Alza's 20,000mAh power bank discounted by 150 CZK. It has excellent ratings and can charge three devices

Looking for an affordable power bank for less than 500 crowns that can charge your phone more than twice? AlzaPower Onyx Gen2 is now available on Alza for 449 CZK instead of 599 CZK with code ALZADNY25. It boasts three ports and has become very popular among users in the Czech Republic. Over 2,000 units have been sold, and its 4.7/5 rating speaks for itself.

Quick summary:
✅ Makes sense if you’re looking for a powerful travel power bank from a domestic brand with a three-year warranty.
⚠️ Consider that charging the power bank itself takes approximately 7 hours.
💡 For 449 CZK, you can charge an average phone with a battery around 5,000 mAh 3 to 4 times.

Why this power bank is interesting

AlzaPower Onyx Gen2 is Alza’s own brand, which has consistently delivered decent quality at low prices in the charging accessories segment. This 20,000 mAh variant is currently one of the best-selling power banks of this capacity on Alza – over 2,000 units sold, a rating of 4.7 out of 5 from 134 customers, 94% recommendation, and a return rate of only 1.01% speak for themselves.

In practice, this means a simple thing: you can charge an average modern phone with a battery around 5,000 mAh 3 to 4 times. For a weekend trip, a festival, a multi-day excursion, or a backup for a cabin without electricity, it offers an ideal balance of capacity, weight, and price.

Key parameters: 22.5 W, three ports, and Low Power Mode

The power bank has three outputs – 2× USB-C and 1× USB-A; both USB-C ports also function as inputs for charging the power bank itself. The maximum output is 22.5 W via USB-A and 20 W via USB-C in Power Delivery mode. When all three ports are used simultaneously, the total output drops to 15 W, which is standard for this category.

In terms of protocols, there’s full coverage for Power Delivery 3.0, Qualcomm Quick Charge 3.0, Samsung Adaptive Fast Charge, and Apple 2.4A, so charging will be fast regardless of the phone brand. Smart IC automatically detects the connected device and sets optimal power, while 6-fold protection addresses overvoltage, overload, short circuit, overheating, overcharging, and undervoltage.

A practical detail not common at this price point – Low Power Mode for charging small devices with low current draw. It’s activated by holding the button for 2 seconds and allows safe charging of wireless headphones, smartwatches, or fitness trackers, which would behave unstably on a regular output. Without this mode, the power bank would turn off automatically after a few seconds.

Practical aspects: ports, LEDs, airplane

Dimensions of 141 × 64 × 23 mm and its weight allow it to be carried in a jacket pocket or a small bag. For illustration – one user describes it as “not heavy or large at all, my older 10,000mAh one was larger and just as heavy.” Charging is indicated by four LED lights, giving you a quick overview of the charge status (there is no digital display here).

For air travel, the 77 Wh value is important – meaning it’s below the 100 Wh limit for carry-on luggage, which applies to most airlines. The package includes a reversible USB-C cable (30 cm), which serves both for charging the power bank and for connecting your devices.

An important note regarding charging the power bank itself: a full charge takes approximately 7 hours with an optimal 18W input. If you want a shorter time, you’ll need a quality 18W+ charger – with a slower 5W charger, you won’t get a reasonable charging time. This characteristic is not a weakness of the power bank, but rather the physics of a 20,000mAh capacity.

What users say

Out of 134 ratings, 109 customers gave a full 5 stars and another 17 gave 4 stars – meaning 94% of customers recommend the product. Over 2,000 units sold make this model one of the most proven in this capacity on Alza. The return rate of 1.01% is among the lowest in its category.

Four things dominate the praise – real capacity, 22.5 W charging speed, compact size, and price. One user praises the power bank for powering Meta Quest VR glasses during use, another describes charging a phone 4 times from 0 to 100%. A Slovak reviewer writes that the USB-A indeed delivers the declared 22.5 W. The 36-month warranty – one year longer than the legal standard – is above average at this price point.

Three points emerge from the criticism. The first is the longer charging time for the power bank itself – however, this is an expected characteristic of a 20,000mAh capacity. The second is its higher weight, which is unavoidable for this capacity. The third, rarer point, is isolated defective units – one user described that the power bank did not respond during the first charge, but Alza immediately replaced it without issues.

If this specific model didn’t catch your eye, but you’re looking for a power bank on sale, you can also browse the current Alza Days, where other discounted power banks and charging accessories regularly appear.

When it doesn’t make sense

If you need very fast charging above 22.5 W (for example, 65 W for a laptop or an iPhone Pro Max at full speed), this power bank will not provide sufficient power. For charging a MacBook or modern laptops, look at the AlzaPower Parade Gen2 100 W or Magma 100 W. Similarly, if you want a compact power bank for daily pocket carry, the 10,000mAh variant of the same model for 399 CZK, which weighs roughly half, makes more sense.

The second case is for people who want wireless charging or MagSafe. This power bank does not provide it – for an iPhone with MagSafe, look for Epico Mag+ or AlzaPower Qi2 Ultra Slim.

Verdict: who it’s worth it for

The AlzaPower Onyx Gen2 20,000 mAh for 449 CZK makes sense for anyone looking for a reliable travel power bank with three ports, Low Power Mode, and a three-year warranty. A rating of 4.7 out of 5, 2,000+ units sold, and a return rate of 1.01% make it one of the safer choices at this price point. Conversely, if you need higher power for a laptop or wireless charging, look for other models.

Do you choose a power bank more by price, or do you prefer premium features like wireless charging or high 100W power?