How to charge the MacBook Pro from 12 Volts?

Question

Aim: I would like to charge my MacBook Pro (MBP) form a 12V lead-acid battery. However there are no official chargers from Apple for that purpose. There exist quite some alternative products on the internet. For example this one simply comes with a MagSafe adapter and lets you choose 18V. However I am afraid that such a solution might hurt my battery.

Does anybody know how exactly the MBP battery is charged? Does it require a particular charge line? Is it OK to simply connect 18 Volts and see what happens?

Answer 1

If you connect 18 V to the power/ground pins, your Mac will be powered off the 12 V battery, but it won't charge: https://apple.stackexchange.com/a/132332/26231

To charge, the laptop needs to identify the charger by communicating over the signal pin in the middle. http://www.righto.com/2013/06/teardown-and-exploration-of-magsafe.html

Solution: Sacrifice an apple charger by cutting the cable and connecting the correct pins to your DC/DC converter. I recommend using the 45 W ones so your DC power supply doesn't have to be very big.

Answer 2

Use a DC to AC inverter. You simply attach the alligator clips to the correct battery terminals, turn the device on and plug your cord into the inverter. It's that simple. Amazon sells a 400 watt inverter for $25, that's all you'll need. http://www.amazon.com/gp/product/B001RNOHBC/ref=oh_details_o01_s00_i00?ie=UTF8&psc=1