What does it mean when my battery light blinks red

The 4 blinks are telling you that there is a fault. The same as Computer POST beeps. Remove the battery and the power adapter and hold the power button down for at least 30 sec. then reconnect the battery and the power. See what you get, should that not work try removing the Memory, and replacing it to a different position. Press and hold the power button for more than 4 seconds, to ensure your computer isn't in standby mode. Should this not work, try to remove the CPU and re-seat it as it may be slightly out of position, or out of it's socket. The other things to check is a bad DC plug, a bad charger (check with multimeter) and of course a bad battery. If nothing works and you need to replace anything, start with the battery. Hope this helps, good luck.