Anker Nano 10K Review: A1259 vs A1638

The Anker Nano Power Bank (10K, 45W), model code A1638, and the Anker Nano Power Bank (10K, 30W), model code A1259, both arrive in Anker’s standard retail box with a short USB-C cable for recharging the bank itself. No wall charger is included, so you need a 30W source to refill either bank in reasonable time.

The A1259 stands out for how flat it is: a 26mm profile that sits flush in a palm or jacket pocket. The A1638 is more block-shaped at 36mm thick, the cost of fitting the retractable cable mechanism inside the housing.

Both units have a physical button that wakes the LED display: press once to check remaining charge, hold to start output. The A1638 display is light-sensitive and brightens outdoors, where the A1259 screen can need a second look.

Both models share Anker’s Nano design language: a rounded rectangular body, a soft-touch matte finish and a color LED display. The A1259 measures 104 x 52.3 x 26mm, the A1638 a shorter but thicker 81 x 50 x 36mm.

The fixed cable on the A1259 exits the curved short edge and folds flat against the body when not in use. The A1638’s InstaCord cable sits flush in the same edge and pulls out to 70cm with firm, smooth resistance.

A USB-A port and the USB-C input sit side by side on the flat short edge of both units. The A1638 adds a rubber cap over its USB-C input, which the A1259 lacks.

Build quality matches Anker’s mid-range standard, with no flex in the chassis on either unit. Anker rates the InstaCord mechanism for 20,000 bends and 20,000 pulls, a higher durability rating than most built-in cables at this price.

The A1259: fixed USB-C cable and USB-A port on the short edge.

The A1638 delivers 45W to a single device through its built-in USB-C cable. Anker confirms up to 40W for the iPhone 17 series and 45W for compatible Samsung devices, while the A1259 peaks at 30W.

Independent testing by TechRadar (October 2025) measured output matching Anker’s rated values, and noted the A1638 runs warm under sustained peak load, consistent with ActiveShield 3.0 thermal management doing its job. The A1259 runs cool at 30W.

Connect a second device through the USB-A port and total output is shared: 24W on the A1259, 22.5W on the A1638. That covers a phone plus earbuds, but two phones at full speed is not what either model is built for.

No outlet has published a measured conversion-efficiency figure for either model, so we are not quoting one. The estimates below assume about 80% efficiency, the typical figure for this class, and they come out the same for both models.

The A1638 supports pass-through charging. With a device plugged in while the bank itself recharges, it prioritizes the device to about 80%, then redirects power to refill the bank, per Anker’s official documentation.

Anker does not list pass-through for the A1259, so treat that model as charge first, then use. If topping up a device while the bank recharges matters to you, the A1638 is the one to pick.

Both models accept 30W input, so a full recharge from flat takes about 2.5 to 3 hours with a 30W charger, which suits an overnight charge cycle. Anker says the A1259 reaches about 50% in 45 minutes.

At 215g and 232g, both models are light enough for daily carry without becoming the heaviest thing in a bag. The A1259’s flat profile disappears into a jeans pocket or slim bag sleeve, while the A1638’s thicker body sits better in a jacket or rucksack pocket.

In power-to-weight terms the A1259 returns 46.5 mAh per gram and the A1638 43.1, both typical for the pocket 10K class. The gap is the cost of the retractable mechanism, and it is a fair trade if you will use the cable daily.

Neither model needs a separate cable, which is the point of the design: the lead you need is always attached. The A1638’s rewind keeps it tidy, while the A1259’s folds flat against the body.

Darleene’s takeI carry a lot on a 12-hour shift, so a heavy bank dragging my bag down is the last thing I need. The Nano 10K goes in and I stop thinking about it, and the built-in cable is the part that counts: no rummaging for a lead at 2am.

At about 36Wh, both Nano 10K models sit well inside the 100Wh carry-on limit that applies on UK, EU and US carriers, so there is no separate airline approval step: every power bank under 100Wh is automatically cleared to fly. Banks must travel in your carry-on, never in checked bags.

Full rules are in our Can you take a power bank on a plane? guide. Check any capacity in seconds with our mAh to Wh calculator.

Anker’s official figures: the A1259 weighs 215g and measures 104 x 52.3 x 26mm, a flat slab that sits neatly behind a phone. The A1638 weighs 232g at 81 x 50 x 36mm, shorter but chunkier. Both carry a 10,000mAh cell, about 36Wh.

Both models meet the relevant safety standards for UK and EU sale, per Anker’s UK product pages: CE marking, FCC certification, RoHS compliance and UN38.3 air-transport battery certification. The A1638 adds ActiveShield 3.0 thermal management.

Neither model appears on Anker’s official recall page, which lists every model covered by Anker’s voluntary power bank recalls; checked September 2026. Anker publishes safety notices there, and both models carry an 18-month warranty. Confirm the certification marks on the unit and packaging when yours arrives.

Port and cable design is where the A1638 earns its premium: the retractable InstaCord is rated for 20,000 bends and 20,000 pulls and carries the full 45W. No fixed-cable rival at this price matches it, including the A1259.

Charging speed favours the A1638 as well. Its 45W output is the fastest available in a 10,000mAh bank with a built-in cable, and TechRadar’s October 2025 testing measured it matching Anker’s rated values.

Carry rating is the A1638’s weakest score. At 232g and 36mm thick it sits upright rather than flat, the honest cost of the rewind mechanism, while the A1259’s 215g flat slab scores 7.5 here.

Value is the A1259’s best score at 8.0: a built-in cable, a bonus USB-A port and 30W output at lower spend. The A1638 scores 7.5, because the premium only pays off if you will use the retractable cable daily.

That is how both land on 7.5. Buy the A1638 for speed and cable convenience, the A1259 for a flatter, lighter carry at lower spend, and look elsewhere if you need to power a laptop.

The Anker Nano 10K solves a real problem: the cable you need is always attached. Both models deliver their rated speeds in independent testing, and both sit well within the airline carry-on limit.

The A1638 is the stronger buy for fast charging: 45W output, up to 40W for the iPhone 17 series, and the retractable InstaCord cable. The cost is a thicker body and a higher spend over the A1259.

The A1259 is the easy recommendation for everyday carry: flatter, lighter and cheaper, giving up 15W of peak speed most phones will never use. If you fast-charge an iPhone 17 or a premium Samsung daily, pick the A1638; everyone else should save the difference.

Quick answer: the Anker A1259 vs A1638 choice is an Anker Nano 30W vs 45W decision. Buy the A1638 if you want 45W fast charging and a retractable cable; buy the A1259 if you prioritize a flatter, lighter carry and do not need more than 30W.

Both score 7.5 out of 10 and both are recommended. The right choice depends on how you charge your phone and where you carry the bank.

The INIU Pocket Rocket P50 matches the 45W output at roughly 160g, but its cable is a detachable lanyard rather than a built-in rewind. The Zendure SuperMini 10K is the compact low-power option at 20W.