Nigel

See edited post for the big picture; I've also set this Avatar thing! Well, my 28-y-o son did it. As a standby, I was going to ask a 6-y-o-they seem to be more genned up than us Oldies.

Bgw70

ahhh, gotta love those young ones to help us out! Keep that young man around to help you out!

OBP

Alright folks, finally happened to me. Was reading how you all had all these issues with battery drain and felt so lucky it had never happened to me in my 9 years of ownership of the SC. I believe I am on to my third battery, OEM first then two Interstates. Left her up on my lift not driven for three weeks ( yeah I know I was pushing it), brought her down this evening and she was dead as a doornail. The only light that I got on the instrument cluster was the CEL. No crank nothing. Called AAA, they arrived in 1 hr 15 and helped me jump start. Started up like a champ first time. Drove 7 or 8 miles to get some charge in the battery, quickly bought a small battery tender from Advance Auto ( Deltran Junior or something ) and she is now sitting in the garage off the lift hooked up to the tender. So I have now joined the club of people suffering battery drain in my SC.

hotrodsrj

First, my comments here are NOT to be construed to denigrate any posters here. Everyone wants to help and many have their own methods to fix their specific problems and I know the help is greatly appreciated. So.. I would like to chime in here after reading several threads on the subject of battery issues. A quick qualification: I have been designing, installing, upgrading, trouble-shooting power systems in automobiles, hotrods, classics, airplanes and even nuclear plants. I have designed and installed completely new systems in literally hundreds and hundreds of applications of all kinds.

Batteries are NOT supposed to discharge in a matter of days, weeks and even months for that matter. Especially in modern cars and trucks. Yes, these cars have parasitic drains, but of course... it does depend what each owner has "hanging off" the battery at rest. Stock SCs should survive months easily without a booster charge or disconnect. I know folks feel better doing that and that's fine! We have stored our SC for months without any extra efforts and it blasted right off! All my other cars do the same.. some sitting as long as 6 months without trouble. However, regular lead acid batteries need a topping charge every six months to prevent the buildup of sulfation.. so 6 months in storage is about the longest a battery should sit without charging to prevent possible damage. AGMs, if that is what you have.. not so much.

Usually the problem of continuous discharge and/or a dead battery can be traced to just several issues. One, the battery is weak or going that way. A fully charged battery should show at least 12.5 VDC at rest. Many will show around 12.6 VDC or slightly more. If your battery voltages are dropping below these figures over time... then it's probably a weak battery. Don't believe the "5/6/7 year" battery myth! Your battery life will depend on how baked it gets under the hood and charging/discharging cycles. So.. because our batteries on these vehicles are under the hood, they get baked usually within 3 years regardless, especially in warmer climates. Obviously autos with trunk batteries do last much longer. If you are sitting and playing the stereo and severely discharging your battery.. this too shortens life.. incredibly so. If you do this.. or have a monster wattage after-market set-up.. think about a "deep-cycle" glass-mat battery such as a Optima, which is perfect for those applications. Optimas are worth their weight in gold IMO and do not cook as readily as standard lead-acid models. There are other AGM batteries available as well.

If your battery is not charged to the maximum after driving.. again the weaker battery will NOT accept a full charge. It's chemically impossible for it to return to it's normal quiescent state and full voltage If the battery is not the issue, then I would be looking long and hard at the charging system including all your cables and connections (these too succumb to heat and moisture). It may be weak or connections could be involved. I am guessing that the alternator for these cars is capable of providing in excess of 100 amps which is plenty for adequately running and charging the SC electrical load, therefore will always charge the battery back to the full voltage required at rest.

While battery voltages at rest should be in excess of 12.5 VDC and preferably higher, charging voltages will vary. Stock alternators may only provide a 13.5 VDC reading at idle (probably lower with all the goodies on)... yet provide over 14VDC at higher RPMs. This is normal. If you have an after-market stereo that sucks down a bunch of wattage, I am sure there are upgraded alternators that will supply more charging both at idle and at speed. If you do an amperage upgrade.. think about upgrading your battery cables and charging wire specifically too.

If you live in high temp areas such as the Southeast or Southwest.... well you get the idea....I would consider further insulating your battery box with a heat blocking material such as Thermotec which can reduce heat build-up by a whopping 20%! Apply this to at least the bottom and sides of the battery box (there is usually room for a 1/16" material. With road temps that can easily see 120 degrees sitting in traffic, I have seen battery box bottoms in excess of 150 degrees that slow-cook your battery. I do this on all my cars here in Atlanta. Makes a difference in lifetime of the battery as well. And.. I am of the opinion that AGM batteries are far superior to the old lead-acid types. So.. keep that in mind the next time you invest in a battery.

Lastly, looking at the parasitic load that may be a culprit. Most security systems in the the low milliamp range intermittently. This is very low and should not have a huge effect on your sitting battery life! If you suspect a parasitic load is the culprit, then running a short test and/or circuit test to see where it's coming from.

I hope some of this helps folks understand a tad more on batteries.

JohnnyCake

I don't know as much about batteries as you do. It is just odd that there is a pattern in the SC that you don't see in other cars. Granted some people have no problems, but it seems like an unusually high proportion do.

Having said that (and now ready for a replacement battery yet again), I am interested in the Optima you recommend. According to a search of the CL forum, it is the 94R with the 770 CCA that fits. Does anyone know if that is correct? Also, a Google search for Optima 94R isn't showing any results -- odd.

hotrodsrj

Johnny... think of it this way. Would Lexus make a car that needed to be "topped off" every few days of sitting... even months for that matte?. I assure you .. your car (and others) have something going on with them if they can't keep a charge over months. Sure.. the design of the overall system may play tricks on you to think of the wrong ending remedy. I have seen this in other brands.. however... can be fixed.

Simplistic help on checking battery health : http://www.wikihow.com/Check-a-Car-Battery

May I ask you a few questions?
1. Have you checked your battery voltage at rest after driving? It should be above 12.5VDC and more likely 12.55 and above. Idling.. what's the voltage read. Should be around 13.3 or above to show charging... and probably more like 14 VDC with the throttle cracked above 2000 rpms. How do your terminals look? If you can measure ANY voltage drop across either one of your terminals (such as a .5volt drop between the post and connector (when it is connected).. then the terminals are likely a problem too. Do you have a DC amp-meter? You can get between the terminal and the connector on your battery and read out how much parasitic drain you have. Should be in the low ma range (I've not measured our SC for this?). If not.. other things going on that you need to trouble shoot to find where it's going.

Like I said, I am of the opinion that no battery will last more than three years under the SC hood anyway. The spot rocks with heat transfer!

Even tho I recommended Optima.. I simply used it as an example. Don't get hung up on necessarily that brand. There are other brands in more conventional packages that are AGM types. The Duralast Platinum battery from Autozone is a model, Duracell makes a AGM battery, Bosch and Exide as well make AGM technology batteries that would do the job.. and are a more conventional footprint. I would stick with the stock footprint. The 94R you refer to is actually an Odyssey AGM shown here in this thread: https://www.carid.com/2006-lexus-sc-car-batteries/

Hope this helps.. fell free to thread me back or email me at hotrodsrj@bellsouth.net

Steve "Jackstands" Jack

mrblister

I have had to replace the battery in my 2005 sc430 after it was 15 months old. Dealer replaced it no charge and mechanic told me that they seem to see a lot of sc430 with early failures . They have admitted to me that there is some drain going on. I know on the forum there are a lot of cars that have the symptom of not starting after sitting for 10 days . I accept your reasoning about this issue but it seems like a lot of vehicles with this symptom.

hotrodsrj

I am not sure what the mechanic means by "failure"? Failure of what I would ask? I have a friend who had a 2007 SC with the same problem in San Antonio....where the heat is brutal. He never had this problem (he's own it since new) in Indiana. So,, I think it's a combination of design and expectations. What we did .. we moved the battery to the trunk (tucked on the passenger-side quarter area.. ran a large 1/0 stereo power cable to the front .. grounded the battery at the rear with the same size (which is what most new cars are doing now)), changed the charging circuit feed wire and voila... no more issues. Battery keeps up for months with no problems. In fact, my daughter's Mazda three battery box under her hood melted the top almost completely also living there. Shooting some of the surrounding surfaces with an IR gun.. you could easily read 175 degrees! Yikes! I had to move her battery to the trunk as well.. So.. heat definitely is a problem with these small under hood spaces and loads of heat being generated.

Also.. as a sidebar to this discussion... think about the electric fans running most of the time! That is like a convection oven technology if you think about it. It pushes hot air into the engine compartment while also moving heat from the engine to the back as well. I think that's a bad design in my experience. Most newer cars at least have their batteries up front in cooler conditions.

Ideally, if ours had this reoccurring problem, I would definitely put the battery in the trunk with all new wiring including the charging circuit wire (from the alternator) to the common positive bus post/point. But.. I think a new AGM battery will be better than the regular technology batteries in its current location... and if you are living where it's a hot summer.. expect only three years at the most from any battery IMO. And.. I would insulate with a good heat shield as well. This keeps core temps in the battery appreciably lower.

Having said all that.. there is another hidden gremlin that needs to be expressed here. Heat not only degrades batteries.. but cables and especially connectors too! Connections degrade due to heat cycling and can easily become "loose" electrically as well as corroded. Careful checking of all the charging circuit wires certainly would be in order as well.

Interesting enough speaking of heat.. my father-in-law's Avalon eats a battery every two years in Phoenix as usual fare.

Now that I have an SC to experiment on.. I'm gonna measure my parasitic drain the next couple of days to see just how much is being gobbled up at rest. I'll report back.

Lastly... the reason to determine what exactly is going on with the battery issue is because battery issues cause charging circuit issues which causes alternators to go tango uniform unexpectedly. Batteries with high plate failure and unable to accept a complete charge can cause the alternator to try and over-charge the battery. This is problematic.

LexMan2003

I've experienced the same as others have noted.

If my car is not driven for 3 weeks, I have to jump-start it. I bought a Battery Tender Jr., which I intend to use if I expect to not drive it for 3 weeks. Otherwise, I'm ok. Sounds like some kind of defect in the electrical system to me, but I'll live with it.

A few times a year on every car I own I check the water level. Sometimes I need to add a tad. I ONLY use distilled water.

mrblister

My battery failed after it had discharged so many times and needed a jump and then a new battery. The charging system alternator was fine. The bottom line was the mechanic said he sees a lot of sc430 that have issues when they sit for 2 to 3 weeks, His words not mine . I understood it to mean that he sees a number of sc430 with same symptoms as mine. Its a large dealership and they have sold a lot of sc430 from 2002 to 2009

JohnnyCake

Agreed, I don't think Lexus would do that. But I do think they would design a car where (perhaps unintentionally) the battery was placed in a spot where it was subject to unusual temperatures or other stress, such that the battery became weak over time to the point where normal parasitic drain would prevent starting after a few days.

Everyone who has this problem does great with a new battery for a year or two. Then the problem starts. My take is that the SC battery environment shortens the battery life. It is not a matter of the battery always needing to be topped off, because it doesn't when it is new. It is a matter of the battery prematurely failing and then needing to be topped off.

Bgw70

I completely agree with this statement as part of the reason the batteries go bad prematurely.

if would be interesting to know if other model cars designed this way have the same issue.

heat kills batteries, the cold just makes the problem show up faster.

GmanSC

What about the battery shield? Is there such a thing ?

hotrodsrj

It's been a day short of three weeks since I made the post above... and that is when we put the SC up and haven't driven it since. I measured the battery voltage when I turned it off at 12.56 volts (the charging system provides a healthy 13.7 volts DC at idle). I measured the battery just before lighting it off today.... and it was 12.40. It fired right up.. no problems. I did check the parasitic drain several times and came up less than .075 amps DC each time. The last one (after three hours) was the lowest at .025 amps DC. Soooo.. I have no clue as to why some will withstand the test of time and sitting and others drain the battery in only days??? Battery capacity obviously has a lot to do with it and of course newer is better. Make sure after driving your car that your battery is getting fully recharged (should read above 12.5VDC) and if it isn't do a system charge test. Thought I would offer up what I found as promised.

Harold57

My battery went down this weekend. Since it is about 2 months after the battery warranty ran out, I decided to check other options out. It was a Diehard but those seem to last about 2 1/2 to 3 years. (This one lasted 3 years and 2 months on a 3 year warranty.) I've heard and read a lot of good things about the Toyota battery, so I thought that I'd check them out and called a local Toyota dealer.

The guy I talked with said that he didn't have access to Lexus part numbers and that I'd do better getting the battery from Lexus. But since Lexus is about a 45 minute drive from here, I pushed on. Then he dropped a bomb. He said that even though the battery carries a 7 year warranty, that they couldn't honor it because this is not a Toyota. (He also said that even when they have a 4 for price of 3 tire sale, that they can't offer it for Lexus vehicles or anything else that is considered non-Toyota.) I responded with, so you can't warranty the battery because this Toyota is not a Toyota. He confirmed. When I pointed out (jokingly, sort of) that isn't very nice, he just laughed and agreed with me.

It sounds like Lexus got word of Lexus owners going to Toyota for parts and to get work done which hurt their business and decided to put a stop to it.

How's that for a fine how do you do?