# MUST PV1800 register map

Derived from the manufacturer protocol document
`PH1800 PV1800 EP1800 PV3500 EP3500 RS485 Modbus RTU communication Protocol 1.4.15.xlsx`
shipped in the [taHC81/MUST-ESPhome](https://github.com/taHC81/MUST-ESPhome)
GitHub repo. Only the registers this monitor reads are listed here;
the full document covers hundreds more.

All values are Modbus RTU holding registers (function code 0x03),
unless otherwise noted. RO = read-only, RW = read/write.

The monitor reads everything below as contiguous blocks:
- CHARGER block: 15201..15221 (with gaps at 15204, 15213, 15214)
- INVERTER block: 25201..25275 (with gaps at 25204, 25220, 25224, 25227, 25228, 25232, 25236, 25243, 25244, 25262..25272, 25276)
- SETTINGS: two short contiguous reads at 10103..10104 and 20118..20132

The firmware ignores the `count` field and dumps the entire block
regardless, so the monitor always asks for the widest range that
covers what we care about.

---

## CHARGER block (start at 15201)

| Addr | RO/RW | Name | Unit | Notes |
|------|-------|------|------|-------|
| 15201 | RO | Charger workstate | — | decoded: Init / SelfTest / Work / Stop |
| 15202 | RO | MPPT state | — | decoded: Stop / MPPT / Current limiting |
| 15203 | RO | Charging state | — | decoded: Stop / Absorb / Float / EQ |
| 15204 | RO | reserved | | |
| 15205 | RO | PV voltage | 0.1 V | |
| 15206 | RO | Battery voltage (charger side) | 0.1 V | |
| 15207 | RO | Charger current | 0.1 A | |
| 15208 | RO | Charger power | W | |
| 15209 | RO | Charger radiator temperature | 1 °C | |
| 15210 | RO | External temperature | 1 °C | |
| 15211 | RO | Battery Relay | bool | 0=Open, 1=Closed |
| 15212 | RO | PV Relay | bool | 0=Open, 1=Closed |
| 15213 | RO | reserved | | |
| 15214 | RO | reserved | | |
| 15215 | RO | Battery voltage grade | V | 12, 24, or 48 |
| 15216 | RO | Charger rated current | 0.1 A | |
| 15217 | RO | Accumulated PV energy MWh part | MWh | combine with 15218 for total kWh |
| 15218 | RO | Accumulated PV energy kWh part | 0.1 kWh | combine with 15217 for total kWh |
| 15219 | RO | Accumulated runtime days | days | |
| 15220 | RO | Accumulated runtime hours | hours | |
| 15221 | RO | Accumulated runtime minutes | minutes | |

The accumulated energy at 15217+15218 combines as `total_kWh = 15217 * 1000 + 15218 * 0.1`.

---

## INVERTER block (start at 25201)

### Operating state & configuration

| Addr | RO/RW | Name | Unit | Notes |
|------|-------|------|------|-------|
| 25201 | RO | Work state | — | decoded: PowerOn / SelfTest / OffGrid / GridTie / ByPass / Stop / GridCharging |
| 25202 | RO | AC voltage grade | V | 230 or 120 |
| 25203 | RO | Rated power | VA | |
| 25204 | RO | reserved | | |

### Voltages

| Addr | Name | Unit |
|------|------|------|
| 25205 | Battery voltage (inverter side) | 0.1 V |
| 25206 | Inverter voltage | 0.1 V |
| 25207 | Grid voltage | 0.1 V |
| 25208 | BUS voltage | 0.1 V |

### Currents

| Addr | Name | Unit |
|------|------|------|
| 25209 | Control current | 0.1 A |
| 25210 | Inverter current | 0.1 A |
| 25211 | Grid current | 0.1 A |
| 25212 | Load current | 0.1 A |

### Power (real / apparent / reactive)

| Addr | Name | Unit |
|------|------|------|
| 25213 | PInverter | W (signed in our script) |
| 25214 | PGrid | W (signed; negative = exporting) |
| 25215 | PLoad | W (signed) |
| 25216 | Load percent | % |
| 25217 | SInverter | VA (signed) |
| 25218 | SGrid | VA (signed) |
| 25219 | SLoad | VA (signed) |
| 25220 | reserved | |
| 25221 | Qinverter | var (signed) |
| 25222 | Qgrid | var (signed) |
| 25223 | Qload | var (signed) |

### Frequencies

| Addr | Name | Unit |
|------|------|------|
| 25225 | Inverter frequency | 0.01 Hz |
| 25226 | Grid frequency | 0.01 Hz |

### Temperatures

| Addr | Name | Unit |
|------|------|------|
| 25233 | AC radiator temperature | 1 °C |
| 25234 | Transformer temperature | 1 °C |
| 25235 | DC radiator temperature | 1 °C | (often 0 on units without that sensor) |

### Relays

| Addr | Name | Notes |
|------|------|-------|
| 25237 | Inverter relay | 0=Disconnect, 1=Connect |
| 25238 | Grid relay | |
| 25239 | Load relay | |
| 25240 | N_Line relay | |
| 25241 | DC relay | |
| 25242 | Earth relay | |

### Energy accumulators (each is a HIGH+LOW pair)

| Addr | Name | Scale |
|------|------|-------|
| 25245 | Acc charger MWh part | 1000 kWh |
| 25246 | Acc charger kWh part | 0.1 kWh |
| 25247 | Acc discharger MWh part | 1000 kWh |
| 25248 | Acc discharger kWh part | 0.1 kWh |
| 25249 | Acc grid-buy MWh part | 1000 kWh |
| 25250 | Acc grid-buy kWh part | 0.1 kWh |
| 25251 | Acc grid-sell MWh part | 1000 kWh |
| 25252 | Acc grid-sell kWh part | 0.1 kWh |
| 25253 | Acc load MWh part | 1000 kWh |
| 25254 | Acc load kWh part | 0.1 kWh |
| 25255 | Acc self-use MWh part | 1000 kWh |
| 25256 | Acc self-use kWh part | 0.1 kWh |
| 25257 | Acc PV-sell MWh part | 1000 kWh |
| 25258 | Acc PV-sell kWh part | 0.1 kWh |
| 25259 | Acc grid-charge MWh part | 1000 kWh |
| 25260 | Acc grid-charge kWh part | 0.1 kWh |

Each accumulator combines as `total_kWh = HIGH * 1000 + LOW * 0.1`. The
monitor does this combination in `_combine_accumulators()` and
displays each as a single `Acc <name> (total) = X.X kWh` line.

### Alarm / warning / status bits

Registers 25261..25268 hold error/warning bits. Not currently polled.

### Battery telemetry

| Addr | Name | Unit |
|------|------|------|
| 25273 | Battery power | W (signed) |
| 25274 | Battery current | 0.1 A (signed) |
| 25275 | Battery voltage grade | V (12, 24, or 48) |

---

## SETTINGS blocks (split into two ranges)

### 10103..10104

| Addr | RO/RW | Name | Unit |
|------|-------|------|------|
| 10103 | RW | Float voltage | 0.1 V |
| 10104 | RW | Absorption voltage | 0.1 V |

### 20118..20132

| Addr | RO/RW | Name | Unit |
|------|-------|------|------|
| 20118 | RW | Battery stop discharging voltage | 0.1 V |
| 20119 | RW | Battery stop charging voltage | 0.1 V |
| 20127 | RW | Battery low voltage | 0.1 V |
| 20128 | RW | Battery high voltage | 0.1 V |
| 20132 | RW | Max combine charger current | 0.1 A |

---

## Decoded state values

These are the canonical values from protocol v1.4.15, verified by
cross-checking the XLSX shipped with the
[taHC81/MUST-ESPhome](https://github.com/taHC81/MUST-ESPhome) repo
against the same document uploaded to
[Scribd](https://www.scribd.com/document/881604771/) (document 881604771).

### Charger workstate (15201)

| Value | Meaning |
|-------|---------|
| 0 | Initialization mode |
| 1 | SelfTest mode |
| 2 | Work mode |
| 3 | Stop mode |

### MPPT state (15202)

| Value | Meaning |
|-------|---------|
| 0 | Stop |
| 1 | MPPT |
| 2 | Current limiting |

### Charging state (15203)

| Value | Meaning |
|-------|---------|
| 0 | Stop |
| 1 | Absorb charge |
| 2 | Float charge |
| 3 | EQ charge (equalization) |

### Inverter workstate (25201)

| Value | Meaning |
|-------|---------|
| 0 | PowerOn |
| 1 | SelfTest |
| 2 | OffGrid |
| 3 | Grid-Tie |
| 4 | ByPass |
| 5 | Stop |
| 6 | GridCharging |

---

## Notes on this unit

- Battery voltage grade is 24 V (24V battery system).
- AC voltage grade is 120 V (120V variant, not the 230V default).
- Confirmed against live readings: `Battery voltage = 28.2 V`,
  `Inverter voltage = 115.5 V`, `Grid voltage = 117.0 V`.
- Frequencies are 60 Hz (US-style).
- The `Acc grid-charge (total) = 1.0 kWh` reading shows the inverter
  has charged the battery from grid once for a total of ~1 kWh.
- The `Acc grid-buy (total) = 17.0 kWh` reading shows the inverter
  has bought 17 kWh from the grid over its lifetime.
- These lifetime counters survive power cycles.