Update: We’ve written an article about how pass-through charging enables power banks to be used in creative ways. Check it out.
Power banks are fantastic inventions, letting you charge your devices while on the go. But, as rechargeable batteries themselves, power banks will sometimes need to take a reprieve from their work to build their energy back up through a wall outlet. This brings about a question that continues to be the cornerstone of ongoing debate: can you charge your device while your power bank itself is charging, without causing any damage? Let’s take a look at the evidence and why pass through charging is needed.
What Is Pass Through Charging?
In very simple terms, pass through is an integrated technology in power banks that allows a device, say a cellphone, to be plugged and charged while the power bank itself is connected to a wall outlet. Today, most devices are embedded with chips that speak to a charge source, like your power bank. These chips indicate to the power source how much power it needs to charge quickly, as well as when its batteries are topped up. The intention here is to make sure that a battery doesn’t get overcharged, which could ultimately shorten its lifespan over time. The use of the chip is why we’ve been able to dismiss, once and for all, the myth that leaving your phone plugged in overnight is poor practice.
Pass through technology itself is in essence a series of power regulating circuits inside a power back that helps match the draw of energy needed by an output device to the amps being pulled from a wall outlet. If done right, pass through will move power directly from the wall outlet to the connected device, via the power bank. This is called prioritization. Depending on load balancing performance in the power bank, the latter should charge at either a regular or slower speed than normal when working with an output device.
How are Batteries Damaged?
We know from research that the most significant source of damage to a battery comes from excess heat, especially for lithium-ion batteries. It impacts maximum storage capacity, charge transfer speeds, and overall effectiveness. In order to deal with this issue, cellphones and other modern electronics will use that handy battery chip to throttle power transfers, slowing energy reaching the device to minimize potential heat creation. The longer the charge takes, the more opportunity there is to build heat, and the greater the potential to damage a battery.
So is Pass Through Potentially Dangerous to Power Banks and Batteries?
The answer, annoyingly, is maybe. If your power bank is able to effectively use designated internal circuitry to match input and output power levels, then you may not see a noticeable difference in charge capacity over time. That said, there doesn’t exist yet a purely efficient pass through system, meaning that it will almost inevitably take longer to charge your power bank if its output is connected to another device. More charge time will likely mean more heat build-up. And more heat could lead to sped-up degradation in a lithium ion battery.
The above also depends on build quality. Reputable companies working with pass through will often build their power bank out of more robust materials, helping to prevent battery degradation. The advice here is if you want to use a pass-through feature, don’t buy a knockoff. If your power bank doesn’t have any pass through tech built in, then you can bet there will likely be damage when attempting a conga-line charge.
In the end, to avoid damaging your device or power bank, follow two simple rules. First, make sure your power bank is equipped with the right circuitry to support pass through. Second, if you need to use it, don’t do it for very long – think emergency rations situations. By limiting pass through to a few hours at most, you should be able to reduce heat and the potential for battery damage.