Hi Everyone.
No wish to bore anyone with yet more threads on the 'flat' battery situation.. I do feel however that this may be of interest to members who have suffered the battery problem on the RX

Following on from my previous postings, I would confirm. My car is a 2002 RX300. 26k miles .As new.
The car was bought only for use as a caravan towcar during the summer months and like many members I ran into trouble very quickly with a flat battery. The battery fitted was a 40amp hour Lucas
battery (I presume it was the OE fit)... A scream of a complaint about this to Lexus Oxford (where I bought the car) arranged for a 70 amp hour battery (AC Delc Toyota branded) under warranty.
OK so far.
I took the car off the road in November 2007 and I will be taxing it again rom 1st May. The car is stored in my garage adjacent to the house. The car is not locked. (the garage is) and the keys are removed.
I then charged the battery correctly on my electronic automatic charger.
The following are the results.

SAT 8th March ..... Following charge. Voltage 12.75 volts.
SAT 15th March Voltage 12.20 volts end of week 1
SAT 22nd March Voltage 12.01 volts end of week 2
SAT 29th March Voltage 11.80 volts end of week 3 (car still starting OK)

TUE April 1st (No jokes please) Voltage 9.47 volts. No Start . Everything completely dead.
Battery back on charge last night and has come back up OK this morning....

My RX is nothing special, it has all the electronic toys that are standard... I am however concerned that
ALL THE TIME the car is standing the RED FLASHING DIODE on the panel is flashing.
personally I do not agree with this. I feel the flashing red light should only be flashing when the car is locked and alarmed as per my BMW and my previous Mercedes. Not when ever the car is parked without the keys in.
I wonder could this be part of the problem ? Obviously the 40 amp hour starter battery should be replaced with the 70 ah one...
I will investigate the wiring of this diode to see if it can be re-routed... In the meantime guys, any ideas and comments on this would be welcome
Roy
From my stand now, the car will NEVER stand for more than 3 weeks without a freshening charge or a long drive.

A number of points:-

1. The flashing diode is not the cause of any significant battery drain. This is likely to average only a few millamps. So a minimum of 100 hours per AH battery capacity.

2. Did you recharge (By engine running?)after the 20th March start? The starting without adequate recharge would account for the subsequent voltage is very low.

3. There is about a 100mA steady drain from other equipment which is much more significant than the diode.

4. Yes, ideally keep charged from a constant voltage 13.6 supply. This will ensure no overcharge to cause premature battery degradation.

5. Such long periods of inactivity are also likely to cause air-con compressor seal failure.

Regards,
Roy

Hi Roy
Thanks for your comments on the flat battery posting.
Like myself you seem to be 'electrically minded' and keen to help to solve or improve this very bad design situation with the RX.

Re your comments.
1.Drain from the diode. All OK and noted. Have you any idea what the other high qiescent drains are from the rest of the alarm system ? my feeling still is that the security alarm system is probably the main culprit with this problem.

2. During this rather 'Heath Robinson' test, I never charged the battery from the alternator. When I checked the car for a start, I immediately switched off.

3. I agree around 100ma from other equipment is around the norm. This figure must be similar on other high quality cars who apparently do not have this problem . Is it back again that Lexus are fitting to small a Ah battery .... My BMW 3 series diesel has a 90 amp hour battery fitted (similar to the starter battery capacity on a standard ambulance.... Never had a starter
problem in the 6 years I have had the car...

4. The only charger I use is a 5 amp constant voltage automatic charger. Never keep it connected all the time...

Since suffering this problem and now learning of the complication of changing a front side light bulb... coupled with the punishment we are having to suffer with the future Road Tax we will be getting rid of the RX during the summer.... A shame really as the car is 'as new' with only 26k on the mileage.
Regards Roy (same name)

Hi Roy,
I have not looked into the separate drain figures and the circuit diagrams do not really help. There would seem to be the following potential areas
a) Alarm and security - and how this varies with locked/unlocked
b) Radio receiver - always on.
c) Digital communications network - possibly always partly on?
d) Computer(s) for display and control
e) SatNav

Perhaps the way would be to measure at the fuse board for each of the above areas and I may do this if there is nobody replying with the information which must be known.

As an aside, I also had exactly the same problem with the 2000 Previa - a "much simpler animal" but again the 90-100 mA drain was present. The battery would die after two weeks. Never has the problem on a GS300, admitedly an older vehicle although the battery once failed AFTER its daily run. My old van would start after 3 months even although that needed to power the 4 glow plugs!

Sorry to hear that you will abandon the RX - I have only recently bought mine. Mainly for the seats, I must admit!

Best regards from Roy to Roy