Guide · 6 min read
Replacing a lost or dead charger.
Two rules cover almost every case: voltage must match, and amperage may be equal or higher. Everything else — connector shape, polarity, protocol — follows from reading the OUTPUT line on the old brick or the device's own port label.
Reading the label
Every legitimate power supply prints two lines. INPUT: 100–240V~ 50/60Hz means it works anywhere in the world. OUTPUT decides your replacement. A USB-C brick lists several profiles — 5V⎓3A, 9V⎓3A, 15V⎓3A, 20V⎓3.25A — and the highest volts × amps is its wattage, 65W here. A barrel-plug laptop supply lists exactly one — 19.5V⎓3.34A, or 65W — plus a polarity symbol showing whether the centre pin is positive.
| Spec | Rule | What happens if you get it wrong |
|---|---|---|
| Voltage | Must match (±5%) | Too low: will not run. Too high: damage. |
| Amperage | Equal or higher is fine | Too low: overheats or the device throttles |
| Polarity | Must match the symbol | Reverse polarity can destroy the device |
| Barrel size | Must match in mm (e.g. 4.5×3.0) | Loose fit arcs; wrong size will not seat |
| USB-C profile | Needs the rail the device wants | Charges slowly or not at all |
If the old brick is gone, the device usually tells you: laptops print the required input beside the DC jack or on the underside label, and phones and tablets state maximum charging input in the spec sheet. Failing both, the model number plus "power adapter specification" in the maker's support documents is reliable. Never guess a voltage — that is the error that costs you the device rather than the charger.
The modern replacement for each old brick
| What you lost | What to buy now | Note |
|---|---|---|
| Apple 5W USB-A cube | 20W USB-C + USB-C to Lightning | Four times faster on any iPhone 8 or later |
| Apple 12W USB-A iPad brick | 30W USB-C | Also fast-charges iPhone and MacBook Air |
| Apple 61W USB-C | 65W USB-C PD (GaN) | Direct equivalent, smaller and cheaper |
| Apple 87W USB-C | 96W or 100W USB-C PD | Superset; charges the older machine fully |
| Samsung 15W micro-USB brick | 25W USB-C with PPS | PPS is required for Super Fast Charging |
| Nintendo Switch 39W (15V/2.6A) | 45W PD with a 15V rail | Docked play needs the 15V step specifically |
| 19V or 19.5V barrel laptop brick | Matched barrel, or USB-C if the laptop supports it | Check for the USB-C charging icon on the port |
| MagSafe 1 / MagSafe 2 MacBook brick | MagSafe brick only | USB-C PD cannot feed a MagSafe 1/2 port |
Sizing up rather than exactly
On anything USB-C, buying more watts than the original is risk-free: the device negotiates its own profile and draws only what it asks for — the whole point of Power Delivery, covered in can I use a higher-wattage charger. A lost 20W phone brick can be replaced by a 65W three-port unit that covers a laptop too. The rule that survives is protocol: a Galaxy needs PPS, a 16″ MacBook Pro the 28V PD 3.1 rail, a Switch dock 15V.
The reverse is not true for fixed-output supplies: a 19V barrel brick must be replaced with 19V, not 20V "close enough", and a device rated for 3.34A should not be fed from a 1.5A supply. See amps, volts and watts explained.
Buying it safely
Replacement chargers are the most counterfeited accessory category, because people buy them urgently and cheaply. Insist on a UL or ETL mark and a published profile table, and read avoiding counterfeit listings before ordering a branded brick at a suspicious discount. Pair it with the right cable — over 60W, a 5A e-marked one, per the cable guide. Start from the wattage map, or browse laptop adapters and USB-C chargers.
FAQ
Can I use a charger with higher amperage than the original?
Yes. Amperage is a supply capability, and the device draws only what it needs. Voltage is the number that must match, and polarity must match on barrel-plug supplies.
How do I find out what charger my laptop needs?
Check the label beside the DC jack or on the underside, which usually prints the required volts and amps. Otherwise search the model number plus power adapter specification in the maker's support documents.
Can I replace a barrel-plug laptop charger with USB-C?
Only if the laptop's USB-C port accepts Power Delivery input, usually indicated by a charging icon or stated in the manual.
Is a third-party replacement charger safe?
Yes, when it carries a genuine UL or ETL mark, publishes its output profiles and comes from a seller you can identify. The risk is counterfeits, not third-party manufacture.