What Problem Are You Actually Trying to Solve?

Peak power and total energy are different problems. A battery may help a site manage a short demand peak by supplementing the grid for a limited period. It cannot compensate for a connection that is too small to deliver the total energy the fleet needs overnight.

Grid connection delay is a separate issue. Where a DNO upgrade will take longer than the fleet project allows, a battery-based interim arrangement may help the depot begin operating at a controlled capacity before permanent infrastructure is available. The result depends on the load profile and the agreed system design.

Energy cost and resilience may also be relevant. Time-of-use tariffs can create opportunities for energy shifting, while battery storage may provide limited backup capability in a suitably designed system. Neither benefit should be assumed without modelling the site.

When Battery Storage May Make Sense

Battery storage is worth investigating when vehicles return within a narrow window and the existing connection can support normal charging but not the temporary peak. The battery can then support the chargers while the site remains within its agreed grid limit.

It may also suit a depot expanding in phases. Storage can extend the useful capacity of an existing connection while the fleet grows, particularly where a grid upgrade is expensive, delayed or uncertain. The business case is stronger when the peak is short, predictable and repeated often enough to justify the investment.

When It May Not Be the Right First Investment

Before commissioning a battery study, check whether simpler changes could solve the constraint. Managed charging may reduce the peak by deciding when each vehicle charges. A detailed grid capacity assessment may reveal more headroom than expected, or a modest connection upgrade may cost less than a battery system.

Distributed charging can also change how equipment and power are arranged across the depot. These options should be compared with storage rather than treated as unrelated decisions. A battery is most useful when it addresses a clearly defined site constraint.

Compare Battery Storage with a Grid Upgrade

Start with the numbers that describe the operating problem:

• Required charging power during the critical period, in kW
• Total energy required during that period, in kWh
• Available grid capacity and any DNO restrictions
• How long the peak lasts and how often it occurs
• The quoted cost and timeline for a grid upgrade
• Expected fleet growth and future charging demand
• Battery capital, maintenance, efficiency and degradation assumptions

As the peak lasts longer or total energy demand increases, the case for a larger grid connection usually becomes stronger. A battery should be compared against the full project cost, including controls, installation, maintenance and future replacement requirements.

A Hypothetical Fleet Depot Example

Consider a depot with twenty electric vans returning between 17:00 and 19:00 each weekday. The existing connection can support ten 7kW chargers at the same time, while all twenty vehicles charging together would require 140kW.

The operator could manage the charging schedule, request a DNO upgrade or use battery storage to support the two-hour peak. If vehicles can charge over a longer overnight window, managed charging may be the lowest-cost solution. If all vehicles must be ready by 06:00 and the connection cannot support the required load, storage or a grid upgrade becomes more relevant.

This is a hypothetical illustration. Actual sizing depends on vehicle energy demand, charging losses, departure times, connection limits and the design of the complete system.

How Storage Works Alongside EV Chargers

A battery does not improve depot charging on its own. Its value comes from the interaction between the grid connection, battery, energy management controls, chargers, vehicle schedules and site operating rules.

The control system must determine when to charge the battery, when to discharge it to support vehicle charging and how to respond to changing demand. Without suitable control logic, the battery may not deliver the peak shaving or energy shifting that justified the investment.

Where HanCang May Fit

Injet HanCang can be considered where battery storage, fleet charging demand and site grid constraints need to be assessed together. The containerised hybrid energy storage system integrates energy storage, PCS, an EMS and a diesel generator set, and can work with solar PV and grid input within the configured system.

This type of integrated approach may be relevant where grid access is constrained, delayed or uncertain, or where a project requires a defined level of supply resilience. The appropriate capacity and operating mode still depend on a site-specific load profile, technical design and project requirements.

HanCang is therefore part of the assessment, not a substitute for understanding the depot's actual energy and power needs.

Let the Load Profile Lead the Decision

Battery storage is a useful tool for specific depot constraints. It is not a default addition to every fleet charging project, and it does not automatically remove the need for grid reinforcement or reduce energy costs.

The right starting point is to understand when vehicles arrive, when they must depart, how much energy they need and what the existing connection can support. From there, managed charging, a grid upgrade and battery storage can be compared as practical engineering and commercial options.