Can a laptop tell if a charger is non-OEM?

Question

A few days ago, my Dell Inspiron 15 7558 started throttling down to 0.48GHz while plugged in. The only way to get the i5-5200U performing back around its native 2.2GHz is to unplug the charging cable and wake the computer from sleep. Waking it from sleep and leaving it plugged in means a return to throttled state within about ~5 minutes.

I recall in the last couple of months seeing "the AC power adapter type cannot be determined..." intermittently, but it still charges the battery just fine (and the message is not consistent).

At this point, my troubleshooting has landed me on "try a new charger/power supply". I'd like to go with a non-Dell brand to keep costs low in case that's not the issue, but I'm concerned:

Can the laptop determine whether it's a 3rd party charger and do I risk it still throttling if so? Or can I reasonably expect it to stop throttling so long as its' replaced with a charger whose specs exactly meet that of the branded Dell charger? (e.g. 45W, 19.5V, 3.1A, correct polarity and plug size)

Answer 1

Unfortunately, there's more to detect than just the specs. Dell has a long history of trying to push non-OEM chargers for their devices off of the market with this sort of thing. Their chipsets often detect fluctuations in power, not just by volume but by frequency. Since this is typically unlisted and is normally something wholly managed by the circuitry on the motherboard which receives the power (which is why the minor differences don't break anything), Dell is aware of its own power signature and uses it like a market-rigging form of hardware DRM. A Dell charger can also cause this error if the charger itself is going out or is plugged into a device which messes with that signature, such as a car power inverter.

This post on Dell's support forums should give you more information. You may find that the adapter is detected as "unknown" or as the wrong wattage in the BIOS. Unfortunately, you can only disable the error message; the hardware throttling and battery refusing to charge are baked into your firmware by Dell. If you get the error and the charger is a Dell genuine, however, it's a sign the adapter or the motherboard has a problem.

Answer 2

It could technically be able to do this, but I don't think this is what's happening.

Dell do a range of chargers for most of their laptops, smaller ones which provide lower power (and are lighter) and then big heavy ones which provide the maximum power a specific laptop can take, at the downside of being bigger and heavier.

When the laptop bios (or uefi) cannot determine the type of charger plugged in, it'll show you a warning message letting you know of this. You can ignore this message, or investigate what's happened to your charger that it's now not providing the correctly expected power.

Your issue with the laptop down clocking can be due to a number of factors including power saving settings (Did you click onto 'maximum battery'?), the laptop detecting that in the incoming power is insufficient to run at maximum speed, or a overheating issue causing it to under clock to protect the hardware.

However, as you recall seeing the AC Power Adapter warning, it's likely this is the issue - when buying a replacement PSU make sure you get one that can do the maximum power for your laptop.