Most of what we build goes to a depot. A site full of vans, a grid connection sized for a warehouse rather than a fleet, and a fairly well understood problem: the vehicles need more power than the site can pull, so you put energy storage between the two. We have done that many times.

Then Tidal Transit asked whether one could charge a boat.

Charging a vessel

Tidal Transit operate crew transfer vessels for the offshore wind sector, the boats that carry technicians out to turbines and back. Electrifying that duty cycle is attractive because the routes are short, repeatable and return to the same berth. Charging one is harder than it looks, for reasons that compound.

Start with size. A van battery is measured in tens of kilowatt-hours. A vessel of this type is an order of magnitude beyond that, so a single charge moves an amount of energy that most quaysides have never been asked to supply.

Then the window. The vessel charges while it is alongside, including overnight, and the amount of energy involved means a trickle will not do it. What the berth needs is real power available whenever the boat is on it, rather than a supply that happens to have headroom at the right moment.

And the berth itself. Quayside electrical supplies were designed for shore power: lighting, hotel load, keeping systems alive while tied up. They were not designed to refuel a ship. Upgrading one means a grid connection application, civils along a working quay, and a timescale measured in quarters rather than weeks.

So the demand is enormous, the window is short, and the supply is small. That is what a buffered charger is for.

Where the conversation started

Tidal Transit had already done the hard part. e-Ginny is a full conversion of a diesel vessel, Ginny Louise, into an electric CTV, alongside the offshore charging infrastructure that goes with it. What was missing was the onshore side.

So the first conversations were open questions. Not which model, but whether a Charge Qube could be made to work at all on a working quay.

A boat wired as a battery

A rapid charger and an electric vehicle hold a conversation before any power moves. The vehicle says what it is, what it can accept, and how it wants to be charged. The charger answers. That handshake is standardised, and everything downstream depends on it working.

This vessel does not present itself as a vehicle. Electrically, it is wired as a battery energy storage system, because from the boat's point of view that is what it is. So a charger arriving expecting to talk to a car finds something that does not answer in the way it expects.

The CQ450's charge control software was adapted to bridge that gap. The unit charges the vessel while presenting the vehicle side of the conversation, so the boat is charged as a battery system by a charger behaving as though it were plugged into a car. As far as we know it is a first for us. It is also the part that took real engineering.

Four weeks

The programme ran roughly like this.

• Week one. Conversations with Tidal Transit about the vessel, the berth, the duty cycle and the schedule, and whether a Charge Qube could be configured to suit. A loose set of requirements rather than a specification.
• Weeks two and three. Build, wiring and testing against the vessel's requirements, with the charge control software adapted to suit.
• Thursday of week four. Delivered to site and commissioned the same day. No groundworks, no connection application, no waiting on the network operator.
• Friday of week four. Charging the vessel at over 160kW, faster than any charger it had been connected to before.
• The following day. Peak output up to 230kW, close to the unit's rated maximum.

The first session ran at over 160kW, already beyond anything the vessel had been connected to. The next day it reached 230kW, against a rated CCS maximum of 240kW. Once the unit and the vessel had settled into each other, the only ceiling left was the hardware's own rating.

Same day commissioning is why four weeks was possible at all. A CQ450 arrives as a 10ft ISO container that is already a complete system, and is designed to be commissioned within a day. If the site work had run to a conventional installation programme, the schedule would have gone whatever the build achieved.

Credit for holding that together belongs to the build side. A loose brief and no slack in the calendar became a build plan that kept wiring and testing on track.

More energy than the unit holds

Over that first weekend the unit put more than half a megawatt-hour into the vessel in a single session.

A CQ450 stores up to 450kWh. So the session moved more energy than the unit contains, which is possible because the unit buffers. While it is discharging into the vessel at high power, it is simultaneously drawing what the quayside supply can give it, and it recharges between and during sessions from that same modest connection.

Capacity figures only tell you half of it. The stored energy sets how hard you can push at any instant, well beyond what the supply alone could deliver. The supply sets how much you can move over a day. A session larger than the battery is the system working as intended.

The quayside connection never had to deliver power at the rate the vessel needs. It only had to keep the unit topped up between sailings, and the unit does the pushing.

Beyond marine

It would be easy to file this under marine. But none of what made it work is specific to boats.

The constraint was a supply too small for the demand, on a site where upgrading it was slow and expensive. That describes most depots we visit. The solution was a unit that arrived complete, was commissioned the day it landed, and put out far more power than the connection behind it could ever have supplied. That is the same product doing the same job it does at a van depot.

The genuinely bespoke part was the software adapting to a load that did not speak the expected language. That flexibility matters more than it sounds. It is the difference between a charger that works for the vehicles it was certified against, and one that can be pointed at an unfamiliar load and made to charge it.

If your site has a load that nothing else will charge, the interesting question is usually not how much energy you need. It is what your connection can support while something else does the pushing.