2005 SC430 Battery
 

My sexy SC430 had a complete check for battery drainage. The company that installed "after market" autostart couldn't find anything wrong. My Lexus dealer checked everything & found nothing wrong But did suggest that I purchase a tender & use it every night. I think I am getting the run-around. Does anyone out there have better suggestions? :(

How frequently do you drive your SC430? Are the trips mostly short?
The typical aftermarket remote start system draws less than 30mA at rest and does put a slight additional drain on the battery. I have a Viper remote start system with an iDatalink bypass module in my SC430, use the car a couple of times a week and have not had any battery / starting issues.

I've had the odd problem with the battery, but only when; a) the car has sat unused for a while or b) when I've been working on the car and had the stereo on to listen to (without the car running).

As per the many posts on this forum, it's pretty clear the SC takes a lot from the battery to start so the battery needs to have plenty of charge to cleanly start. It's also pretty clear that there is a significant, although mysterious, draw from the battery when not running.

Makes me think that someone ought to try running a pair of batteries in parallel. Batteries connected in series add voltage, and when connected in parallel they add their capacity together.

Modern batteries are quite a bit smaller than the ones of yesteryear so I think it is possible physically with some effort. You'd need a little custom cabling to make it work and some sort of restraints to keep the batteries from moving around but it certainly doable.

Armed Forces around the world do this in their vehicles to; a) get to 24V to power various stuff and b) get much more capacity (so many vehicles have lots of 12V's connected in Series Parallel). Of course the same applies in hand held torches and radios etc that have more than one battery.

Lately I've just been concious to ensure I don't leave the radio running and I put a trickle charge on for a while every couple of months.

How old is your battery ? I changed my OEM battery at about 5 years ( 36k miles ) with an Interstate battery that is rated above the OEM battery ( but cheaper). Perfect performance for the last three years.

I've had my SC since 06. I am on my third battery. The Lexus OEM battery sure fits great, but doesn't last long.

My battery bit the dust this past summer. It was the same battery that came with the car when I bought it in the summer of 2001.

You can check the battery draw by hooking up a volt meter between the ground post on the battery and a ground on the car. On some you can read milivolts. Test it out by turning on the parking lights and see the voltage running through the ground cable. Find a scale on the meter where you can see this voltage.

Now turn off the lights and see what the voltage reads. It should be a very small voltage just to keep the radio memory. On your car I assume it will be more substantial. Pull fuses until that voltage reading goes down. Start with the aftermarket stuff. When the voltage usage goes down you found the circuit with the problem.

Battery draw is measured in current (amps or ma) not voltage.

You have to disconnect one battery lead and insert the multimeter (in current measuring or amps mode) in-between the vacant battery post and the disconnected lead. It's best to disconnect the negative lead rather than the positive lead. Then you can connect one of the multimeter/ammeter leads to car frame and other to the vacant negative battery post and measure current draw.

Most small multimeters can only stand small amounts of current so don't turn on headlight etc.

JR

Voltage = pressure
Amp = current
Ohm = resistance

You can measure based on voltage too. Because a handheld meter is very limited in the amount of current it can measure, usually 10amps max, I recommend using the voltage method. The amps would not be flowing if they did not have voltage to push them. If their was nothing pulling current it would not be showing voltage either. Voltage is easily measured with a handheld meter.

The OP has an issue with dead battery after letting the car sit for several days. I'm not sure what you are suggesting. Hooking up a VOLTMETER and measuring millivolts between ground post and car frame ground you should read zero volts unless you have a high resistance connection or bad ground cable. Neither of these will cause a battery to drain when the car is parked due to parasitic discharge.

Your suggestion works well to identify a bad ground cable or connection that would cause poor starting with a good battery.

To accurately measure current draw in the milliampere range you MUST put the multimeter probes in series with the circuit and measure current, not voltage. One should normally measure something less than 50 ma. This is the current to keep alive the clock memory, radio station memory, various ECU settings, receiver for remote fob etc. Some have reported they measured 41ma with stock car and an additional 40-50 am with aftermarket Luxlink. Regardless you should be able to start a car after sitting for 3 weeks even at an 80 ma draw with a standard Lexus Battery.

My SC does not have any mods. It started fine this week after sitting 14 days in the garage.

JR

Hey Susie I was having the same problem with my Solara, battery(brand new) would go dead after about 10 days sitting without running, took it to the Toyota dealership and of course they said it would take a long time to find where the drain is coming from. To make a long story short after about 5 yrs of putting up with this I found an auto electric place that specializes in this type of thing and they found where the drain was coming from, the ipod interface. They tested everything on the car, took the car to where I had the interface installed and they changed it to only charging when the ignition is on, everything is cool now, hope this helps.

Went to start the car last night after sitting for 3 days. Completely dead battery. 4 volts. Trunk was closed. Put it on charger and checked interior lights. All lights off. Charged full last night.

Dead again this morning. Nothing left on. Charged full again. Next, I checked current draw with my Fluke 87 mk V.

When battery is first connected, it jumps to about an amp, but then quickly settles down to 8mA after about 15 seconds where I held it sitting there for 5 minutes just to make sure. Never exceeded 8mA.

A good battery fully charged should last at least 4 months at that draw.

So I'm stumped. Nothing left on. It's a 2007.

Take your car to a BM Auto store, they will test it plus your alternator.

sorka, are you sure that it isn't just that the battery has gone bad?

Harold57 is right in asking the question. Is this the original battery?