How to diagnose makita 18v impact losing power. Already replaced battery

It slides onto the top of the battery pack.

The Makita 18V LXT Lithium - Ion Cordless Impact Driver Kit Model BTD140 us the BL1830 battery, there are several types for it, 1.5Ah, 3.0Ah, 4.0 Ah. Maybe 5.0Ah battery for it will be available. And, the inside of the BL1830 uses the 18650 battery cell. If you have a good knowledge and skill about electronic, you can buy some 18650 cell to do it yourself. If not, I suggest you to buy a brand new one.

You can buy some original battery for replacement battery for Makita BTD140 Battery

Some of the Makita 18v LXT tools require the BL1830 3.0AH battery and are designed that the 1.5AH battery will not fit.

This is more then likely caused by the plastic gears inside the drill wearing down. Makita may replace/repair under warranty depending on when you purchased the drill.

Worn brushes or wrong trigger.

http://broncosis.blogspot.com/2010/01/my-intro-well-to-start-of-i-guess-i.html

http://makita.com/en-us/Assets/images/Products/BTL061/owners_manuals/BTL061%20Owners%20Manual.pdf

Battery has to be cool before you put in charger,also check contacts for dirt etc..cheers

might be cam or eccentric problem

try toolpartsdirect.com & go to makita & type in model #