Capacity Comes First
We can’t exactly calculate how many times a power bank can charge a phone. But the simple rule is more mAh indicates more capacity. Normally, a 10,000mAh external battery is fairly enough for your daily usage. Smartphone batteries typically have between 1300-2500mAh capacity (take iPhone 8 as an example, the battery capacity is 1821 mAh). More powerful devices such as iPads / Tablets are normally between 6000-12000mAh. If you want to purchase a power bank for business travels, and it is going to work with not only phones but cameras, laptops and more, a power bank over 20,000mAh should be a better choice.
What people have to keep in mind is that larger capacity always has a bigger size. If you are looking for an ultra-portable charger, you will have to sacrifice a bit of battery capacity.
Conversion Rate Matters
Technically, all power banks don't produce output as printed in the catalog. There is some loss in efficiency due to batteries and AC to DC conversion. The power bank conversion rate is related to the types of batteries and output current & voltage. Generally speaking, the AC to DC conversion loss plus heat generation, and power loss, the real capacity of a 10,000mAh external battery could be 6500 to 8500mAh.
The power conversion rate of qualified products should be more than 70%. “The higher the conversion rate is, the higher the price will be,” explained by ZENDURE, an electronics company in California, “The truth is unreliable batteries may be made of old laptop batteries. At present, power banks priced at over 20 dollars are relatively reliable.” To avoid being cheated, do not buy too cheap and go for the major reputable brands.
Understand Charging Specifications
There is a series of fasting charging technology like QC2.0 / QC3.0 / PE+ / VOOC / SCP / FCP / Dash / PD developed by different factories. They seem like something complex but actually, the theory is simple. There are only 2 ways to increase charging speed - increase current or increase voltage.
You can check the charging specifications (always printed on the plug) of your phone to know if it supports any quick charge technology. If the output is 9V or 12V, it obviously supports increasing voltage, like QC 2.0 / 3.0. Once the output displays 3A, 4A or 5A, it supports increasing current. If it only shows 5V2A or 5V1A, then I am afraid the device doesn’t support any quick charge technology. Now you have a clear idea about whether your device accepts a fast charge. Last but not least, please make sure you got a compatible cable together with the compatible power bank.
One more tip, if you are looking for a power bank especially for Apple products, it is better to get power banks that support USB Power Delivery (USB PD), which is a fast charge standard, able to control more watts and deliver more power.
The battery is the Core
There are 2 main battery types in the power bank market. One is Li-polymer battery and the other is lithium-ion (known as 18650) battery. Li-polymer batteries are safe and have a longer service time (around 500 times). It has a work output conversion rate that is generally 85% -95%. The disadvantage is the cost - compared with 18650, the price is double. 18650 batteries have a relatively lower price. They are portable and safe. However, 18650 battery possesses a lower output conversion rate between 75% - 90%. And the lifetime is shorter - it can only work around 300 times.
One piece of news is, we can look forward to Lithium iron phosphate batteries and 21700 batteries, which are around the corner of the power bank market. Due to their high price and relatively big size, they are mainly serving electric bikes, cars, and lights for now.
Nothing is more important than safety. As a bank to save & supply energy, the external batteries are a kind of a dangerous item. Instead of worrying about any danger or taking every power bank we purchased in the lab and test its safety, the most reliable way is to buy power bank from known brands, which has a series of safety protections, like SONY, XIAOMI, and SUAOKI.
To conclude, power banks vary in size, battery capacity, charging specifications, designs, and performance. I hope the above points let you understand power banks better and distinguish a good power bank from others. What power banks you like most? Let us know by leaving a comment below!