RC F Sport 12v battery not holding charge.

[BRYAN C]

Bought an RC nearly 4 years ago and only use it occasionally. After about 13 months the 12v Battery started to go flat and left me waiting for the recovery service to bail me out. Lots of trips to the dealer they eventually changed the Battery and no more problems, until 4 months ago when it all started again. 

I am unable to leave the car for four days or it tells me " hybrid system stopped. put park brake to park" and refuses to start.

Before I start on at the dealer again I wondered if anyone else had the same problem. Any help would be appreciated. 

[Texas]

Any possibility you can connect a CTEK charger for example? They are highly reccomended for Classic and Performance cars that ( unfortunately ) don’t get used on a regular basis.

[mr2lad]

1 hour ago, BRYAN C said:

Bought an RC nearly 4 years ago and only use it occasionally. After about 13 months the 12v battery started to go flat and left me waiting for the recovery service to bail me out. Lots of trips to the dealer they eventually changed the battery and no more problems, until 4 months ago when it all started again. 

I am unable to leave the car for four days or it tells me " hybrid system stopped. put park brake to park" and refuses to start.

Before I start on at the dealer again I wondered if anyone else had the same problem. Any help would be appreciated. 

You’ve posted in the wrong sub section… this is the big boys F section 

youll get more responses via the RC300h fsport section 👍🏻

[Herbie]

1 hour ago, BRYAN C said:

Bought an RC nearly 4 years ago and only use it occasionally.

That right there is your problem............^^^^^^^^^^^^^^^^^^^

A conventional car will have a 12V Battery rated at something like 75Ah, quite probably more, to supply 300A plus to the starter motor.

Hybrids don't have a starter motor and only take about 20A to 'start' the car, ie, get it into READY mode. This was probably just one of the factors that drove Toyota/Lexus to fit lower capacity batteries of around 45Ah or even just 41Ah in their hybrids.

When parked up and unused, there is still a current draw from the Battery to feed the alarm, the clock, the radio presets and more. This is called the quiescent current and a figure of around 50mA is considered to be the norm. Plus, all batteries will self-discharge anyway, but we'll leave that out of the mix for now.

I don't know what capacity your Battery is but we'll use 45Ah for this example and we'll also assume that it's brand new and fully charged. 45Ah means that it can supply 45A for one hour or 22.5A for two hours and so on.

45Ah divided by 50mA (0.05A) = 900 hours or 37.5 days or 5.35 weeks between fully charged and fully discharged. Don't forget though, that for the purposes of starting the car, it will become useless and not be able to provide enough power long before becoming fully discharged.

In reality we may be looking at getting 4 to 4.5 weeks maybe? I don't know, it may be even less. And that's for a brand new, fully charged Battery. Look at one a couple of years old and the figures may be even lower.

So, you either have to use it more or keep a trickle charger on it.

[NemesisUK]

1 hour ago, BRYAN C said:

I am unable to leave the car for four days or it tells me " hybrid system stopped. put park brake to park" and refuses to start.

 

This seems a little unusual as if the 12v Battery were flat one wouldn't be able to open the car with the remote and there would be no display?

Your timescales are a little difficult to follow. Was that 13 months after you bought it i.e. nearly 3yrs ago? Everything was then ok for 2.5yrs and now you're having issues again?

As Herbs posts, you need to drive it more or leave it on trickle charge

[BRYAN C]

Thanks for the replys, except for one. It seems when you spend £40+ it doesn't  guarantee you a Battery that lasts for a week.

[NemesisUK]

5 minutes ago, BRYAN C said:

Thanks for the replys, except for one. It seems when you spend £40+ it doesn't  guarantee you a battery that lasts for a week.

You got a Battery for £40? 

[Herbie]

11 minutes ago, NemesisUK said:

You got a battery for £40? 

If he did, that may well be his problem - but I rather suspect that he meant £40k+ for the car

[dublet]

I think you'd need something like this: https://www.tayna.co.uk/motorcycle-batteries/types/068-agm/

Cheapest option is £120 for a Lucas brand Battery, which is fine but not even premium. Where are you getting one for £40? Was the replacement AGM type?

[janey]

Moved to the right section 😉

[ColinBarber]

5 hours ago, BRYAN C said:

Thanks for the replys, except for one. It seems when you spend £40+ it doesn't  guarantee you a battery that lasts for a week.

The standard Battery on the RCh is rated at 48 Ah (5 hours) which is about 56 Ah (with the more normal 20 hours test).

If we assume you have a 50 mA power draw when the vehicle is not be using, and at 30% state of charge you can no longer 'start' the vehicle, then the standard Battery will last about 4.5 weeks. Certainly we have members here that have left an IS300h/RC300h for three weeks and returned without an issue.

But the above is based on the Battery being in excellent condition and being fully charged when it is first left.

If you are using your vehicle occasionally then you are most likely not fully recharging the Battery and so it slowly discharges to the point where you can no longer start. The above uses figures of 8.4 Ah consumed per week, but to make things easier lets say 10 Ah and the point at which the Battery no longer can start the vehicle is with 20 Ah capacity left. Let's also assume you only put back in 5 Ah at the end of each week.

Week 0: 56 Ah starting capacity

Week 1: 56-10+5 = 51

Week 2: 51-10+5 = 46

Week 3: 46-10+5 = 41

Week 4: 41-10+5 = 36

Week 5: 36-10+5 = 31

Week 6: 31-10+5 = 26

Week 7: 26-10 = 16, cannot start to add back in 5 Ah.

At week 7 you encounter the situation where the vehicle cannot be left for a week without the Battery going flat but that is because of the previous 6 weeks slowly discharging the Battery.

 

What is also happening is that the Battery is being left for weeks in a discharged state which lead acid batteries don't like. Weeks 5 through 7 are damaging the Battery, shortening its life. Therefore when you recharge the Battery you probably don't have 56 Ah capacity and the vehicle only lasts 5.5 weeks rather than 6 weeks the next time.

 

All of this happens whether you have a hybrid vehicle or not. The difference is that for a normal petrol/diesel vehicle the Battery is larger and therefore week 7 may extend to week 12, but you still end up in the same place eventually.

 

[TeDClubLexus]

During the COVID lockout, I used my 2019 RC300h far less than I usually do. Three times in 2 months, the Battery went dead.
I had to call Lexus support which, by the way, is very helpful and efficient.
The mechanics told me that this is a very common problem on Lexus hybrid cars, as they fitted with very limited Battery power.
I never had this problem before and reported it to my Lexus dealer. He was not at all surprised as it seems to be a common problem. He did confirm that Lexus hybrids have a smaller Battery. There is no real solution other than the dealer recommended that I start the car at least once a week, which I don't consider a very practical alternative.

My son-in-law had the same problem around this time on his IS300h.

[NemesisUK]

11 minutes ago, TeDClubLexus said:

There is no real solution other than the dealer recommended that I start the car at least once a week, which I don't consider a very practical alternative.

By this they mean put the car into the Ready state in Park and let the hybrid Battery recharge the 12v aux Battery. If the hybrid Battery get low on charge the petrol engine will fire up briefly to top up the charge.

Perfectly practical ....

[ColinBarber]

3 hours ago, TeDClubLexus said:

There is no real solution other than the dealer recommended that I start the car at least once a week, which I don't consider a very practical alternative.

Practical alternative to what?

You have four choices: use the vehicle as it was meant, use a Battery charger at least once a week to top up the Battery charge lost through normal self-discharge and the small drain the alarm/stereo/central locking systems consume, let the vehicle recharge the Battery by putting it in 'Ready' mode for at least an hour a week or put the Battery on permanent trickle charge.

[GTN]

Interested re comments above. Battery has discharged five times this year, it is only two and a half years old. Lexus dealer said Battery in perfect condition after an overnight test and charge. Drove the car five times in the ensuing nine days, three days later car again wouldn't start! Hardly the five to six weeks described above. Trickle charger is not a solution for many e.g. living in a high rise with on street parking. 

Been told that my mileage is insufficient to charge Battery. That being the case, I should have been warned that this could be an issue with low mileage. The car is clearly not suitable for my use and I would not have purchased that basis

[rayaans]

On 12/31/2021 at 3:00 PM, GTN said:

Interested re comments above. Battery has discharged five times this year, it is only two and a half years old. Lexus dealer said battery in perfect condition after an overnight test and charge. Drove the car five times in the ensuing nine days, three days later car again wouldn't start! Hardly the five to six weeks described above. Trickle charger is not a solution for many e.g. living in a high rise with on street parking. 

Been told that my mileage is insufficient to charge battery. That being the case, I should have been warned that this could be an issue with low mileage. The car is clearly not suitable for my use and I would not have purchased that basis

If you're driving it 2 miles down to the supermarket, turning it off and then turning it back on and driving 2 miles back and parking it up for 3 days, it probably doesn't matter how many journeys you do. It'll still discharge eventually.

Our IS300h was driven somewhat like that and the Battery started playing up after 4-5 years. My car is fine as I do around 8k a year so it gets regularly used

[Linas.P]

On 12/31/2021 at 3:00 PM, GTN said:

Drove the car five times in the ensuing nine days, three days later car again wouldn't start!

That sounds a little bit excessive, but it depends on what you mean by "drove". Realistically you need to drive for 15-20 min just to recharge the energy you have used to start the car and whatever was used overnight by alarm. If you drove it for 2 miles and back, then not only it did not recharge the Battery, it most likely discharged it more. This is not some sort of Lexus problem, it is how lead-acid batteries always worked, the only difference is that we living in kind of unprecedent times.

I do agree that when it comes to Lexus hybrid, Lexus could have made it better, on some other cars hybrid Battery automatically charges lead Battery, so this is never an issue, or at least it take a lot longer for both batteries to die. 

Actually, this was one of the final reasons I decided to sell my RC200t, the Battery never died on me, but there were times where I would have left car for over 3 weeks under cover. I live in large housing estate so trickle charging was not an option and I started worrying that one day I am going to come and car won't start - at which point I made conclusion that if I am worrying about such things then I don't need a car. 

Another option is to remove the Battery and charge it at home, or install "kill switch" - Battery would still discharge, but at much slower rate. Obviously this would mean no alarm, but I can't see thief carrying suitable batteries for the cars they want to steal. This is very common issue for classic car owners as well, or any car which is not being driven often - hence things like trickle chargers and "kill switches" exists.

There are other less conventional solution - lithium/capacitor batteries, but they would be very expensive solutions and may even need to be custom made. Besides I believe it would be possible to design the device which would charge lead Battery from hybrid Battery and could be retrofitted as trickle charger - but again this would be experimental, custom designed for you. Fairly simple in principle - converting 244 V to ~12.8 V and with two sensors to monitor both batteries, for discharge/overcharge (and I am sure that they already exists in other hybrids which already uses hybrid Battery to maintain lead battery), perhaps another one to disconnect the device once car is in ignition mode.

This is official Lexus advise which is in line what was said before:

https://www.lexus.co.uk/discover-lexus/lexus-news/lexus-hybrid-parked/

Edit:

Almost forgotten - there are solar trickle chargers, which may be an option for you. It wasn't for me and UK overall is not the sunniest place, but if you keep your car outside apparently they are enough to keep the car charged, or at least significantly prolong the Battery life. 

[NemesisUK]

Not forgetting 12v Battery management is handled completely differently between hybrid and non-hybrid models

[Linas.P]

Yes and batteries are different, but my point remains the same - when I started worrying about the Battery going flat that helped my decision to sell the car.

It is not Lexus fault that one does not drive the car for extended periods of time, although it could argued they could have designed the hybrid in particular a bit better (other makes maintains the Battery without need of owner intervention). 1-2 weeks once in a while are fine, maybe even a month, but if car is constantly parked then Battery will eventually die, there is no other way around it. On top of that all lead-acid batteries are not suitable for "deep-cycling" and even single deep discharge can damage them - meaning they deteriorate quickly and lifetime shortens rapidly after each cycle.

[rayaans]

Do the latest RC have connected services? We found the Battery was being drained by the connected services in our UX300e. Wouldn't hold charge for 2 days! Turned it off and it's been ok since

[Linas.P]

Yes 2018 should have connected services together with improved widescreen sat-nav for F-Sport/Takumi trims. I think only "luxury" version doesn't get it. 

[rayaans]

8 minutes ago, Linas.P said:

Yes 2018 should have connected services together with improved widescreen sat-nav for F-Sport/Takumi trims. I think only "luxury" version doesn't get it. 

On some cars it's draining the Battery as it's not turning off properly as it should. When I tested my car, the Battery was still being used almost 4 hours after turning off. 

Once the connected services was turned off the drain was very little in comparison 

[Linas.P]

1 minute ago, rayaans said:

On some cars it's draining the battery as it's not turning off properly as it should. When I tested my car, the battery was still being used almost 4 hours after turning off. 

Once the connected services was turned off the drain was very little in comparison 

I am not an expert of how connected services work, but probably over the air updates? I guess if it has good access to internet then it could download it quickly and shut down, but if slow maybe it take hours/days.

That is indeed possibility, because system being up can draw say 100w, this would equate to about ~7.8Ah - so 10 hours draw can easily kill the Battery. 

[rayaans]

9 minutes ago, Linas.P said:

I am not an expert of how connected services work, but probably over the air updates? I guess if it has good access to internet then it could download it quickly and shut down, but if slow maybe it take hours/days.

That is indeed possibility, because system being up can draw say 100w, this would equate to about ~7.8Ah - so 10 hours draw can easily kill the battery. 

Potentially

Something definitely changed with it as it started doing it about 1 month ago. Did not happen before this.

[NemesisUK]

No OTA updates on the  RC300h