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Will USB charger drain motorcycle battery & How to install via switch

Image of a USB charger fitted on the motorcycle handlebar
3354 Views Feb. 21, 2021, 12:01 a.m.

While riding a motorcycle, a motorcyclist relies on one or multiple electronic devices. There is a need to keep the phone charged, GPS ON, or have an audio system running on the road. All these external accessories or devices require a USB charger that is mounted on the motorcycle. Many riders complain about their bike battery getting drained by using a USB charger.

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Will the USB charger drain the motorcycle battery? This article will answer all your questions regarding types of USB charging for your motorcycle, whether it affects battery performance and some considerations while buying a USB charger.

Types of USB connections to your motorcycle battery


SAE Connection

Image of SAE cable connection for motorcycle

SAE cables have male and female connectors and are directly connected to the bike battery. The exposed cable terminal is connected to the negative outlet of the battery. The battery’s positive terminal is connected to the concealed SAE connector. This type of connection is safe from the chances of any short circuit. Buy a good quality SAE cable as Lead-acid batteries are more prone to experiencing short-circuits.

SAE to USB Motorcycle Handlebar Waterproof Phone Charger - Purchase link

DIN Connection

Image of DIN battery connection

Some motorbikes like BMW, Triumph and KTM have an in-built double pole DC 4165 connector. DIN sockets can handle large electrical current and perform well under the motorcycle’s vibration because they are shorter and smaller in diameter than existing car lighter plugs.

Direct Connection

These USB chargers are connected to the battery directly. Usually mounted on the handlebar, the wires are plugged directly into the motorcycle battery. The installation is easy, and all it takes is appropriately connecting the wire from the charger to the battery.

Does USB charger drain & affect motorcycle battery life?

Short Answer: Yes, it drains the battery if the connection is not via a switch but the charge drained is very low. Only a worry if parked for days or months and installing a fuse at battery terminal can be a solution which can be removed before a long parking spell.

The impact on your motorcycle’s battery depends on the type of device and the duration for which it is connected via the USB cable. Different connected devices draw power as per their power requirement and the time for which they are connected to the battery. If the device remains directly connected to the battery even when the bike is not running, there can be a drain on your motorcycle.

Image of bike battery fitted on the motorcycle

USB chargers have a 0.5A or 1A amperage, which is too low to make any noticeable difference to a battery. But when the USB charger is left connected for many days or weeks, there is undoubtedly a drain in your motorcycle battery. Hence, directly connecting external bike accessories via USB chargers to the battery is not recommendable as the battery drainage continues even while the ignition is off.

Another thing worth noticing here is the performance and health of your motorcycle battery. Over time, the battery sulfation occurs when the lead-acid motorcycle battery is undercharged or excessively charged. Defective battery or USB charger, bad terminal or rectifier/regulator problem too impacts the battery drainage. It is advisable not to use the USB charging for too long when the motorcycle is not running.

Use a voltmeter to check the performance of your motorcycle battery. Connect the voltmeter to the battery when the engine is not running, and the reading should be approx 12.5V. With the engine running, the reading should be approx. 13.1V and with the battery unplugged, not less than 0.1V higher than when connected. 

Ways to avoid battery drainage while connecting USB Chargers

  • Instead of connecting the USB charger directly to the battery, use a relay switch. With the relay correctly in place, unless the motorcycle is running or the key is in the ignition, no power will flow in the USB charger. Connecting the USB charger to the ignition causes the connected device to turn off when the ignition is off.
  • If you're going to install a USB charging port on a bike, it's highly recommended not to wire it directly to the motorcycle’s battery, but rather to one of the switched +12v wires that only have power when the ignition is turned on.
  • Some users even suggest making the connection with a low-beam headlight wire. This will act as a switch for your USB connected device thus killing an unnecessary charge drain.
  • Check for connected devices like the phone when the engine is not cranking. You may often need to charge the phone when the motorcycle is not running. Just be careful not to keep it connected for extended periods.
  • Avoid using excessive accessories. Apart from phone and GPS, which are more important, high power LED lights, MP3 players and heavy load bike accessories that work even when the ignition is off lead to excessive battery drainage.
  • Often there are ongoing issues with your bike battery that lead to drainage. Regularly get your bike battery checked at the workshop. Maybe your battery is flat or just done, and you are looking for drainage issues in the external connections.

Considerations while buying a USB charger for your motorcycle


Quality and Safety

USB chargers are prone to short circuits and other damages. Buy a weather-resistant USB charger and protect the unit from rain, dust, debris, and other electrical faults.

Check for technical specifications

Depending on the technical specifications, not all USB chargers are compatible with all the devices. Two units with different specifications can cause a short circuit or electrical damage. Some phones also require fast charging, which becomes too delayed when connected to a slower USB charger. Hence, check for the voltage and power specifications beforehand. 

Number of Charging Ports

Consider the number of USB charging ports before buying one. You may probably need to connect multiple devices at the same time. So look for at least a dual-port USB charger in case of multi-device charging.

Look for the power switch

A power switch turns off the charger when not in use. USB chargers with a power switch ensure more safety for your connected device and the motorcycle battery.

usb charger battery drain ignition connection switch charger
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