How to choose the right laptop charger or battery (and avoid fakes)

Quick answer: what must match on a laptop charger?

• Voltage (V): must match the original. This is not flexible on traditional barrel chargers.
• Current (A) or power (W): the replacement must be equal to or higher than the original. A higher rating is safe; the laptop only draws what it needs. A lower rating can overheat the charger and charge slowly or not at all.
• Connector: the plug size, shape and centre pin must fit and make good contact.
• Polarity: which part of the plug is positive. Almost all laptop chargers follow the same convention, but check the symbol on the label.

If you are replacing a charger, the surest method is to read the label on the old one, then buy one with the same voltage, the same or higher watts, and the same connector.

How to read the label on your charger

Look at the small print on the charger brick, not the plug. You will find two sets of numbers.

• INPUT: what the charger takes from the socket, such as 100-240V and 50-60Hz. A range like that means it works on Nigerian mains. Ignore the input numbers when choosing a replacement, apart from checking the range.
• OUTPUT: what it gives the laptop, such as 19V and 3.42A. This is what you match.

Working out watts. Multiply volts by amps. For example, 19 volts at 3.42 amps is about 65 watts. If a label shows watts but not amps, divide watts by volts to get amps. If you want a spare, buy the same watts or higher.

The polarity symbol. A small circle diagram shows whether the centre pin is positive or negative. Most laptops use a positive centre pin. Match the symbol.

If the label has worn off, find the laptop's model number on the sticker under the laptop or in Settings, System, About, then look up the original charger specification for that model from the maker, and confirm with the seller.

Connector types and why a fitting plug is not enough

Laptop chargers use several connector types:

• Barrel connectors. Round plugs in different sizes. A plug that seems to fit but is slightly loose gives an unreliable connection. Measure and compare with the old one. Some barrels have a pin in the middle.
• Rectangular or slim-tip connectors. Used by several makers.
• Proprietary connectors with a data pin. Some chargers have an extra centre pin or wire that tells the laptop what charger is plugged in. Without the correct signal, the laptop may show a message that the adapter is not recognised, limit charging or run slowly.
• USB-C. Many modern laptops charge through USB-C, using Power Delivery. Buy a charger that supports Power Delivery with enough wattage for your laptop, and a cable rated for that power. A phone charger will usually charge a laptop very slowly or not at all.

Never force a plug, and never use an adapter tip that wobbles. A bad connection creates heat at the plug and can damage the charging port on the laptop, which is a harder repair.

Genuine, compatible and fake chargers: what is the difference?

• Genuine (original): made or authorised by the laptop maker. Usually the safest, though not always the cheapest.
• Compatible, from a reputable maker: made to the right specification by an established company, with safety markings and a warranty. Often a good option.
• Poor copies: unmarked or cheap units that copy the look of the original but use weak components and poor safety design.

Signs of a poor charger:

• It is much lighter than the original of the same wattage, because it lacks proper internal parts.
• The label is blurry, misspelt, has no model number or has output figures that do not make sense.
• There are no safety or certification markings, or the markings look pasted on.
• The plug shakes or the casing has rough seams, sharp edges or gaps.
• The cable is thin, stiff or very short compared to the wattage.
• The price is far below that of the same model elsewhere.

Chargers carry mains voltage inside, so quality is a safety matter, not just a performance matter. A poor charger can overheat, damage the laptop's board and battery, or cause a fire.

How to find the right replacement battery

1. Find your laptop's exact model. Look for the label under the laptop, or Settings, System, About. Write down the full name and model number.
2. Find the battery part number, if you can. Removable batteries have a label showing part number, voltage and capacity. For built-in batteries, the model number of the laptop is used.
3. Match the key figures: voltage, the number of cells, the physical shape and the connector. Capacity in mAh or Wh can be equal or slightly higher.
4. Check compatibility with the seller. Give the seller your exact model number and ask them to confirm.
5. Ask about the warranty and return policy. Batteries wear, so a reputable seller gives a clear written warranty.

Be careful with claims of huge capacity at a tiny price. Capacity figures are easy to print and hard to verify. Check what a battery really delivers with a Windows battery report a few weeks after fitting.

Built-in batteries. Many modern laptops have batteries behind the back cover and are glued or screwed in place. Replacing them involves opening the laptop and dealing with a lithium cell. Unless you have experience, ask a technician.

Is my battery worn out, or is it the charger?

Check before buying. Start with the charger: try a different, known good charger of the same rating if you can borrow one, and check the cable for kinks, cuts or loose parts. See our article on a laptop not charging for step-by-step checks.

To test battery health in Windows:

1. Right-click Start and open Terminal or Command Prompt as administrator.
2. Type powercfg /batteryreport and press Enter.
3. Open the file path it displays in a browser.
4. Compare Design capacity with Full charge capacity. If full charge capacity has fallen well below design capacity, the battery has aged and holds much less than when new.

A battery that drains in minutes, shuts the laptop down suddenly, or only works while plugged in is probably worn. A laptop that does not react when plugged in, or charges only when the cable is held a certain way, points to the charger, cable or charging port.

Safety: signs of a bad charger or battery

Stop using the charger or battery and disconnect it if you notice:

• A burning, fishy or chemical smell.
• Sparks, popping, crackling or a loud buzz or whine.
• A charger that is too hot to touch comfortably. Warm is normal; hot enough to be uncomfortable is not.
• Melted or discoloured plastic, or marks around the connector.
• A frayed, cracked or exposed cable.
• Charging that stops and starts when you move the cable.
• A laptop casing that bulges, a trackpad that lifts, or a gap opening around the case. These are signs of a swollen battery.

If a battery is swollen, switch the laptop off, unplug it, and do not charge, press on, puncture or try to open it. Keep it on a hard, non-flammable surface away from anything that burns and take it to a technician. Swollen lithium batteries can catch fire. Do not throw one in ordinary rubbish.

Everyday habits that help: do not charge under a pillow or on a bed, do not wrap the charger tightly around the brick, keep it away from liquids, and use a good surge protector or stabiliser where power fluctuates. Unplug during storms.

Frequently asked questions

Written by the ICT AccessPoint team

We repair laptops and build websites and business systems. Have a question this guide did not answer? Message us.

This guide is general advice. Every device and business is different, so if you are unsure, ask a technician before you act.