Battery drain

lawler999 · January 28

After 5 years ownership and at least 3 good quality batteries I decided to try and find out why my car Battery goes flat after being left for a few days especially in the winter . I tried looking for parasitic drain by pulling the fuses one at a time and could only find a 20 milliamp drain , this is supposed to be perfectly acceptable , anything over 50 milliamps is not . So I either went along the Battery tender route or Battery isolator. I opted for the later and bought a remote Battery isolator. It was less than £20 and thought I'll give one a try.I installed it the other day and although it's early days it seems to work perfectly. It's basically a solenoid switch that goes between the negative post on the Battery and the Battery negative cable . It completely isolates your Battery from the car , so your alarm will not work unless you wire it directly to the Battery posts . Well after only one night I can tell it works a treat I tested my Battery today and it was showing 12.9 , this is that high its still showing the surface charge .

ColinBarber · January 28

Ideally it would be better to find your parasitic drain cause. By disconnecting the Battery your engine ECU is always losing the stored fuel trims, engine idle position and gearbox shifting settings.

If you are pulling fuses then you are unlikely to find the source as things aren't going into standby modes if power is being turned off/on. Ideally you need to fool the vehicle into thinking all doors are closed and wait 30 mins before measuring the voltage drop across the fuses, rather than taking them out.

Neil E · January 28

I haven't identified what exactly causes it but I've read that it may be one of the alarm components that continues to draw more juice than it should. I think I read somewhere that Paul Frost advises it is a component in the centre console near the seat heater switches.

That points to the 'intrusion sensor' but there is also the separate alarm horn so I suppose that may also continue to draw power to charge up its Battery. I will do it 'the right way' when I next have time to play with the car. Is there an obd reader that can snoop the systems for a drain without the ignition or aux on?

lawler999 · January 28

I agree finding the parasitic draw would be better but I bought one of these

https://cpc.farnell.com/tenma/ten01047/automotive-current-tester-mini/dp/IN05470

and tested every fuse in the car , I tricked the car into thinking the doors were closed and like I said earlier I could only find a 20 milliamp draw.

The tool I used seemed to work as i could see the draw on the circuits drop to zero as the car went to sleep . I have heard that you can get a parasitic draw outside of the fuses , like direct from the alternator, but I can't see how , I thought everything on a car went through a fuse ?

I have also removed an old tracker that was previously fitted to the car and also removed the alarm sensor under the gear shifter ( which Paul Frost suggested) .

I understand the car will have to relearn certain things after being shut down for a few days but that's something I'm going to have to put up with at this moment in time .

https://youtu.be/r7m2xiVn_i4?si=lZlHsvntX0RrjzD8

Boomer54 · January 29

11 hours ago, lawler999 said:

After 5 years ownership and at least 3 good quality batteries I decided to try and find out why my car battery goes flat after being left for a few days especially in the winter . I tried looking for parasitic drain by pulling the fuses one at a time and could only find a 20 milliamp drain , this is supposed to be perfectly acceptable , anything over 50 milliamps is not . So I either went along the battery tender route or battery isolator. I opted for the later and bought a remote battery isolator. It was less than £20 and thought I'll give one a try.I installed it the other day and although it's early days it seems to work perfectly. It's basically a solenoid switch that goes between the negative post on the battery and the battery negative cable . It completely isolates your battery from the car , so your alarm will not work unless you wire it directly to the battery posts . Well after only one night I can tell it works a treat I tested my battery today and it was showing 12.9 , this is that high its still showing the surface charge .

I fitted a new Battery fairly recently and although it is without a doubt holding a charge far better than the old Battery I still have that sense that as you say with the cold weather there is an above expected draw on the Battery, and perhaps more than I could just attribute to cold weather. Hence, I would be very interested if you could take the time to post your observation over a small period following the fitting to see how effective it is.

Are we talking about a device like this ?

Richbrook Dis-Carnect Battery Immobiliser | Halfords UK

I also wondered if a device is fitted that were to disconnect the alarm system are there any insurance implications?

lawler999 · January 29

The one you have showed from Halfords is a mechanical isolator switch so you have got to lift the bonnet everytime you want to isolate the Battery .

This is what I have fitted , it works from a small remote fob. Yes it will isolate your alarm as well , it will isolate everything on the car , these cars just do not get pinched , let's face it most people don't know what they are and they don't make a good getaway car with only 2 doors 😉

ColinBarber · January 29

9 hours ago, lawler999 said:

I have heard that you can get a parasitic draw outside of the fuses , like direct from the alternator, but I can't see how , I thought everything on a car went through a fuse ?

The alternator does go through a fuse but it's a 120 A bolt in fuse, not a little push in automotive one - there are several other higher current fuses that you wouldn't be able to test with your mini tester. Ideally you need an accurate DC clamp meter put on the main lead from the Battery before any other circuits are branched off - that will give you the total coming from the Battery (everything except tracking across the top of the Battery if you have dirt and moisture on it - only a couple of milliamps but worth keeping the top of the Battery clean).

For the SC430 the common source of Battery drain is the stereo amplifier. I would also check the alarm backup Battery, which has no doubt failed by now and so the vehicle may well be constantly charging it.

lawler999 · January 29

1 hour ago, ColinBarber said:

The alternator does go through a fuse but it's a 120 A bolt in fuse, not a little push in automotive one - there are several other higher current fuses that you wouldn't be able to test with your mini tester. Ideally you need an accurate DC clamp meter put on the main lead from the battery before any other circuits are branched off - that will give you the total coming from the battery (everything except tracking across the top of the battery if you have dirt and moisture on it - only a couple of milliamps but worth keeping the top of the battery clean).

For the SC430 the common source of battery drain is the stereo amplifier. I would also check the alarm backup battery, which has no doubt failed by now and so the vehicle may well be constantly charging it.

Where's the alarm Battery back up Battery ?

That would be protected by one of the fuses in the fuse boxes though so would show up on my tester , still worth disconnecting though .

ColinBarber · January 29

1 hour ago, lawler999 said:

Where's the alarm battery back up battery ?

I believe it is built into the alarm siren, number 5 below. Not sure how you access it, either via the boot (removing trim) or via the cabin/seats.

Certainly I would expect this to be connected via one of the fuses you probably did test - I imagine via one in the engine bay rather than in the cabin.

Glyn Jennings · January 29

I found this thread with a detailed description about how to change the Battery in the siren on a 2005 Lexus IS which although looks different it might be a starting point if you are brave enough to attempt to change the Battery. You can buy a new unit for just under £100 but even a new one may have been made many years ago so the Battery may not be that much better.

https://charsiurice.wordpress.com/2018/08/14/siren-backup-battery-replacement/

lawler999 · January 29

Battery was fine again today . Car idled OK and shifted OK considering everything had been isolated parameters relearned .

I will disable the automatic steering column using techstream as that's a bit of a pain .

Glyn Jennings · January 29

1 hour ago, lawler999 said:

Battery was fine again today . Car idled OK and shifted OK considering everything had been isolated parameters relearned .

I will disable the automatic steering column using techstream as that's a bit of a pain .

Whats the auto position? Down, middle, up? I assume you don’t have to reset the mirrors every time as well.

lawler999 · January 29

1 hour ago, Glyn Jennings said:

Whats the auto position? Down, middle, up? I assume you don’t have to reset the mirrors every time as well.

I think the auto position is when the column goes in when you take the key out and then resets to the same position when you get back in the car .

Techstream should be able to disable the auto function , so you can still manually set the column to where you want it using the buttons and it stays where it is unless you move it yourself .

lawler999 · January 31

On 1/29/2024 at 7:34 AM, Boomer54 said:

I would be very interested if you could take the time to post your observation over a small period following the fitting to see how effective it is.

Not used the car for a couple of days , Battery was showing 12.7v today when I went out this morning , fuel trims having to be re learnt is a bit of a pain as you can see the mpg is lower but I can live with that .

Glyn Jennings · January 31

Hi Paul,

I have just sent a message on messenger regarding the device.

lawler999 · January 31

Here's the link for the one I bought if anyones interested .

https://www.ebay.co.uk/itm/225741715521?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=57riy_92qve&sssrc=4429486&ssuid=484skHs8RUe&var=&widget_ver=artemis&media=COPY

2Tanks · April 24

I have recently gambled on an SC430. I've owned two LS400's over the past 16 years.
This 03 model has an aftermarket switch installed in the centre console box alongside the 12v outlet.

Removing the heated seat panel revealed that there were no connections to it, however, after removing the radio it was obvious the loom had been modified and exploring further two cables with blade connectors were there in the transmission tunnel. I will re-instigate this.

The radio head unit had a blown 5A pcb fuse which I have replaced and the unit now runs well. I'm unsure if this "dirty" switch is the cause...

The question is: Which feed should be switched to lessen parasitic loss?

There is a 12v permanent (White/Red), a 12v momentary [or switched](Grey), and the Amp Turn-On trigger wire (also Grey).

2Tanks · October 22

Just chasing my cause of Battery drainage and checked the price of the rechargeable siren 7.2v Battery pack in case it is the cause.
eBay £16
Lexus £276.84

I ordered a new Yuasa YBX3096 from batterycharged co uk and as noted above £82 incl delivery, so a bargain.
I am also looking into the solar sensor as it too may be an issue. I have codes 21 & 24 on the A/C which both point to it. My binnacle lights are very low compared to the A/C unit and although the rheostat/variable resistor works, I don't believe it is correct. It is difficult to read the speedo in daylight. Cursory searches on youtube suggest much work behind the dash, so not rushing at that job yet...

Bob King · October 22

This is how the back up Battery in the alarm can go after time ☹️

2Tanks · October 23

A great help Bob, thank you.
Is it accessed from inside the boot space?

Bob King · October 23

4 hours ago, 2Tanks said:

A great help Bob, thank you.
Is it accessed from inside the boot space?

The electrical diagram says it’s in the boot.

Guy on another forum years ago had a very bad Battery drain, and after stripping the boot trim out found two dealer fit trackers still working.

Took them out and things got better but still not right. He found the alarm in the boot on the nearside , very hidden among the roof linkage. Once he took that corroded alarm Battery out he had no more drain…he just left it out .