European Commission has officially issued the Guidance Document: Digital Batteries Passport – data points by category (Ver. 1.0), marking a critical milestone for the EU Battery Regulation ((EU) 2023/1542). Outline 71 meticulous data points, this guidance establishes the technical blueprint for the mandatory Digital Battery Passport (DPP) effective February 18, 2027. As a specialized OEM/ODM manufacturer of custom Light Means of Transport (LMT) battery packs (e.g., e-scooters, e-bikes), Hypercell has successfully upgraded its factory MES (Manufacturing Execution System) and ERP infrastructure. Combined with its proprietary smart BMS dynamic data architecture, Hypercell provides global B2B clients with fully compliant custom battery solutions tailored for seamless market entry into Europe.

1. Key Takeaways of the EU Guidance for LMT Batteries

Under the latest European guidance, LMT batteries installed in e-scooters and e-bikes are prioritized for mandatory DPP implementation. Unlike standard industrial batteries, LMT batteries demand both “static supply chain traceability” and “dynamic operational monitoring”:

2. Case Study: Compliance in Action for the INR21700-13S10P Custom LMT Pack

Highlighting Hypercell’s engineering excellence, the high-demand INR21700-13S10P custom battery pack (48V / 50Ah class), designed for European premium e-bikes and e-scooters, exemplifies complete DPP readiness across its lifecycle:

Factory-Level Digital ID (UID Integration):Including Hypercell’s manufacturing site location (GPS), battery weight, nominal energy (kWh), and official CE / UN38.3 certification records.
Proprietary BMS Telemetry for Dynamic Health:Equipped with Hypercell’s in-house developed BMS, the pack measures internal resistance (mΩ), cumulative throughput energy, and cycle counts during operation. Via CANbus/UART or integrated IoT modules, the BMS transmits real-time State of Health (SOH) updates to the DPP database—solving the primary compliance challenge for LMT brands.
Green Manufacturing & LCA Footprint Readiness:Leveraging ERP energy-monitoring modules, Hypercell provides a verified Cradle-to-Gate carbon footprint ledger compliant with ISO 14064 standards for every INR21700-13S10P unit produced.

3. Turnkey Compliance Roadmap for Global B2B Partners

To safeguard global OEM/ODM clients ahead of the 2027 enforcement deadline, Hypercell offers end-to-end regulatory support:

1. ODM Custom Engineering: Tailoring voltage (36V / 48V / 52V), form factor, and smart BMS communication interfaces according to client specifications.
2. Digital Production & Serialization: Binding component traceability to the final pack UID inside our MES system to ensure unalterable data authenticity.
3. Data Interface & Cloud Integration: Assisting European brand owners in hosting battery data onto EU-approved DPP systems (such as Catena-X) for frictionless customs clearance.

Partner with Hypercell for EU Market Access

Hypercell is dedicated to driving sustainable mobility through engineering innovation and digital transparency.

We empower global e-mobility brands to overcome regulatory barriers and thrive in the European market.

Whether holding inventory in a warehouse or shipping products internationally, ambient storage conditions and State-of-Charge (SoC) are the defining factors in battery safety, performance, and longevity. For most battery chemistries, cool and dry conditions around 15°C (59°F) are recommended for long-term storage. Depending on battery chemistry and product specifications, allowable storage temperatures may range from –40°C to 50°C for short-term exposure.
Based on industry testing standards, this guide provides a clear breakdown of storage protocols for Lithium-ion, Sealed Lead Acid (SLA), Nickel-based, and Alkaline batteries, as well as the latest IATA regulations regarding air transportation.

1. Lithium-ion (Li-ion): Ideal 40% SoC Storage and Sleep Mode Prevention

Lithium-ion chemistries are sensitive to voltage levels and ambient heat during long-term storage. Storing a Li-ion pack at 100% SoC in warm environments drastically accelerates permanent, unrecoverable capacity loss.

• Optimal Storage State: approximately 40% SoC (typically 3.7–3.85V per cell depending on chemistry). This level minimizes chemical stress while allowing sufficient leeway for self-discharge.
• Over-discharge & Copper Shunts: Most Li-ion batteries should not be stored below their manufacturer-specified discharge cutoff voltage, which is typically between 2.5V and 3.0V per cell. Many protection circuits may enter sleep mode when cell voltage approaches approximately 2.5VIf left below 2.0V/cell for an extended period, copper current collectors begin to dissolve, forming copper shunts that cause internal micro-shorts and severe thermal runaway risks upon recharge.

Engineering Tip: Before taking open-circuit voltage (OCV) readings, allow the battery to rest for 90 minutes to eliminate voltage bounce-back (the “rubber band effect”).

2. Air Transport Compliance (AirShip): The 30% SoC Mandate

In compliance with IATA and FAA regulations, all standalone or removable Lithium-ion battery packs transported via air cargo must be shipped at a maximum of 30% State-of-Charge.

• Safety Rationale: Keeping batteries at or below 30% SoC significantly reduces volatility and energy release potential in the rare event of a thermal anomaly during transit.
• Automated Shipping Prep: Modern industrial chargers and BMS platforms feature dedicated “AirShip” programs. Using Coulomb counting or advanced Kalman filters, these systems automatically charge or discharge packs to the precise 30% SoC threshold prior to packaging.

3. Sealed Lead Acid (SLA): Preventing Sulfation and The 70% SoC Recharging Rule

Sealed lead acid batteries can typically be stored for 6–24 months depending on storage conditions, provided they are monitored to prevent sulfation—an oxidation layer that builds up on negative plates due to low charge states.

• Recharge Threshold: Apply a topping charge as soon as the battery drops to approximately 70% (2.07V/cell OCV or 12.42V for a 12V pack; specific gravity ~1.218).
• Sulfation Reactivation: For small SLA cells (such as Hawker Cyclone) affected by prolonged storage, recovery is often possible by applying elevated voltage with a strictly limited low current to dissolve sulfate crystals back into active material.

4. Nickel-Based and Alkaline Batteries: Storage & Capacity Priming

• Nickel-Based (NiMH / NiCd): Store at approximately 30–50% SoC or in a fully discharged state (for single cells). Nickel-metal-hydride can be stored for 3–5 years. Capacity drop during storage is largely reversible through 1–3 priming (charge/discharge) cycles.
• Primary Alkaline Batteries: Alkaline batteries store well at cool room temperatures and ~50% relative humidity for up to 10 years. Avoid prolonged freezing conditions unless specified by the manufacturer, as extremely low temperatures may affect seals and performance.

Key Takeaways for Warehouse and Fleet Management Environment

Control: Keep storage areas cool (ideally 15°C / 59°F) and dry (~50% relative humidity). Avoid direct sunlight.
Li-ion Protocols: Store at 40% SoC for long-term inventory; in accordance with IATA Dangerous Goods Regulations, standalone lithium-ion batteries classified as UN3480 transported by air must not exceed 30% SoC.
Routine Maintenance: Check lead-acid voltages every 3–6 months and top-charge immediately if the pack drops below 12.42V.

When developing a high-performance device, a custom battery is far more than a power source. It directly influences system performance, safety, product lifespan, and regulatory compliance. For medical devices, industrial equipment, robotics, and IoT products, standard batteries often cannot meet demanding application requirements

At Hypercell, our custom battery solutions follow a highly disciplined, end-to-end engineering methodology. Backed by over 19 years of experience, here is our streamlined 6-step blueprint for bringing your power solution from initial concept to certified production.

Step 1: Discovery & Requirements Gathering

Every successful battery project begins with absolute clarity. Our engineering team collaborates directly with you to establish a comprehensive technical envelope:

Electrical Profiles:Nominal voltage, peak current draw, dynamic power profiles, charging requirements, and targeted capacity.
Mechanical Constraints:Exact 3D dimensions, enclosure materials, and connector interfaces.
Environmental Tolerances: Operating temperatures, vibration levels, humidity conditions, and ingress protection (IP ratings).

Step 2: Integrated Cells, Smart BMS & Mechanical Design

Once specifications are locked, we initiate the core design phase. We optimize the battery cell, Battery Management System (BMS), and mechanical enclosure as an integrated system.

1. Cell & Chemistry Selection: We source from Tier-1 manufacturers, balancing energy density, cost, and lifecycle. Options include high-capacity Li-ion ,LiFePO4 or NiMH.
2. Smart BMS Engineering: Protection functions include overcharge, over-discharge, overcurrent, short circuit, and temperature monitoring.We design custom PCBAs with precise State-of-Charge (SOC) tracking and integrated communication protocols (I2C, SMBus, CAN bus, or Modbus) so your device can read real-time battery diagnostics.
3. hermal & Enclosure Design: Using 3D CAD, we engineer rugged enclosures focused on Thermal Management. We simulate stress to prevent thermal runaway propagation under heavy discharge curves.

Step 3: Rapid Prototyping & Rigorous Testing

Before committing to production-grade tooling, we construct functional, high-fidelity prototypes. Using in-house 3D printing and rapid spot-welding technology, we put the prototype through grueling physical and electrical stress tests:

Thermal Cycle Testing: Verifying pack integrity under extreme temperature swings.
Load & Capacity Testing: Simulating real-world device duty cycles to verify runtime.
Drop & Vibration Testing: Validating mechanical durability for industrial and military standards.

Step 4: Regulatory Compliance & Safety Certification

Navigating global approvals is one of the biggest bottlenecks in product launches. We partner with accredited third-party labs to secure crucial compliance certifications for your target market.

Step 5: Scaled Production & Quality Control

Once validated, your project transitions seamlessly into our advanced manufacturing facilities, where quality and consistency are prioritized:

Cell Matching: Sorting and pairing cells with identical internal resistance and capacity to maximize pack lifespan.
100% Automated EOL Testing: Every pack undergoes automated safety, protocol communication, and functional testing before packaging.
Full Traceability: End-to-end component tracking from BMS chipsets to individual lithium cells.

Step 6: Global Logistics & Class 9 Hazmat Compliance

The process doesn’t end when production finishes. Shipping lithium batteries requires navigating complex global regulatory frameworks, as they are classified as Class 9 Dangerous Goods (Hazmat).

Compliant Packaging: We design and supply UN-certified packaging (compliant with IATA, ADR, and IMDG codes).
Regulatory Documentation: We manage UN38.3 test summaries, Material Safety Data Sheets (MSDS), and shipper declarations.
Lifecycle Support: Ongoing supply chain management, future design revisions, and obsolescence tracking for critical components.

At Hypercell, we combine over 19 years of engineering expertise with state-of-the-art assembly to deliver safe, smart, and resilient power solutions.

Ready to kickstart your next project? Contact our sale today to discuss your custom power requirements!

Lithium-ion battery performance is not only determined by chemistry but also by how the internal electrodes are assembled. Among the most widely used manufacturing methods, stacking (lamination) and winding (jelly-roll) define the core structure of a battery cell.

While cylindrical batteries typically use winding technology and pouch cells mainly use stacking, prismatic batteries can adopt either process depending on performance and cost requirements.

Understanding these two technologies is essential for selecting the right battery solution for applications such as electric vehicles, medical devices, robotics, and consumer electronics.

Lithium-Ion Battery Manufacturing Overview

The battery manufacturing process generally includes four key stages:

• Electrode slurry mixing
• Coating, drying, calendaring, and slitting
• Cell assembly (stacking or winding)
• Electrolyte filling, formation, and grading

Among these, cell assembly is the most critical stage, as it directly determines the internal structure and performance of the battery.

What Is Winding Technology?

Winding technology, also known as the jelly-roll process, is the most mature lithium-ion battery assembly method.

In this process:

• Positive electrode
• Separator
• Negative electrode

are continuously wound into a cylindrical or prismatic structure.

This creates a spiral internal structure commonly referred to as a “jelly roll.”

Applications of Winding Batteries

• 18650 cells
• 21700 cells
• 4680 cylindrical cells
• Power tools
• Consumer electronics
• Energy storage system

Advantages of Winding Technology

1. Highly mature manufacturing process
Winding has been developed over decades and is widely standardized.

2. High production efficiency
Continuous manufacturing enables large-scale automation.

3. Lower cost
Mature equipment and stable yield reduce overall production cost.

4. Excellent consistency
Suitable for mass production of standardized battery cells.

Limitations of Winding Technology

• Internal stress concentration in jelly-roll structure
• Limited space utilization due to cylindrical geometry
• Slight constraints in energy density improvement

What Is Stacking Technology?

Stacking technology assembles electrodes by cutting them into individual sheets and stacking them layer by layer.

The typical structure is:

Positive electrode → Separator → Negative electrode → Separator → repeated stacking

This creates a flat and uniform electrode structure.

Applications of Stacked Batteries

• High voltage batteries
• Blade batteries
• High-energy-density prismatic batteries
• Drones
• Medical devices
• High-performance robotics

Advantages of Stacking Technology

1. Higher energy density potential
Better space utilization increases active material ratio.

2. Improved thermal management
More uniform heat distribution reduces hotspots.

3. Longer cycle life
Lower mechanical stress improves durability.

4. Enhanced safety performance
Reduced internal resistance and improved thermal stability.

5. Better fast-charging capability
Lower polarization improves charge acceptance.

Limitations of Stacking Technology

• Higher equipment investment
• Lower production efficiency compared to winding
• More complex process control requirements

Stacking vs Winding: Key Differences

Why Stacking Offers Higher Energy Density

Stacking technology improves energy density through:

1. Better space utilization

No central void like cylindrical winding structures.

2. Higher active material ratio

Less inactive structural space inside the cell.

3. Uniform electrode alignment

Improves ion transport efficiency.

4. Reduced internal resistance

Shorter electron and ion pathways.

Fast Charging Performance Comparison

Fast charging performance is increasingly important in modern applications.

Stacked cells generally perform better because:

• More uniform current distribution
• Lower internal polarization
• Better thermal stability during high-rate charging

This makes stacking ideal for:

• Electric vehicles
• Drones
• High-performance industrial systems

Safety Considerations

Battery safety is influenced by both design and manufacturing precision.

Key safety factors include:

• Burr control during electrode cutting
• Separator integrity
• Internal short-circuit prevention
• Thermal runaway resistance

While both technologies can be safe when properly engineered, stacking often provides improved thermal uniformity in large-format cells.

Industry Applications

Winding Battery Applications

• Power tools
• Consumer electronics
• Portable energy storage
• Industrial equipment
• Cylindrical battery platforms (18650 / 21700 / 4680)

Stacking Battery Applications

• Electric vehicles
• High-end drones
• Medical devices
• Robotics systems
• High-energy-density prismatic batteries

Industry Trends

The lithium battery industry is evolving toward higher energy density and improved safety.

Key trends include:

• Growth of large-format prismatic batteries
• Increased adoption of stacking technology in EVs
• Continued dominance of cylindrical winding cells in consumer and industrial applications
• Development of high-speed stacking equipment

Companies such as Tesla continue to use winding-based cylindrical platforms like 4680 cells, while manufacturers like BYD promote blade battery designs based on stacked architectures.

How Hypercell Selects the Right Technology

At Hypercell, battery design is application-driven rather than technology-driven.

We evaluate multiple factors:

• Energy density requirements
• Discharge rate
• Cycle life targets
• Size and weight constraints
• Operating environment
• Cost efficiency

Based on these parameters, we select the most suitable cell architecture—whether winding or stacking—to ensure optimal performance for each application.

Frequently Asked Questions (FAQ)

1.Is stacking better than winding?

There is no absolute “better” option. The best choice depends on application requirements.

2.Why do cylindrical batteries use winding?

Because winding is highly efficient and well-suited to cylindrical geometry.

3.Why are pouch batteries usually stacked?

Stacking maximizes space utilization and improves energy density.

4.Which technology lasts longer?

Stacking may offer longer cycle life due to reduced mechanical stress, depending on design and usage conditions.

5.Is stacking more expensive?

Yes, due to higher equipment cost and lower production efficiency.

6.Can both technologies be used in prismatic batteries?

Yes, prismatic batteries can adopt either stacking or winding depending on design goals.

7.Which is better for fast charging?

Stacking generally performs better in high-rate charging applications.

Conclusion

Stacking and winding are two fundamental lithium-ion battery manufacturing technologies, each with distinct advantages.

Winding offers cost efficiency, mature production, and high scalability.
Stacking provides higher energy density, better thermal performance, and improved electrochemical stability.

The optimal choice depends entirely on application requirements rather than a universal superiority of one technology.

At Hypercell, we provide customized lithium battery solutions tailored to performance, safety, and cost objectives across diverse industries.