A battery-buffered DC charger keeps a stationary battery between the grid connection and the car. While no car is charging, the grid refills that battery slowly, at a rate the connection can easily supply. When a car plugs in, the battery and the grid feed the session together, so the car receives fast-charging power that the site’s connection alone could never deliver in real time.
Key Takeaways
- A battery-buffered charger stores grid energy between sessions and releases it fast during a session.
- The grid connection can be much smaller than the charger’s peak output — that is the point of the design.
- The buffer is finite: back-to-back fast sessions drain it, and delivery falls back toward the grid rate.
- EVDANCE sells grid-fed chargers only; no EVDANCE unit has a battery buffer.
The Parts of the System
An ordinary DC fast charger is a pass-through machine: it converts grid AC to DC and delivers it as the car asks for it, which is why commercial charging stations need a grid connection as large as the charger itself. A buffered design adds one more component:
| Part | Its job |
|---|---|
| Grid connection | Supplies a steady, modest flow of power — sized well below the charger’s peak output |
| Buffer battery | Stores that flow between sessions, then releases it quickly during a session |
| Power electronics and dispenser | Combines battery and grid power, converts it to the DC the car requests, and runs the session |
| Control system | Decides how much comes from the battery and how much from the grid, moment by moment, and protects the battery |
A Session, Step by Step
- Idle: with no car connected, the grid side works on refilling the battery. This is the state the station sits in most of the day.
- Arrival: a car plugs in and the charger runs the usual checks and handshake, exactly as a conventional fast charger does.
- Delivery: the car asks for high power. The grid contributes what it can and the battery supplies the rest, so the car sees a rate the connection alone could not support.
- Finish: as the car’s own charge rate falls toward the end of the session, the draw on the battery falls with it.
- Recovery: the car leaves and the grid goes back to refilling the battery for the next arrival.
The U.S. DOT’s charger types and speeds page sets the context: DC fast charging sits in the 50–350 kW band. Buffering is a way of reaching into that band from a smaller connection.
The Honest Limit: Buffers Run Down
The battery holds a finite amount of energy, and a fast session spends it far faster than the grid side replaces it. One car, or a few cars spaced through the day, is exactly the pattern the design serves. Cars arriving back-to-back, each asking for a full fast session, drain the buffer — and once it is empty, delivery falls back toward what the grid connection alone can supply until the battery recovers.
That is why the useful question for any buffered-charger maker is not the headline power but the duty pattern behind it: how the unit behaves across a busy hour, stated in writing. The installed cost of a commercial station also changes shape — more of the budget sits in the charging system, less in the connection work.
What EVDANCE Sells Is Grid-Fed
EVDANCE does not sell a battery-buffered charger, and no EVDANCE listing claims one. Its DC unit, the EV-RHDC30K-L compact DC charger (22 kW DC, OCPP 1.6J, IP54), is a conventional grid-fed machine: it converts and delivers supply power in real time, sized for depots, workplaces and destinations where cars park longer and a large connection is not the point. The wider range is on our commercial EV charging page. If a buffered system is the right answer for your site, it will come from a supplier that builds them — the mechanism above is what to check their claims against.
Frequently Asked Questions
Is the battery inside the charger or beside it?
Both layouts exist: some integrate the battery in the cabinet, others pair the dispenser with a separate battery unit on the same site. Either way, the battery is part of the system the operator buys — never inside the car or the plug.
Does a battery-buffered charger work during a power cut?
Do not assume so. The buffer is sized and managed for session support, not for backup duty, and whether a given system can charge through an outage is a written specification to confirm with its manufacturer — not a property of the category.
Can I add a battery to my existing DC charger?
Buffering is a system design, not an accessory: the charger, battery and controls are engineered together. A separate site battery installed alongside existing chargers is a different project, specified and warranted on its own.
Related Reading
- How Do Commercial EV Charging Stations Work?
- How Much Does It Cost to Install a Commercial EV Charging Station?
- How Much Do Commercial EV Chargers Cost?
