I have a HP 15s and it have the same problem like this thread https://forums.tomshardware.com/thr...ksum-error-after-pc-is-off-overnight.3757823/. My laptop CMOS checksum invalid always appear when i left my laptop overnight with around 40% of battery left. Even though i just have an battery replacement, my laptop cant not start and its even dont have the red light to inform that its run out of battery. When i plug in it started and CMOS checksum is invalid. Thanks