The Wireless Charger in Your Mystery Box: Qi, Qi2 and Slow Charging
A wireless charging pad is a common find in an electronics mystery box, and the first thing you notice is that it charges slowly. That is usually not a fault. Wireless charging has a standard with two power levels and a newer magnetic version, and a budget pad sits at the bottom of all three. Here is what the Qi logo promises, why "15W" on the box is not what your phone gets, and how you test it.
What Qi Is, and What the Number on the Box Means
Qi is the wireless charging standard run by the Wireless Power Consortium, and nearly every phone you can charge wirelessly uses it. Inside the standard are two power levels. The baseline profile delivers up to 5 watts, and almost any pad can do it. The extended profile goes up to 15 watts, but only when the pad, the phone and the power adapter behind the pad all support it, and only when the coils line up. In 2023 the consortium added Qi2, which puts a ring of magnets in the phone and the pad so they align every time, and delivers 15 watts through that magnetic profile to phones built for it, if you own one.
The wattage printed on a budget pad is usually its input, meaning what the pad draws from the wall, not what reaches the phone. A pad marked "15W" fed by a 10W adapter over a thin cable will deliver 5 watts to the phone, and even a well-fed pad loses a third of its power as heat in the transfer. So the slow pad on your desk is often a correctly labelled pad on a weak adapter. What the adapter and the cable can carry, and how you read them, is in how to read the USB cables in your mystery box.
Why It Is Slow, in Order of Likelihood
- Qi has a 5W baseline and a 15W extended level, plus the magnetic Qi2 profile; a budget pad usually delivers the baseline whatever its box says.
- The printed wattage is input, not output; the adapter, the cable, the alignment and your phone's own limit all cap what arrives.
- Test it on a wall adapter of at least 18W, phone centred, case off, for thirty minutes; a gain of 10 to 20 percent is normal, none is a fault, and a hot pad is one to retire.
- The adapter. A pad needs more power in than it delivers out. Plug it into a wall adapter rated at 18W or more, on a cable that can carry it. Feeding a pad from a laptop USB port or an old 5W phone cube gives you the slowest charge the pad can produce.
- Your phone's ceiling. Phones cap wireless input from the receiving side. Many take 7.5W or 10W on a third-party pad regardless of what the pad could give, and only a certified magnetic pad reaches the higher figure on phones that support it.
- Alignment. Without magnets, the coils have to overlap. A phone you leave an inch off centre charges slowly or not at all, and a phone that slides on a flat pad drifts out of range overnight.
- The case. Plastic cases under about 3mm are fine. Thick cases, metal plates, card holders and pop-out grips block or weaken the field. Test with the case off before you blame the pad.
- Heat. Wireless charging makes heat, and phones slow the charge when they get warm. A pad you leave on a sunny sill or under a pillow charges slower than one on a cool desk.
Work down the list before you decide anything is wrong. Most "broken" pads that sellers hear about are working pads you would recognise: a 5W cube and a thick case.
Pad, Phone and Adapter: What Combination Gets What
| Pad | Adapter | Phone | Realistic power to the phone |
|---|---|---|---|
| Basic Qi pad, no logo | Old 5W cube | Any | Under 5W; overnight only |
| Basic Qi pad | 18W or more | Any Qi phone | 5W, sometimes 7.5W |
| Qi-certified pad with logo | 18W or more | Android with extended profile | Up to 10W or 15W, if aligned |
| Qi-certified pad with logo | 18W or more | iPhone | 7.5W on most third-party pads |
| Qi2 magnetic pad, certified | 20W or more | Qi2 or magnet-ring phone | 15W, aligned by the magnets |
| Any pad | Any | Phone in a thick or metal case | Little or nothing |
Read your own row. If your pad has no Qi logo, no maker's name and no stated output, the first two rows are where it lives, and 5 watts is what you should expect. That is enough to charge a phone overnight and top it up on a desk, which is what most people use a pad for. It is not enough to replace a cable when you are in a hurry, and the pad was never going to be.
Note: Warm is normal; hot is not. A pad and phone that are warm to the touch after half an hour are doing what wireless charging does. A pad you cannot keep your hand on, one that smells, or one that makes the phone show a temperature warning is a pad to unplug and not use again. The mains adapter behind it carries the real risk, and its safety marks are worth a look before anything else; those are in UL and ETL marks on chargers from your mystery box.
The Thirty-Minute Test
- Plug the pad into an 18W or better adapter using the cable it came with, or a known good one.
- Take the case off and put the phone on the pad, centred. Confirm the charging indicator on the phone and the light on the pad both come on.
- Note the percentage and the time. Leave it alone for thirty minutes on a cool surface while you do something else.
- Read the gain. Ten to twenty percent in half an hour is a working basic pad. Twenty-five or more is an extended-profile pad doing well. Zero, or a pad that cycles on and off, is a fault after you have confirmed the adapter and alignment.
- Put the case back on and repeat if you want to know whether your case is the problem.
A pad that fails step four on a good adapter, case off, is the only outcome to report. Photograph the pad's label, the adapter's label and the phone's percentage at start and finish, and send them inside the seller's window; the routine is in how to document a mystery box on arrival.
Does It Fit Your Phone at All?
Wireless charging needs a phone with a receiving coil, and not every phone has one; many budget and some mid-range phones you might own charge by cable only. If your phone does not list wireless charging, the pad will light up and nothing will happen, and that is not a fault of the pad. Magnetic pads add a second question: they hold and align only on phones with the magnet ring, or on a case that adds one, and on other phones they behave as an ordinary flat pad. Which accessories fit which phones is in will the accessories in a mystery box fit your phone.
What This Means When You Order
You should expect a wireless pad from a mystery box to be a 5W desk charger and judge it as one. If you want 15W, buy a certified pad as a named product with the logo on it. What you can ask a seller is whether the pads in their boxes carry a Qi logo or a maker's name, and whether devices are powered on before dispatch; Mewoo tests devices before packing and states what its boxes are built around, and any seller should tell you the same. Then run the thirty-minute test on a real adapter, and you will know whether you have a slow pad or a dead one.
FAQ
Why does the wireless charger from my mystery box charge so slowly?
Because almost everything in the chain limits it. The wattage on the packet describes what the pad draws, not what it gives; your phone caps what it will accept from an unknown pad; a weak adapter starves the pad; a thick case or an off-centre phone weakens the field; and heat slows the whole process. Feed it from an 18W adapter, case off, phone centred, and a basic pad manages around 5 watts, which is normal.
What is the difference between Qi and Qi2?
Alignment, mostly. Original Qi relies on you placing the phone squarely over the coil, and its faster extended mode only works when that placement is right. The 2023 revision adds a magnet ring to both pad and phone, so the two snap together in the correct spot every time and 15 watts flows reliably to handsets built for it. Put a magnetic pad under a phone with no ring and you are back to ordinary Qi.
Does the "15W" on the box mean my phone charges at 15W?
Almost never on a budget pad. That figure is usually the input rating, and after the adapter, the cable, the transfer losses and your phone's own limit have taken their share, a third or less reaches the battery. iPhones in particular hold most third-party pads to 7.5W. Treat an unqualified wattage as marketing and treat the thirty-minute percentage gain as the measurement.
Will the pad work through my phone case?
Through a plain plastic or silicone case a few millimetres thick, yes, a little slower. Through a rugged case, a wallet case with cards, a metal plate for a car mount, or a pop-out grip, poorly or not at all, because those sit between the coils. Test once with the case off to see what the pad can do, then decide whether your case is worth the slowdown.
Is it safe to leave a cheap wireless charger on overnight?
If it stays merely warm, yes; wireless charging is designed for overnight use and phones stop drawing when full. What you should not ignore is a pad that becomes hot to hold, smells of plastic, or triggers a temperature warning on the phone. Unplug that one for good. The greater risk sits in the mains adapter behind the pad, so check its safety marks first.
How do I know if my phone supports wireless charging?
Look up the model's specifications or search the settings for a wireless charging option; many budget and mid-range phones charge only by cable, and a pad will light up under them without doing anything. Phones that do support it will show the charging animation within a second or two of being placed. No animation on a pad that works with another phone means your phone lacks the coil.
Final Thoughts
A budget wireless pad is a 5W desk charger, and the number on its box is the input, not what your phone gets. Qi sets the baseline, the extended level needs a certified pad and a willing phone, and Qi2 adds magnets for alignment. Feed the pad from an 18W adapter, take the case off, centre the phone, and read the gain after thirty minutes. Slow is the product; zero, or hot, is the fault.
If you want a box whose accessories are powered on before dispatch and whose categories are stated on the product page, start with the Triple Reveal Electronics Mystery Box (3 items) or the Party Electronics Mystery Box (6 items). Compare every tier side by side on the electronics mystery box category page.
See how devices are tested before dispatch →
