Service Robot Battery Chemistry: NMC vs LFP vs LTO by Duty Cycle

Duty Cycle Is the Deciding Variable

Two robots with the same pack capacity can have completely different chemistry requirements, because what wears a pack out is not its capacity but its duty cycle. Three properties of the duty cycle matter, and they interact.

The first is depth of discharge per cycle. A scrubber that runs a two-hour pass and returns to dock at 40 percent state of charge cycles shallowly; a delivery robot that runs a full shift to 15 percent cycles deeply. Deep cycling consumes cycle life faster, and the two chemistries age differently under depth. The second is the continuous discharge rate. Cleaning duties draw continuously from motors, pump and vacuum; delivery robots draw in bursts accelerating and climbing; standby patrol platforms draw a small baseline with occasional high peaks. The third is thermal exposure, which depends on whether the pack sits in a plant room, a chilled area or a sunlit car park. Chemistry selection is the resolution of these three against cost.

The Three Chemistries at Pack Level

Property	NMC	LFP	LTO
Energy density	High	Moderate	Low
Cycle life (to 80%)	1,000-2,000	3,000-5,000	15,000-20,000
Continuous discharge	High	Moderate	Very high
Low-temperature behaviour	Moderate	Weaker	Strong
Fast-charge tolerance	Good	Moderate	Excellent
Relative cost per kWh	Higher	Lower	Highest
Thermal stability	Lower	Higher	Highest

The pattern is consistent across sources: LFP buys cycle life and thermal stability at the cost of energy density and cold-weather performance; NMC buys energy density and cold-weather behaviour at the cost of cycle life and thermal margin; LTO buys cycle life, discharge rate and low-temperature performance at a significant cost premium. A robot fleet specification that names a chemistry without naming the duty is therefore incomplete. The pack-level detail of these differences is developed further in battery pack specification and sourcing.

The Selection Matrix: Duty to Chemistry

Applied to the common service robot duties, the matrix resolves as follows.

Duty	Cycle pattern	Recommended chemistry	Reason
Floor scrubbing (nightly full pass)	Shallow-moderate, daily	LFP	Cycle life dominates over density; weight is not critical
Indoor delivery (multi-shift, deep)	Deep, high frequency	NMC or LFP by payload	Density matters for payload; cycle depth leans LFP
Outdoor / cold-area cleaning	Moderate with cold exposure	LTO or NMC	Low-temperature behaviour is the binding constraint
Standby patrol / long idle	Very shallow, many micro-cycles	LFP or LTO	Cycle count is extreme; capacity is small
High-throughput swap-pack fleets	Deep, rapid turnaround	LTO	Discharge rate and fast-charge tolerance

The matrix is a starting position, not a verdict, because the binding constraint differs by site. A cold-store delivery robot in a chilled facility is an LTO case even though its cycle pattern suggests NMC. A high-ambient plant-room cleaning robot is an LFP case even though its duty is continuous. The method is to identify which of the three duty properties, depth, rate or temperature, is most extreme for the site, and select the chemistry that is strongest on that axis.

Cost Per Energy Delivered Over Pack Life

The purchase price of a pack is the least informative number in the decision. The number that matters is cost per kilowatt-hour delivered over the pack's life, because that includes how many cycles the pack will actually give under the site's duty. The arithmetic is straightforward: take the pack's usable energy, multiply by its realistic cycle count under the site's depth of discharge, and divide the total cost of the pack, including replacement labour and disposal, by the total energy delivered.

Worked example for a cleaning duty. A 5 kWh usable LFP pack costs 4,000 currency units, delivers 3,500 cycles at the site's depth, so total energy delivered is 17,500 kWh and the cost per kWh delivered is about 0.23. An NMC pack of the same usable energy, at 1,500 cycles, delivers 7,500 kWh at a total cost of 4,500, giving about 0.60 per kWh. The LFP pack is more than twice as economical per unit of work despite a similar purchase price, because it delivers more cycles. An LTO pack at 12,000 cycles and a 9,000 purchase price delivers 60,000 kWh at 0.15 per kWh, but only if the fleet genuinely uses those cycles, which requires the duty to be high-frequency.

Chemistry	Usable kWh	Cycles at site depth	Energy delivered	Total cost	Cost per kWh
LFP	5.0	3,500	17,500 kWh	4,000	0.23
NMC	5.0	1,500	7,500 kWh	4,500	0.60
LTO	5.0	12,000	60,000 kWh	9,000	0.15

The conclusion from the arithmetic is that LTO only wins when cycle count is genuinely high; a low-frequency duty makes its purchase premium unrecoverable. Where to specify these figures in a procurement document is set out in battery pack specification and sourcing, and the overall fleet cost model that this feeds is covered in cleaning robot total cost of ownership.

Charging Behaviour Differences That Change Your Dock Plan

Chemistry choice does not only affect the pack, it affects the charging infrastructure, and that changes the dock plan for the whole fleet. LFP tolerates partial state-of-charge operation and does not require a full charge cycle for balancing as frequently, so it suits opportunity charging, short top-ups between routes. NMC is less tolerant of sitting at high state of charge and prefers a defined charge cycle, which pushes the fleet toward scheduled overnight charging rather than continuous docking. LTO accepts very high charge rates, so it enables a small number of high-power docks serving many packs on rapid turnaround.

The infrastructure consequence is significant: an LFP fleet can be specified with more, lower-power docks and opportunity charging, an LTO fleet with fewer, higher-power docks, and an NMC fleet with a scheduled charge regime that constrains shift design. Charging power planning for those options is covered in fleet charging infrastructure and power planning, and demand-charge implications in fleet demand charge and peak load. Selecting chemistry without modelling the dock plan is how a fleet ends up with the right packs and the wrong charging strategy.

Thermal, Fire and Transport Consequences

Thermal stability differs by chemistry and this is a compliance matter, not only a performance one. LFP and LTO have higher thermal runaway onset temperatures than NMC, which affects the containment strategy, the charging-room design and the fire-suppression specification. The charge-room requirements differ accordingly, and are set out in battery fire safety and charging-room design.

Transport classification also differs. Lithium packs are regulated for transport, and the chemistry and state of charge affect how a pack may be shipped, what documentation is required and whether it can travel by air. This matters for a fleet with packs moving between sites or returning for service, and the compliance gate is described in battery certification and transport. Both considerations should be resolved before a chemistry is locked, because they can rule out an otherwise economic choice.

When to Swap Chemistry Mid-Fleet

A fleet rarely starts with one chemistry and keeps it forever. Three situations justify changing. The first is a duty change: a site that starts with light cleaning and later adds a heavy continuous duty may need to move from LFP toward LTO on the new units. The second is a cold-environment expansion: adding a chilled or outdoor zone to a fleet that was previously all indoor makes the low-temperature performance of LTO or NMC relevant for the new units. The third is pack-availability economics: if a supply constraint makes one chemistry disproportionately expensive, the cost-per-energy arithmetic shifts and the decision should be re-run.

The practical constraint on mixing is that a mixed-chemistry fleet needs per-pack identification and chemistry-aware charging, because a dock that is safe for one pack may not be optimal for another. Charging must be chemistry-aware, which is why cell identification and the BMS register set matter; the communication side of that is covered in battery communication protocols and RS485 integration. A fleet that tracks pack identity and health per unit, as described in battery health and replacement planning, can mix chemistries safely; one that treats packs as interchangeable cannot.

A Five-Line Chemistry Spec

A specification that survives procurement review has five lines. Name the chemistry and justify it against the site's most extreme duty property. Give the usable energy and the realistic cycle count at the site's depth of discharge. Give the continuous and peak discharge rating against the robot's actual draw. Give the operating temperature range against the site's environment. And give the transport classification and charging-room requirement. Those five lines separate a considered specification from a datasheet copy, and they are the lines the pack-specification page recommends for the wider document, applied specifically to the chemistry decision.

How AOMAN Specifies Battery Chemistry

AOMAN specifies battery chemistry per duty, not per model, because the same robot platform can be deployed into a chilled store, a plant room or a sunlit car park and each demands a different pack. We start from the site's duty cycle, depth of discharge and temperature extremes, select the chemistry that is strongest on the binding axis, and then work the cost-per-energy-delivered arithmetic with the operator so the choice is defensible in front of finance. Charging infrastructure is specified alongside, since chemistry and dock plan are one decision. If you are specifying a fleet and want the pack sized to the duty rather than the datasheet, send us the duty cycle and the site conditions and we will model the chemistry against them.