We have had a problem with our SC430 battery going dead if it sits more than a week. We have had this car for a number of years and I am tired of putting a trickle charger on it all the time to keep it from going dead!

I can not believe that Lexus does not know what the big drain is on this vehicle when it sits even for a small period of time....I went to a Lexus dealer several years ago to have a new timing belt/water pump put in it and asked how to keep my battery from going dead. They pointed over the parts counter to a motorcycle type battery charger as they answer!

A friend has a late model Mercedes hardtop convertible, they (Mercedes) solved the problem by putting two batteries in it. One is isolated for just cranking!

So, before I start with a fully charged battery and pulling every fuse and disconnecting everything until I find it. Does anyone have an idea what is the big battery eater?

Thanks,

NOsburn

 

welcome to the club I have had this problem for as long as I own my car. if you start the car every 2 or 3 days you will not have this problem otherwise keep a charger on it when not being used. I think its the clock doing it.

 

One old trick for finding heavy load/draw items is too remove fuses one at a time, and slowly place them back into their location. When the fuse touches the contact the heavy load circuit will cause a spark or snap. Now you have located which circuit has the largest load.
This is not a end all do all, but it might help locate the big draw.

 

Other than making sure that there are no lights on somewhere, the fuse testing route may be the easiest. (I've left my car sitting in the garage for a week or two at a time without any issues.)

One way to narrow down your search is to check all the fuses that have power when the car is off. It is possible one of the circuits that is supposed to be shut down when the car is off, is actually powered when the car is off.

Or just check all the fuses for power and mark those that are powered and then do the fuse test (as described above). Another test would be to pull the fuse and insert an ammeter in to check which circuits are drawing power. Document how much each one is drawing and determine who the offender is that way. (Or you can take it to your trusted mechanic and ask them to track it down, but first ask them if they have experience in doing that type of debugging.)

Best of luck and let us know how it goes.

 

I did measurements on my 2008 SC430 and posted results a while back. I was told by my dealer that pre 2006 SC430's have more parasitic drain than later models like mine.

Basically, the best I can get with a fresh brand new battery that is fully charged is 3 weeks before it will not start. My 39 month old battery in my 2007 SC was only giving me about 1 week before it would not start. I brought it to the dealer and they replaced it under prorated warranty. My 2008 had a Autozone battery that would not start after sitting 1 week. I took it to Autozone and it not pass load test after just 32 months. They replaced it or free. Mind you these cars most times had battery tenders on them when parked more than 3 days.

If you have a Luxlink installed some have reported that it draws an additional 50 ma, so getting more than 2 weeks would be unusual.

Here is the text of my old posting.

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"Starting up a SC430 and driving it just a few miles 2 or 3 times a month is not enough running time to fully recharge a battery that has been drained due to parasitic drain and cranking the starter motor. All that the few miles of driving will do is provide a surface charge. Eventually the battery will fail.

Keeping it fully charged with a smart charger such as a Battery Tender Plus or Battery Tender JR will extend the battery life significantly.

The only way to accurately check parasitic drain is with an ammeter. These cars draw about 50 ma of current when parked and turned off. I've measured current provided by my battery tender JR to maintain battery after fully charged. It puts out 47 ma to maintain voltage by providing current necessary to replace parasitic drain.

A battery tender JR will slowly (0.75 amps or 750 ma) bring voltage up to 14.2 vdc or so and then switch to float mode to maintain voltage at about 13.0-13.1 vdc. It can take a few days at 0.75 ma to top a battery off and for the charger to go to float mode. It took me 3 full days to get a previously fully charged battery that was sitting for 6 weeks to go to float mode. When I initially measured the resting voltage after 6 weeks it indicated the battery had lost 75% of its charge.

A Battery Tender Plus will do the same thing but time to fully charge will be reduced by about 1/2.

I've used smart chargers on my cars, motorcycles and aircraft that are not used frequently. They work very well to extend battery life.

JR"

 

Here is some reading about my battery saga in my 2 SC430s
https://www.clublexus.com/forums/sc-...estions-2.html

JR

 

My 02 wasn't good for more than 1 week. Finally discovered a dry cell and replaced the battery last year. Mine has sat in the garage for two weeks recently without a hint of cranking/starting issues. Parasitic amp readings (ammeter connected in series at the battery are within specs.

 

Good info. I was worried from reading all of the stories about needing to keep the car on a trickle charger or it not starting when I got mine. I have to leave it at the airport for days or week + at a time and I was just dreading coming out in the winter cold and finding it wouldn't start. Got an Antigravity Battery Booster just in case but I usually get in late at night and I know I'd be ripped having to jerk around with the car at midnight just to get home. I haven't had any problems though and I was wondering what made my car different - like was I missing some component everyone else had. (Funny that not having a problem that's widely reported makes you think that you're missing out on something ). At any rate, I've got an '08 so now my little mystery is solved. Thanks!

Jim

 

Thanks, everyone. For grins I sent an e-mail to Lexus Customer Service. I stated my problem with my SC430 and said someone at Lexus knows specifically where the drain is coming from. They said in a return e-mail that they respond within 24 hours. I will see what they come up with....in the meantime I will start pulling fuses.

NOsburn

 

So here's one drain that I feel I've noticed. I changed all my interior lights to LED's. LED's require less wattage to light and thus light respectively of the amount of power given to them. So rather than illuminate at a full 12v (like incandescent bulbs) they will illuminate very dimly at even 8v (etc). While incandescent will NEED the full 12v to activate. I noticed that specifically my driver door panel puddle light would stay constantly lit with the LED even when the car was locked and parked; all night long. This observation lead me to summarize that it was pulling voltage even with the incandescent light but not actually enough to light the incandescent bulb. This could be a parasitic draw in our stored cars, if left for a few days, right?

 

Lexus Customer Service is ranked #1 for a reason. Hope you find the fix soon.

 

Received response from Lexus Customer Service today. They say it is the digital control module that causes the drain and the cure is a battery tender. Now, I am going to go looking for it on my SC. Anyone have any idea where it is located?

Thanks

 

to me this would be a problem lexus new about. lexus should have to fix this problem. at no charge. I should not need a battery tender after 3 or 4 days sitting. save that reply.

 

I've never heard of "digital control module," nor does one appear on the sc430 parts list. Any idea where its located or a part number? Doesn't seem right if Lexus is suggesting a battery tender rather than fix the actual problem (ie. part that is drawing parasitic drain).... ie leading to countless dead batteries over the years esp if they knew about this part (I smell reimbursement).

 

I haven't counted lately but there's approximately 20+ computers on board. And they're all digital.