MagSafe 45W charger

PS:

• Apple Portables: Troubleshooting MagSafe Adapters - Apple Support

https://support.apple.com/en-us/HT203207

• About Mac notebook batteries - Apple Support

https://support.apple.com/en-us/HT204054

• Using and Maintaining your Apple MagSafe Adapter - Apple Support

https://support.apple.com/en-us/HT202451

• Mac Repair - Official Apple Support

https://support.apple.com/mac/repair/service

Good luck & happy trails!🌞

There is a subjective factor and an objective one in this. To know what will trigger the MagSafe

to output a suitable power flow to charge the battery and/or power the Mac, does not require

the adapter to be 45W or 80W. There is an automatic function that enables the MagSafe to see

what kind of power may be required, the draw-down, on initial contact, to a demand source.

The trigger point in this is much lower; without any load the factor is very insignificant, like when

the battery is charged and the Mac is turned off. The math is partially explained in this article; but

may not answer your real question.

• What voltage readings should I get from my 60 watt Magsafe?

https://apple.stackexchange.com/questions/237025/what-voltage-readings-should-i-get-from-my-60-watt-magsafe

A more technical answer to how the MagSafe adapter works probably

goes further afield than your initial curiosity, or need to know, goes:

• Teardown and Exploration of Apple's MagSafe Connector:

http://www.righto.com/2013/06/teardown-and-exploration-of-magsafe.html

So without a load, be it a 45W or 85W magsafe adapter, there's nearly no voltage output.

However your mileage may vary; depending on how these are tested & results you seek.

PS: and when the unit no longer functions, and troubleshooting per Support articles fail

an answer maybe to get another MagSafe adapter. Also check the DC-in Board or I/O Board

because these can fail; they are less costly than logic board replacement. +Check the pins.