DC fast chargers are rarely built as one converter sized exactly to the nameplate. Manufacturers assemble the rating from standard power modules — commonly 20 kW, 30 kW or 40 kW blocks wired in parallel — so the charger’s output is the sum of its blocks. The block size a manufacturer standardises on shapes the ratings it can offer, what happens when a module fails, and which spare parts the whole range shares. Engineering buyers comparing manufacturers should read the range through its blocks.
Key Takeaways
- Charger ratings are sums: output equals block size multiplied by block count.
- Block size sets rating granularity and the size of the step lost in a failure.
- One shared block across a range means one shared spare — a real service saving.
- Fault behaviour and block size are specification questions; get both in writing.
One Block, Many Ratings
The U.S. DOT puts public DC fast charging at roughly 50–350 kW, and almost every rating in that span is a multiple of a maker’s block size. A single module design can serve an entire product family: cabinets differ in how many blocks they hold, while the block, its connectors and its service procedure stay the same.
| Charger rating (illustrative) | 20 kW blocks | 30 kW blocks | 40 kW blocks |
|---|---|---|---|
| 60 kW | 3 | 2 | Not a multiple |
| 120 kW | 6 | 4 | 3 |
| 240 kW | 12 | 8 | 6 |
The consequences go beyond arithmetic. Smaller blocks give finer rating steps — a maker can offer 60, 80 and 100 kW from the same parts bin — and each failure removes a smaller slice of output. Larger blocks mean fewer parts to purchase, rack, wire and cool, and a simpler cabinet. Neither is a quality signal by itself.
What Happens When One Block Fails
Because blocks share the load, one failure removes one block’s share — provided the design lets the rest keep running. In an illustrative 120 kW charger built from four 30 kW blocks, losing one leaves 90 kW; built from three 40 kW blocks, the same failure leaves 80 kW. Some designs carry extra capacity so the full nameplate output survives a single failure; others simply derate and report the fault. Which behaviour a model has is a specification question, and the answer belongs in the quotation: ask what the charger delivers with one module out, and how the operator platform is told.
Spares and Service Planning
For distributors and fleet buyers, block strategy becomes a stocking strategy:
- Same block across the range: one spare on the shelf can cover several models.
- Field-replaceable blocks: ask whether a trained technician swaps a module on site, and what the swap involves.
- Documented fault behaviour: derating, alarms and shutdown should be described in the model documents, not discovered in service.
- Long-term availability: modules are model-specific parts, so confirm spare supply and warranty terms for the model’s service life.
A range built on one block is cheaper to support than the same range built on three — a difference that rarely appears on the price list but always appears in the service budget.
EVDANCE and Module Questions
EVDANCE builds its chargers in Shenzhen and exports to more than 30 countries. Its compact DC model, the EV-RHDC30K-L, is listed at 22 kW with OCPP 1.6J — the small end of the DC span, where a compact cabinet holds only a few blocks. The published listing does not state the internal block size, and buyers comparing module strategies should ask for it in the model documentation rather than assume it. Module and range questions can be sent through the OEM program or the contact page.
Frequently Asked Questions
Is a charger with more, smaller modules better?
Not automatically. More blocks mean finer steps and a smaller loss per failure, but more parts to buy, rack and wire. Fewer, larger blocks simplify the cabinet. Match the choice to the ratings you sell and the service model you run.
Do all models from one manufacturer use the same block?
Often a family does, but a range can span generations and power classes built on different blocks. Map it before you stock spares: ask which block each model uses, and where one spare covers more than one model.
Are power modules interchangeable between manufacturers?
No. A block’s connectors, control interface and cooling are matched to its charger family. Treat modules as model-specific service parts sourced from the original manufacturer.
Related Reading
- How Do DC Fast Chargers Work?
- How Fast Is a DC Fast Charger?
- Is DC Fast Charging Level 3?
- Level 1 vs Level 2 vs DC Fast Charging: A Practical Comparison
