I found a slightly older 87w Apple power adapter. My new 16" Macbook Pro came with a 96w power adapter - is it safe to use the lower-wattage adapter on the 16" MBP? Will it cause any issues, or just charge more slowly?
MacBook Pro 16″, macOS 10.15
Yes. It's perfectly fine. USB-PD Specification (Power Delivery) defines how the power adapter will "negotiate" with your MacBook to deliver power for charging. Since your Mac requires 91W, but the charger is only capable of 87W, it will charge at 87W. It will just do so slower.
In the past (MagSafe days), this was not the case. You couldn't use a charger with a lower wattage than what was required but you could use a higher wattage charger. The way it works is that the load (MacBook) draws power from the adapter - the adapter doesn't "push" current into the device. So, if the MacBook required 61W and you had a 90W charger it would only draw 61W from the 90W adapter.
With the new USB Power Delivery ports - things are negotiated. There are USB chips on both the device and the the charger that "talk" to each other about how much power is being requested and how much there is to be delivered. You can use a lower wattage charger; it will just be painstakingly slow to charge.
Yes. It's perfectly fine. USB-PD Specification (Power Delivery) defines how the power adapter will "negotiate" with your MacBook to deliver power for charging. Since your Mac requires 91W, but the charger is only capable of 87W, it will charge at 87W. It will just do so slower.
In the past (MagSafe days), this was not the case. You couldn't use a charger with a lower wattage than what was required but you could use a higher wattage charger. The way it works is that the load (MacBook) draws power from the adapter - the adapter doesn't "push" current into the device. So, if the MacBook required 61W and you had a 90W charger it would only draw 61W from the 90W adapter.
With the new USB Power Delivery ports - things are negotiated. There are USB chips on both the device and the the charger that "talk" to each other about how much power is being requested and how much there is to be delivered. You can use a lower wattage charger; it will just be painstakingly slow to charge.
It’s fine to use the lower wattage adapter occasionally, I would not do so routinely. On a couple post-Covid trips into the office, I left the 87W charger for my 15” MBP at home, and used a 61W charger there when the battery got low. Charging was slower, but it fully charged the battery while I was using the MBP.
It is not safe to do that. You should not use a charger that is not rated the same as the one that came with the computer. Although the lower wattage charger can charge the battery, but slower, it cannot provide sufficient power to the computer. This will cause the battery to drain even though you are not running on the battery.
87w charger with 2019 Macbook Pro 16"?
