Reliance RS50 Battery Evaluation for High-Power Electric Aviation and eVTOL Applications

1 Reliance RS50 Cell Overview and Positioning

The Reliance RS50 is a 5.0 Ah high-performance lithium-ion cylindrical cell in the 21700 form factor, developed for applications that demand strong discharge capability alongside competitive energy density. This balance is particularly important for electric aviation systems such as eVTOL aircraft, where batteries must sustain large propulsion loads during take-off and climb while maintaining sufficient energy for cruise and reserve operation.

From the manufacturer's specification, the RS50 delivers a minimum capacity of 4 950 mAh, 18.0 Wh of energy, and a nominal voltage of 3.6 V. The cell supports a maximum continuous discharge current of 70 A (14C) with an 80°C thermal cut-off, and a maximum continuous charge current of 15 A (3C).

To ensure consistency across manufacturers, The Voltt reports energy density using the maximum specified cell mass. Under this convention, the RS50 achieves a minimum gravimetric energy density of approximately 269 Wh/kg. When combined with the specified continuous current capability, this corresponds to a gravimetric power density of roughly 3.7 kW/kg under continuous discharge, positioning the cell among the stronger combined energy-and-power performers within the 21700 format and placing it well into the upper-right region of the energy-power landscape. For eVTOL applications, where both axes of the energy-power trade-off carry system-level consequences, this balance is a meaningful design consideration.

Figure 1 Energy-power positioning of the Reliance RS50 within the lithium-ion cell landscape.

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For eVTOL engineers, the RS50's positioning raises practical questions relevant to aircraft-level design:

• How does voltage behave under the high sustained currents demanded during take-off and landing?

• How much energy remains accessible across a realistic flight cycle, and where does thermal behaviour begin to constrain operation?

• Does the cell maintain performance electrically and thermally through the mid-SOC cruise window where the majority of flight time is spent?

  
  

These questions are not resolved by the datasheet alone and require validated simulation under mission-representative conditions to answer with confidence.

The Importance of Accurate Cell Selection

Choosing the right cell is one of the most important decisions in battery system design. It directly influences pack mass, thermal architecture, discharge limits, and overall system performance. In electric aviation platforms such as eVTOL aircraft, where both energy storage and high power delivery are tightly constrained by safety and weight requirements, small differences at the cell level can translate into significant system-level impacts.

While manufacturer datasheets provide baseline specifications such as capacity, voltage limits, and maximum current ratings, they rarely offer enough detail for confident system design. Information on temperature rise under sustained load, voltage behaviour across the discharge window, and performance under realistic cooling conditions is often missing or based on idealised test setups.

As a result, engineering teams face three recurring challenges in the traditional cell selection process:

• Inconsistent data and benchmarking difficulty: Manufacturer data is rarely reported under identical test conditions, making direct comparisons difficult. Engineers must also validate whether published performance claims translate to their specific application and mission profile.

• High testing overhead: Accurate characterisation and validation require specialised cyclers, environmental chambers, safety systems, and instrumentation. For many teams, this represents significant capital and time investment before meaningful conclusions can be drawn.

• Delayed development cycles: Cell sourcing, shipping, and full qualification testing can add weeks or months to development timelines, particularly when down-selection involves multiple candidates.

  
  

To address this, this white paper applies lab-validated electrical models in The Voltt to evaluate the RS50 under application-relevant conditions. By simulating rate-dependent discharge, sustained power loading, pulse demand, and eVTOL mission cycles, we move beyond static datasheet values and define the cell's practical operating envelope for electric aviation platforms under realistic scenarios.

2 Reliance RS50 Cell Performance Characterisation

2.1 Constant Current Test - Capacity Check

Figure 2.1 Laboratory capacity check of the Reliance RS50 at C/30 and 1C at 25°C, showing a measured capacity of approximately 5.27 Ah at C/30, exceeding the manufacturer's minimum specification of 4.95 Ah.

To verify the nominal capacity of the Reliance RS50, a capacity check was conducted at 25°C under controlled laboratory conditions. The cell was discharged at C/30 to minimise voltage polarisation and establish baseline accessible capacity, with a comparison curve at 1C to observe the influence of higher current on voltage behaviour.

At C/30, the cell delivered a measured capacity of approximately 5.27 Ah, exceeding the manufacturer's minimum specification of 4.95 Ah. This confirms strong baseline energy availability and validates the cell's capacity credentials ahead of simulation. The voltage profile is smooth with a gradual decline through the upper SOC region, a relatively stable mid-discharge plateau between approximately 3.6 V and 3.7 V, and a steeper drop toward end of discharge.

The separation between the C/30 and 1C curves reflects the expected influence of internal resistance at higher current, with the 1C profile depressed by approximately 100–150 mV across the mid-discharge region. For eVTOL engineers, this confirms that the RS50 delivers its rated capacity reliably under standard conditions, and that the voltage window available for propulsion system design is well defined and stable across the usable discharge range.

This baseline capacity verification establishes the reference point for the higher-rate discharge, power capability, and thermal simulations examined in the following sections.

2.2 Reliance RS50 Constant C-rate Simulation

To assess how the Reliance RS50 responds to increasing discharge demand across its operating range, constant current discharges were simulated at 1C, 3C, 5C, 10C, and 14C under controlled thermal conditions. This sweep covers the range from moderate cruise-representative loads through to the manufacturer's maximum continuous discharge rating, providing a clear view of rate capability, voltage polarisation, delivered capacity, and thermal response as current demand increases.

Figure 2.2.1 Voltage response of the Reliance RS50 under constant current discharge at 1C, 3C, 5C, 10C, and 14C, plotted against delivered capacity.

At 1C, 3C, and 5C, the voltage curves show progressive but moderate separation, with all three profiles delivering above 5.0 Ah before reaching the voltage cut-off. The characteristic NMC graphite shape is preserved across these rates, with a stable mid-discharge region and a steeper decline toward end of discharge. Polarisation increases noticeably between 1C and 5C, but capacity retention remains strong across this range, confirming that the RS50 maintains good electrical performance under load conditions representative of eVTOL climb and cruise phases.

At 10C, polarisation is significant from the outset, with discharge terminating at approximately 4.14 Ah (~84% capacity retention) as the cell reaches the 80°C thermal cut-off before the electrical capacity is exhausted. At 14C, polarisation is severe, with the profile starting below 3.6 V and discharge terminating very early at approximately 2.53 Ah (~51% capacity retention), again limited by the thermal cut-off rather than the voltage limit.

Figure 2.2.2 Power output of the Reliance RS50 during constant current discharge at 1C, 3C, 5C, 10C, and 14C, plotted against delivered capacity.

The power response scales directly with discharge rate and reflects the underlying voltage behaviour at each C-rate. At 1C, delivered power remains essentially flat at approximately 20 W throughout discharge. At 3C, initial power output reaches approximately 55 W, declining gradually toward end of discharge. At 5C, power starts near 100 W and tapers through the discharge window as voltage falls. At 10C, initial power approaches 185 W before declining as thermal cut-off is approached. At 14C, initial power approaches 250 W per cell, but the short discharge duration resulting from rapid thermal accumulation significantly limits the total energy delivered at this rate.

Figure 2.2.3 Temperature rise of the Reliance RS50 during constant current discharge at 1C, 3C, 5C, 10C, and 14C, plotted against delivered capacity.

Thermally, the cell behaviour diverges sharply above 5C under the assumed cooling conditions. At 1C, temperature rise is minimal, peaking at approximately 31°C. At 3C, peak temperature reaches approximately 44°C, which is elevated but manageable under moderate forced air cooling. At 5C, peak temperature rises to approximately 57°C, indicating meaningful thermal load that must be accounted for in pack thermal design for sustained operation at this rate. At 10C, temperature rises rapidly and reaches the 80°C thermal cut-off before the electrical capacity is fully discharged, resulting in early termination at approximately 4.14 Ah. At 14C, the thermal cut-off is reached within the first approximately 1 Ah of discharge, confirming that sustained operation at the manufacturer's maximum rated current is not achievable under moderate forced air cooling and requires either more aggressive active thermal management or strict duty cycle limitations.

Summary of Performance Metrics (Simulation)

Simulations were performed at C-rates of 1C, 3C, 5C, 10C, and 14C, starting from:

• Initial SoC: 100%

• Initial Cell Temperature: 25°C

• Heat Transfer Coefficient: 50 W/m²K (representing moderate passive cooling)

Why This Matters for Electric Aviation Design

The constant C-rate results define the thermal operating envelope of the RS50 clearly. Within the cruise and climb regime, up to approximately 5C, the cell delivers strong capacity retention and manageable thermal rise, confirming suitability for the sustained mid-power phases that dominate eVTOL mission profiles. At 3C, the 44°C peak temperature and near-full capacity delivery indicate that climb-phase current demands in this range are well within the cell's electrical capability, though thermal management should be sized accordingly for repeated cycles. At 5C, the 57°C peak temperature confirms that active thermal management is advisable for sustained operation at this rate.

Above 5C, thermal constraint becomes the primary design consideration. At 10C and 14C, the thermal cut-off is reached before the electrical capacity is exhausted, confirming that sustained high-rate discharge at these levels is not viable even under moderate forced air cooling.It is worth noting that 10C and 14C represent exceptionally high discharge rates. Most high-performance cells would not be rated for continuous operation at these levels and the RS50's ability to deliver meaningful capacity at 10C before thermal cut-off reflects the cell's strong power capability. For take-off and landing phases where peak current demands approach these rates, pack configurations that distribute current across a greater number of parallel strings are necessary to maintain per-cell current within thermally safe bounds. These results provide the quantitative foundation for defining per-cell current limits and cooling strategy requirements in eVTOL battery system design.

3 Reliance RS50 Simulation and Mission Performance Analysis

3.1 Reliance RS50 Constant Power Simulation

While constant current testing establishes rate-dependent behaviour under fixed discharge currents, constant power discharge captures a more representative operating condition for eVTOL propulsion systems, where motor controllers draw current dynamically to maintain thrust as cell voltage declines during discharge. This amplifies the effects of internal resistance and heat generation toward end of discharge, providing a clearer view of practical operating limits under application-representative loading. To evaluate this behaviour, the RS50 was simulated at 10 W, 25 W, 50 W, 100 W, and 150 W.

Figure 3.1.1 Voltage response of the Reliance RS50 under constant power discharge at 10 W, 25 W, 50 W, 100 W, and 150 W, plotted against delivered capacity.

The voltage response shows progressive separation across all five power levels, with the characteristic NMC graphite profile preserved throughout. At 10 W and 25 W, voltage remains high and stable across the majority of discharge, with near-full capacity delivered. As power increases to 50 W and 100 W, polarisation becomes more pronounced, with voltage curves shifted downward but still tracking the expected discharge shape across the full capacity window. At 150 W, polarisation is more significant and discharge terminates at approximately 4.40 Ah (~89% capacity retention) as the cell reaches the 80°C thermal cut-off before the voltage limit is reached.

Figure 3.1.2 Current response of the Reliance RS50 during constant power discharge at 10 W, 25 W, 50 W, 100 W, and 150 W, plotted against delivered capacity.

The current response illustrates a defining characteristic of constant power operation. Unlike fixed current discharge, current rises dynamically throughout discharge as voltage falls, intensifying electrical stress toward end of discharge. At 10 W and 25 W, peak currents remain at approximately 4 A and 10 A respectively, well within the continuous discharge rating throughout the full discharge window. At 50 W, peak current reaches approximately 20 A, remaining comfortably below the 70 A continuous limit. At 100 W, peak current rises to approximately 40 A (~8C), which is well within the rated continuous discharge capability of the RS50, illustrating the cell's high-power credentials in a propulsion context. At 150 W, peak current reaches approximately 55 A (~11C) toward end of discharge as voltage declines, approaching the continuous discharge rate limit and contributing to the accelerating thermal rise that triggers cut-off. This behaviour is not captured in fixed-current testing and is particularly relevant for propulsion-driven applications where current demand increases as voltage declines.

Figure 3.1.3 Temperature rise of the Reliance RS50 under constant power discharge at 10 W, 25 W, 50 W, 100 W, and 150 W, plotted against delivered capacity.

Thermally, the cell shows a clear and progressive relationship between power level and heat generation. At 10 W and 25 W, peak temperatures reach approximately 29°C and 36°C respectively, representing modest rises above ambient that would be readily managed by any reasonable pack cooling system. At 50 W, peak temperature reaches approximately 47°C, which is elevated but within manageable bounds under moderate forced air cooling. At 100 W, peak temperature reaches approximately 67°C, indicating meaningful thermal load and confirming that active thermal management is required for sustained operation at this power level. At 150 W, temperature rises steeply and reaches the 80°C thermal cut-off at approximately 4.40 Ah. While this early termination represents a capacity penalty, 150 W per cell corresponds to a current demand approaching 11C at the point of cut-off, which is a demanding operating condition and emphasise the importance of pack-level thermal design for high-power eVTOL phases.

Summary of Performance Metrics (Simulation)

Simulations were performed at power levels of 10 W, 25 W, 50 W, 100 W, and 150 W, starting from:

• Initial SoC: 100%

• Initial Cell Temperature: 25°C

• Heat Transfer Coefficient: 50 W/m²K (representing moderate forced air cooling)

  
  

Why This Matters for Drone Design

Constant power simulation provides an application-relevant view of the RS50's capability for eVTOL propulsion design, where power rather than current defines system requirements across flight phases. The results show that the RS50 maintains strong capacity retention and controlled thermal behaviour across a wide power range. At 10 W through 50 W per cell, which covers the cruise and approach phases of a typical eVTOL mission, the cell delivers near-full capacity with modest thermal load, confirming its suitability for sustained cruise operation.

At 100 W per cell, capacity retention remains at ~99% and the cell stays below the thermal cut-off, demonstrating the RS50's ability to sustain high power output that would challenge cells with lower continuous discharge ratings. The 150 W result, while thermally limited, highlights the importance of pack parallelisation for the most demanding flight phase

These findings provide a clear framework for system designers to:

• Define continuous vs peak power limits

• Size parallel strings for current sharing

• Design cooling systems to maintain thermal margin under peak load

  
  

Ultimately, constant power simulation reveals not just how much power the cell can deliver, but how sustainably it can deliver it within real mission constraints.

3.2 Reliance RS50 Mission Profile Pack Simulation

While constant current and constant power testing define cell-level capability under controlled steady-state conditions, real eVTOL systems operate under highly dynamic load profiles. Power demand varies substantially across take-off, climb, cruise and landing phases, producing current transients and fluctuating thermal stress that cannot be assessed through fixed-rate testing alone. To evaluate pack-level behaviour under representative electric aviation loading, a 222s16p RS50 configuration was simulated in The Voltt using the eVTOL passenger duty cycle scaled to an 800V pack architecture.

The configured pack delivers:

• Pack configuration: 222s16p

• Nominal voltage: 222 × 3.60 V = 799.2 V (~800 V class)

• Capacity: 16 × 5.00 Ah = 80 Ah

• Total energy: ~63.9 kWh

• Estimated pack mass (cells only): ~238 kg

  
  

Simulation conditions assumed:

• Initial SoC: 100%

• Initial cell temperature: 25°C

• Ambient temperature: 25°C

• Heat transfer coefficient: 70 W/m²K (moderate forced air cooling representative of an active eVTOL thermal management system)

• Voltage cut-off: 2.5 V per cell

• Thermal cut-off: 80°C

Figure 3.2.1 Electrical response of the Reliance RS50 222s16p pack under a simulated eVTOL passenger duty cycle, showing pack voltage, SOC, power, and current plotted against time.

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Pack voltage begins at approximately 880 V and dips to around 840 V during the take-off phase as peak current demand reaches 536.68 A (33.54 A per cell, approximately 6.7C). Voltage recovers partially during the climb transition before declining gradually through the extended cruise phase to approximately 810 V, reflecting stable and predictable discharge behaviour under sustained moderate loading. During the landing phase, voltage declines more steeply as power demand returns to take-off levels, reaching a minimum of 690.97 V, corresponding to 3.112 V per cell. This minimum remains comfortably above the 2.5 V cut-off, confirming that no voltage-driven termination occurs at any point during the mission.

Across the approximately 1210-second (~20-minute) mission, the pack delivers 45,924 Wh, corresponding to a 70.9% SoC reduction from 100% and finishing at 29.1% SoC.

Peak pack power reaches 370.8 kW (104.4 W per cell) during take-off and landing phases, while average power across the mission is 136.7 kW (38.5 W per cell), reflecting the dominance of the lower-demand cruise phase. Average per-cell current of 10.55 A (~2.1C) across the mission remains well within the continuous discharge rating, with peak per-cell current of 33.54 A (~6.7C) limited to the short-duration thrust phases.

Figure 3.2.2 Thermal behaviour of the Reliance RS50 222s16p pack during the eVTOL passenger mission profile, showing cell temperature and heat generation plotted against time.

The thermal response across the mission reveals a distinctive profile driven by the contrast between high-power thrust phases and the extended low-power cruise segment. Cell temperature rises from 25°C to approximately 33°C during the initial take-off phase as peak heat generation at pack level reaches 51.7 kW (14.55 W per cell). As the mission transitions into cruise, heat generation drops substantially to an average of approximately 2 W per cell, and the 70 W/m²K forced air cooling proves sufficient to actively reduce cell temperature through the cruise phase, with temperature declining to approximately 27°C by mid-cruise. During the final landing phase, power demand returns to take-off levels and temperature rises sharply, reaching a peak of 40.8°C at mission completion. The total temperature rise across the mission is 15.8°C and no thermal cut-off threshold is approached at any point during the simulation.

Why This Matters for Electric Aviation Design

The mission simulation confirms that the RS50, configured in a 222s16p 800V architecture, can support a full passenger eVTOL flight cycle including two high-power thrust phases of take-off and landing and an extended cruise segment, while remaining within both electrical and thermal operating limits throughout. The 29.1% SoC remaining at mission completion represents a meaningful reserve margin, consistent with aviation safety requirements for energy reserves.

The thermal behaviour observed across the mission is particularly relevant for system design. The active cooling system's ability to reduce cell temperature during cruise means that the pack enters the landing phase from a lower thermal baseline than it left take-off, providing additional margin for the final high-power demand. This behaviour underscores the value of adequate thermal management in eVTOL pack design, not only to manage peak thermal events, but to recover thermal headroom during lower-demand phases and support repeated flight cycles.

For engineers designing electric aviation battery systems, these results provide insight into how the RS50 performs under realistic mission loading. The simulation captures voltage stability under transient thrust demand, current distribution across the parallel string configuration, and cumulative thermal behaviour under representative operating conditions, none of which are visible from static datasheet specifications alone.

3.3 Pulse Power Capability Mapping

While constant power simulations define sustained operating limits, eVTOL missions also involve short-duration power bursts above continuous ratings, such as during rapid climb, wind gust response, or emergency manoeuvres. Pulse power capability mapping evaluates how much instantaneous power the RS50 can deliver across the full range of state of charge and temperature, providing a more complete picture of the cell's transient capability beyond what the datasheet alone can reveal.

Figure 3.3.1 Surface plot of the maximum pulse power capability of the Reliance RS50 as a function of SOC and temperature, based on 30-second discharge pulses constrained by voltage (2.5 V), temperature (80°C), and C-rate (14C).

Pulse discharge simulations were performed under the following conditions:

• SOC range: 5% to 95%

• Temperature range: 10°C to 60°C

• Pulse duration: 30 s (discharge)

• Minimum cell voltage: 2.5 V

• Maximum cell temperature: 80°C

• Maximum C-rate: 14C

• Ambient temperature: 25°C

• Heat transfer coefficient: 50 W/m²K

Figure 3.3.2 Maximum pulse power of the Reliance RS50 plotted against SOC at 10°C, 25°C, 35°C, 50°C, and 60°C, highlighting the steep SOC knee region below 20% and the convergence of temperature curves above 40% SOC.

The results show that maximum pulse power scales strongly with SOC across all operating temperatures. Below approximately 20% SOC, pulse capability drops sharply, driven by elevated internal resistance and the reduced voltage headroom available to sustain a 30-second pulse above the 2.5 V cut-off. A clear knee is visible between 15% and 20% SOC across all temperature isotherms, below which rate capability falls rapidly. At high SOC and elevated temperature, peak pulse power approaches approximately 256 W per cell, at which point the 14C C-rate constraint becomes the binding limit rather than voltage or thermal boundaries. This confirms that within the mid-to-high SOC operating window, the RS50 can reliably deliver short-duration thrust bursts at or near its pulse rating. Temperature has a clear and measurable influence on pulse capability, particularly at low SOC.

At 5% SOC and 10°C, maximum pulse power is limited to approximately 38 W, rising to approximately 92 W at the same SOC but at 60°C, a difference of approximately 54 W attributable to temperature alone. This reflects the strong influence of internal resistance on transient capability under cold and depleted conditions. At moderate operating temperatures of 25°C to 35°C and SOC levels above 30%, the curves converge with performance differences between isotherms becoming small across the mid-to-high SOC window. The 10°C isotherm remains notably suppressed relative to the others across the full SOC range, which is a relevant consideration for cold-weather eVTOL operations where pre-heating strategies may be required to restore full transient capability.

Why This Matters for Electric Aviation

For eVTOL platforms, pulse power mapping defines the transient capability envelope across the discharge window and identifies the SOC regions where thrust response margin is greatest. Above approximately 40% SOC and at operating temperatures above 25°C, the RS50 demonstrates strong and stable transient response, sustaining pulse demands up to the 14C limit without voltage or thermal cut-off. These results enable engineers to:

• Define safe burst-power limits for take-off, climb, and emergency manoeuvre phases based on per-cell SOC and temperature state

• Quantify transient performance margins across the operating temperature range, including the reduced capability at 10°C that may warrant pre-heating strategies for cold-weather operations

• Validate that the mission reserve SOC is adequate. The 29.1% final SoC observed in the mission simulation confirms the pack comfortably avoids the region of reduced transient capability under the simulated passenger duty cycle

This mapping bridges the gap between continuous discharge ratings and real flight behaviour, providing the data needed to design control strategies and safety margins around actual cell performance rather than nominal datasheet specifications.

4 Engineering insights and conclusion

The simulated results show that the Reliance RS50 combines competitive energy density with strong high-rate discharge capability, delivering stable electrical and thermal behaviour across steady-state, sustained, and transient loading conditions. Through constant current, constant power, pulse mapping, and a dynamic eVTOL mission simulation, the cell's performance has been characterised from cell-level measurement through to pack-level mission assessment.

At cell level, the RS50 demonstrates strong capacity retention across the moderate discharge rates that dominate eVTOL cruise and climb phases. At 1C through 5C, capacity retention remains at or above 101% relative to the manufacturer's minimum specification, with peak temperatures of 31°C, 44°C, and 57°C respectively under moderate forced air cooling. Above 5C, thermal constraint becomes the primary design consideration. At 10C and 14C, the 80°C thermal cut-off is reached before electrical capacity is exhausted, confirming that sustained operation at these rates requires active thermal management or strict duty cycle control.

Constant power simulation reinforces this picture where capacity retention remains at or above 99% up to 100 W per cell, with the 150 W result highlighting the importance of pack parallelisation to reduce per-cell power demand during the highest-load flight phases.

At pack level, the 222s16p 800V configuration comfortably supports the full simulated eVTOL passenger mission, delivering 45,924 Wh across an approximately 20-minute flight cycle with a final SoC of 29.1% and a peak cell temperature of 40.8°C. Voltage remains stable throughout, and the thermal recovery observed during cruise provides additional margin for the landing phase and supports repeated flight cycles without progressive heat accumulation.

Pulse power mapping confirms that above approximately 30% SOC and at operating temperatures above 25°C, the RS50 sustains pulse power approaching 256 W per cell, with the 14C C-rate constraint as the binding limit. Below 20% SOC, pulse capability declines sharply, defining a practical minimum operational SOC threshold. The 29.1% final SoC from the mission simulation confirms the pack operates comfortably above this threshold throughout the duty cycle.

Together, these results define the practical operating envelope of the RS50. Dynamic simulation clarifies:

• Usable energy under mission-representative load conditions

• Thermal behaviour under realistic cooling conditions across all flight phases

• Continuous and transient power capability across the discharge window

• SOC-dependent transient performance margins and minimum operational thresholds

  
  

By linking validated laboratory data to system-level modelling, engineers can make informed decisions on pack configuration, parallelisation strategy, cooling system sizing, and operational SOC limits based on actual cell behaviour. The Voltt enables this transition from datasheet evaluation to mission-level validation, supporting earlier and more confident design decisions in electric aviation battery development.

Frequently Asked Questions

What is the continuous discharge rating of the Reliance RS50 and can it sustain that rate in practice?

The Reliance RS50 is rated for a maximum continuous discharge current of 70 A (14C). In practice, sustained operation at this rate is thermally constrained. Under moderate forced air cooling (50 W/m²K), the 80°C thermal cut-off is reached within approximately 1 Ah of discharge at 14C, meaning practical continuous use should be limited to lower rates. At 5C, the cell delivers above 5.0 Ah with a peak temperature of approximately 57°C, which represents a more realistic upper bound for sustained continuous discharge under active cooling.

How does the Reliance RS50 perform in an eVTOL battery pack?

Simulated in a 222s16p 800V architecture, the RS50 supports a full 20-minute eVTOL passenger mission including take-off, cruise, and landing, delivering approximately 45,924 Wh with a final SoC of 29.1%. Peak pack power reaches 370.8 kW during thrust phases, and peak cell temperature reaches 40.8°C, well below the 80°C thermal cut-off. The pack completes the full mission without triggering any voltage or thermal limit.

What is the energy density of the Reliance RS50?

Calculated using the maximum specified cell mass, the RS50 achieves a minimum gravimetric energy density of approximately 269 Wh/kg. Combined with its 70 A continuous discharge rating, this corresponds to a gravimetric power density of approximately 3.7 kW/kg, placing it among the stronger combined energy and power performers in the 21700 format.

At what state of charge does pulse power capability drop significantly for the Reliance RS50?

A clear performance knee is visible between 15% and 20% SoC across all temperature conditions. Below this threshold, pulse capability falls rapidly due to elevated internal resistance and reduced voltage headroom. Above approximately 30% SoC and at temperatures of 25°C or higher, the RS50 sustains pulse power approaching 256 W per cell, with the 14C C-rate constraint becoming the binding limit rather than voltage or temperature.

How does temperature affect Reliance RS50 performance?

Temperature has a meaningful effect on both sustained and transient capability, particularly at low SoC. At 5% SoC, maximum 30-second pulse power ranges from approximately 38 W at 10°C to approximately 92 W at 60°C. Across the mid-to-high SoC window, temperature differences between isotherms become small, with the exception of the 10°C curve, which remains noticeably suppressed across the full SoC range. Cold-weather eVTOL operations may require cell pre-heating to recover full transient capability.

How does the Reliance RS50 compare to datasheet specifications under real operating conditions?

At low to moderate discharge rates, the RS50 exceeds its rated minimum capacity. Laboratory measurement at C/30 delivered approximately 5.27 Ah against a minimum specification of 4.95 Ah. At 1C through 5C under constant current discharge, capacity retention remains at or above 101% relative to that minimum specification. Under constant power loading up to 100 W per cell, capacity retention stays at or above 99%. Performance diverges from datasheet values primarily at high rates above 5C, where thermal behaviour rather than electrical limits becomes the primary constraint.