2011 RX450h 12V battery - a possible solution

[Barry14UK]

My factual viewpoint is based on what Lexus/Toyota say and is supported by Battery manufacturers, suppliers and others of standing, and not anecdotal views of a few members of a forum who have not set out their detailed qualifications to contradict Lexus/Toyota and show why the manufacturers are wrong and unnecessarily adding to the cost of their cars.   Suggest one at least of these members who consider Lexus/Toyota is wrong, takes this up with them specifically and reports back to us since it is these members are suggesting departing from specification, not me.  I have nothing to prove, the onus is not on me.   It is of no concern to me what people do to their cars (as long as it does not adversely affect the safety of other road users) but feel people suggesting to others they depart from manufacturers specifications have a responsibility if this leads to a problem.

Incidentally, I did find a record with pictures on this forum going back away,  of a Battery that had exploded with nasty results but unfortunately did not bookmark it.  However, I only got my car back recently after repair from being rear ended.  Fortunately, I was in forward  motion  at the time.   Had I not been moving it is very possible that the 12v Battery which is located just inside the very rear of the car would have suffered damage and been propelled forward.

I have said all I intend to on this subject on this thread. For the benefit of anybody who wishes to stay with the AGM Battery that is cheaper than the Panasonic one and provides more capacity, I will report back in due course on another thread I started, as building work is currently preventing further research. 

[TouringRob]

Just come in from the cold - installing a lintel in winter is a silly silly idea so need to time to digest your reply Barry but while I do I will state this: 

While I am stating that a regular lead acid Battery is compatible and is a good alternative to the OEM Battery I am not discouraging anyone from using their own judgement and to draw their own conclusions from what I've written my only motivation is to assure people that they are not doing anything wrong or outrageously dangerous - they can sleep easy and save some money. 

As for my anecdotal views and qualifications? Other than being a long term home mechanic having restored and maintained quite a number of vehicles I am also a qualified electronic engineer and for some time owned a company which designed automotive electronics. The endless research and development that role required does give me some faith that what I've written is not dangerous and will not cause harm to those who follow it, their vehicles or their wallets. However I would encourage anyone to not let their low voltage Battery run flat routinely and to use their own best judgement - I will freely admit that I have not worked for any OEM and that Lexus/Toyota will have done their R&D so take my view point as opinion. 

EDIT* I'm not a Battery engineer so only really know the basics, my father however has a life times worth of knowledge in this field and has I believe several patents specifically covering Battery charge technology - next time we speak I will ask for his views as they will be more in depth and qualified than mine, it might very well be that he totally disagrees with me but he will at least be able to give educated reasons for his disagreement. 

Sorry to hear your car was rear ended and glad your weren't injured - let us know if you find the thread with the exploding Battery, would be interested to know if the Battery was improperly vented. 

Rob

[Zotto]

Just to say my opinion from a different starting point, let's the the different full charge V in AGM vs WET batteries.

AGM  are full charged at 13 V, while wet ones are at 12,6 V. What does this mean? That if I use a external charger (like CTEK) , where I have 2 different settings, if I try to charge a AGM leaving the setting on "simple" 12V Battery, I will charge my Battery without problems but NOT totally; not such a great problem indeed. Else, if I set to AGM, I will continue to charge my connected Battery risking to "overcharge" it, with the consequences of it, mainly heating and eventually developing gas. Also this in modern chargers is not so risky because the internal processor is monitoring current, and if you give a look to CTEK instructions the AGM setting is also indicated for better in "cold" temperatures * .

So, what's the problem with internal charging systems of hybrid cars? If they are programmed to charge AGM they manage currents for a little higher  full charge V than that optimal for wet batteries, so they could continue to send current even in full charged wet Battery. Is this a problem? Probably not a big one, as in parallel with Battery there are all other 12 V services working , but neither a "optimal" working state. 

A possible test could be to read the real V in 12V circuit with car in ready  (ON) and decide accordingly to reading if it's possible to use a cheaper wet Battery or not: if we read something lower than 13,5 V it could be worth the risk, if 14 , or if you like to live in peace of mind, use the original Battery type.

[Herbie]

32 minutes ago, Zotto said:

So, what's the problem with internal charging systems of hybrid cars? If they are programmed to charge AGM they manage currents for a little higher  full charge V than that optimal for wet batteries, so they could continue to send current even in full charged wet battery. Is this a problem?

I doubt it would work in that sort of way like a switch, ie, either wet or AGM.

Irrespective of chemistry and construction, as a Battery ages it will present different characteristics to the charging circuits (or I would think so anyway) so I would expect the electronics of the DC/DC converter to be intelligent enough see what it's dealing with and to act accordingly, automatically.

[TouringRob]

Lead acid and AGM self regulate. That means that if you charge with a constant voltage, regardless of set current when the Battery approaches full charge it will draw less and less current. 

The float voltage of AGM is 13.6V, while lead acid (wet) is 13.4 this takes a lead acid upto 2.26v per cell which is permissible and within spec for most (all?). 

The absorption voltage (which is the maximum charge voltage) is 14.7 for AGM and 14.8 for standard lead acid which is also so similar so as not to be an issue. 

The float voltage should be adjusted according to Battery temperature. Flooded lead acid batteries are relatively indifferent to higher temperature charging, thats why the majority of old tech cars do not have a temperature sensor on the Battery while most agm equipped cars will. An agm battery requires the float voltage to be lowered more than a fla for every extra degree in temperature.  

AGM batteries come with a maximum charge current recommendation, this is typically 0.2C-0.3C, so 0.2 x capacity, fla batteries are less intolerant of charge current and can often be charged at 1C (if not more) without damage. An overcharged fla Battery will vent and require 'topping up' so one of big (marketed) advantage of an agm is that it is maintenance free. 

Regular cars will simply charge their batteries at 14.4V forever, this poses no real issue to a fla other than the need to very occasionally add distilled water, since an agm is sealed and cannot be maintained this 14.4 (2.4/cell) at some point may represent an overcharge - most information simply states that overcharging an AGM will dramatically shorten its life, likely because they have a pressure relief and so vent which means lost electrolyte(?) 

The charge system in an AGM equipped Toyota/Lexus will likely be doing a number of things. It will charge the Battery to absorption voltage and then drop charge voltage to float voltage (where it will be maintained) these values will be altered depending upon Battery temp (hence the additional sensor). Above a certain voltage charging will be indefinitely halted. The maximum charge current will be limited since a flat or low voltage lead acid of any type will draw a lot of current, enough that the electrolyte can boil, not such an issue if they vent and can be topped up - incidentally the gassing voltage for fla is 14.4V at 25deg C, at higher temps the gassing voltage is lower. The gas is hydrogen which is explosive at concentrations of over 4%, a normal cause of Battery explosion is a single low (fluid) cell, the cell fills with hydrogen and at some point explodes. The other gas emitted by overcharge is hydrogen sulfide which is both explosive and toxic - filling up a car with that would be bad and likely another consideration for using an agm when the Battery is located within the car. 

So from that blurb. 

You should NOT charge an AGM type lead acid using a regular charger (unless you know what your doing a little) OR install an AGM in a car which usually has a regular flooded/wet Battery, the Battery maybe overcharged which will at best shorten its life.  

You CAN install a flooded lead acid where an AGM has previously been used because the charging method is compatible this way round. 

AGM is maintenance free, a non sealed flooded Battery is not. An AGM is able to be deep cycled to 80% without damage, a wet lead acid can be deep cycled to 50% without damage, an AGM has a lower self discharge rate (so can be left for longer with needing to be charged) I believe around half that of FLA. So another consideration when installing a FLA where an AGM previously was fitted is that you do not allow the car to sit idle for long periods otherwise you will shorten the life of your new Battery. Apparently an AGM can accept charge faster than a FLA however I dispute that due to the fact that the don't like high charge currents but I'll leave that for others who know more. 

On the bench an AGM is technically 'better' in practice with this application I do not believe it is so clear cut. 

Thats charging covered, 

Now the biggest advantage an agm has, and possibly a very big tick in their favor for an OEM - They can be shipped as non hazardous goods and require no paperwork. 

Health and safety I'll leave to others. 

PS - apologies for interchanging terms so much, its late and I can't be bothered to go back and correct it all, maybe a few typos too so please forgive me. 

AGM - Absorbent glass mat 
FLA - Flooded lead acid 
WET - Flooded lead acid 

 

 

[TouringRob]

Jesus, that was longer than anticipated. Congrats if anyone makes it through. 

TL:DR - Charging is a non issue.

[TouringRob]

5 hours ago, Zotto said:

 if you give a look to CTEK instructions the AGM setting is also indicated for better in "cold" temperatures * .

 

AGM mode will have a lower current limit. Regular batteries also don't like high current charging when at low temperatures. 

Your charge voltages are wrong, and the hybrid charge scheme will not overcharge a regular lead acid. The issue is actually the other way round, a regular charge system is bad for an AGM, while you can charge a regular lead acid using the AGM scheme (as proven by you CTEK AGM/Low temp mode). 

 

[GSLV6]

I'll have to check my Battery.  I set my CTEK to "recover" mode and it doesn't differentiate by having a separet one for AGM in recover mode....just one recover to desulpate a flattened Battery of any sort and trickle charge in steps with varying current pulses and voltages.  I normally leave it on "car" (or LA) as my oversight is I cannot remember if my current replacement is an AGM.  If it was, I may have shortened it's remaining life by not using the AGM charge option.  If not, it should be ok.  Either way, thank you Rob for some most informative and instructional posts.  I'm a chartered engineer too but in my case a civil engineer.  (I have though retrained in electronics as I now run my own hifi/loudspeaker company).

[TouringRob]

1 hour ago, GSLV6 said:

I'll have to check my battery.  I set my CTEK to "recover" mode and it doesn't differentiate by having a separet one for AGM in recover mode....just one recover to desulpate a flattened battery of any sort and trickle charge in steps with varying current pulses and voltages.  I normally leave it on "car" (or LA) as my oversight is I cannot remember if my current replacement is an AGM.  If it was, I may have shortened it's remaining life by not using the AGM charge option.  If not, it should be ok.  Either way, thank you Rob for some most informative and instructional posts.  I'm a chartered engineer too but in my case a civil engineer.  (I have though retrained in electronics as I now run my own hifi/loudspeaker company).

Thats awesome, I have a keen interest in high end audio! 

[Barry14UK]

Appreciate your thoughts and standing Rob.  I can't easily find the pics and details of the exploded Battery but I did read a lot of posts going back a long way on this and other forums as well as communicating with Battery manufacturers and suppliers when looking for an alternative Battery. Here is the Scotty Kilmer video I mentioned although there will be nothing new in it for you  https://www.youtube.com/watch?v=NXInSFfvTmw

I would welcome your view on the following though as it is Battery and charging related.

I generally charge my Battery with a CETEK which is not a problem when the car is on my drive.  However, due to building work I have had to park it on the road temporarily and the rain has been continuous, so I have not wanted to leave the hatch open while I remove the Battery for charging in the dry.  I therefore used the Lexus method of initiating 'Ready' mode for an hour so the 12v Battery could be charged from the traction Battery.  It seems counterintuitive that whilst the 12v Battery is being charged up the running lights take power from it as they can't be easily turned off.  This was raised on another forum and a procedure to remove a relay given but probably for somebody who permanently wanted no running lights.  I wonder whether the running lights could be switched off during this charging process. Perhaps they only draw a very small current so make little difference but a neighbour rang to say I had left my lights on.     

 

[Herbie]

42 minutes ago, Barry14UK said:

Perhaps they only draw a very small current so make little difference

That's correct Barry. They're LEDs so will take very little current, so little as to be negligible in this context.

[TouringRob]

6 hours ago, Barry14UK said:

Appreciate your thoughts and standing Rob.  I can't easily find the pics and details of the exploded battery but I did read a lot of posts going back a long way on this and other forums as well as communicating with battery manufacturers and suppliers when looking for an alternative battery. Here is the Scotty Kilmer video I mentioned although there will be nothing new in it for you  https://www.youtube.com/watch?v=NXInSFfvTmw

I would welcome your view on the following though as it is battery and charging related.

I generally charge my battery with a CETEK which is not a problem when the car is on my drive.  However, due to building work I have had to park it on the road temporarily and the rain has been continuous, so I have not wanted to leave the hatch open while I remove the battery for charging in the dry.  I therefore used the Lexus method of initiating 'Ready' mode for an hour so the 12v battery could be charged from the traction battery.  It seems counterintuitive that whilst the 12v battery is being charged up the running lights take power from it as they can't be easily turned off.  This was raised on another forum and a procedure to remove a relay given but probably for somebody who permanently wanted no running lights.  I wonder whether the running lights could be switched off during this charging process. Perhaps they only draw a very small current so make little difference but a neighbour rang to say I had left my lights on.     

 

No problem Barry, I really only know Battery basics compared to some out there so I will watch your video with interest! 

As Herbie mentioned above the LED lights are pretty efficient, I'm not sure what the power rating of the LED units is but I would guess at 5-10watts each, so 10-20watts total, which is a total current draw of between .8 and 1.6 amps which given the capacity of your HV Battery is not an issue. 

The charge controller will account for this so other than the occasional helpful neighbor it shouldn't be a problem. I'm not familiar with the 450h but I wouldn't be surprised if there was a fuse you could temporarily pull while building work is going on and its parked? 

Good luck with the building chaos, we've had scaffolding up since 4th Jan for a 1 week job - then all the roofers caught covid 🤦‍♂️ 

And PS - don't let the engineer bit fool you I get plenty wrong - met many non qualified engineers whos knowledge has humbled me. 

[Barry14UK]

Wish to thank Herbs and Rob for replies. I am very conscious of how electronics  have advanced and continue to do so, whereas when it comes to vehicles, I am just an old amateur spanner man better equipped to deal with more simple cars of a few decades ago. Those were the days when you only needed basic knowledge and simple tools some of which you designed and fabricated yourself.  They did the job if crude like my welding.  I therefore have to look to you members with much better electrical knowledge for information on this aspect nowadays and of course the internet.  For my part, I am happy to contribute in the more limited way I can now.

If the weather had been better it would have made outside projects more productive during restrictions.  The guys doing my groundwork are working in a quagmire.  ....unsurprisingly they have just decided to stop today. 

[TouringRob]

I couldn't agree more, I have a 1968 Vauxhall Viva tucked. I am hoping to restore this summer and it looks VERY easy to work on compared to anything from this century!

[Barry14UK]

When you get the Viva sorted you might consider showing it at the Bromley Pageant of Motoring,  a show I attended for many a year when I lived quite near the Surrey/Kent border. If you don't know it, it largely comprises classic car, commercial and military vehicles plus a fair amount of old/new spares.  This walkabout gives some idea but was taken late in the day after a lot of exhibitors had gone.  So interesting to see so many old cars with some marques sadly no more. Hopefully show will take place in 2022 as doubt it will go ahead this year. https://www.youtube.com/watch?v=gc2Vpi-N8sc

(Apologies to OP for nostalgic digression). 

 

[TouringRob]

Thank you Barry, I have a friend who attends yearly (out of the virus era) but have not been myself, I will indeed aim to go - will be a nice day trip for my son before he gets too old to not want to spend time looking at old cars with me any more! 

Yes sorry for the digression OP 🙂 

[Walus]

Happy to report that there is nothing to report :). The Battery is performing such that I forgot that it is there. Just gave it a quick check. All good, no leaks etc. 

[Spacewagon52]

On 2/2/2021 at 12:59 AM, Barry14UK said:

When you get the Viva sorted you might consider showing it at the Bromley Pageant of Motoring,  a show I attended for many a year when I lived quite near the Surrey/Kent border. If you don't know it, it largely comprises classic car, commercial and military vehicles plus a fair amount of old/new spares.  This walkabout gives some idea but was taken late in the day after a lot of exhibitors had gone.  So interesting to see so many old cars with some marques sadly no more. Hopefully show will take place in 2022 as doubt it will go ahead this year. https://www.youtube.com/watch?v=gc2Vpi-N8sc

(Apologies to OP for nostalgic digression). 

 

Thank you for the link. At 3.31 I saw a model I used to own - NSU Prinz! That brought back happy memories.

[Barry14UK]

Back to batteries!

Some of you folks will be aware that Lexus Parts Direct were reducing the discount they gave us to as not to be so close as trade prices.  I therefore checked their web site to see how this would affect their prices.  They show the RX450hL 2017 on as £199,04 (inc VAT), Battery ref 28800-31291 also with free shipping  for Gold Club Members.  During my conversation with 'Josh', I asked out of curiosity how much it was for the 3 series like mine and he checked it out on their system using my reg number and it came up with the same Battery as above.  (I was under the impression that the 4th series had a larger Battery but perhaps not.  So far from increasing the cost of this Battery, they have now reduced it!  (Strange!) So anybody wanting a Battery might do well to contact them while the offer is still there but check the series as some earlier series used a different Battery.

Now in order that it doesn't keep me awake at night, LOL,  I would be grateful if somebody with a 4 series could post the Battery dimensions of their 4 series along with any designation so I may know for certain whether that miniscule  battery in my 3 Series has indeed been carried over into the 4th Series or that Parts Direct have got it wrong. /lexuspartsdirect.co.uk/parts/lexus-rx/lexus-rx-phase-iv-2015-present/lexus-rx-4-engine-service-kits/lexus-rx450hl-phase-4-12v-starter-battery/

Finally, I mention in passing that I have purchased a Halfords 027 AGM 5 Year warranty (Yuasa) Battery for my 3 series, while these were on offer and with Gold Member discount.  I have assembled all the parts and have just to modify the original Battery tray.  This will increase the Ah over the original Pan Battery by almost 20%.  It also has other advantages.  I will detail how I did it, show pics and give links on another thread I started within the next 2 weeks, hopefully.

 

 

[Walus]

58 minutes ago, Barry14UK said:

Back to batteries!

Some of you folks will be aware that Lexus Parts Direct were reducing the discount they gave us to as not to be so close as trade prices.  I therefore checked their web site to see how this would affect their prices.  They show the RX450hL 2017 on as £199,04 (inc VAT), battery ref 28800-31291 also with free shipping  for Gold Club Members.  During my conversation with 'Josh', I asked out of curiosity how much it was for the 3 series like mine and he checked it out on their system using my reg number and it came up with the same battery as above.  (I was under the impression that the 4th series had a larger battery but perhaps not.  So far from increasing the cost of this battery, they have now reduced it!  (Strange!) So anybody wanting a battery might do well to contact them while the offer is still there but check the series as some earlier series used a different battery.

Now in order that it doesn't keep me awake at night, LOL,  I would be grateful if somebody with a 4 series could post the battery dimensions of their 4 series along with any designation so I may know for certain whether that miniscule  battery in my 3 Series has indeed been carried over into the 4th Series or that Parts Direct have got it wrong. /lexuspartsdirect.co.uk/parts/lexus-rx/lexus-rx-phase-iv-2015-present/lexus-rx-4-engine-service-kits/lexus-rx450hl-phase-4-12v-starter-battery/

Finally, I mention in passing that I have purchased a Halfords 027 AGM 5 Year warranty (Yuasa) battery for my 3 series, while these were on offer and with Gold Member discount.  I have assembled all the parts and have just to modify the original battery tray.  This will increase the Ah over the original Pan battery by almost 20%.  It also has other advantages.  I will detail how I did it, show pics and give links on another thread I started within the next 2 weeks, hopefully.

 

 

The one you were quoted is already of an increased capacity - 70Ah. Originally in 3rd gen were small, but they discovered the problem and upgraded to a higher spec Battery that retrofits with no issues all across the Gen 3 vehicles.

[Barry14UK]

Tom, 

I think something may be incorrect here as I inferred in my last post, so I will spell it out in terms of what I know and what I have been told, which is not necessarily the same thing!

My 450h is one of the last of the 3 series with the 12v Battery in the boot.  It is a valve regulated lead acid (VRLA)  AGM Battery (Absorbed Glass Mat unit),  being OEM Panasonic giving 51 Ah.  This is the biggest size of AGM Battery you can fit unless you carry out some work to raise it in the Battery compartment to effectively increase the length available or you can fit a non AGM free flowing type lead acid Battery within the Battery compartment to increase Ah without alterations. The pros and cons of doing the latter have been discussed at length both in this thread and others.  However, Battery suppliers, manufacturers and emergency service providers  all agree that if a car was originally fitted with an AGM Battery, it should be replaced with an AGM one and this will be the route I take.  I am going to replace my Pan Battery with a 60Ah AGM  but that is really a side issue.  

I noticed that Lexus Parts Direct (from whom I and others have purchased various discounted items previously), were advertising batteries said to be for the RX4 series from 2017 onwards at a cost of £199.04.  As this was less expensive than the asking price for my Pan 51Ah in my car, I asked out of interest how much this would be.  I was told it was the same price and the same Battery ref.  I was further told it was a S55DL23L which is indeed the reference on my Battery.  So if that is correct, which I doubt, this means my Battery ran on to series 4 which I think must be wrong - hence my request for somebody to post dimensions and references of a 2017 onwards RX450h.  Sorry, but I don't believe you can retrofit a 70 Ah AGM Battery in the late 3 series without seriously cutting and welding  the Battery box to take it.  I have had to raise the Battery base in order to accommodate a 60 Ah AGM  one and this is a very tight fit only allowing a couple of mm each end for expansion.

Regardless, it does mean the S55DL23 at £199.04 is far less expensive than hitherto and  I thought somebody might benefit from this.  I would carefully check references before purchasing though.  I don't remember how long the S55DL23 goes back as some early cars had the battery under the bonnet and were able to accommodate a larger one and possibly used a non AGM one at that.

 

[Walus]

7 hours ago, Barry14UK said:

Tom, 

I think something may be incorrect here as I inferred in my last post, so I will spell it out in terms of what I know and what I have been told, which is not necessarily the same thing!

My 450h is one of the last of the 3 series with the 12v battery in the boot.  It is a valve regulated lead acid (VRLA)  AGM battery (Absorbed Glass Mat unit),  being OEM Panasonic giving 51 Ah.  This is the biggest size of AGM battery you can fit unless you carry out some work to raise it in the battery compartment to effectively increase the length available or you can fit a non AGM free flowing type lead acid battery within the battery compartment to increase Ah without alterations. The pros and cons of doing the latter have been discussed at length both in this thread and others.  However, battery suppliers, manufacturers and emergency service providers  all agree that if a car was originally fitted with an AGM battery, it should be replaced with an AGM one and this will be the route I take.  I am going to replace my Pan battery with a 60Ah AGM  but that is really a side issue.  

I noticed that Lexus Parts Direct (from whom I and others have purchased various discounted items previously), were advertising batteries said to be for the RX4 series from 2017 onwards at a cost of £199.04.  As this was less expensive than the asking price for my Pan 51Ah in my car, I asked out of interest how much this would be.  I was told it was the same price and the same battery ref.  I was further told it was a S55DL23L which is indeed the reference on my battery.  So if that is correct, which I doubt, this means my battery ran on to series 4 which I think must be wrong - hence my request for somebody to post dimensions and references of a 2017 onwards RX450h.  Sorry, but I don't believe you can retrofit a 70 Ah AGM battery in the late 3 series without seriously cutting and welding  the battery box to take it.  I have had to raise the battery base in order to accommodate a 60 Ah AGM  one and this is a very tight fit only allowing a couple of mm each end for expansion.

Regardless, it does mean the S55DL23 at £199.04 is far less expensive than hitherto and  I thought somebody might benefit from this.  I would carefully check references before purchasing though.  I don't remember how long the S55DL23 goes back as some early cars had the battery under the bonnet and were able to accommodate a larger one and possibly used a non AGM one at that.

 

I think you are wrong. The new/replacement battery for the Gen 3 RX is 70Ah and that is what the dealers quote. It has the same form factor, same enclosure as the 51Ah one. That is at least what I was told by the dealer when I asked for he spec of the new Battery. 
I did not go ahead with it because I already had the 65Ah Yuasa 5005 ordered, which does the job well.

[Barry14UK]

Tom,

Firstly, I am pleased for you that your Yuasa Battery is serving it's purpose to your satisfaction.  I am familiar with Yuasa from my motor cycling days where they were widely used.

As you may be aware, there is not such an extensive range of Battery sizes with AGM batteries as with standard flooded lead acid batteries, so due to restraints of the Battery compartment size, we are looking at the S55D23L for the 3rd series RX 450h  and some of the previous series too, unless you are prepared to alter the size of said compartment.

So what you have been LED to believe, (wrongly I strongly suspect), is that the Ah for the AGM S55D23L Pan Battery has been increased from 51 to 70, a large increase that no other manufacturer I can find can match for this size of Battery.  This in itself is strange because if you examine the specifications of leading Battery suppliers across the board you will find that the figures are all very close.  I do agree you can buy a free flow or EFB 70amp Battery that will fit but not an AGM. Here is a current advertisement for a new S55D23L OEM Panasonic Battery and you will note that it is 51 Ah, not 70.  

https://www.ebay.co.uk/itm/383745967499?campid=5338627314&mkevt=1&mkcid=1&toolid=10050&customid=EAIaIQobChMI5LfokfiN8QIVS7rVCh3ukQSZEAQYGCABEgItZvD_BwE&mkrid=710-53481-19255-0&customid=EAIaIQobChMI5LfokfiN8QIVS7rVCh3ukQSZEAQYGCABEgItZvD_BwE&gclid=EAIaIQobChMI5LfokfiN8QIVS7rVCh3ukQSZEAQYGCABEgItZvD_BwE 

I will check this with a couple of Lexus dealerships  tomorrow and come back with what is correct. 

[Barry14UK]

As promised, I contacted the parts departments today of two major Lexus franchises regarding the 12v Battery for my car representing the 3rd generation and some earlier generation RX450h cars.  These were the franchises of Snows Exeter and Thistle Groups Cheltenham Branch.  Both confirmed that there was only one Battery specified for my car, the AGM S55D23L and that it was only available as a 51Ah Battery.  Cheltenham kindly unboxed a new one to check the specification.   So this further supports what I thought was the case.

I could not establish the specification of the 12v Battery of the 4th generation because either the chassis number or the registration number of a car is needed and I have neither.  In the circumstances, I repeat my request for somebody to give me the specification and size of the Battery on their car so I can check how this compares with previous generations.  Thank you.

[Walus]

Just a quick update. After nearly 12 months the Battery is holding up well. No issues with leaks or oxidation of the terminals. I would have no issues replacing it with the same type in the future.
 

I notices that Yuasa have released the exact replacement for the original Panasonic that is fitted by Lexus. The model number is: HJ-S55D23L. It ain’t cheap though.