Encoders, bearings and a 90-minute battery: what decides humanoid uptime

Agility rebuilt its pitch around the battery

Fact In its Sep 30, 2026 SEC filing, Agility Robotics described Digit v4 as having a four-hour runtime with autonomous charging, a 2:1 run-to-charge ratio. Digit 5, unveiled on Sep 15, 2026, uses a new battery that runs 90 minutes and charges in 9. Agility says that 10:1 ratio allows more than 20 hours of productive work in a 24-hour day.1

Fact The same filing lists other Digit v4 specifications: a 35-pound carrying capacity, 360-degree sensing and deployments that passed field evaluations by an OSHA-recognized Nationally Recognized Testing Laboratory. Digit 5 raises payload by about 40%, to 50 pounds. Agility says it has $300 million of committed multi-year orders for Digit 5, subject to contractual milestones and specifications, with early access due in the first half of 2027.1

Fact Agility says Digit 5 also adds a cooperative safety architecture meant to let it work alongside people. Customer deployments, the filing says, kept pointing to four priorities: working safely near people, higher utilization across shifts, heavier payloads and a wider range of workflows.1

Our read Agility traded runtime per charge for hours per day, and it is right to. A customer paying a monthly fee is paying for hours worked, and a four-hour battery with a two-hour charge leaves a third of the day idle. The spec that matters to a buyer is productive hours across a shift pattern, and every humanoid vendor should be ready to quote it.

Three answers to the same runtime problem

Fact Apptronik took a different route with Apollo, unveiled in August 2023: a battery pack rated at up to four hours that can be swapped instead of charged in place. Figure's F.03 battery, described in July 2025, holds 2.3 kWh, is rated for five hours at peak performance and charges at 2 kW. Figure said the pack costs 78% less than the F.02 version.65

Fact Figure says the F.03 pack serves as a structural member of the torso, survives a one-meter drop onto concrete and was built for the BotQ line, designed for up to 12,000 humanoids a year. Apptronik's Apollo, for comparison, is 5 feet 8 inches tall, weighs 160 pounds and carries up to 55 pounds.56

Fact Figure says battery energy density rose 94% across three generations starting with F.01, and that the F.03 pack was in process for UN38.3 and UL2271 certification when it was announced. Its BotQ line targets 100,000 robots over four years.54

Fact Figure 03, introduced on Oct 9, 2025, charges wirelessly through coils in its feet when it steps onto a stand, at 2 kW, and offloads data over a 10 Gbps mmWave link.4

Our read Swapping, fast charging and wireless docking each put a different cost on the customer's floor. Swaps need spare packs and someone to change them. Fast charging and docking need power at fixed points, which may mean electrical work. The proposal should name which one the site needs and who pays, because a buyer who finds it after signing treats it as a hidden cost.

Our read The fastest-charging pack is not automatically the best fit. A site running a single day shift can live with a five-hour battery and an overnight charge. A three-shift distribution center needs either swaps or a high run-to-charge ratio, and that is the customer Agility built Digit 5 for. Matching battery strategy to shift pattern is a qualification question, and it belongs in discovery.

Why the second encoder matters

Our read A joint encoder mounted on the motor reports where the motor shaft is. Between the motor and the limb sit a reducer and bearings, which add backlash and flex. A policy trained in simulation assumes the limb is where the model says it is, so any gap the motor-side encoder cannot see shows up as error on the real robot.

Fact Component makers are packaging a fix. On Feb 11, 2026, RLS launched the AksIM-4 Dual Concentric, a thin magnetic encoder that gives both motor and joint position feedback in one device, aimed at humanoid joints with little internal space. RLS said combining the two encoders cuts component count and simplifies cabling.2

Fact RLS said samples were available at launch and offered design support to joint builders, with a standard connector or a board-to-board interface to connect straight to the servo drive.2

Fact Tier-1 suppliers now ship encoders inside the actuator. The rotary actuators Schaeffler agreed in April 2026 to supply to Hexagon Robotics combine electric motors, integrated power electronics, precise encoders and strain-wave or planetary gears.3

Our read Joint-side sensing is a cost that pays back in deployment time. Each policy that transfers with less on-site tuning shortens the pilot. A vendor that has paid for output-side encoders should say so and connect it to a shorter commissioning schedule, because that is the number a buyer's operations team will hold it to.

Our read Encoders bundled inside a Tier-1 actuator also change who the buyer talks to about failures. If the actuator arrives as one sealed module, the humanoid vendor's service team swaps modules and the Tier-1 repairs them. That shortens on-site repair time, but it puts a third party's lead times inside the vendor's uptime promise.

Bearings became a catalog part

Fact THK's cross-roller ring arranges cylindrical rollers crosswise so that a single bearing takes radial, axial and moment loads, and the company lists it for robot joints. THK says it offers three to four times the rigidity of conventional double-row thin angular ball bearings.7

Our read When one catalog bearing does the job of a paired set, joint design gets simpler and bearings stop being a reason one humanoid outperforms another. The money and the differentiation have moved to reducers, encoders and control software, and that is where a sales team should point a technical buyer.

Touch moves into the hand

Fact Figure 03's fingertip sensors detect forces as small as 3 grams, and each hand carries a palm camera for close-range feedback. Figure says its cameras run at twice the frame rate with a quarter of the latency and a 60% wider field of view per camera compared with the previous model.4

Fact Figure also says Figure 03 weighs 9% less than Figure 02, and that it moved production from CNC machining to tooled processes such as die-casting, injection molding and stamping, which cost more upfront but lower unit cost as volume grows.4

Our read Tactile and palm vision matter most in tasks with fragile or variable items, such as picking mixed goods or handling packaging. That defines a customer segment. A vendor with strong hand sensing should qualify for those tasks first and leave rigid-tote moves, where most humanoids can do the job, to rivals competing on price.

Single sources sit inside the sensing stack

Fact Agility's filing says some of its critical components, including battery cells, sensors and vision systems, may have to come from a single source or a limited number of suppliers. It names battery cells among the materials whose price increases could cut its margins if it cannot pass them on.1

Our read A buyer signing a five-year subscription is betting that the vendor can keep spare encoders, sensors and packs flowing for five years. Vendors should answer that in the sales cycle with named second sources and a spares plan, before it surfaces in legal review.