GS450h - dead hybrid battery?

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Hi all 

I posted on this forum almost a decade ago when I bought my 1995 LS.  Well, I've still got that and it now has 340,000km on the clock.  A few hiccups along the way, but more or less what one would expect from such a distance.  A few suspension problems (which are common but probably made worse with our earthquaked roads), a temperamental stereo and AC unit, and that's about it. 

I'm posting because I'm a bit worried about the new car I've bought - a 2006 GS450h with 64,000 KM on the clock (yes - KMs).  It was owned by an elderly friend of mine who has had it more or less since new.  In fact I remember driving it when he bought it wishing one day that I'd have such a car - and in the end, I have that exact one.   My friend died actually, so we bought it from his estate.  Of course we can't ask him about any of it now, and there doesn't seem to be record of problems at the dealer.  

Anyway, the point is the economy, even when driving sedately on highway averaging just shy of 30mpg - I had expected better (9.4l/100 after a 100km 70% highway 90kph trip).  In fact, I can get 30mpg driving the same trip my 95 LS400. 

Also, this morning started the car the info display showed hybrid Battery had all but 1 bar, and within 1 minute (not moving at all) hybrid Battery emptied at engine started.  Are these the same sort of symptoms one would expect with a dead hybrid Battery?  There have not been any warnings or issues with the hybrid system.  At the same time, when was sitting in the car before 'starting' the ignition, within 10 minutes the Battery went weak and I had several problems getting the ignition to start (I know this is not hybrid Battery related). 

The car does have a wall plug in the boot.  I guess this is a hybrid conditioner (which I've learnt about today), or perhaps it is a normal Battery charger?  The only other background I have (other than what's in the paperwork), which my friend mentioned several times, is that it always gets a flat Battery (the 12v standard Battery).  I vaguely remember him saying that replacing the Battery didn't help, but perhaps I'm imaging that.  He only ever drove it for small trips in the city, because he had a larger luxury car for longer trips.  

If the hybrid system is dead - would I know for sure? Would that affect the 12v Battery

I look forward to your help guys (and girls)


NB - photos below are of the far left inner part of boot 

- Car does shut off V6 when coasting and will stay shut off for a minute or two at traffic light.

-Car did say check VGRS system, or something like that, when struggling to start after the Battery went very low. 

- Car started fine the next few times on the same day


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Your batteries loosing charge sounds worrying.

I mostly work from home and my GS can stay parked up all week before turning a wheel. Touch wood it's never given any bother so I'd say that you have an underlying issue somewhere as my traction Battery holds a good charge when not in use.

The low mileage of the vehicle may also have contributed to low use issues, poor Battery performance, etc.

When you go on a long trip, does the traction Battery show/hold more charge?

The hybrid system will cause the petrol motor to kick in when the traction Battery gets low, so that sounds okay on yours. You can't drive for long on the traction Battery either, as the GS 450H is more performance orientated.

Have you done any research on the charger in the boot? At first glance I'd say it was to charge the smaller 12v CPU boot up Battery.

Does the vehicle have any aftermarket radio, amp or other system that might drain the 12v Battery?

Are you anywhere near Northants to get the car checked over by Richard or Hybrid Battery Solutions? (I'm on my mobile and Tapatalk doesn't show your location).

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Thanks so much for the information. 

Before posting my original I called our local Lexus dealer (the only place the car has been taken its whole life - there's a full history there thankfully) and they didn't have anything up front.  However, a few hours later I received an email with details.

It turns out that in 2011 the Battery was replaced, and I assume shortly after that, when (also assuming) the new Battery continued to under perform for the previous owner, the dealership also installed the 'Battery minder', as they call it, and from the records they haven't had any issues or complaints related to the traction Battery or main Battery.  So yes - it's what I'd call a trickle charger for the 12v Battery

Without the exact timeframes or distances its hard to know, but it may just be that the car was used infrequently with such small trips (the previous owner lived in the very centre of the city - 1 or 2km from the centre) that the car never ran enough. As I've mentioned, the previous owner had a large highway car, and this was his city car, so it's possible it was just that. 

Given the Battery is over 6 years old now, it could purely be a mix of coincidence, and the fact the car has hardly been used in the last year, that it went flat on us so suddenly.  It might be that we need to change the Battery and fingers crossed - that's it. 

The car does not have any modifications.  I"ve looked in the boot and it has what I assume is the original Mark Levinston amplifier unit. 

The Lexus dealership did tell me that on their system it was noted, during the last service, that the front right shock absorber is weeping.  Is this a common problem?  I wonder what a repair entails. 

So starting the GS in the morning, it would be normal for the traction Battery only to run things for a minute or so even when stationary? I suspect my (limited) experience with a late model Prius has coloured my expectations of the GS's Battery

I will monitor the consumption monitor and EV mode times and see how we go 


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Put the phrase "sinergex purecharge 10" (without the quotes) into Google and the first link returned is to a user manual in pdf form.

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Regarding the shocks,this is very common on the GS every one i checked history on always had advisories for misting or weeping shocks.They can only really be replaced by Lexus and they do have fixed pricing for them,i think the fronts are also more expensive than the rears.Some i have seen have had the advisory for three years or so which says that they couldn't have been that bad.

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From personal experience, every time I go abroad for three continuous months my car starts every time first time. If the 12v Battery is flat, all it needs is charging and then the car starts.

In your case, it is possible that the HV Battery is not charged properly or, there is a current leak from the HV Battery to the ground. This would indicate damaged HV cables from the Battery to the inverter converter and from the gearbox.  Testing the Battery power output will eliminate the remote possibility of being damaged. A techstream scan would be a great help. Normally a visual inspection of the orange cables underneath the car running from the HV Battery and the gearbox to the engine compartment will show any damage to the cables.

To carry out the foregoing you must be competent with electricity. You also need the right equipment to do it. 

If you need more information and precise details how to locate the fault, I will be more than happy to help you.


Kindest regards,




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