85w to 60w

From: Find the right power adapter and cord for your Mac notebook - Apple Support

"Power adapters for Apple notebooks are available in 29W, 45W, 60W, and 85W varieties. You should use the appropriate wattage power adapter for your Apple notebook. You can use a compatible higher wattage adapter without issue, but it won't make your computer charge faster or operate differently. Lower wattage adapters will not provide enough power."

Yes, that is the official statement but it does not draw a distinction between charging when not in use and in use. When in use the device needs supply which can meets its peak demand but if one were only using the adapter for charging when not using the computer I suspect the lower wattage would serve, just be slower.

As a point of information, there are rare occasions when using very resource intensive applications the battery will be called on to provide additional power when connected to AC. These conditions will occur more often if you are using a 60w charger as opposed to an 85w charger.

If you have nothing better available, use the 60w as a temporary one until you get the proper replacement. Do monitor the temperature of the charger when in use.

Ciao.

The reason you need an 85 watt charger is to meet the maximum CPU power demands when connected to an AC outlet. In theory this might not damage the 60 watt charger, but it is possible that at the highest current demands the 60 watt charger will fail. There is no risk of damage to the computer, and you can operate the computer from the charger alone with the battery removed, but at a lower clock rate.

daisyrie21 wrote:

I am charging my Macbook Pro 15" using MBP 13" 60w charger. Will this damage my laptop is I use a lower watts charger?

PS.

The ICenter nearest me is making me wait for more than a month already for my original charger to be replaced. What should I do?

What is an iCenter? Have you contacted Apple? Even if you haven't purchased AppleCare you have a one year warranty on the charger that came with your MacBook Pro.

I use a 60W charger regularly and sometimes for weeks on end with my 15" rMBP because it is better for travelling. Some business class seats only support 75W of power and the 85W will kick the breaker after a few seconds - which resets in a few minutes but makes the larger charger unusable. The 65W charger works perfectly fine and keeps the battery at 100% but the 65W charger will heat up under heavy GPU/CPU use and - I suspect - shortens the chargers life.

One thing no one has mentioned is that the 65W charger is 16.5V versus the 18.5V of the 85w charger. My concern is whether this has any affect on long-term battery performance. Just speculating, but the laptop battery may develop "chemical memory" for a lower voltage which limits how much charge it will take.

If it should ever fail, be sure NOT to mention that you used the wrong charger when you take it in for service. Having not followed the instructions might constitute a breach that nullifies the warranty.

theratter wrote:

There is no risk of damage to the computer, and you can operate the computer from the charger alone with the battery removed, but at a lower clock rate.

Help is always appreciated, but even more so when it is correct. The OP has stated from the start that it is a Retina model, meaning it is a sealed unit with no removable parts. And in the old days when batteries were user replaceable, operating a laptop without them was a very effective way of risking system damage and data loss in case of power failure.

tradikal2 wrote:

...

One thing no one has mentioned is that the 65W charger is 16.5V versus the 18.5V of the 85w charger. My concern is whether this has any affect on long-term battery performance. Just speculating, but the laptop battery may develop "chemical memory" for a lower voltage which limits how much charge it will take.

Since the battery voltage is around 11 Volts the difference between 16.5 V and 18.5 V should have no impact on the battery.

"Chemical memory" is not a problem with Lithium Polymer batteries. It is a problem that the much older NiCad batteries could experience.

The break point with LiPo batteries is time, not the number of charge cycles. The chemical system used is inherently unstable and degrades over time, diminishing the charge capacity independent of usage. So after awhile, say 3-4 years in this case, the battery starts to lose it whether it was in use or on the shelf. And also, as it ages it becomes more fragile so deep discharges by then can cause yet more damage and degradation. Hence the recommendation to never discharge more than 20-30% full. And to use it without worrying too much about "wearing it out".

Finally, all these products are mass-produced, which means that they follow a statistical behavior best modeled by a bell curve. The maker advertises mean averaged behavior/lifetime/reliability, meaning the top of the curve. Your particular unit might be on the far end of the curve and appear to last forever (lucky you). OR be on the near end and turn out to be a lemon.

you can operate the computer from the charger alone with the battery removed, but at a lower clock rate.

This can be done for testing, but you should not operate your Mac in daily use without a battery installed, for a completely different reason.

In Desktop computers, large capacitors in the power supply smooth out peaks and valleys in DC power to avoid having power spikes do damage to the electronics.

In notebook computer, the battery is used as a buffer, smoothing out the peaks and valleys and serving to protect the electronics from power spikes. Without a battery in place, your computer is more vulnerable to damage from power fluctuations.

It should be fine to use it, the MBP will charge slower is all. 🙂