A solar power bank's built-in panel is too small to do much: testers measured only a few per cent of charge after hours in strong sun. For a power cut, keep an ordinary 20,000 mAh power bank charged, which gives several phone charges. If you want solar, add a separate folding panel, which collects several times as much.
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Slowly. What testers and makers found for banks with a panel on the case:
A separate folding panel does much better. OutdoorGearLab measured 2,351 mAh in an hour of direct sun from EcoFlow's 45 W panel, and 1,389 mAh in its indirect-light test. None of these tests tells you what a panel will collect in a UK winter, so treat solar as a top-up, not a plan.
Roughly four from a 20,000 mAh bank for a typical smartphone: eReviews.dk got two full iPhone 15 Pro charges, from about 10%, out of a 10,000 mAh bank. Bigger phones and tablets get fewer.
Why it isn't simply the bank's mAh divided by the phone's: capacity in milliamp-hours is measured at the battery's own voltage, so the energy in watt-hours is mAh × volts ÷ 1,000: a 20,000 mAh bank at 3.6 V holds 72 Wh. Some is lost in conversion: EcoFlow says its 25,000 mAh RAPID bank gives 14,500 mAh at 5 V.
Anker's UK safety guide gives an operating and storage range of 0-35°C and recommends recharging a stored power bank every three months. Anker.
| Model | Capacity | Ports | Weight | Price |
|---|---|---|---|---|
| UGREEN Nexode Power Bank 20000mAh 165W | 20,000 mAh | Retractable USB-C cable, plus USB-C and USB-A; 100 W from one, 165 W in all | Not published | £79.99 |
| Anker Laptop Power Bank 25K 165W (A1695) | 25,000 mAh (about 90 Wh) | 2 built-in USB-C cables, plus USB-C and USB-A; 100 W from one, 165 W in all | 594 g | £89.98 |
| Anker Power Bank 20000mAh 22.5W with built-in cable (A110E) | 20,000 mAh | Built-in USB-C cable, 22.5 W; three devices at once | 392 g | £27.99 |
| Nitecore NB20000 Gen3 | 20,000 mAh (72 Wh) | 2 x USB-C, 20 W | 291 g | £104.95 |
| Sandberg Solar 6-Panel Powerbank 20000 | 20,000 mAh (74 Wh) | USB-C 20 W, 2 x USB-A 18 W | 660 g | See the price at Amazon |
| Sandberg Outdoor Solar Powerbank 10000 | 10,000 mAh (37 Wh) | USB-C 20 W, USB-A 22.5 W | 250 g | See the price at Amazon |
The makers' figures.
20,000 mAh with a retractable USB-C cable plus USB-C and USB-A sockets: up to 100 W from one USB-C port, 165 W across two. Enough to charge phones for a household through a day or two, and a laptop at a push.
25,000 mAh, about 90 Wh by Expert Reviews' figure, with two built-in USB-C cables and two more sockets. Anker says it can charge from the mains while it charges your devices, if the charger is rated at least 20 W and puts in more power than the devices draw. USB-A tops out at 33 W, and two devices share 165 W (130 W for three or four). At 594 g it's a brick.
See today's price at AmazonWhat testers found (Expert Reviews)
20,000 mAh with a built-in USB-C cable at 22.5 W, enough for a phone to charge at a normal speed, and it charges three devices at once. Anker says it recharges in about 5.5 hours.
20,000 mAh (72 Wh) at 291 g, splash-proof to IPX5, with up to 20 W through one USB-C port, or 15 W shared. Slower than the others and no cable included, but small enough to live in a coat pocket.
£104.95 at Nitecore UKSearch AmazonWhat testers found (Techtest.org)
A 20,000 mAh bank with six panels that fold out to 7.5 W, far more than a panel on the case. Sandberg still says 12 hours of sun for a full charge, so treat it as a power bank that tops up in sunshine.
See today's price at AmazonSold out at CurrysWhat testers found (CHIP)
A tough 10,000 mAh bank with a small panel on the case. Sandberg says 30 hours of sun for a full charge, so charge it from the mains and treat the panel as a bonus.
A 45 W folding panel with a USB-C socket for a power bank or phone, and a DC plug for EcoFlow power stations. EcoFlow's manual limits the USB-C output to 15 W (5 V, 3 A), so a phone charges at about the speed of an ordinary charger.
Sold out at EcoFlow when we checked on 4 November.
See today's price at AmazonSold out at EcoFlowWhat testers found (OutdoorGearLab)
A 30 W folding panel with USB-C (5 V, 3 A) and USB-A sockets, at 1.1 kg. Cheaper than the EcoFlow, and charges a phone or power bank directly.
These are findings other testers have published, credited with links.
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