DC 12V DIY UPS Battery Box — 3×18650 Cells, 24W, True 0ms Switchover (No Battery)

Build your own uninterruptible power supply with this compact 12V UPS battery box. Designed for electronics enthusiasts and DIY builders, it delivers true 0ms seamless switching — meaning your router, modem, CCTV camera, or fish tank pump stays on without a single blip when the power cuts out.

⚠️ Batteries not included. Requires 3×3.7V flat 18650 cells (user-provided).

Why It Stands Out

• True 0ms switchover — No interruption, no restart. This is a genuine UPS, not a delayed backup.
• No special charger needed — Built-in 0.4A constant current circuit charges from any standard 12–13V switching power supply.
• 97.3% efficiency — Direct 3-cell series output minimizes energy loss. Efficiency approaches 100% at higher battery voltages.
• Charging status indicator — Red light while charging, off when full. Simple and intuitive.
• Full protection suite — Overcharge (4.25V×3), low voltage (2.75V×3), and overcurrent protection built in.
• Wide temperature range — Operates from -20°C to 60°C.

Compatible With

WiFi routers · Fiber modems · CCTV cameras · Fish tank pumps · Monitoring systems · Tablets · Smartphones · Any 12V DC device drawing up to 2A

Technical Specifications

Output: DC 12V / 2A (24W max)
Output Voltage Range: 8V (low protection) – 12.6V (full charge) — unregulated, varies with battery level
Battery: 3×3.7V flat 18650 (not included) — ~37Wh at 3400mAh
Charger Input: 12–13V (12.7V recommended) / 0.4A
Charging Power: ~4.8W (input must exceed load + 5W)
Switchover Time: 0ms
DC Port: DC 5.5×2.1mm (center positive)
Operating Temp: -20°C to 60°C

⚠️ Note: Do not perform short-circuit protection tests on this board — it may damage the diode. Short-circuit protection only activates after the diode has been triggered.

What's in the Box

• 1× UPS battery box
• 1× Wire