This document describes the design of a remote surveillance system using a 48 V DC power backbone, passive Gigabit PoE transport, a 12 V regulated power system, a CM4-based NVR, and LiFePO₄ battery backup.
The design goals are:
SOURCE LOCATION
48V DC Supply
Mean Well GST160A48-R7B
48V / 160W
|
|
v
Tycon POE-INJ-1000-WTS
Passive Gigabit PoE Injector
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| CAT6 cable
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| Data + 48V DC
|
v
REMOTE LOCATION
Tycon POE-INJ-1000-WTS
Passive PoE Splitter
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| 48V DC output
|
v
Mean Well DDR-120C-12
48V → 13.8V DC Converter
120W output
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|
v
13.8V DC Power Bus
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+----------------+
| |
v v
12V LiFePO₄ Battery LVD / UPS Controller
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+----------+----------+
| |
v v
CM4 NAS System LINOVISION PoE Switch
NVMe Storage 12V Input
4G Modem 4 × PoE Ports
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|
Amcrest IP5M-T1179EW
Cameras ×4
Mean Well GST160A48-R7B
Purpose:
Specification:
Used as:
Purpose:
Rating:
48V × 2.25A ≈ 108W
The Tycon pair is the limiting point of the system.
Purpose:
Convert the transported 48 V supply into a regulated 12 V system.
Configuration:
Input:
48V DC
Output:
13.8V DC
Maximum output:
120W
≈ 8.7A at 13.8V
The output voltage is set to 13.8 V to support:
Purpose:
Outputs:
Quantity:
Expected consumption:
Approximately:
6–10W per camera
Estimated total:
24–40W
Components:
Estimated consumption:
15–25W
depending on storage activity and modem usage.
Typical operating load:
| Component | Estimated Power |
|---|---|
| Four PoE cameras | 30–40W |
| PoE switch losses | 3–5W |
| CM4 + NVMe | 8–12W |
| 4G modem | 5–10W |
| Total | 50–65W |
Available Tycon capacity:
≈108W
Normal operation has adequate margin.
12 V LiFePO₄
Capacity:
8Ah
Purpose:
The DDR-120C-12 is a regulated power supply, not a dedicated LiFePO₄ charger.
Recommended:
Recommended charge current:
2–3A
This maintains margin for the Tycon power limit.
Example:
13.8V × 3A ≈ 41W charging power
A supervisory controller should monitor battery voltage.
Recommended thresholds:
Battery voltage < 12.2V
↓
Send shutdown command to CM4
↓
Wait for shutdown completion
↓
Remove power from CM4 and PoE switch
48V power returns
↓
DDR outputs 13.8V
↓
Battery begins charging
↓
Battery voltage reaches 13.1V
↓
Reconnect CM4 and PoE switch
↓
System boots
The delay allows the battery to recover before the main load is restored.
The CM4 should shut down cleanly before power removal.
Recommended method:
systemctl poweroff
or:
shutdown -h now
Benefits:
ONVIF can manage many camera functions, including reboot, but most PoE cameras do not support a software power-off command.
Recommended approach:
The cameras are designed to tolerate power cycling.
Recommended protection:
| Circuit | Fuse |
|---|---|
| Battery | 10A |
| CM4 system | 3A |
| PoE switch | 10A |
The completed system provides:
The main design constraint is the Tycon injector/splitter pair (~108 W capacity). Keeping battery charging current controlled ensures reliable operation.