I've encountered an odd problem after upgrading the stock Samsung CM871 SSD on my XPS 13 9350 where the battery life drops from the previous ~10 hours to 6-7 hours. I've seen this take place on the following 3 drives and with both the manufacturer and Windows drivers.
I've done a clean install each time I've installed a drive, updated the BIOS to 1.7.0 and have fully updated device drivers and Windows. In each case I have seen the drop in battery life which is restored once the stock drive is reinstalled.
I'm genuinely at a loss to understand what the issue is, but it seems unlikely that all 3 drives are causing a ~4 hours in the device's battery life. Anyone got any ideas?
Check the battery -- make sure it's not swelling (remove the base cover). If it's showing signs of swelling, replace it immediately.
Absent that, the battery is likely at or over two years old - you're likely seeing a normal loss in capacity (the design life of the battery is 18-24 months, so start budgeting for a battery replacement).
The battery was replaced with a new OEM battery this year and isn't swelling. In any case, if the battery had degraded, it would not return to its expected battery life once the stock SSD is reinstalled.
The common denominator here appears to be that my laptop doesn'tt like 3rd party SSDs for some reason.
I think it's more likely your installation of Windows is lacking some power management the original system had. Did you try making an image of the original configuration and cloning it to one of the new drives?