PDU1 vs PDU3 on the AI-W5.1 — and why neither has a screen
What the PDU1 and PDU3 do in an AI-W5.1 stack, the eight LEDs on the PDU faceplate and what each colour means, and where the settings screen actually is — on the inverter, not on the PDU.
The PDU (Power Distribution Unit) is the module that sits on top of an AI-W5.1-B battery stack. It is a breaker, a set of ports and a row of indicator lights — nothing more. No PDU in the AI-W5.1 range has a screen, a touch display or settings buttons. Everything you configure is set on the inverter.
PDU1 vs PDU3 — which stack takes which
| PDU3 | PDU1 | |
|---|---|---|
| Model code | AI-W5.1-PDU3-B-ESS | AI-W5.1-PDU1-B |
| Sits under | the hybrid inverter head | nothing — it is the top of its stack |
| Used for | the main system: inverter + PDU3 + modules + base | a battery-only expansion cluster: PDU1 + modules + base |
| Role in a multi-cluster system | Master | Slave |
| Built-in breaker | Two-pole moulded case, 250 A, 1000 V | identical |
Deye’s PDU3 quick guide gives three wiring modes: PDU3 + PDU3, PDU3 (master) + PDU1 (slave), and PDU3 (master) + external PCS + PDU1 (slave). In every one of them the PDU3 is the master and carries the inverter; a PDU1 stack never has an inverter on top of it.
Stacking order is base → battery modules → PDU → inverter. The PDU goes over the batteries and the inverter goes over the PDU — the PDU is not a plinth, and it is not the thing you look at.
The eight lights on a PDU
The faceplate carries five blue SOC LEDs plus three status LEDs — eight in total, and that is the entire user interface:
| Indicator | What it shows |
|---|---|
| 5 × blue SOC LEDs | Battery state of charge, 20% per light — 20 / 40 / 60 / 80 / 100% |
| RUN (green) | Working |
| ALARM (yellow) | Alarming |
| ERROR (red) | Protecting / fault |
Deye’s spec tables write the three status lights as “working, alarming, protecting” while the faceplate labels them RUN / ALARM / ERROR. These are the same three LEDs, not six.
Don’t confuse the PDU’s eight with the battery module’s three. Every stacked AI-W5.1-B module has its own RUN / ALARM / ERROR trio and no SOC arc — only the PDU carries the five-segment SOC display.
The one physical button on the PDU is the BMS switch, used to sequence the system on and off. It is not a settings control and it is not a factory reset.
Where the settings actually are
On the inverter’s front panel — not on the PDU. The inverter carries four indicators, four function keys and an LCD, and that LCD is a touchscreen. From its System Setup screen you reach:
- Basic Setup
- Battery Setup
- Grid Setup
- System Work Mode
- Generator port use
- Advanced function
- Li-Batt info
Module addresses need no setting at all — modules auto-network, so there is no DIP switch or address to configure anywhere on the stack.
To read detailed per-pack battery status you have two documented routes, and neither is the PDU:
- Through the inverter — link the first pack’s PCS port to the inverter’s 485 port, switch the inverter to lithium mode, and read the packs on the inverter display.
- Through a PC — connect Deye’s Windows tool to the communication port of any pack.
If someone asks you to “change a setting on the PDU”, the answer is that you can’t. The PDU reports; the inverter controls. Confirm anything you are about to commission against the AI-W5.1-B (PDU1) user manual and the inverter’s own manual.
Cluster limits
A battery-only PDU1 stack takes 1–6 battery modules; the inverter’s own PDU3 stack takes 1–5 (Deye AU brochure, 28 Aug 2026). Up to 6 clusters parallel through the RJ45 IN/OUT daisy chain. Maximum current for a single battery system is 250 A — cable cross-section at least 55 mm². Exceeding 250 A overheats the connectors and cable.
Full figures are on the AI-W5.1 All-in-One BESS page and the AI-W5.1-B battery page; assembly steps are in Stacking AI-W5.1-B battery modules.
