Battery Drain Problem

[RX400h]

If you are not adept at electrical troubleshooting, take your vehicle to an Auto Electric shop. They deal with battery drains every day and many are VERY good at troubleshooting.

[Charles Van]

I had the engine swapped out by a friend and car has had this problem since. Drains battery overnight. Killed brand spanking new battery in 2 days. 

Just watched a video on You tube for a hybrid parasitic drain test. Involves a DC Amp clamp And a DC Multimeter.

Before you test, make sure battery has 12 amps charge, anything below 9 will mess up all the vehicles electronics. Also, since you will need access to the fuse box, you have to fully engage the door latches, while leaving them open, turn off the dome light and bypass the hood light switch, then put the car into sleep mode with  the hood up (takes approx. 1 hour). 

Also, look up the millivolt  draw for car in sleep mode. Max for any standard vehicle is 50 or less.  

You put the Amp Clamp in DC mode at about 40; and set the Multi meter in the DC millivolt setting,  The amp clamp goes on the positive  battery cable, You are looking for a large draw  (could be intermittent, so give it a minute to show up) then test when it is present.

This version of the test does not require removal of any of the fuses, you simply test each fuse with the Multimeter. 

 I plan to try this next week, after picking up another battery.  It's 7 PM on a Sunday night, so I cannot really try it now.

Guy diagnose the problem visually, but was demoing several variations of the test and this method proved most accurate. The problem, which is apparently pretty common on vehicles with a rear wipers is the arm sticking and the motor cycling on & off to reset the wiper (thus intermittent) and its a 6 amp draw which could easily drain the battery overnight. RX's have these wipers, so it could easily be a common thread problem.