How to fix high kernel_task CPU usage on El Capitan

I acquired an early 2011 powerbook pro in great shape other than the battery is toast, swollen and dead, and had to be disconnected. Without the battery connected, the computer would often go into high kernel cpu usage to the point of making the mouse pointer stop and go when moved. Resetting PRAM and SMC did not fix it for more than a day or two at a time. The below fix worked on El Capitan where the file to be moved was now locked even to the root user.

Great blog here.

Excerpts are:
And the meat … to be done in terminal booted up normally
# Find the model
$ system_profiler -detailLevel mini | grep "Model Identifier:"
Model Identifier: MacBookPro8,2
# Move and backup the file
$ cd /System/Library/Extensions/IOPlatformPluginFamily.kext/Contents/PlugIns/ACPI_SMC_PlatformPlugin.kext/Contents/Resources
$ sudo mv MacBookPro8_2.plist MacBookPro8_2.bak