Battery Charger
Control Frame (ID 0x15/0x18) - Commands to Dometic Charger
Frame Format: [ID=15] [01] [FF] [01] [FF] [FF] [FF] [FF] [FF]
Note: Uses different IDs (0x15/0x18) possibly for different charger models
Frame Layout:
| Byte | 0 | 1 | 2 | 3-7 |
|---|---|---|---|---|
| Content | Charge Voltage | Solar V LSB | Control Flags | Reserved |
Byte 0: Charge Control
Charge Voltage Setting:
- Formula:
Voltage × 0.5 - Range: 0-255 → 0-127.5V
- Resolution: 0.5V increments
- Example: 0x1A = 26 → 13.0V (typical 12V system)
Byte 1: Solar Panel Voltage (LSB)
Format: Lower byte of 16-bit solar voltage
- Formula: Combined with control byte for voltage setting
- Range: 0-50000 (0x0000-0xC350 for 0-500.00V)
- Resolution: 0.001V (1mV)
Byte 2: Control Flags
Bit 1: Silent Mode
- 0: Normal operation (fan active)
- 1: Silent mode (reduced fan/noise)
Bytes 3-7: Reserved
Fixed values [FF] [FF] [FF] [FF] [FF] - unused
Info Frame (ID 0x16/0x19) - Status from Dometic Charger
Frame Format: [ID=16] [Current] [Status] [FF] [FF] [FF] [FF] [FF] [FF]
Frame Layout:
| Byte | 0 | 1 | 2-7 |
|---|---|---|---|
| Content | Output Current | Status Flags | Reserved |
Byte 0: Output Current
Format: Direct amperage reading
- Range: 0-50.8A
- Resolution: 0.2A increments
- Formula:
255 × 0.2A = 51.0A max - Example: 0x19 = 25 → 5.0A output
Byte 1: Charger Status Flags
| Bit | Flag | Description |
|---|---|---|
| Bit 0 | Silent Mode | 0=Normal, 1=Silent mode active |
| Bit 1 | Reduced Power | 0=Full power, 1=Power reduction active |
| Bit 2 | Error Status | 0=No errors, 1=Error condition present |
| Bit 3 | Charging Active | 0=Not charging, 1=Charging in progress |
Bytes 2-7: Reserved
Currently unused in this frame format.
Communication Example
Setting Charger to 13.8V with Silent Mode
Control Frame (0x15):
[0x1B] [0x58] [0x02] [FF] [FF] [FF] [FF] [FF]
Byte 0: 0x1B = 27 → 13.5V (27 × 0.5)
Byte 1: 0x58 = Solar voltage LSB
Byte 2: 0x02 = Silent mode on
Reading Charger Status
Info Frame (0x16) Response:
[0x14] [0x0A] [FF] [FF] [FF] [FF] [FF] [FF]
Byte 0: 0x14 = 20 → 4.0A output current (20 × 0.2)
Byte 1: 0x0A = Silent + Charging active
Typical Charging Voltages
12V Lead-Acid Systems
- Bulk/Absorption: 14.4V - 14.8V
- Float: 13.6V - 13.8V
- Equalization: 15.0V - 16.0V (periodic)
12V Lithium Systems
- Bulk/Absorption: 14.2V - 14.6V
- Float: 13.6V - 13.8V
- Note: Lithium batteries typically don’t require float charging
Silent Mode Operation
Silent mode reduces fan speed or disables it entirely for quiet operation, typically used:
- During nighttime hours
- In noise-sensitive environments
- When charging current is low enough not to require active cooling