The “universal charge” for notebooks! How to choose a power bank that supports PD protocol?(二)

Let’s continue the topic .

A rational view of the capacity of virtual bids

It is not difficult for a careful friend to find that the capacity unit of the built-in lithium battery of the power bank is generally “mAh”, such as 10000mAh, 20000mAh, 27000mAh and 30000mAh. The capacity unit of the built-in lithium battery in the notebook is mainly “Wh”, and 40Wh is basically the lower limit of the current battery capacity of thin and light notebooks. The question is, how to convert and calculate between mAh and Wh?

In fact, Wh should be regarded as the standard unit of lithium battery energy. The 10000mAh marked by the power bank belongs to the capacity of the battery cell, and the default working voltage of the battery cell is 3.7V, so its energy calculation method is 10000mAh×3.7V÷1000= 37Wh. The question comes again. If the 10000mAh power bank has 37Wh of energy, can it charge 92.5% of the power to a notebook with a built-in 40Wh battery?

50000mah power bank

Unfortunately, you think too much.

CFan has emphasized more than once that the capacity marked by the power bank has the problem of false standard. 3.7V is the standard voltage of lithium battery cells, but it needs to increase the voltage to 5V during charging, and this boosting process will inevitably cause about 26% loss (10000mAh×3.7V÷5V=7400mAh).

Take the 10000mAh power bank as an example. Its rated capacity is generally not higher than 6500mAh, which is 24Wh. In theory, it can only charge a laptop with a built-in 40Wh battery to about 50% of the power. That’s right, if you want to buy a PD power bank that can charge your notebook at least once, you must choose a product with a capacity of not less than 20000mAh. If you use a laptop battery with a capacity close to 60Wh, you need a 30000mAh PD power bank to “feed”.

 

There is another problem here. The capacity of the power bank is directly proportional to parameters such as thickness and weight. The weight of the capacity of 10000mAh, 20000mAh and 30000mAh is about 200g, 400g and 600g respectively. Among them, the 30000mAh power bank is not only very bulky, but its built-in battery energy has reached 114Wh, which has exceeded the energy limit of civil aviation for passengers to carry the power bank-no more than 100Wh can be boarded directly, (between 100Wh and 160Wh ) It is necessary to fill in the lithium battery and power bank transportation application form to approve the boarding. Queuing and other approvals are often very troublesome.

Therefore, many power bank companies will be very smart to launch 27000mAh PD power bank, its battery cell energy is controlled to 99.9Wh, hit a set of “side ball” that can be boarded directly.

Cell type and interface function

According to the author’s experience, the 20000mAh and 27000mAh models of PD power banks are the most worth buying. The former is relatively slim and the latter provides the maximum energy for boarding without approval.

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The built-in batteries of the PD power bank are mainly cylindrical 18650 batteries (common in the 27000mAh version, 8 batteries) or flat lithium polymer batteries (common in the 30000mAh version, 3 batteries), 18650 batteries The core is relatively resistant to puncture and deformation due to the external hard shell, but it is easy to explode in extreme situations such as a short circuit; because the lithium polymer battery is a soft bag, puncture and squeeze are avoided, and it is easier to burn in extreme situations such as short circuit. Of course, the above-mentioned events are extremely small and can be avoided as long as we develop a safe use habit of power banks (not soaking in water or squeezing them vigorously).

 

If you use the most common 10W charger to charge the PD power bank, it may take more than 24 hours

You know, the capacity of PD power bank suitable for notebooks starts at 20,000mAh. If you want to shorten the charging time, you must choose a model that supports “two-way PD fast charging”, that is, the maximum output power of a single port is similar to the input power. Take a 30000mAh power bank as an example. If it supports 45W PD fast charging, it takes at least 6 hours to fully charge; if it supports 65W PD fast charging, it takes 4 hours; if it supports 90W or higher fast charging, it can be controlled to about 2.5 hours.

Follow the random accessories of the power bank

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In order to shorten the charging time of the PD power bank itself, most products support “two-way fast charging”, but due to cost concerns, some products do not have a standard charging head, or the standard charging head is not supported The maximum power. For example, although a certain PD power bank supports the maximum input power of 90W, it only comes with a 18W charging head. The charging cable supplied does not support 5A high current. If you want to charge it at full speed, you need to purchase it yourself. With a 90W power PD charging head and a charging cable with a built-in E-Marker chip, this additional cost also needs to be included in the overall purchase cost.

 


Post time: Feb-15-2021