RX400h and flat main battery

Mickscores · June 7, 2019

Hello all,

thank you first of all for being so helpful all times and to be such a great source of informations, i hope one day i will be able to do the same.

i am writing this new post because my lexus dealer is confusing me continuously.

to make a long story short, i own an old RX400h, 2009 production, so one of the last of this model. Not long ago i did the complete service in lexus dealer and the replaced the main Battery. After couple of months i left for a business trip for 2 weeks and when tried to turn the car on, i found main Battery completely flat.

i went to the local dealer (i am not in Uk by the way) and they confirmed Battery was good and there was no power leakage so the charge the Battery and gave back the car. The week after i was in same situation.

reading on this forum i found out it is quite a common issue which seems to be unsolvable due to the main Battery being low-sized for actual requirements (it is strange that it didn’t happen in the past) and space not big enough for higher capacity one.

reading in those posts i found out that many of you find a workaround with a solar collector made from AA so I ordered one of those. Car was again at the Lexus service in meantime where they tried replacing the Battery again with a new one as for them, all parts work as expected and no power leakage was identified.

the problem came when i went to pick the car up and show them the solar panel and they have told me that OBD is not active when car is without key therefore it is a waste of money if i do not connect it directly on the main Battery.

question is then: can somebody confirm or deny what i’ve been told based on personal knowledge and/or experience? should i send the panel back or use it?

thank you in advance for your help.

BROUWERS · June 7, 2019

The OBD port does have a live 12V pin when the key is not in the ignition, so I've been using a solar panel connected to the OBD in the past with good results. As standard, the cigarette lighter sockets are not live when the ignition is off, so dont try and connect a solar panel to one of those.

Herbie · June 7, 2019

First of all Michele, just to avoid confusion, the 'main' Battery in a hybrid is the big traction Battery (nominally 288V), not the 12V auxilliary or starter Battery.

Personally I've never been a fan of the solar panels. They do appear to work alright and there's nothing wrong with them but I just think that there may be times when the car may not be parked out in the open (hotel underground car park for instance) and so they are rendered useless just when you might need it.

I much prefer proper jump leads or, even better because you don't have to depend on a 'donor' car, a jump start Battery pack like this one here. This particular one is capable of supplying 800A peak power but, as you'll see from the photo below, my RX450h only draws 15.32A to get the car into the READY state so you could go for a smaller, cheaper unit if you wish. I've got one but decided to get the 800A one in case I ever need to use it to jump start someone else's car - you never know when someone may ask for help.

I've had it in the glove compartment of the car for over a year now and never needed it yet. It does hold its charge very well, still being more than 80% charged after five months, but I suppose a small charge every three months or so will ensure that it's almost fully charged for if it's ever needed.

I suppose what I'm saying is that I'd be inclined to return the solar panel and get a jump start Battery pack instead, but that's just my own personal preference and not based on any technological argument.

Mickscores · June 8, 2019

Thank you very much for such a quick answer, first of all.

it is pity that lexus cannot find a solution , you expect a bit more effort but it seen they gave up quite quickly.

@BROUWERS: the clarification is great and i trust your experience more but is there a way to test that charging is really happening when connected?

@Herbie: let me tell you first that i love your car model, i hope one day i will be able to do the swap. Regarding your advice, i did order also one of these jumpstarter (different model with 1200A) just for the cases you mentioned but, to be honest, i am not really big fan of jumpstarting especially on a car full of electronic gigs like a lexus so i’d rather avoid this, reason why it would be nice a permanent and less invasive workaround.

BROUWERS · June 8, 2019

I will see if I can provide some numbers testing my small solar panel over next weekend.

Herbie · June 8, 2019

4 hours ago, Mickscores said:

let me tell you first that i love your car model,

Thank you Michele, she certainly is a superb car and most definitely the best car I've ever owned :thumbsup:

4 hours ago, Mickscores said:

but, to be honest, i am not really big fan of jumpstarting especially on a car full of electronic gigs like a lexus

That's fair enough, I understand your concerns, but if I can I'd like to try to put your mind at rest.

As long as you're careful to make sure you get the polarity correct (red or + to red or + and black or - to black or -) then there is absolutely no problem with jump starting a hybrid at all. And I'll just mention that I'm a qualified and time-served electrician by trade, when the factory closed down I then went to work as a telephone engineer on BT, after a back injury and medical retirement I'm now self-employed doing computer repairs, and I'm also a licenced radio ham.

I only mention all that to show you that I'm someone who has been around electricity and electronics my whole working life (I'm 61 now) so I'm fairly confident in saying that there's nothing wrong with jump starting a hybrid. After all, all you're doing is providing one good 12V source to help one not-so-good 12V source. One thing I absolutely would not do is to use a hybrid to give someone else a jump start. That's an absolute no-no as far as I'm concerned and one reason why I got the Battery pack, so that I wouldn't have to refuse to help a fellow motorist in distress if someone needed it.

If you're still a bit apprehensive about the possibility of getting the polarity wrong, you could always do what I did in the topic below and fit a socket that is keyed so that it only goes in one way round and cannot possibly be reversed.

Geoffers · June 8, 2019

I absolutely agree with everything Herbie says. The standard 12v Battery is just for the control electronics.

When you are away, do you disable keyless entry? It will save about 300mA on the early models. Not solving sourcing the problem I know but may help your situation. I actually disable mine every night. Habit now.

It's a pity Lexus haven't yet built in a circuit to pull some current from the traction batteries if the 12v Battery is too low. Not something you would use all the time but in an emergency would help. Hyundai have done that with the Ioniq and Nero having a "temporary Battery reset routine" which they call it. Nice touch.

Mickscores · June 9, 2019

Hello all,

thanks in advance for your advices; what i did in the end is to place the jumpstarter in the trunk and solar panel on dashboard. The Battery is now brand new should see if all worked in couple of months and worst case scenario, workaround will be waiting in the trunk.

@Geoffers as far as i am aware, the 400h doesn’t have keyless entry. Can you please clarify what do you mean?

Brian26 · June 9, 2019

Hi all, Whilst I bow to Herbs electronoc knowledge I can say that I have jump started several 'conventional' cars from both my RX400 & later my RX450 and have never had a problem.But perhaps I have just been lucky (doubtful!). Just remember red (+) to red(+) and black (-) to black(-) from the Battery terminals ( although the 450 is a bit of a faf) alternativly you can use the dedicated jump start points as noted in the manual. I really do not see the issue providing the Battery is connected correctly and the hybrid system is in the 'Ready' mode after connecting to the conventional vehicle. However I do carry a 'booster LiOn Battery with me if I am going to leave the car for a fortnight or more shpuld I ever need it. Bri

Geoffers · June 9, 2019

2 hours ago, Brian26 said:

Hi all, Whilst I bow to Herbs electronoc knowledge I can say that I have jump started several 'conventional' cars from both my RX400 & later my RX450 and have never had a problem.But perhaps I have just been lucky (doubtful!). Just remember red (+) to red(+) and black (-) to black(-) from the battery terminals ( although the 450 is a bit of a faf) alternativly you can use the dedicated jump start points as noted in the manual. I really do not see the issue providing the battery is connected correctly and the hybrid system is in the 'Ready' mode after connecting to the conventional vehicle. However I do carry a 'booster LiOn battery with me if I am going to leave the car for a fortnight or more shpuld I ever need it. Bri

Not doubtful at all. The 12v Battery on a Hybrid car is not designed to start an engine. It has a much lower continuous current and even lower CCA (cold cranking). As above, it is there to start the control circuits and some other backwardly compatible 12v systems. The 12v is charged not via a conventional alternator, instead it uses a DC-DC converter. If you are jump starting another car and your Battery doesn't have the available current, this will be load the DC-DC and there is a good chance of damage as that certainly isn't there to start another vehicle. This then results in not being able to start your own car. Yes you've been lucky and I'm glad. Unfortunately, lots of people have suffered failure. There are now warnings in the newer manuals advising you not to jump start other vehicles, something that should have been there from the start as the risk is too high.

If someone was say, holding your puppy to ransom and you really, really, really must do it, then leave your car jumpered to the other car for a few minutes WITHOUT turning the engine over in the other car, allowing the other Battery to charge a little. Disconnect and try to start the other car. That is probably the absolute furthest I would go if I had to. Glad I haven't got a puppy really....

12 hours ago, Mickscores said:

@Geoffers as far as i am aware, the 400h doesn’t have keyless entry. Can you please clarify what do you mean?

Some models don't need you to press a button on the keyfob to unlock the car. Providing the key is on you or in close proximity to the sensors, the car will unlock as you touch the handles.

This uses a lot more power in standby as the method for communicating and searching with the keyfob is very different than a conventional alarm/central locking that just 'listens' for a signal.

Mickscores · June 10, 2019

4 hours ago, Geoffers said:

Some models don't need you to press a button on the keyfob to unlock the car. Providing the key is on you or in close proximity to the sensors, the car will unlock as you touch the handles.

I doubt my car has it as you need always the key to get in.

Herbie · June 10, 2019

18 hours ago, Brian26 said:

Hi all, Whilst I bow to Herbs electronoc knowledge I can say that I have jump started several 'conventional' cars from both my RX400 & later my RX450 and have never had a problem.But perhaps I have just been lucky (doubtful!). Just remember red (+) to red(+) and black (-) to black(-) from the battery terminals ( although the 450 is a bit of a faf) alternativly you can use the dedicated jump start points as noted in the manual. I really do not see the issue providing the battery is connected correctly and the hybrid system is in the 'Ready' mode after connecting to the conventional vehicle. However I do carry a 'booster LiOn battery with me if I am going to leave the car for a fortnight or more shpuld I ever need it. Bri

As @Geoffers says above, you've been very lucky.

A traditional car only uses the Battery to crank the engine and the starter motor will draw a current of 300A upwards whilst it's doing so. Once the engine fires and the alternator is spinning it's the alternator that feeds all the car's electrical demands and also keeps the Battery charged.

If your 12V Battery in the hybrid isn't up to providing the 300A or more cranking current, it will look to the very expensive DC-DC converter (which is our substitute for the alternator) to provide it and if it does so, you'll very quickly hear a loud bang and see the magic smoke that makes it work, escaping at a rapid rate of knots.

mikesands · June 11, 2019

On 6/9/2019 at 12:22 AM, Geoffers said:

I absolutely agree with everything Herbie says. The standard 12v battery is just for the control electronics.

When you are away, do you disable keyless entry? It will save about 300mA on the early models. Not solving sourcing the problem I know but may help your situation. I actually disable mine every night. Habit now.

It's a pity Lexus haven't yet built in a circuit to pull some current from the traction batteries if the 12v battery is too low. Not something you would use all the time but in an emergency would help. Hyundai have done that with the Ioniq and Nero having a "temporary battery reset routine" which they call it. Nice touch.

Yes this seems so obvious, that there must be a good reason why Lexus didn't do it

Mike

mikesands · June 11, 2019

My 12v Battery has just started to misbehave - I assumed it just needs a replacement Battery as it's probably pretty old now. But on finding this thread I'm worried that it's maybe the DC to DC converter that Herbie mentions. Hope not as the extended warranty ran out last month 😞

I'm carrying round a spare charged 12v car Battery and jump leads, but it's a chew using them in the rain. I can't see from the pic how the jump start device works - or rather how it connects to the negative or ground - is there a built in trailing black lead?

Mike

Herbie · June 11, 2019

Not sure which pic you're referring to Mike but this is how you would normally use one of these small Battery packs:

If, on the other hand, you're referring to my more convenient jump start point that I fitted, this is how mine hooks up (I've still got the standard lead with the big croc clips on so that I can help others, but I made up this lead specifically for my own car):

black-on-black · June 11, 2019

On 6/7/2019 at 9:35 PM, Mickscores said:

Hello all,

thank you first of all for being so helpful all times and to be such a great source of informations, i hope one day i will be able to do the same.

i am writing this new post because my lexus dealer is confusing me continuously.

to make a long story short, i own an old RX400h, 2009 production, so one of the last of this model. Not long ago i did the complete service in lexus dealer and the replaced the main battery. After couple of months i left for a business trip for 2 weeks and when tried to turn the car on, i found main battery completely flat.

i went to the local dealer (i am not in Uk by the way) and they confirmed battery was good and there was no power leakage so the charge the battery and gave back the car. The week after i was in same situation.

reading on this forum i found out it is quite a common issue which seems to be unsolvable due to the main battery being low-sized for actual requirements (it is strange that it didn’t happen in the past) and space not big enough for higher capacity one.

reading in those posts i found out that many of you find a workaround with a solar collector made from AA so I ordered one of those. Car was again at the Lexus service in meantime where they tried replacing the battery again with a new one as for them, all parts work as expected and no power leakage was identified.

the problem came when i went to pick the car up and show them the solar panel and they have told me that OBD is not active when car is without key therefore it is a waste of money if i do not connect it directly on the main battery.

question is then: can somebody confirm or deny what i’ve been told based on personal knowledge and/or experience? should i send the panel back or use it?

thank you in advance for your help.

I'm actually quite curious now where in the world are you? I'm just curious of the standards of other Lexus dealers across the world.

Mickscores · June 12, 2019

19 hours ago, black-on-black said:

I'm actually quite curious now where in the world are you? I'm just curious of the standards of other Lexus dealers across the world.

I am located in Prague, Czech Republic.

regarding dealers, reading on internet about my issue, it seems that the answer is pretty much the same everywhere, they are well aware of the undersized Battery, but have no valid alternative solution for it!

Herbie · June 12, 2019

47 minutes ago, Mickscores said:

it seems that the answer is pretty much the same everywhere, they are well aware of the undersized battery, but have no valid alternative solution for it!

That's because it's not really a 'problem' as such or something that can be fixed or repaired. It's a design flaw and should really have been spotted and changed at the drawing board stage, before the cars ever went into production.

The only thing we can do is to put in a higher capacity Battery. I've never looked at doing this myself but as long as it physically fits in the Battery tray and has the right terminals that are the correct way round, there's nothing wrong with doing it. Although we don't need the higher capacity for cranking the engine, if you did put one in it should last longer before going flat.

Quote

I am located in Prague, Czech Republic

What a beautiful place!

My wife and I first visited Prague when the country was still called Czechoslovakia, back in 1991, and we've been back on holiday almost every year since, although only three times in Prague itself.

We've stayed in various places around the country, including Český Krumlov and the Lake Lipno area, Liberec (a few nights in the town itself and also a few nights in Hotel Ještěd, the hotel in the television tower), Karlovy Vary, Cesky Budejovice (including a tour round the Budvar Brewery 😊) Olomouc, Hradec Kralove and Ostrava, plus many more over the years.

Lost it · June 14, 2019

From what I can gather that "box of bits" on the jump starter Lithium things is there to stop the car's charging system from "boosting" the booster if it manages to start the car. Because lithium batteries don't apparently like 60 amps being shoved at them.

Anyway, to the point, if your booster stops working, it's probably because this "safety device" has melted..

I cut the one on mine off and joined the wires, I had to get a generator running for a shop over xmas and it was the only way. The poor thing got so hot it melted the jumper cable. Did the job, but trying to get another set of leads for it was almost impossible. If I hadn't got the genny running, the sprinklers would likely have gone off... Just what they needed on Xmas eve.

So be aware, they are good pieces of kit, but they can be a bit fragile. I don't think I'd want to plug one directly into my car without the "protection" pack being in there as well?

garyallman41 · July 13, 2019

Has anybody had problems with your Aircon after replacing a dead Battery? my 400h now has minimal fan on the aircon, the air just dribbles out. Anyone know how to fix this?