How to Test a MacBook Charger Without Extra Hardware
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You can test a MacBook charger without buying a USB-C power meter: macOS already knows the charger’s identity, its negotiated wattage, and the history of every connect and disconnect. The test has three parts: read the negotiation, compare it with the rating, and watch reliability over time. The first two take five minutes; the third is what usually gets skipped, and it is where broken chargers hide.
How do you read what the charger negotiated?
Open System Information (hold Option, click the Apple menu, choose System Information), then select Power in the sidebar. Under AC Charger Information you will see the connected charger’s wattage, manufacturer, and whether it is charging. This is the negotiated figure: what your Mac and the charger agreed on, through the cable you used. On a healthy setup it matches the charger’s rating or a standard USB-C PD level just below it.
What does a mismatch between rating and negotiation mean?
A large, persistent gap means a weak link. A 96W charger negotiating 60W usually means the cable is not rated for high current; the same charger negotiating 20W points at a degraded cable, a damaged charger, or a port problem. Swap the cable first, since cables fail far more often than chargers, and re-check the number. The ladder for isolating the guilty part is covered step by step in MacBook not charging? Find the broken part.
Why is a five-minute test not enough?
Because the worst charger faults are intermittent. A charger can negotiate its full wattage at 9:00 and drop power for a minute at 23:47. Snapshots cannot catch that; only observation can. macOS quietly records these events in its power log (the /var/log/powermanagement folder), but the log is unreadable for most people and rotates away after a couple of weeks.
This is the part Broken Charger automates. It watches charging continuously from the menu bar, records every dropout with a timestamp in plain words, and with your one-time permission reads that same power log so it can judge roughly the past two weeks on day one. A charger that misbehaved last Tuesday at midnight is caught without you having been awake for it.
What does a full charger test look like?
- Identity and negotiation. Plug in, read the negotiated watts (System Information, or live in Broken Charger’s menu bar item). Compare with the printed rating.
- Cable cross-check. Repeat with a second cable if you have one. If the number jumps, the first cable is the problem.
- Load check. Do something heavy (a video export, a game) and watch whether the battery still gains. A healthy, sufficient charger keeps up; if it cannot, check whether the wattage fits your Mac.
- Reliability over a day or more. Use the Mac normally and count unexplained power losses. Zero is the only good number. One-off blips after plugging in do not count; repeated losses with nobody touching the setup do.
When should you replace the charger?
Replace it when a known-good cable and socket still produce dropouts or a badly reduced negotiation that follows the charger around. That last phrase is the key evidence: Broken Charger remembers each charger by name, so when the “Travel 67W” misbehaves at your desk and in a cafe while the “Desk charger” is clean in both places, the verdict writes itself, and the money goes to the right replacement.
Frequently asked questions
Can I test a charger with a multimeter? Not usefully. USB-C Power Delivery only supplies higher voltages after a digital negotiation, so a bare multimeter reads 5V or nothing. Inline USB-C meters exist, but the software route above answers the same questions without hardware.
Does Apple’s own hardware diagnostics test chargers? Apple Diagnostics (hold D at startup) focuses on the Mac’s internal components, including its power system, and can flag adapter issues, but it is a snapshot too; it cannot see intermittent failures over days.
Is a swollen or crackling charger worth testing? No. A charger that is physically damaged, buzzing, crackling, or running alarmingly hot should be retired immediately, whatever any test says.
Let your Mac watch its own charging
Broken Charger is a menu bar app for Mac (macOS 12.0 or later, Apple Silicon and Intel) that watches how reliably your Mac charges, catches power that comes and goes, and walks you through finding the broken part: wall socket, plug piece, cable, or charger. No subscription, no accounts, no ads, and no data collection; the app contains no network code at all.
Download on the Mac App Store