Car battery USB Charger

The 12V jack in a car (once the cigarette lighter) is a pretty common place for many of us to put a USB charger these days. In a lot of car models, that 12V jack doesn’t stop getting power, which means it’s technically draining your battery even when the car’s off. How much? Big Mess O’ Wire decided to figure that out.

Using some alligator clamps and a multimeter, Big Mess o’ Wires figured out much the USB charger draws in standby mode, then figured out what effect, if any, it’d have on a car’s battery:

Is a constant 14.2 mA draw enough to worry about discharging the car’s battery? Probably not. From a few quick searches, I learned that a typical car battery has a capacity of around 40 ampere hours. At 14.2 mA, it would take 2817 hours or 117 days to completely discharge the car’s battery. Assuming I drive the car every day, then, it’s not a concern. Even parking the car for a week or two should be fine. But if I ever need to leave the car in storage for an extended period of time, that 14.2 mA could add up. Of course the car itself has its own standby current draw for the anti-theft system and keyless entry, so the USB charger may not even be the largest concern. For typical driving, at least, it appears the USB charger’s standby current draw won’t be a problem.

So, not much, really. Which means you can freely leave that USB charger plugged into the car’s 12V jack if you want, provided you don’t plan on putting the car in storage for around 117 days, that is.

VINSIC Car Charger, Quick Charge Mini USB Car Charger for iPhone 7 / 6s / Plus, iPad Pro / Air 2 / mini, Samsung Galaxy S7 / S6 / Edge / Plus, Note 5 / 4, LG, Nexus, HTC, Android phone and More
Wireless (VINSIC)
  • QC 3.0 Car Charger: Adopts QC 3.0 technology,compatible with QC 1.0/2.0 and smart charge. It can automatically identify and allocate reuqired current to your devices...
  • Real Quick Charge: input is 12V-24V, output is up to 3A(max). Charge your phone (compatible with QC3.0) to 72% of the battery within 30mins (QC2.0 to 62%, ordinary...
  • Wide Compatibility: iPhone/Samsung etc. Equipped with a blue LED indicator, shows the working status. Yet, the soft light won t cause distraction in car. Safe to...
  • Six Safety Protection:over-temperature protection, over-current protection, over-voltage protection, input over-current protection, short-circuit protection, anti-reverse...
  • High Quality Materials: Made of high hardness fire proof materials, delicate workmanship. Efficient and secure. Compact and portable size for easily use in your...
Car Charger Adapter, Car USB Charger 50W/10A 6-port Fast Smart Car Phone Charger with 2Ft DC Power Cord for Backseat Passenger+ Built-in Fuse for iPhone, iPad, Galaxy, Nexus, HTC, Blackberry and More
Wireless (Hunda Technology)
  • 6 Ports USB Car Charger - Impressive 50W/10A output to charge up to 6 USB devices simultaneously on the road, Perfect for family long trip drive.
  • Intelligent Recognition Technology - The smart recognition chip can recognizes your device and distribute the maximum charging current up to 2.4 amps per port.
  • Built-in Safe Fuse - Built-in fuse provide over-current, over-voltage, and short-circuit protection, ensure the safety of your car and multiple devices.
  • 2FT Charging Cable - 2 feet adapter cable to make sure everyone can reach the charger, even the back-seat passengers.
  • What You Get - HUNDA 6 ports usb car charger, 2 ft detachable adapter cord, user manual, 12 month warranty and friendly customer service.
Car Charger, Maxboost 4.8A/24W 2 Smart Port Car Charger [Black] for iPhone 7 6S Plus 6 Plus 6 5SE 5S 5 5C 4S, Samsung Galaxy S7 S6 Edge, Note 7 5 4 S5 Tab S,LG G5 G4,HTC,Nexus 5X 6P,iPads Pro Portable
Wireless (Maxboost)
  • 24W / 4.8A USB Car Charger charges your favorite mobile devices including the iPad (max speed), iPhone (max speed), iPod, HTC, Galaxy, Blackberry, MP3 Players, Digital...
  • Double injected frame consists of a polycarbonate inner layer coupled with the flexible external molding of TPU (thermoplastic polyurethane) for a soft grip
  • Maxboost Intelligent circuit design protects against short circuiting, over-heating, over-currents, and over-charging. Charging stops when battery is full.
  • Dual smart USB ports quickly and easily identify yours mobile devices, to provide optimal charging efficiency.
  • Compact design for added portability, featuring of input:12-18V; Output: DC 5V 4.8A or 24W (Shared by two ports). One Year Warranty.
PowerBear Qualcomm Quick Charge 3.0 Car Charger | 2-Port USB Car Charger [45W] Dual-USB Ultra Fast Car Charger USB [Qualcomm 3.0 Certified] - Black [24 Month Warranty]
Wireless (PowerBear LLC)
  • GO BEYOND YOUR POWER: Stay connected anywhere you go with the PowerBear USB car adapter. Plug in up to 2 USB cables at a time for reliable charging in your car.
  • QUALCOMM TECHNOLOGY: PowerBear auto USB charger uses Qualcomm s newest charging to power your electronics. Charge your Qualcomm compatible phones and devices twice...
  • PREMIUM DESIGN: PowerBear Dual USB car charger is designed to always be there for you. Strong grip connectors keep your devices plugged in all the time. Bright LED...
  • SAFETY GUARANTEED: Quality built-in electronics protect all of your plugged in devices against short-circuiting, overheating, and overcharging.
  • 24 MONTH WARRANTY: PowerBear stands behind our products. If you are not 100% satisfied with your new USB car charger adapter, just let us know! Contact us via Amazon...
Jebsens 4.8A 24W Dual USB Car Charger Volt Meter Car Battery Monitor with LED Voltage & Amps Display, for iPhone 7 / 6s / Plus, iPad Pro / Air 2 / mini, Galaxy S7 / S6 / Edge / Plus, Note 5 / 4
Wireless (JEBSENS)
  • ADVANCED CHARGING TECHNOLOGY: Dual USB Ports pumps out 24W of power charge up to 4.8 amps or 2.4 amps per port. Easily charge your favorite mobile devices including...
  • LED DISPLAY - LED digital luminescence tubes; Monitor the voltage of the vehicle s car battery when not charging any devices. When charging a device, it cycles between...
  • OVER-CHARGE PROTECTION - The mini USB car charger is auto power off when input/output is greater than safety current, protects against over-heat, over-current and...
  • COMPACT DESIGN - One of the industry s smallest USB car chargers, featuring two USB ports and an LED Display make it easy to access after dark.
  • PACKAGE INCLUDES: 1 x Jebsens 4.8A Dual USB Car Charger with LED Display. (Charging Cable NOT included) 1 Year Guarantee provided by Manufacturer. Money Back Guarantee...

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