Amprius SA88 for Drones: A Battery Engineerʼs Guide Beyond the Datasheet
- About:Energy
- Mar 17
- 11 min read
1 Amprius SA88 Cell Overview
The Amprius SA88 is a 10.5 Ah high-power lithium-ion pouch cell using a silicon-based anode, designed for applications where both energy density and discharge capability must coexist within a tightly constrained mass budget. For drone platforms operating under aggressive manoeuvres, rapid climb and thrust demands, that balance becomes critical.
From the manufacturer’s specification, the SA88 delivers 10.5 Ah capacity, 36.23 Wh of energy, and a nominal voltage of 3.45 V. It uses an NMCA positive electrode chemistry and supports a maximum continuous discharge and charge current of 105 A (10C). Gravimetric energy density is specified at 375 Wh/kg, alongside a volumetric energy density of 800 Wh/L.
To ensure consistency across manufacturers, The Voltt (see: https://voltt.aboutenergy.io/) reports energy density based on maximum cell weight. With a maximum specified mass of 98.5 g, this yields a minimum gravimetric energy density of 368 Wh/kg. Based on the specified continuous current limit, this corresponds to a gravimetric power density of approximately 3678 W/kg under continuous discharge, placing it firmly in the upper-right region of the energy–power landscape. As shown in the Voltt cell library comparison, the SA88 sits among the stronger combined energy and power performers in its class, rather than trading one attribute for the other.
Explore the Voltt platform to view detailed performance data and make faster, more informed decisions. Reduce cell selection time and cost by up to 90%.
For drone engineers, this positioning raises practical questions:
How much energy is accessible at sustained power demand?
How does voltage behave under rapid current changes?
What thermal limits appear under realistic cooling conditions?
Does the cell maintain performance deep into the discharge window?
High-energy cells often struggle under sustained high-power loads due to voltage polarisation and thermal rise. Pure high-power cells frequently sacrifice endurance. The SA88 is positioned to deliver both energy density and high discharge capability within the same format. These questions are not answered by the datasheet alone. They require validated characterisation and mission-level simulation.
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 drone platforms, where weight and power delivery are tightly constrained, small differences at cell level can compound 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.
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, we apply lab-validated electrical models in The Voltt to simulate performance under application-relevant conditions in this whitepaper. By evaluating SA88 under dynamic mission-level load profiles, we move beyond static datasheet metrics and assess how the cell behaves in realistic drone operating scenario.
2 Cell Performance Characterisation
To verify the nominal capacity of the Amprius SA88, we conducted a capacity check at 25 °C under controlled laboratory conditions. The cell was discharged at C/30 to minimise voltage polarisation and measure baseline capacity, with comparison curve at 1C to observe current influence on the voltage behaviour. At C/30, the cell delivered a measured capacity of 10.474 Ah, closely matching the manufacturer’s typical specification of 10.5 Ah. The voltage profile remains smooth and stable across the discharge window, with no abnormal inflections or early drop-off near end-of-discharge.
2.2 Constant C-rate Simulation
To assess how the Amprius SA88 responds to increasing discharge demand, we simulated constant current discharges at 0.5C, 1C, 3C, 5C, and 10C under controlled thermal conditions. This provides a clear view of rate capability, voltage polarisation, delivered capacity, and thermal response as current increases.
The voltage curves show minimal separation between 0.5C and 1C, indicating low polarisation and strong access to available capacity. At 3C and 5C, divergence becomes more noticeable across mid-capacity, though the profiles remain stable through most of the discharge window. At 10C, separation increases significantly, with the discharge terminating earlier due to increased overpotential and internal resistance under elevated current demand.
Capacity retention remains strong through 3C, with 10.05 Ah delivered, corresponding to approximately 99% retention relative to the manufacturer’s minimum rated capacity of 10.2 Ah. At 5C, delivered capacity reduces to 9.78 Ah, representing approximately 96% retention, indicating strong accessible capacity at higher rates. At 10C, delivered capacity decreases to 8.72 Ah, or roughly 85% retention, with discharge ending at thermal cut-off.
The power curves scale proportionally with current at lower C-rates. However, at 5C and 10C, increasing voltage polarisation limits sustained power delivery toward end-of-discharge, which narrows the practical operating window for sustained high-power operation.
Thermally, the cell remains well controlled up to 3C, with peak temperatures of approximately 42 °C. At 5C, peak temperature reaches around 54 °C, while at 10C, the cell approaches 80 °C, triggering thermal cut-off. The sharp temperature rise at 10C confirms that sustained maximum discharge is thermally constrained before electrical limits are reached.
Summary of Performance Metrics (Simulation)
Simulations were performed at current levels of 0.5C, 1C, 3C, 5C and 10C, starting from:
Initial SoC: 100%
Initial Cell Temperature: 25°C
Heat Transfer Coefficient: 50 W/m²·K (representing moderate passive cooling from airflow in motion in ventilated drone enclosure)
Why This Matters for Drone Design
For high-power multi-rotor systems, current demand frequently exceeds 3C during climb and manoeuvre phases. The SA88 maintains strong capacity retention and controlled thermal rise in this region, indicating it can support aggressive mission segments without significant derating.
However, sustained operation at 10C is thermally constrained, indicating that pack-level design must distribute load across parallel strings or improve heat rejection to avoid thermal cut-off during prolonged high-power phases.
This analysis clarifies the practical discharge envelope of the SA88. Rather than relying on static datasheet ratings, engineers can identify where voltage polarisation and thermal rise begin to limit usable performance under realistic cooling assumptions.
3 Simulation and Mission Performance Analysis
3.1 Constant Power Simulation
While constant current testing establishes rate-dependent behaviour, constant power discharge captures a more realistic operating condition in drone systems, where current dynamically increases as voltage declines during discharge. This amplifies the effects of internal resistance and heat generation toward end-of-discharge, providing a clearer view into practical operating limits rather than fixed-current tests alone. To evaluate this behaviour, the SA88 was simulated at 25 W, 50 W, 100 W, 150 W, and 200 W.
At 25 W and 50 W, the voltage profile remains smooth and well-spaced, with near-full capacity utilisation. Delivered capacity reaches 10.33 Ah at 25 W and 10.20 Ah at 50 W, corresponding to ~101% and 100% capacity retention relative to the 10.2 Ah minimum specification. As discharge power increases to 100 W, 150 W, and 200 W, voltage polarisation becomes more pronounced. Delivered capacity reduces progressively to 9.92 Ah (~97%), 9.71 Ah (~95%), and 9.45 Ah (~93%) respectively. This gradual reduction reflects increasing overpotential rather than abrupt instability, indicating that SA88 maintains strong capacity retention even under sustained high-power demand.
Current rises dynamically throughout discharge under constant power operation. Peak current increases from approximately 10 A at 25 W and 20 A at 50 W, to ~40 A at 100 W, ~59 A at 150 W, and ~79 A at 200 W. The end-of-discharge current ramp highlights how electrical stress intensifies as voltage declines to sustain constant power. This behaviour is not visible in fixed-current test.
Thermally, the cell remains well controlled at lower power levels, with peak temperatures of ~29 °C at 25 W and ~34 °C at 50 W. At 100 W, peak temperature reaches ~44 °C. Higher power operation increases thermal rise further, reaching ~54 °C at 150 W and ~63 °C at 200 W, while remaining below the 80 °C cut-off under the assumed cooling conditions.
Overall, the SA88 maintains strong capacity utilisation and controlled thermal behaviour throughout the simulated power range under moderate cooling assumptions, which supporting its suitability for drone applications. Even at 200 W, the cell operates within defined thermal limits, highlighting its high-power capability when pack-level current distribution and thermal design are appropriately engineered.
Summary of Performance Metrics (Simulation)
Simulations were performed at current levels of 25W, 50W, 100W, 150W and 200W, starting from:
Initial SoC: 100%
Initial Cell Temperature: 25°C
Heat Transfer Coefficient: 50 W/m²·K (representing moderate passive cooling from airflow in motion in ventilated drone enclosure)
Why This Matters for Drone Design
Drone propulsion systems rarely operate at fixed current. Engineers design around power and thrust targets, with current dynamically adjusting as voltage declines. Constant power simulation therefore defines the electrical and thermal envelope of the cell under application-representative loading.
The results show that the SA88 maintains strong capacity utilisation through moderate-to-high sustained power levels, with thermal rise scaling predictably rather than accelerating uncontrollably. This allows engineers to estimate usable energy under thrust conditions, define safe continuous operating bands, and determine whether parallelisation or enhanced cooling is required for mission endurance
3.2 Mission Profile Pack Simulation
While constant current and constant power testing define cell-level capability, real drone systems operate under highly dynamic load profiles. Thrust demand varies continuously during take-off, climb, hover, manoeuvre, and descent, producing rapid current transients and fluctuating thermal stress. To evaluate pack-level behaviour under representative loading, a 12s2p SA88 configuration was simulated in The Voltt using a drone-style duty cycle with rapid transients and sustained mid-power phases.
The configured pack delivers:
Pack configuration: 12s2p
Nominal voltage: 12 × 3.45 V = 41.4 V
Capacity: 2 × 10.50 Ah = 21.0 Ah
Total energy: ~869 Wh
Estimated total cell mass: 24 × 98.5 g = 2.37 kg
Simulation conditions assumed:
Initial SoC: 95%
Initial cell temperature: 25 °C (typical indoor staging prior to flight)
Ambient temperature: 20 °C
Heat transfer coefficient: 15 W/m²K (natural convection in an enclosed drone compartment)
Voltage cut-off: 2.5 V per cell
Thermal cut-off: 80 °C
The simulated profile produces peak pack power of approximately 2.0 kW, with an average discharge power near 1.15 kW. Peak current reaches ~42.6 A, while average current remains around 25 A across the cycle.
Voltage declines gradually from approximately 48.3 V to a minimum of 44.7 V, with visible recovery during reduced-load phases. This behaviour reflects healthy voltage stability under transient demand, with no abrupt collapse or instability during peak thrust events.
Over the ~600 s mission profile, the pack delivers ~192 Wh, corresponding to a 19.7% SOC reduction, finishing at 75.3% SOC. The mission therefore uses less than one-quarter of available capacity, indicating significant remaining endurance margin.
Thermally, the pack remains exceptionally stable throughout the duty cycle. Cell temperature remain within 25 °C, with negligible net temperature rise across the cycle. Average heat generation is approximately 25.6 W, resulting in a calculated thermal efficiency of 97.8%. Although instantaneous heat generation peaks near 78 W during high-power bursts, these events are short in duration and do not accumulate into sustained thermal stress. The temperature profile shows minor fluctuation but no progressive thermal ramp towards thermal thresholds
Why This Matters for Drone Design
Overall, the drive cycle simulation demonstrates that the SA88, configured in a 12s2p architecture, comfortably supports typical drone-style thrust cycles within defined electrical and thermal limits. Voltage remains stable under transient loading, current stays within practical parallel-sharing bounds, and thermal behaviour remains controlled under modest cooling assumptions. No voltage or thermal cut-offs are approached during the simulated mission, and significant usable energy remains at completion, suggesting suitability for extended flight time or higher payload operation.
For drone engineers, this defines the practical mission envelope at pack level. The results provide confidence that the system can sustain high-power manoeuvres without excessive derating, while maintaining thermal stability and energy margin for extended endurance or increased payload demand. Unlike static datasheet specifications, simulations capture voltage recovery, current ramping, and cumulative thermal effects under realistic propulsion demand. This translates cell-level characterisation into real-world propulsion performance, enabling engineers to design against actual power targets rather than nominal rating
3.3 Pulse Power Capability Mapping
While constant power simulations define sustained operating limits, many drone manoeuvres require short-duration power bursts above continuous ratings, such as rapid climb and evasive manoeuvres. Pulse power capability mapping therefore evaluates how much instantaneous power the SA88 can deliver across state of charge and temperature.
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: 10C
Ambient temperature: 25 °C
Heat transfer coefficient: 50 W/m²K
The results show that maximum pulse power scales strongly with SOC. At low SOC (~5–10%), available pulse power is limited, particularly at lower temperatures, reflecting increased internal resistance and voltage constraints. As SOC increases beyond the ~20% knee point, pulse capability rises sharply and stabilises across the mid-SOC region. Above ~60% SOC, the SA88 sustains pulse power levels exceeding 350 W per cell, with peak values approaching 380 W at elevated temperatures.
Temperature has a clear influence on pulse capability. At 10 °C, pulse power is noticeably reduced at low SOC due to higher internal resistance. At moderate temperatures (25–35 °C), performance improves significantly across the SOC window. At higher temperatures, pulse power increases further due to reduced resistive losses; however, practical operation must consider long-term thermal degradation effects.
Why This Matters
Across most of the usable SOC window above ~20%, the SA88 demonstrates strong and stable transient power capability, indicating suitability for high-power bursts without excessive voltage polarisation. This mapping defines the short-duration electrical pulse envelope of the cell and highlights the SOC regions where performance margin is greatest.
Pulse power mapping bridges the gap between continuous ratings and real flight behaviour. By understanding how transient capability varies with SOC and temperature, engineers can:
Define safe burst-power limits
Identify minimum operational SOC thresholds
Size packs to avoid voltage knee-point collapse during climb
Quantify performance margin across temperature conditions
Unlike static datasheet maximum current ratings, this mapping reveals how power capability evolves dynamically across real operating windows. It enables informed decisions on derating strategy and control limits for system-level safety margins.
4 Engineering insights and conclusion
The simulated results show that the Amprius SA88 combines high specific energy with stable electrical and thermal performance across steady-state, sustained, and transient loading. Through constant current, constant power, pulse mapping, and dynamic drone duty cycle simulations, the cell’s behaviour has been defined from laboratory characterisation to pack-level mission performance.
At cell level, the SA88 exhibits low voltage polarisation and strong capacity retention across moderate-to-high discharge rates. Thermal response scales predictably with load, with limits governed by temperature rise rather than abrupt electrical instability. Pulse mapping confirms robust transient power capability above ~20% SOC, providing meaningful burst margin for propulsion spikes.
At pack level, the 12s2p drone configuration maintains voltage stability under rapid load transients while remaining well within thermal limits under realistic cooling assumptions. The drive cycle simulation demonstrates support for high-power manoeuvres without excessive derating, with significant usable energy remaining after the mission window. No voltage or thermal cut-offs are approached under the simulated conditions.
Together, these results define the practical operating envelope of the SA88. Beyond static datasheet ratings, dynamic simulation clarifies:
Usable energy under mission-representative load
Safe continuous and burst power limits
SOC-dependent performance margins
Thermal behaviour under realistic cooling conditions
By linking validated laboratory data to system-level modelling, engineers can reduce uncertainty in cell selection and pack sizing, optimise parallelisation and cooling strategies, and design against real propulsion power targets rather than nominal specifications.
The Voltt enables this transition from datasheet evaluation to mission-level validation, allowing engineers to assess performance trade-offs early and make data-driven battery design decisions with confidence.
Get started with a 14-day free trial and access 40+ high-performance cells from EVE, Molicel, Amprius and more. Reduce cell selection time and cost by up to 90%.
