Sunslice Gravity 20
(3 reviews)
With 20000mAh and up to six smartphone charges claimed, the Sunslice Gravity 20 is built for long stretches outdoors, far from any mains socket.
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Characteristics
- Capacity: 20000mAh, or 74Wh
- Weight: 400g (140 x 69 x 26 mm)
- Output: 1x USB-C + 2x USB-A, 18W (PD/QC3.0)
- Input: USB-C, 18W
- Up to 6 smartphone charges, built-in LED torch
Detailed overview: Sunslice Gravity 20
The Gravity 20 is the high-capacity reference in the Sunslice Gravity range, built for multi-day trips far from a mains socket. At 400 grams for 140 x 69 x 26 mm, it still fits in a hiking backpack without disappearing, a sensible trade-off for 20000mAh of capacity.
Its 20000mAh (74Wh) capacity can, according to Sunslice, recharge a smartphone up to six times on a single charge, a figure that holds up for reasonable use once typical conversion losses are factored in. Power is spread across three ports: a USB-C port with Power Delivery and two USB-A ports with Quick Charge 3.0, each capable of up to 18W, enough to charge up to three devices at once. The battery itself recharges via its USB-C port, also capped at 18W: expect around 50 minutes to reach 60% with a fast charger, and several hours with a standard mains charger.
Four LED indicators show remaining charge, and a built-in LED torch comes in handy while camping, wild camping or during a power cut at home. Like the rest of the range, the Gravity 20 is designed to pair with Sunslice's foldable Fusion Flex solar panels, letting you top up your energy reserve outdoors without relying on a socket.
Up against rivals like the Baseus Bipow Pro 20000mAh or the Anker Zolo 20000, the Gravity 20 is neither the lightest nor the most powerful in its category, but it stands out with its built-in torch, the Sunslice solar ecosystem and a two-year warranty. It's a safe choice for long-distance hikers, families living out of a van, or anyone wanting a reliable energy reserve for power cuts, rather than a battery built for ultra-fast city charging.
Full specifications
Detailed characteristics
Battery
| Rated capacity?Cell capacity in milliamp-hours, as stated by the manufacturer. | 20000 mAh |
|---|---|
| Actual energy?Actual stored energy in watt-hours; what matters for runtime and air travel (100 Wh cabin limit). | 74 Wh |
| Battery chemistry?Cell type; LFP lasts longer, Li-ion/LiPo is lighter. | Li-ion |
Output (device charging)
| Max output power?Maximum total power delivered; above 60 W it can charge a laptop. | 18 W |
|---|---|
| USB-C ports?Number of USB-C ports and the fastest port's power. | 1 × 18 W |
| USB-A ports?Number of USB-A ports and maximum power. | 2 × 18 W |
| Fast-charge protocols?Supported fast-charge standards (PD, QC, PPS…); PD/PPS is the most universal. | USB PD, QC 3.0 |
| Wireless charging (Qi)?Inductive charging of a phone placed on top, and its power. | No |
| Magnetic attachment (MagSafe)?Attaches magnetically to the back of a MagSafe-compatible iPhone. | No |
Recharging the power bank
| Recharge power (input)?Maximum input power to recharge the power bank; higher means faster. | 18 W |
|---|
Cable and interface
| Built-in cable?A cable is permanently attached to the power bank (nothing extra to carry). | No |
|---|---|
| Retractable cable?The built-in cable retracts into the housing. | No |
| Cable included?A cable is included in the box. | Yes |
| Display?Level display: simple LED indicators or a digital screen (%, watts). | LED indicators |
| LED light?Built-in LED torch / light. | Yes |
Form factor
| Weight?Weight of the power bank, in grams. | 400 g |
|---|---|
| Dimensions (L × W × D)?Length × width × depth, in millimetres. | 140 × 69 × 26 mm |
Availability and warranty
| Warranty?Length of the manufacturer's warranty. | 2 years |
|---|
⚡ How many charges with this power bank?
With 74 Wh of capacity, the Sunslice Gravity 20 power bank recharges iPhone 16 ~3.9 times or Samsung Galaxy S25 ~3.5 times.
| Smartphone | Charges |
|---|---|
| iPhone 13 | ~4.3 |
| iPhone 16 | ~3.9 |
| iPhone 17 Pro | ~3.2 |
| iPhone 17 Pro Max | ~2.7 |
| Tablet / console | Charges |
|---|---|
| Nintendo Switch 2 | ~2.7 |
| iPad Air | ~1.8 |
| iPad Pro (M5) | ~1.7 |
| Xiaomi Pad 7 | ~1.6 |
Rough estimate: real-world losses (conversion, cable, heat) are around 25 to 35%.
Comparison
Around £25-45, the Gravity 20 goes up against many 20000mAh power banks popular in searches like "Gravity 20 vs Baseus Bipow" or "best 20000mAh power bank for hiking". Here's how it compares to three alternatives of equal capacity: the Baseus Bipow Pro 20000mAh, very affordable; the Anker Zolo 20000, more powerful; and the Xiaomi Redmi 20000mAh, a budget option.
| Criterion | Sunslice Gravity 20 | Baseus Bipow Pro 20000mAh | Anker Zolo 20000 | Xiaomi Redmi 20000mAh |
|---|---|---|---|---|
| Capacity | 20000mAh (74Wh) | 20000mAh (76Wh) | 20000mAh | 20000mAh |
| Output power | 18W (3 ports) | 22.5W | 30W | 18W |
| Weight | 400g | ≈ 340g | ≈ 353g | ≈ 434g |
| Built-in LED torch | Yes | No | No | No |
| Works with solar panels | Yes (Sunslice ecosystem) | No | No | No |
| Observed price | £44.94 | ≈ £22 | ≈ £38 | ≈ £23 |
In short, the Baseus Bipow Pro and the Xiaomi Redmi remain noticeably cheaper, and the Anker Zolo 20000 wins on raw power with its 30W output. The Gravity 20 stands out with its built-in LED torch, a more compact shape than the Xiaomi despite matching capacity, and above all its direct compatibility with Sunslice solar panels, a real advantage for anyone after a self-sufficient energy reserve on a long hike rather than the fastest charge at the lowest price.
Our tester's review: Guillaume Hoarau
We tested the Gravity 20 on a long bikepacking trip with wild camping, exactly the kind of use Sunslice designed this range for. With 20000mAh, it easily covered three days recharging a phone, a GPS bike computer and a headlamp without breaking a sweat, matching other users' reports of at least four full smartphone recharges. The three ports let you top up several devices at once, handy in a group or with family. The one genuine complaint, echoed in several customer reviews, is the weight: at 400g it's noticeable in an already-loaded bag, and the casing showed light micro-scratches after a few weeks of daily carrying. Nothing dramatic, but we'd rather keep it in a dedicated pocket than loose with the keys. For regular outdoor use or family emergency back-up, it's a safe bet, as long as you accept the weight-to-capacity trade-off that comes with any battery this size.
Frequently asked questions: Sunslice Gravity 20
Sunslice claims up to 6 smartphone charges from its 20000mAh (74Wh), a figure that holds up for reasonable use once typical conversion losses are factored in.
Yes, at 74Wh it stays within the 100Wh cabin baggage limit with no special permission, as long as it's carried in hand luggage: lithium batteries are banned from the hold.
400 grams for 140 x 69 x 26 mm, a reasonable size for 20000mAh, though it's still noticeable in an already-loaded bag, as several customer reviews confirm.
Expect around 50 minutes to reach 60% with an 18W USB-C fast charger, and several hours with a standard mains charger, which isn't included.
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Published on 30/08/2026