High-voltage battery design involves considerably more than connecting enough cells in series to achieve a target voltage.
As industrial equipment moves toward higher power requirements, architectures such as 400V and 800V can provide important advantages. Higher system voltage allows a given amount of power to be delivered at lower current, which can influence cabling, connectors, electrical losses and thermal demands.
However, increasing voltage also changes the requirements of the wider electrical system.
The battery, Battery Management System (BMS), inverter, motor, charger, contactors, protection devices, communications and safety architecture all need to work together.
Effective high-voltage battery design therefore starts with the application—not the battery.
The objective is to develop the right electrical architecture for the equipment's power, energy, operating and integration requirements, while ensuring that safety, thermal management and validation are considered from the beginning.
There isn't one universal voltage at which every industrial battery becomes “high voltage.” Definitions can vary depending on the application, standards and regulatory context.
From an engineering perspective, however, increasing system voltage introduces additional considerations around electrical isolation, protection, component selection, service procedures and integration.
For demanding industrial and mobility applications, 400V and 800V architectures are increasingly relevant where substantial continuous or peak power needs to be delivered efficiently.
The appropriate voltage should always be selected around the application.
Higher voltage isn't automatically better.
Instead, it becomes valuable when the equipment's power requirements, charging strategy and wider electrical architecture justify it.
The relationship between power, voltage and current can be expressed simply as:
Power = Voltage × Current
For a given power requirement, increasing voltage reduces the current required.
Consider a simplified 160kW application:
80V → approximately 2,000A
400V → approximately 400A
800V → approximately 200A
Actual battery voltage and current vary with state of charge, load and system conditions, but this illustrates why higher-voltage architectures become increasingly relevant as power requirements rise.
Very high current can create challenges around cabling, connectors, contactors, heat generation and electrical losses.
A higher-voltage architecture can therefore provide significant engineering advantages in the right application.
But those benefits have to be considered alongside the additional requirements associated with high-voltage system design.
400V and 800V aren't interchangeable solutions.
Each architecture needs to be evaluated against the powertrain, charging requirements, component ecosystem and intended duty cycle.
A 400V architecture can provide an effective balance for many high-power industrial and mobility applications.
Compared with lower-voltage architectures, it can substantially reduce the current required to deliver high levels of power while providing access to an established ecosystem of high-voltage motors, inverters, chargers and related components.
Depending on the application, 400V can therefore provide an appropriate architecture for equipment with demanding continuous and peak-power requirements.
An 800V architecture can become relevant as power and charging requirements increase further.
At a given power level, doubling voltage from 400V to 800V approximately halves the required current.
This can provide advantages where very high power needs to be transferred between the battery, inverter and motor, or where high charging power is an important part of the operating strategy.
However, the complete system must be designed around the higher voltage.
Motors, inverters, chargers, DC/DC converters, connectors, contactors, cabling, insulation monitoring and protection systems all need to be suitable for the selected architecture.
An 800V battery therefore shouldn't be viewed simply as a higher-voltage version of a 400V battery.
It is part of a complete 800V electrical architecture.
High-voltage battery design requires multiple requirements to be considered simultaneously.
The important point is that these aren't independent design decisions.
Changing one can influence several others.
As battery voltage increases and more cells or modules are connected in series, battery management becomes increasingly important.
The BMS needs visibility across the battery system while providing the monitoring, protection and control required by the application.
Depending on the battery architecture, this can include:
For high-voltage systems, the BMS also forms part of a wider safety and control architecture.
It may need to interact with components and systems responsible for high-voltage isolation, contactor control, pre-charge and emergency shutdown.
Communication with the equipment is equally important.
The battery doesn't operate independently—it needs to exchange information with the inverter, charger, vehicle or machine controller and other relevant systems.
High-voltage battery management therefore needs to be considered as part of the complete equipment architecture.
Moving to high voltage introduces additional electrical safety considerations.
The exact requirements depend on the application and applicable standards, but areas that may need to be addressed include:
These considerations need to be incorporated into the architecture from the beginning.
Trying to add high-voltage protection after the battery and powertrain have already been designed can result in unnecessary redesign and integration challenges.
Safety architecture should be part of system architecture.
Higher voltage reduces current for a given power level, but high-power batteries can still generate significant heat during operation and charging.
Thermal management therefore remains a fundamental part of high-voltage battery design.
Engineers need to understand how temperature develops throughout the pack under representative operating conditions.
This can include evaluating:
The appropriate thermal strategy depends on the application.
Some battery systems may be able to use relatively simple thermal approaches, while demanding high-power applications can require more sophisticated active thermal management.
Cell selection, module design, power requirements, charging strategy, enclosure design and cooling should therefore be considered together.
Battery voltage and charging architecture are directly connected.
A 400V or 800V battery requires charging equipment designed to operate with the battery's voltage range, current requirements and communications.
But maximum charging power shouldn't be considered in isolation.
The real question is:
How quickly does the equipment actually need to recover energy?
That depends on:
For some applications, very high charging power may be essential because equipment has limited time between operating cycles.
For others, a longer charging window can make a lower charging rate entirely appropriate.
The battery and charger should therefore be developed as part of the same energy strategy.
A high-voltage battery can perform correctly on a test bench and still fail to meet the needs of the final application if integration hasn't been considered properly.
The battery may need to operate with:
Battery → Inverter → Motor
while also communicating with:
Charger + Vehicle Controller + DC/DC Systems + Thermal System + Telematics
Each interface needs to be defined and validated.
This includes electrical characteristics as well as communication and control behaviour.
For OEMs, this is one of the reasons why involving the battery engineering team early in the equipment development process can be valuable.
Decisions made around voltage, powertrain components, charging and packaging can significantly influence the eventual battery architecture.
The battery needs to be designed around how the equipment actually operates.
Average power alone rarely provides enough information.
Engineers may need to understand:
This information helps determine the appropriate voltage, cell chemistry, module configuration, energy capacity and thermal strategy.
For high-power applications, understanding peak loads can be particularly important.
A battery capable of providing sufficient average energy may still be unsuitable if it cannot repeatedly provide the peak power required by the equipment.
High-voltage battery validation shouldn't begin once the design is complete.
Testing should form part of the development process.
Depending on the application, validation can include:
Testing the battery in isolation is only part of the process.
The battery also needs to be validated as part of the complete equipment architecture, including its interaction with the inverter, motor, charger and control systems.
The objective is to demonstrate that the complete high-voltage system operates as intended—not simply that the battery reaches the required voltage.
Lithion develops high-voltage lithium-ion battery systems around the requirements of the application, including 400V and 800V architectures for demanding industrial and mobility applications.
Our development process starts by understanding the equipment:
What power does it need?
How much energy does it consume?
What are the peak loads?
How will it be charged?
What environment will it operate in?
How does the battery need to communicate with the equipment?
These requirements inform the battery architecture, cell and module configuration, BMS, thermal management, mechanical design and electrical interfaces.
Lithion's proprietary Battery Management System technology can provide monitoring, protection, control, data logging and communications as part of the wider battery architecture.
Our engineering teams support customers from initial requirements and feasibility through system design, prototyping, validation, integration and production.
This means high-voltage development isn't approached as an isolated battery project.
It is approached as a complete system engineering challenge.
Selecting 400V or 800V doesn't define a successful high-voltage battery system.
The voltage needs to make sense for the power requirement, while the battery needs to work correctly with the powertrain, charger, controls, thermal system and operating environment.
For OEMs developing increasingly powerful electric equipment, having a battery partner capable of considering all of these requirements together can simplify the development process.
The principle is straightforward:
Choose the voltage around the application.
Design the battery around the duty cycle.
Engineer the battery, BMS, charger and powertrain as one system.
That's what turns a high-voltage battery into a high-performance battery system.