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Devices and Methods to Cool Smartphones Attached to Bicycles

July 20, 2021   Keiji Saito

Prevention of Thermal Runaway of Smartphones Attached with Smartphone Holders

We sometimes want to check the screen of smartphones while riding a bicycle or motorcycle. It's convenient to check maps and navigation in smartphone applications while biking. In this case, for safety and convenience, it is common to use a smartphone holder to fix the smartphone on the handlebars. However, When riding a bicycle/motorcycle with a smartphone attached to a smartphone holder, the smartphone sometimes heat up. In particular, if the smartphone is set on the smartphone holder in summer or in direct sunlight, Thermal runaway occurs and will not work properly. In order to avoid the thermal runaway, you need to choose the right smartphone cooler and smartphone holder.

In this article, I guide devices and methods to control the thermal runaway of a smartphone attached to a bike/motorcycle.

Smartphone attached to bicycle by smartphone holder (being cooled by smartphone cooler)

[1] Thermal Runaway of Smartphone Due to High Temperature and Direct Sunlight

Using a smartphone holder to secure your smartphone to the handlebars of a bicycle or motorcycle is a convenient way to check the screen of your smartphone while riding. It also increases safety by freeing up both hands and makes it easier to operate your smartphone when stopped. Smartphone holders are a necessity when using map/navigation applications in touring, Uber Eats and other deliveries, and when playing location-based games on a bike.

Smartphone holders also allows us to charge our smartphones while riding. A mobile battery can be placed in a bag in the front basket or in a pouch attached to the handlebars. The charging cable can be connected from the battery to the smartphone. Even if we ride bike/motorcycle for half a day, we will not have to worry about running out of charge.

However, there are some drawbacks for using a smartphone holder. If we use a smartphone in hot weather, it will easily heat up. A smartphone placed in a smartphone holder is exposed to sunlight, making it prone to heat. Charging will cause the smartphone to heat up even more. When a smartphone holder is used in the summer or on sunny days, there are cases where the smartphone will malfunction due to thermal runaway. Including the protective response of smartphones, examples of malfunction caused by thermal runaway are as follows;

  • Action goes into slow motion
  • Application force close
  • Camera function does not start
  • Mobile phone radio goes into low power mode, reducing radio transmission performance
  • The screen will become dark (almost invisible, and increasing the brightness does not work)
  • Charging becomes slower or impossible (to reduce heat generation)
  • Rapid charge loss

Even if we can't clearly admit these malfunctions, operating electronic devices under high temperatures can cause them to fail. This article shows you devices and methods to dissipate and cool your smartphone while using a smartphone holder on a bike.

[2] Smartphone Cooler (Peltier Effect Cooling by Semiconductors)

At First, consider a smartphone cooler to cool our smartphones. There are several types of smartphone coolers, and one type that efficiently cools a smartphone is the Peltier effect cooling type. In the case of Peltier effect cooling by emiconductors, a heat-absorbing surface and a heat-dissipating surface are created on the metal using electricity, and the smartphone side is cooled by absorbing heat.(Generally, a small fan attached to the heat dissipation surface enhances the cooling effect.)

Peltier-type smartphone coolers are usually connected via a cable such as micro USB. A mobile battery for charging a smartphone, placed in a bag in the front basket of a bicycle, can also be used as a power source for a Peltier-type smartphone cooler. If the mobile battery has multiple output ports, it can send electricity both to the smartphone and the smartphone cooler at the same time.

For a Peltier-type smartphone cooler that can be used on bikes, I recommend one of the following products available on Amazon.com. It can be used together with the smartphone holder described in [3], both in terms of installation method and size.

[3] Smartphone Holder Compatible with Cooler Installation (Fixed at the Bottom Half)

Next, consider a smartphone holder that can hold the smartphone while smartphone cooler of [2] is attached. There are several types of smartphone holders. However, the common types that are fixed at the four corners of the smartphone cannot be used to attach a smartphone cooler. On the other hand, the type that is fixed at the lower half of the smartphone, which can be purchased from Amazon.com, can be used with the smartphone cooler attached of [2].

[4] Smartphone Protection (bumper type) Compatible with Smartphone Cooler

If your smartphone is placed in a case or cover, you may not be able to install the smartphone cooler in [2]. Even if the smartphone cooler can be installed on top of the case, the case will have an insulating effect and will not be able to cool the smartphone efficiently. In order to cool the smartphone efficiently, the back of the smartphone must be exposed. However, exposing the smartphone completely will make it more fragile when it is dropped. Attaching and removing the smartphone from the smartphone holder also increases the risk of dropping it. (As shown in the picture, the upper left part of the screen of my smartphone was cracked by dropping.) For this reason, it is better to protect the smartphone while the back is exposed.

A smartphone bumper is a way to protect a smartphone while leaving the back of a smartphone exposed. A smartphone bumper is a type of protector that encloses only the frame of the smartphone. By attaching the bumper, the smartphone will be less likely to break even if it is dropped. An additional benefit is that it widens the width of the smartphone, making it easier to touch the lower left and right sides of the smartphone even when it is in the smartphone holder described in [3]. Bumpers need to match the size of the smartphone you are using, and below are metal and rubber bumpers that can be purchased from Amazon.com.

[4a] Silicon Pad to Improve Heat Conduction between Cooler and Smartphone

In the rubber bumper type smartphone protector shown in the second row of [4], the bumper is higher than the smartphone to improve safety. If you install a smartphone cooler on top of these types of bumpers, a space will be created between the cooling plate and the smartphone, preventing efficient cooling. Even if the height of the bumper and the smartphone are roughly the same, a small space between the cooler and the metal plate of the smartphone may reduce the cooling efficiency. In such cases, a thermally conductive silicon pad can be placed between the cooler and the smartphone to improve heat conduction and cooling efficiency. Attaching a thermally conductive silicone pad as shown below to the cooling surface of the cooler or the back of the smartphone may improve the cooling efficiency.

[5] Use of Smartphone Holder and Smartphone Cooler Together on a Bicycle or Motorcycle

Once the above products are collected, assemble the products. Firstly, install the bumper-type smartphone protector in [4] to increase safety while exposing the back of your smartphone. Next, install the smartphone holder of [3] on the handle bar of bikes. Place the smartphone on that smartphone holder and move the tab on the right side to secure the smartphone. Then, attach the smartphone cooler of [2] to the upper side of the smartphone. Finally, connect the cable from the mobile battery to the smartphone and the smartphone cooler.

In addition, a fully charged mobile battery with a capacity of over 20000mAh can keep your smartphone charged and the smartphone cooler running for more than 10 hours. In the case of the iPhone, it is recommended to use the device with the ambient temperature is between 0º and 35ºC. Even if you cool your smartphone with this efficient cooling method, you will not overcool it.(Even with this efficient cooling method, your smartphone in direct sunlight would get hotter than body temperature.)

Take care of your own heat stroke, and enjoy your biking activities using your smartphone.

Smartphone attached to bicycle by smartphone holder (being cooled by smartphone cooler)

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