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Gs450H 12-Volt Battery


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Hi all, I have a March 2006-build GS450h which I bought a couple of years ago - a beautiful motor car. However the 12v battery is likely the original one and is now suffering from my only-occasional use of the car and yesterday the battery was too flat to start the system; first time this has happened.

NRMA Road Service confirmed the issue was a flat battery. Trickle charging overnight allowed it to start OK next morning and I gave it a 1 hour run to boost the charge. Got NRMA Battery Road Service back to give the battery a (free) "health check" and he pronounced the battery fully charged.

Yesterday's printout of their test instrument had showed 9.83 volts and 187 CCA ("Cold Cranking Amps" I think this is) and was deemed "flat". Today's test after the trickle charge and 1-hour run run showed 12.29 volts and 459 CCA and was deemed "fully charged".

Despite this "good news" I figure that if the battery (Panasonic brand) is in fact almost 8 years old, I am on borrowed time before it does let me down again. So I will talk to Lexus about the cost of a new battery - but I expect a big number.

FYI NRMA says they cannot supply this type of battery - only available from Lexus they say. It apparently has a temperature sensor wired in which makes it special. I can in fact see this item on the battery. Does anyone know of any alternative sources?

In the interim I am considering possibility of using my Smart Charger, an auto-shutoff trickle charger, which should allow me to trickle charge the battery without disconnecting the positive or negative leads (and hence not have to reinitialise the power windows and moon roof each time). But I need to know what type of lead acid battery this is - is it a standard "wet" lead acid, or AGM (Absorbent Glass Matt, or calcium type? Can anyone help me here?

Sorry for the long story but I thought the details (and any forthcoming comments/answers) might be of help to anyone else who encounters this problem with their hybrid's 12v electrical system battery.

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See a Lexus dealer immediately. All Lexus hybrid vehicles ever sold in Australia have an 8-year warranty on the battery:


At worst, they may say the charge looks good and you can't get it replaced. But it's worth a shot.

I'd also be interested finding out the price of the replacent battery. The talk about an expensive replacement seems more urban legend than reality. (Might depend on your definition of "expensive".)

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Thanks for the quick response Lance. Lexus of Chatswood tell me that the 8-year warranty only applies to the HV hybrid traction battery, not the 12-volt accessories battery. So I ended up paying $425 for a new 12-volt battery which they said was trade price in consideration of having quoted me an incorrect lower price over the phone. Apparently about $500 normal list, so I guess this about (only) twice the price of a battery for a Holden or Ford.

But I have yet to find an answer as to what type of technology is used in these batteries. It may just be a normal lead-acid, but NRMA put me wise to the fact that BMW use AGM (black case) and calcium (white case batteries). So I am still searching for an answer so I can use my trickle charger if needed on the on the right setting.

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  • 1 year later...

Lexus batteries have a thermistor embedded in them to monitor the battery temperature during charging.

All you have to do is buy a thermistor from any electronic spare parts shop with similar characteristics, mount it on top of the battery and connect it.

Make sure that the replacement thermistor has the same value as the existing one at ambient temperature and the resistance varies in the same manner and by the about the same amount as the original.

It is also possible to recover the existing thermistor and use it for the replacement battery.

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