Tom's Hardware tested 13 power banks, ranging from slim 5,000 mAh units with a single 22W port to 25,000 mAh multi-port bricks rated at 220W. Prices run from $24.99 for the Cuktech CP12 to $129.99 for the Anker Prime A110B. The review notes that the right choice depends on ports, output, capacity, size, and safety features, not just the number on the box. All tested units support USB Power Delivery 3.0 or higher, but a small 25W bank that can top up a phone will not fast-charge a laptop that can draw around 90W.
One of the most important caveats is that rated capacity is based on the battery's 3.7V cell voltage. Actual usable capacity changes with the voltage needed by the device being charged: at 5V it can be roughly 60% of the listed capacity, but at 20V for laptop charging it can drop to around 20%. That means a high-capacity bank may still deliver far less laptop runtime than its label suggests.
Pass-through charging—charging the bank while it charges another device—is supported by most models, but not all. Belkin's Ultracharge limits output to 15W while charging, and Tom's Hardware could not confirm support on the Cuktech CP12 or Baseus PicoGo Air. The review also advises sticking with name-brand banks, which typically include overcharge, over-current, over-voltage, and over-temperature protection; off-brand units should at least carry UL/CE/CCC certification.