Jcatt has posted a patch to test on 1.8.5 MIUI4D2 on this thread:
Don't flash this over any MIUI version other than 1.8.5! Versions after 1.8.5 already have the battery updates included.
If you want to try it and report results that could help...usual warnings, blah, blah, blah.
I installed it and had no issues, booted up normally, etc.