I have a laptop with an extra battery. Currently the smaller one in the bay normally reserved for a CD/DVD drive drains first, leaving the main one untouched until the smaller one is totally discharged.
How can I change the order in which the batteries drain so that the main battery discharges first?
For a couple of years, I serviced the laptops of a larger German car manufacturer. I've seen all kinds of Toshibas, Compaqs, IBMs / Lenovos and HPs.
On some (I can't recall the brand though), you could see a read-only BIOS entry, listing the "battery order", but it was neither changeable through the BIOS nor the system.
On none of all these laptops it was possible to change the battery usage order.