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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?

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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.

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  • Could you add which models that is refering to? And, do you mean: It is set read only in the BIOS, so it can not be changed; Or: It can not be changed from Linux, but it can in the BIOS setup? Oct 8, 2014 at 21:51
  • Edited my answer
    – Jan
    Oct 9, 2014 at 6:55
  • Thanks for the idea, but no, there is no setting in the BIOS (it's a Lenovo T420s, if that matters). The batteries used to drain in the opposite order until I replaced the main one because it was at <50% capacity.
    – Fern Moss
    Oct 9, 2014 at 17:07
  • I've seen almost every model from back when they actually were manufactured by IBM, i.e. from 2004 onwards. None of them emptied the main battery first and on none it was configurable.
    – Jan
    Oct 9, 2014 at 18:51
  • Huh, I might be wrong then. I'll have to check when I get back home in a week, since I still have the old battery. So this is really something that can only be configured at the BIOS level, nothing to do with the OS? Thanks for the info.
    – Fern Moss
    Oct 11, 2014 at 13:23

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