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?