What is developed, tested and released in the prototype phase
The prototype phase has a clear goal: to eliminate all uncertainties before tooling is ordered, cells are purchased in bulk or certification procedures are initiated. In this phase, cell chemistry and cell type are defined, the BMS is configured and parametrised, the form factor (housing, connector, cooling concept) is structurally secured and the interaction between pack and machine controller is validated.
A functional sample differs from a series sample: it proves the concept works — not that it can be manufactured in series. A build sample therefore typically follows the functional sample, already built with near-series components and manufacturing processes. Only the build sample shows whether tolerance stacks, assembly processes and thermal mass behave as expected in real operation. Releases based on functional samples regularly lead to rework during the small series phase.
At Hellpower, the prototype phase begins with a technical briefing: voltage level, capacity, discharge current (continuous and peak), operating temperature range, ingress protection class, communication protocol and mechanical boundary conditions (envelope, installation orientation, connector side). Only when these parameters are fixed in writing does cell selection begin.
Small series vs. large series: certification, procurement and manufacturing depth
The transition from small series to large series is not a gradual transition — it is a jump in system complexity. In the small series (typically 10–200 units per year), cells can still be sourced from distributor stock, BMS parameters adjusted manually and assembly processes performed manually. Quality assurance is based on complete visual inspection and functional test per pack.
In the large series (from approximately 500 units per year, depending on unit cost), the requirements shift: cells come directly from the cell manufacturer under a framework agreement with defined capacity limits (matching classes); BMS parameters are flashed via an automated flash station; assembly is standardised through fixtures and test adapters; quality assurance includes statistical process control and end-of-line tests with automatic classification.
Certification requirements also differ. For the small series, a UN 38.3 test report (transport testing) on a build sample basis and a CE declaration of conformity under the applicable directive are generally sufficient (LVD 2014/35/EU for battery packs as an electrical product, possibly the Machinery Directive 2006/42/EC or 2023/1230/EU for integrated machinery systems). IEC 62619 (safety requirements for lithium cells and batteries in stationary and motive applications) is de facto mandatory for industrial applications, even without formal certification obligation.
Typical pitfalls in first-time development
Cell discontinuation: Cell manufacturers discontinue cell types sometimes without long notice — especially in the consumer segment from which many industrial cells originate. A custom pack built around a discontinued cell faces the choice: expensive requalification of a replacement cell or production stop. Mitigation: selecting cells from the manufacturer's industrial portfolio (longer product cycles) and a contractually agreed discontinuation notice of at least 12 months.
BMS protocol conflict: The BMS speaks a protocol — CAN with manufacturer-specific PDO mapping, SMBus, RS485 — that the machine controller does not understand or has not fully implemented. This conflict almost always surfaces at the first integration test in the field, not in the lab. Remedy: the communication protocol, message structure (PDOs, register addresses) and timing requirements must be agreed in writing between battery supplier and controller developer before BMS design begins.
Form factor collision: The pack fits geometrically into the intended installation space — but once installed it blocks access to a maintenance point, collides with a cable routing or exceeds the permissible axle load. Such problems arise because CAD models of the pack are integrated into the overall design late. Early handover of a preliminary 3D model (even as a STEP file) to the machine designer prevents most of these collisions.
Missing transport documentation: The first series export fails at customs or with the freight forwarder because UN 38.3 test reports are not available in the required form or are based on a cell type not installed in the delivered pack. UN 38.3 must cover the delivered pack in its final configuration — cell type, arrangement, capacity, housing — not just the individual cell.
Cell selection, BMS integration and form factor in the early phase
Cell selection in the early phase should not be based on a single cell. A shortlist of two to three candidates, electrically and thermally specified and checked for availability, is recommended. Final selection is made after initial sample qualification. Criteria: capacity (nominal value and limits for matching), internal resistance, cycle characteristics (at realistic C rate and DoD), thermal behaviour and supply chain stability.
For industrial applications in the DACH region, two cell chemistries dominate: LiFePO4 (LFP) for applications requiring long cycle life, a wide temperature window and strict safety requirements — typically AGV, automated guided vehicles, stationary storage; and Li-NMC for applications requiring higher gravimetric energy density (Wh/kg) with acceptable cycle life — typically hand-held devices, medical technology, drones. LTO (lithium titanate) is a niche solution for extreme temperature ranges and fast-charge requirements.
BMS integration does not begin with BMS procurement — it begins with protocol definition. Which values must the BMS deliver to the supervisory controller (SoC, SoH, cell voltages, temperatures, fault codes)? Via which protocol (CAN, CANopen, Profinet, SMBus, RS485)? With what timing (cycle time, priority)? These questions must be answered before BMS selection — not after.
The form factor — housing shape, connector side, cooling concept — is determined by the mechanical boundary conditions of the end device, not by the battery supplier. The earlier a binding 3D envelope model is handed over, the fewer iterations are needed. Special attention goes to the connector concept: which interface (voltage, current, signal)? What mating cycle requirement? What ingress protection class (IP)?
Hellpower Energy as development partner
Hellpower Energy GmbH & Co KG develops and manufactures custom lithium battery packs — LiFePO4, Li-NMC and LTO — for OEM and start-up customers at its facility in Hausleiten, Austria. The development process begins with a technical briefing meeting in which requirements, boundary conditions and certification targets are fixed in writing.
Development support covers cell selection and sampling, BMS selection and parametrisation, housing and connector concept, thermal design and the preparation of the required certification documents (UN 38.3, IEC 62619, CE declaration of conformity). For small-series projects with a defined series start date, a structured milestone plan (briefing → specification → functional sample → build sample → series sample → series launch) is standard.
All Hellpower packs carry CE marking. UN 38.3 test reports and IEC 62619 compliance documentation are part of the delivery package. For enquiries regarding prototype and small-series projects: Hellpower Energy in Hausleiten, Austria, via the enquiry form on hellpower.at.
Checklist: Setting up battery pack development correctly from the start
- ✓Technical briefing in writing — voltage level, capacity, discharge currents, temperature range, communication protocol, IP class, envelope fixed?
- ✓Cell selection as shortlist — at least two candidates, supply chain stability and discontinuation risk checked?
- ✓Communication protocol agreed — BMS-side values, message structure and timing coordinated with controller developer?
- ✓3D envelope model handed over — form factor collision and connector position checked before design begins?
- ✓Certification scope defined — UN 38.3, IEC 62619, CE directives (LVD, Machinery Directive) identified for the planned application?
- ✓Milestone plan available — briefing → specification → functional sample → build sample → series sample → series launch scheduled?
- ✓Series supply secured — minimum order quantity, lead time for replacement packs and cell substitution process agreed?
The first four points protect against the most expensive development mistakes. The last three secure series production. We are glad to work through this checklist based on your briefing — before the first cell is ordered.