Laptop randomly shuts off when unplugged

I have an Acer Aspire E15 running Windows 10. When it is unplugged it randomly shuts down, even though the battery is almost fully charged (can't really use it unplugged due to the shutting off issue, so the battery is almost always fully charged). I took it back to the store I bought if from and they changed the power management settings so that it doesn't enter power saving mode ever when in battery mode. That made no difference.