Battery Telemetry and the Data Contract Behind a Claim
The Battery Claim You Cannot Make Without Records
A battery claim is decided by evidence about what the pack did, not by how the machine now behaves. Two fleets can present the same symptom, a cleaning robot that finishes 30 percent less area per charge in month 26 than it did in month 3, and receive different answers from the same vendor. In one case the pack averaged 1.1 equivalent full cycles a day, was almost always charged inside a 20 to 85 percent band, and spent its working life at moderate ambient temperature. In the other it averaged 1.8 cycles a day, was routinely deep-discharged, and spent every August in an unventilated plant room at 41 degrees. Both packs now deliver 68 percent of rated capacity. Only the first is a warranty matter.
None of that can be established after the fact. The BMS counted it, or nobody did. That is why the telemetry fields in a battery contract matter more than the capacity guarantee printed beside them: the guarantee is only as collectable as the record that demonstrates when it was breached.
The Fields That Decide a Battery Claim
A battery management system exposes far more than most operators ever retrieve. The useful subset is small, and each field exists because it answers a question that arises in a claim, an accounting entry or a resale conversation.
| Field | Typical unit | Decision it supports | Retention needed |
|---|---|---|---|
| Equivalent full cycles | count | Whether the pack is inside the warranted cycle life | Whole life, cumulative |
| State of health | % of rated capacity | Threshold breach under the capacity clause | Monthly minimum, daily preferred |
| State of charge at charge start and end | % | Whether duty cycle or charging practice caused degradation | Every charge event |
| Pack and cell temperature, max and mean | degrees C | Thermal abuse exclusion clauses | Every charge and discharge event |
| Charge and discharge current, peak | amperes | Whether specified limits were exceeded | Event-level peak capture |
| Voltage spread across cell groups | millivolts | Cell imbalance, the earliest sign of a failing group | Daily |
| Fault and protection event log | coded events | Over-current, under-voltage, over-temperature history | Whole life |
| Energy throughput in and out | kWh | Operating cost allocation and scope 2 accounting | Monthly minimum |
Two of these deserve emphasis because they are the ones buyers most often forget to secure. The charge event record, with state of charge at the start and end of each charge, is what distinguishes a pack that was managed well from one that was not; without it, a vendor can attribute degradation to buyer practice and the buyer has no rebuttal. The protection event log is what shows whether a pack was ever driven into a condition the specification prohibited, which is the usual basis for a warranty exclusion.
The measurement definitions behind these fields, and the thresholds that decide whether a claim passes, are set out in battery health and replacement planning and battery warranty, cycle life and claim evidence.
Reading the Register Map Out of the Vendor
Every industrial battery BMS speaks a bus protocol, most commonly RS485 carrying Modbus RTU, sometimes CAN with a manufacturer-specific frame layout. The practical question in procurement is not which protocol is used but whether the register map is documented and stable. Three tests establish that in a single meeting, and all three should be in writing before the order.
- Ask for the map itself, not a sample. A vendor supplying a documented register map provides a table of addresses, data types, scaling factors and units. A vendor offering a "telemetry API" instead is offering a product, not documentation, and the product may change.
- Ask for the polling impact. A 30 second poll cycle across the fields above is a few hundred bytes per pack per interchange, which is trivial for a building network but not trivial for 40 packs on a shared RS485 segment with a slow device. Get the recommended poll interval and the maximum supported node count per segment in writing.
- Ask what happens when the BMS is replaced. Packs get serviced, boards get swapped, and a replacement BMS with a different firmware revision can rename registers. The contract should require that any register change is notified and that the previous map remains readable for the life of the fleet.
The field-level details of these two buses, including the register classes that map to the quantities in the table above, are covered in battery communication protocols. The pack specification side, including the difference between a pack sold as a component and one sold as part of the machine, is in battery pack specification and sourcing.
Who Owns Telemetry, and Why the Answer Must Be Contracted
Telemetry ownership is usually granted in the sale of the machine and then quietly limited in the software licence. A contract may state that all data generated by the fleet belongs to the buyer, while the only mechanism for retrieving it is a dashboard account that terminates with the service contract. The ownership statement is then worth nothing at exit, because the buyer never had the extraction route.
Four provisions convert ownership from a statement into a capability, and each is worth arguing for individually:
| Provision | What to demand | Why it fails without it |
|---|---|---|
| Bulk export | Full-history export of all fields above, in a documented machine-readable format, at any time on request, without charge | A dashboard screenshot is not evidence; a support ticket becomes the only extraction route |
| Export schema | Field definitions, units, sampling interval and timestamp format documented in the contract annex | A CSV of unexplained columns cannot be used to prove a threshold breach |
| Post-termination access | Export rights for 90 days after any termination, including for cause | Disputes arise at exit, exactly when access is removed |
| Direct read access | The buyer's own systems may poll the documented API or the local bus, not only the vendor cloud | Vendor cloud dependency converts a data right into a subscription |
The exit mechanics of a fleet contract, including how data export sits alongside buy-out and spares obligations, are examined in contract renewal and exit terms. The commercial framing of data as an asset, including API access levels, is in data ownership and API interoperability.
Telemetry as an Accounting and Residual-Value Asset
Battery telemetry stops being an engineering nicety when the fleet reaches the balance sheet. Three finance processes need the same record, and each currently gets it — if at all — from a different, unreliable source.
Operating cost allocation. Energy consumed per site, per unit and per shift is a direct cost, and sub-metering a charging dock is expensive and imprecise compared with reading energy throughput from the BMS. A fleet of 30 scrubbers drawing roughly 6 kWh of charge per productive hour is a material line at any commercial tariff, and the split between sites will be contested by site managers until there is a measured figure. The tariff mechanics and the demand-charge interaction are covered in electricity cost for service robots and fleet demand charges and peak load.
Depreciation and impairment. A pack's remaining useful life is a state-of-health curve, and the accounting treatment is only defensible if the curve is measured rather than assumed. An asset carried at a five year life while the measured state of health predicts replacement at month 44 is an impairment that surfaces through an unplanned capital request.
Resale and second life. A used pack with a documented cycle history sells for more than an identical pack with no history, because the buyer is purchasing a known quantity. The resale arithmetic, and the leasing structures that depend on it, are in battery second life and residual value. A fleet owner who cannot produce a cycle count has effectively made the pack unremarkable at disposal.
The Data Clause to Attach to the Order
The following is short enough to insert in a purchase annex and specific enough to be enforceable. Each item is stated as a deliverable rather than a principle.
- A register or field map, versioned and dated, delivered before shipment and updated in writing at least 30 days before any change takes effect.
- Full-history export on request in an open format such as CSV or JSON, with field names, units and sampling intervals defined in the same annex.
- No charge for export, no minimum plan, and no requirement to renew a service contract to receive historical data.
- On-premise read access to the documented bus or a local API, so an operator can capture data without routing through a vendor cloud.
- Retention obligation of at least 24 months in the vendor system, plus the buyer's own retention of the full history for the life of the asset.
- Assignment on transfer of the data and the access rights if the fleet or the site is sold, which is the provision that matters in an asset sale.
- A named contact and a response time for data extraction requests, typically five working days, with the remedy stated if it is missed.
Read together, these terms do one thing: they ensure that the buyer, not the vendor, holds the evidence needed to claim a warranty, allocate a cost and value a used asset. That is a commercial position worth more than a slightly higher capacity guarantee, because a guarantee without records is a promise about the future rather than a claim on it.
Starting the Record on Day One
Telemetry that is not collected from commissioning cannot be reconstructed later, and the first ninety days are the most valuable because pack behaviour is still close to its rated baseline. Three practical steps set the record up correctly.
- Capture a baseline state-of-health reading at commissioning for every pack, serialised to the unit and archived outside the vendor system.
- Set the polling interval deliberately. Daily state-of-health and voltage spread, plus every charge event, is enough for claims and accounting; minute-level current logging is only needed for a fault investigation.
- Store the export in the buyer's own system on a fixed schedule, monthly at minimum, so that a terminated contract cannot take the history with it.
Doing this on a fleet of ten units takes under a day at commissioning and removes the single most common reason a legitimate battery claim fails. For pack specifications, BMS interfaces and the telemetry fields available on our fleets, see the AOMAN C1 scrubber and AOMAN C2 Pro, or contact us for the register map and export schema ahead of an order.
