12 Volt Battery Monitor

GMC Dual USB Car Charger with Voltage Display

All-Metal | Smart Charging | LED Voltage Meter | Fits the Tesla Roadster

Upgrade your in-car charging experience with the GMC Dual USB Car Charger, engineered for performance, safety, and convenience. Designed with a sleek all-metal body and integrated voltage meter, this compact powerhouse delivers fast, intelligent charging to two devices simultaneously—while monitoring your Roadster’s 12 Volt battery in real-time.

⚙️ Product Features

🚘 Why Choose the GMC USB Car Charger?

• Smart IC Technology: Each port intelligently detects your device to deliver maximum charging speed (up to 2.4A per port). Charging automatically stops when your device is full.
• Built-In Voltage Monitor: The red LED screen displays your car’s real-time voltage the moment it’s plugged in—helping detect low voltage or battery issues instantly.
• LED Ring Light: A soft green halo helps you locate ports easily at night while alerting you to abnormal voltage conditions without distracting the driver.
• All-Metal Durability: Crafted from premium fire-retardant zinc alloy, this charger is cool to the touch, anti-static, and designed for long-term use.
• Universal Compatibility: Works with virtually all smartphones and tablets, including Apple, Android, and any USB-powered device. Supports AT&T, Verizon, T-Mobile, Sprint, Boost, Cricket, Metro, and more.
• Certified Safe: CE / FCC / RoHS Certified with protection from overcharging, overheating, short-circuiting, and overcurrent—keeping your devices and car safe.

📏 Product Dimensions

• Length: 1.34 inches
• Ports: 2 x USB-A
• Weight: Ultra-light yet durable all-metal design

The 12 volt indicator will typically report around 13.2 – 13.6 Volts DC with a healthy battery dependent on 12 volt accessories in use in the Roadster.  Devices fed by the 12 volt system include exterior lighting, the audio system, seat heaters, trunk lock, and certain electronics such as the Vehicle Management System module and certain PEM functions.

If you find the monitor begins reporting voltages below 13 Volts DC, especially after vehicle non-use, it indicates this battery is on its way out and due to be replaced.

Gruber Motor Company makes a retrofit 12 Volt battery relocation kit that eliminates Service Center visits for this battery swap, allowing a 3 minute DIY battery replacement, with an additional battery condition monitor mounted on the trunk mounted enclosure.