When an electric machine cannot complete its required duty cycle on one charge, an OEM has several options: fit a bigger battery, introduce opportunity charging, or design the machine around swappable batteries.
The right choice depends on more than battery capacity alone. Weight, packaging, charging infrastructure, downtime and the customer’s operating model all influence which architecture makes the most sense. Here the lowest-cost battery is not necessarily the solution that delivers the lowest total cost of operation for the end customer.
This article looks at the main factors OEMs should evaluate when choosing between a larger fixed battery and a swappable architecture, and when each approach makes technical and commercial sense.
How much energy is really needed?
When the design requirement is for the machine to complete a full shift without intermediate charging, the fixed battery needs to cover the most demanding expected duty cycle, including appropriate margins for temperature and battery ageing. For the OEM, that means allocating extra weight and volume to battery capacity, that will only be used during the most demanding operating conditions.
Weight matters more on compact/semi-compact machines than it does on a car. On a compact loader, mower or excavator, every kilogram of battery is a kilogram that reduces the weight available for payload, equipment or other machine functions. It can push the product into a different ergonomic or regulatory class altogether.
A swappable architecture gives the OEM another option: only the required energy for the next operating period is on the machine and store additional capacity off-board in a charging station.
What charging infrastructure will your customer need?
This is where the two architectures really separate. With a fixed pack, the charger has to be sized to the machine’s daily energy divided by the length of a break. With swappable packs, it is sized to the daily energy divided by the length of the night.
Consider a site with six compact machines, each consuming around 10 kWh over a working day. If those machines carry fixed batteries and have to be topped up during a 45 minute break, each one needs roughly 13 kW. If they all break at the same time, which they will, the site has to be able to deliver around 80 kW. On top of that come six chargers and the cabling to reach wherever each machine happens to be standing.
Now put the same 60 kWh through swappable modules, charged overnight on site. Spread over twelve hours, that is an average of 5 kW. Spreading the same energy requirement over twelve hours reduces the average charging demand to around 5 kW, dramatically reducing the peak power required from the site and the machines need no on-board charging hardware at all.
For an OEM this matters, because charging infrastructure can become part of the customer’s purchasing decision. A machine that can be deployed without significant electrical infrastructure upgrades may be easier to introduce across existing sites.
Depending on the site, lower peak charging demand can avoid or reduce the need for grid upgrades, additional cabling or high-power chargers. This can be particularly relevant for temporary worksites or locations where electrical capacity is limited.
The same decoupling has a second effect. Energy charged overnight is charged at night-time tariffs, which implies the charging at a low, steady and battery-friendly rate. Longer charging windows also allow lower charging rates, reducing the need for repeated high-rate opportunity charging. Slow charging under moderate temperature conditions is generally more favourable for lithium-ion cells, removing the compromises in battery life, that can come with repeated fast charging.
Downtime is the number that actually moves the TCO
Nobody solves a longer operating time for a diesel machine with a bigger fuel tank. They kept a jerrycan, to avoid a machine stadstill. The same principle is useful when defining an electric machine: additional runtime does not necessarily have to come from carrying more energy on the machine. Electrification does not change that consideration. An easy to operate, blind-mating, battery module can be exchanged quickly, single-handedly, No tools are needed and the machine does not leave the spot.
A fixed battery pack suitable for fast charging still requires the machine to travel to the charger, stay there, and travel back. Suppose that is 45 minutes a day. Over 220 working days that is ca. 165 hours, or the better part of twenty shifts a year, per machine.
Whatever the internal hourly rate is for a machine and operator, multiplying it by twenty shifts and comparing the result with the price of two spare modules and a charging station is a useful exercise. Depending on the hourly cost of the machine and operator, avoided downtime can become one of the largest contributors to the TCO comparison.
Could one battery platform serve several machines in your portfolio?
For an OEM developing several electrified machines, standardizing around a common battery platform can reduce the number of battery variants, charging systems, interfaces and service procedures that need to be managed. Where different machines are designed around the same battery and docking interface, the customer’s battery inventory can also be shared across compatible equipment.
A fixed pack is idle whenever its machine is idle, which on a mixed fleet is most of the time. A standardized swappable module is not. The same 48V module can move between a compactor in the morning, a light tower in the evening and a mini-excavator the following week.
That has three consequences worth putting into a business case:
- The fleet of battery packs can be smaller than the machine fleet,
because the battery packs follow the work rather than the asset - One set spares, chargers, training & service procedures instead of one set machine type
- When a machine reaches the end of its life, the battery packs do not go with it, but they carry their remaining value to the next machine
Interchangeability requires the battery pack, docking interface, charging system and machine integration to be considered together from the beginning of development.
When is a bigger fixed pack still the better choice?
Battery swapping is not the answer to everything. There are clear cases in which a single larger fixed pack is both the better engineering and the better economics:
Many characteristics found in construction and agricultural equipment are particularly suitable for battery swapping.
Once an OEM has established that a swappable architecture fits the application, the next question is how to implement it without developing a new bespoke battery ecosystem. Cleantron’s modular battery platforms are designed to address this integration challenge.
How Cleantron supports a modular battery architecture
All Cleantron swappable modules are 48 V and support Multi Pack Configuration (MPC), the masterless parallel architecture that allows up to sixteen modules to work together.
For OEMs that are still defining the machine’s duty cycle or evaluating fixed versus modular battery concepts, P4P provides flexibility because the same battery platform can support both approaches.
The CLP, weighing only 9 kg, is designed for applications where compact dimensions, low module weight and quick manual exchange are important. Its blind-mating interface, machine docking station and charging solution allow the battery to be considered as a complete integration system rather than an isolated pack.
For OEMs developing machines for construction, agriculture and other demanding outdoor environments, CLP XL extends the swappable architecture to applications where dust, dirt and humidity place greater demands on the battery system. It comes with an on-board docking station for integration into the construction or agricultural machine and an off-board charging station. At 13,5 kg, it allows single-handed exchange in a professional environment and it is available in three variants:
- The standard CLP XL,
- The higher-capacity CLP XLe, suitable for applications where longer runtime is the priority
- The high-current CLP XLp for machines with higher peak-power requirements
Cleantron’s MPC Battery Management is what makes the architecture scale. A machine that needs more capacity takes more of the same battery packs, rather than a different battery. Combined with the adaptive charging algorithms, which sets the charging current and the end-of-charge voltage based on the measured temperature, State of Charge and State of Health of the pack, the battery packs are charging quietly overnight aging more slowly compared to repeated opportunity charging.
Conclusion
The question worth asking is not how big the battery should be, but where the energy is needed.
For an OEM, the right battery architecture is the one that combines the machine’s technical requirements with the way customers will actually use, charge and maintain it.
Where a fixed battery pack is sized for the worst day of the year, a swappable battery system gives just enough on the machine to get through.
Wherever the cost of swappable battery packs is lower than the cost of the fixed battery, a heavier machine, a heavier grid connection and the hours lost standing at a charger, the swappable battery pack is not only the more flexible choice; it is also the cheaper one.
Fixed or swappable for your application?
If you are defining the battery architecture of your new electric machine, then share your required runtime, duty cycle, available charging window and power requirements with our engineering team.
