As a matter of fact, it is possible for a power bank to charge and discharge simultaneously. But not all power banks (or portable chargers) have this feature (pass-through charging). So if you want to buy a power bank that can charge and discharge simultaneously, look for those that have pass-through charging.
In our power bank review section, we even offer a filter that allows you to see all the power banks that have this feature:
Is it safe to simultaneously charge and discharge your power bank?
Although it is generally safe, there are some drawbacks when using pass-through charging:
- The power bank can heat up. When this happens, the heat build-up will potentially shorten the lifetime of your power bank. Since it also has a certain amount of charge cycles, it will allow a specific amount of energy to pass through before it dies down. So, when an electronic gadget is being charged via the power bank, higher amounts of electricity will flow through it until it’s fully recharged. As a result, the unit will die quicker.
- It will take longer for your battery pack to reach a full charge, especially because you’ll be taking electricity from it and using that to power a connected device.
- A connected device will power-up a bit slower compared to when you charge it regularly. Some power banks may have ratings of 5V/1A while pass-through charging. If that’s the case, you may need to keep your device plugged in for several hours until it reaches 100% since it won’t be able to activate any fast-charging technology.
The main concern here is energy waste. By connecting an electronic device while the power bank itself is recharging, you’ll be losing power in the electronic circuits of the unit. Even if it’s only a tiny amount of electricity not being put to use, that’s what causes heat build-up. Assuming you’re using a high-quality power bank, the internal circuit and built-in safety features will help deal with this issue.
There are also a few things you can do to keep it from heating up too much. Using it in a room where the temperature isn’t too high will help keep it cool. So you shouldn’t let it sit in direct sunlight or in a hot car and you should ensure it’s not covered by something or stored away in a pouch, case, or bag while it’s in use. Doing so will cause heat to be trapped and that will affect the battery and potentially the circuits in the power bank. You should also be sure that your unit is on a flat surface with space around it. This will maximize the safety of your device and prevents it from becoming too cluttered.
You should also know that the battery itself isn’t what’s heating up. Instead, what happens is the heat from the electronics spreads to the battery through thermal conduction since the two are placed beside each other. The heat is usually concentrated on one end of the power bank, where the USB ports are found.
It’s generally not a problem if the power bank is slightly warm, but it’s also not a good practice to let the Lithium batteries heat up constantly, so you should check into this before it happens. Doing so will ensure the battery is kept at a sustainable temperature. If the power bank has built-in safety features to keep it from overheating then that will also be beneficial for you in the long run.
Some power banks do not support charging and discharging at the same time. That’s because the power bank will need to be able to provide enough power to the output ports and it will also need to recharge its own battery as well. So you should check to be sure your power bank supports this feature. If not, it will likely just switch power from the output to charge mode whenever the input port is in use. If there is a button, it will turn on the output. Some manufacturers, like Xiaomi, support this feature.
You should also be sure of these three things:
- The wall charger output amperage should exceed the power bank’s output amperage
- Input current should be greater than the discharge current
- The power bank capacity should be higher than your device’s capacity.
Normally, you wouldn’t take two adapters with you to charge the power bank and any device at the same time. However, there are some instances when you would need to recharge both simultaneously. In this case, you can connect your power bank to an adapter and connect an electronic device to the USB A port. This will then cause the power bank to recharge your phone first. Afterward, it will start recharging your power bank.
It’s generally ok to use this feature, as long as it’s not done frequently. It’s not a good idea to use your device with pass-through charging because it can potentially strain the unit. Power banks should always be fully replenished before you start using it. This is to ensure you will have power since they always discharge while it’s powering a device. A good precaution to note is that you should not use the connected device at all until it’s fully charged from the power bank. Otherwise, it will just take longer for it to replenish, contributing to battery degradation.
This should only be used as a last resort. In such circumstances when your phone is nearly out of power and you also need to refresh your power bank. Otherwise, it’s not an efficient way to charge mainly due to heat build-up, energy waste, and the overall effect it has on the power bank’s health.