LEXUS IS300h 12V battery problems/parasitic current

BogdanSpac · April 4

Hello everyone! About 2 years ago i have noticed that if i park my car (2018 Lexus IS300h Fsport) for about 4-5 days, the 12V Battery would die. I have replaced 3 12V batteries, and now it's time for the 4th one to be replaced. Everything was done at lexus, and they claimed that there were no issues with the car. Last week i went again to them, and they told me that they found an 0.154A parasitic current, which is 3 times more than it should be. They also told me that the operation to find the problem can take more than 3 days, and the price for this starts at about 600 euros because it is very complicated.

I am tired of throwing money at this car, cause every visit that i made to the dealership made my wallet cry, and i am getting almost tired of disconnecting the 12 V Battery after parking my car.

Do you guys have any suggestions or heard about this issue? I have tried to search on the forums but didn't found anything specific only something about a MPX-B fuse, but no solution.

Thanks!

ColinBarber · April 4

It can be time consuming to find the source of the issue, certainly to the point where it isn't worth getting a main dealer at £200 per hour to diagnose the issue. An auto electrician should be able to help.

You can DIY - you need to leave a door open, but fool the car into thinking it is shut, then lock it and wait an hour for all the systems to sleep. Then you measure the voltage drop across the fuses to see which circuit is consuming too much power - then you can hopefully narrow down the problem. Typically it is stereos/amps, alarms or third party trackers/dash cams that cause the issue.

Here's the procedure to measure the voltage drop across the fuses. You shouldn't remove fuses - it can cause systems to wake which makes finding the issue harder.

NemesisUK · April 4

Curious ...

Were the batteries not replaced under warranty?

Your location is showing as Buckinghamshire but you quote the Investigation cost in euros?

You also say you are tired of disconnecting the Battery, how often do you do this? Each time you park up? Since when did you start disconnecting the Battery?

IS300FSPORT · April 4

I have been watching my 12v Battery like a Hawk. Installed a Victron 12v Battery Bluetooth monitor even after a long drive or after fully charging it using a Noco Genius 5 it seems to rest around 12.2v within 24 hours. Iv left mine 2 weeks straight without use & it starts up right away.

- How close is your key to your car when locked up its constantly sending a signal?

- Disable smart entry or put the key in a signal blocker pouch.

- Turn off your auto headlights?

- Any hardwired dashcam? Or other accessory

Recommend you Invest in a Noco GB40 JUMP START pack charged in the boot, you wont be left stranded again. If its left unused these batteries draining quick is normal due to low capacity 45AH is a small Battery.

keep us updated pls

BogdanSpac · April 8

First of all thanks for the replies!

ColinBarber, i tought about going to local reapir shop, and i will do so next week. I will also try the instructions that you gave me above, maybe this will get me closer to the root of the issue. Thanks so much!

NemesisUK, i am actually in Romania, Bucharest. I have bought the car back in 2020, and i noticed the problem soon after that, but everytime the dealer told me that it's either a problem with the Battery or that i don't drive often enough. Almsot 4 batteries later, they found out that there is a 154mA parasitic current. The batteries came with 1 year warrnity, but according to them, if they drop under x volts (can't remember exactly the number) the warrnity is voided. I disconnect the Battery everytime i know i won't use the car for several days, which often happens becaus i don't drive that much.

IS300FSPORT, what you have there looks pretty smart. I tried to look for the name of your device and it got me to a Remote Battery Disconnect Switch which would be more suitable for me, at least for now. I bought a 12V power bank, which saved me a lot of times. I have tried the things you said, beside disabling smart acces (i am not sure how do that), and the car is always parked far away from the keys.

I will continue my journey with the 12V Battery and i will come back here as soon as i get any news.

Thanks for the help and suggestions!

IS300FSPORT · April 8

Try this link for the Bluetooth Battery monitor:

https://www.amazon.co.uk/Victron-Energy-Battery-10-meters-Chargers/dp/B07RTYGMBD/ref=asc_df_B07RTYGMBD/?tag=googshopuk-21&linkCode=df0&hvadid=218091934260&hvpos=&hvnetw=g&hvrand=16198952007030427484&hvpone=&hvptwo=&hvqmt=&hvdev=m&hvdvcmdl=&hvlocint=&hvlocphy=1006886&hvtargid=pla-753464671886&psc=1&mcid=2c7883ebed4c32e59dcb2bbdfe1f201d

Alternatively

https://www.amazon.co.uk/Battery-Monitor-Campervans-Compatible-bluetooth/dp/B08VHMJYXY/ref=mp_s_a_1_3?dib=eyJ2IjoiMSJ9.g3ROYjuAUFy5eUCi_SnmeMqf-MnlHrtBucJTAGR84I8gOl27RVXZdPR-sx3hQDsuRBzLx8Fjnt6Flf2KYeom-EzLvavKbQ_zOkkcahPEK01E70glNgY28d3Y43hG_pHC-SRadYtPrw1gfB6dykoZaYPmthCjnONwxIbsEn7z1--PYalH257U6rDiVJ_cPUe5MQ9LwAzrfPmWgUTdCTylTA.G_pg3nidzVUFcROai8SBnw3XWQzUrOqysFtVt1bu4BI&dib_tag=se&keywords=12v+battery+monitor&qid=1712602103&sr=8-3

Maxz · May 31

My is300h just started having the same or similar issue. The Battery is less than 2 years old (bought June 2022 from Lexusparts Direct Swindon, only 12 month warranty). Parked for 4 days, when trying to start, got the Hybrid system won't start warning. Charged the Battery and it now starts. However, when holding the Menu button and flicking the light switch from auto to side light 3 times, on the vehicle signal screen only 11v is shown and drops all the way to 10v, when just sat in accessory mode. When engine is running 13.7v is displayed. In accessory mode should the voltage really drop as low as 10v? If anyone else can share their readings in accessory mode would be interesting. I ran techstream and there are no DTC codes reported either. Can shorts be found using Techstream?

RONNIE W HODGEKINSON · May 31

On 4/4/2024 at 2:31 PM, ColinBarber said:

It can be time consuming to find the source of the issue, certainly to the point where it isn't worth getting a main dealer at £200 per hour to diagnose the issue. An auto electrician should be able to help.

You can DIY - you need to leave a door open, but fool the car into thinking it is shut, then lock it and wait an hour for all the systems to sleep. Then you measure the voltage drop across the fuses to see which circuit is consuming too much power - then you can hopefully narrow down the problem. Typically it is stereos/amps, alarms or third party trackers/dash cams that cause the issue.

Here's the procedure to measure the voltage drop across the fuses. You shouldn't remove fuses - it can cause systems to wake which makes finding the issue harder.

Great Information Video

DBIZO · June 1

On 5/31/2024 at 9:53 AM, Maxz said:

My is300h just started having the same or similar issue. The battery is less than 2 years old (bought June 2022 from Lexusparts Direct Swindon, only 12 month warranty). Parked for 4 days, when trying to start, got the Hybrid system won't start warning. Charged the battery and it now starts. However, when holding the Menu button and flicking the light switch from auto to side light 3 times, on the vehicle signal screen only 11v is shown and drops all the way to 10v, when just sat in accessory mode. When engine is running 13.7v is displayed. In accessory mode should the voltage really drop as low as 10v? If anyone else can share their readings in accessory mode would be interesting. I ran techstream and there are no DTC codes reported either. Can shorts be found using Techstream?

Reading 12.6V starting in accessory, dropped to 12.4V in a minute and then stays there for a while, now 12.3V. Battery is 3 years old, changed by mains dealer, don’t remember the make.

I’m planning on replacing at year 4 regardless of readings as I learned the hard way what it’s like to be stuck with a dead car - airport park lot, late night, cold and rain, 4 hour wait for roadside as I couldn’t charge it enough to boot the car up.

BogdanSpac · June 1

I went to the dealership and they finally found the problem. Long story short, my windshield was replaced, and the shop that did that, made it bad and I had a leakage trough the A pillar. The water made some circuit rust on the left of the dashboard. The current measured before when the car was in sleep mode was 0.154A, now it's 0.05A.

About the accessory mode, I'll take some pics and post them in here so you can compare the stats.

I also recommend this type of gadget to any hybrid owner:

Maxz · June 2

On 6/1/2024 at 4:12 PM, DBIZO said:

Reading 12.6V starting in accessory, dropped to 12.4V in a minute and then stays there for a while, now 12.3V. Battery is 3 years old, changed by mains dealer, don’t remember the make.

I’m planning on replacing at year 4 regardless of readings as I learned the hard way what it’s like to be stuck with a dead car - airport park lot, late night, cold and rain, 4 hour wait for roadside as I couldn’t charge it enough to boot the car up.

Many thanks for this, I defo have a problem. Attached reading after charging the car on trickle for a whole day.

DBIZO · June 3

14 hours ago, Maxz said:

Many thanks for this, I defo have a problem. Attached reading after charging the car on trickle for a whole day.

It's likely you have a dead cell, and also your remaining cells are degraded or undercharged. In any case, it's a concern how long it will be able to boot your hybrid system up. Any chance it's low on charge? It takes longer drives (at least an hour or so) to meaningfully charge even a smaller lead-acid Battery after it's deeply discharged. In any case, I'd get it replaced, it's a relatively minor expense compared to the massive inconvenience and time you lose if your car doesn't start up.

Also, be mindful that while replacing a 12V Battery is something anyone could easily do following simple instructions, some people reported issues when it's not done by a professional, ideally a Toyota/Lexus garage. I think some people lost the amplifier.

Maxz · June 4

19 hours ago, DBIZO said:

It's likely you have a dead cell, and also your remaining cells are degraded or undercharged. In any case, it's a concern how long it will be able to boot your hybrid system up. Any chance it's low on charge? It takes longer drives (at least an hour or so) to meaningfully charge even a smaller lead-acid battery after it's deeply discharged. In any case, I'd get it replaced, it's a relatively minor expense compared to the massive inconvenience and time you lose if your car doesn't start up.

Also, be mindful that while replacing a 12V battery is something anyone could easily do following simple instructions, some people reported issues when it's not done by a professional, ideally a Toyota/Lexus garage. I think some people lost the amplifier.

Many thanks Daniel and others for posting up your readings. The annoying thing is the vehicle at least once a week has an hour long drive and during winter on days I work from home I'll stick the Ctek charger on it also. I did the same with my previous car (an old Skoda Superb) and the Varta factory Battery went 10 years before requiring replacement. Where I did get the car started I have driven it to get both the hybrid Battery and 12v up as much as possible until replacement is arranged. The problem is it starts maybe a 2nd or 3rd time, but by the time I attempt to start it for the 4th, there is no longer sufficient charge to power the systems to get the Hybrid motor started. This is too much a risk of my wife and kids ending up stranded somewhere. Also transpires any Battery sold by a Lexus dealer should have a 3 year warranty (part or fitted). Given this one is less than two, I'm waiting a call back today to discuss next steps.

I also had an independent come over and run an OBD scanner. The only DTC codes were B150A and U0594, which had generated from there being insufficient voltage to power the hybrid and navigation systems i.e. they were a result of the Battery voltage being insufficient and not a fault that are causing the Battery to discharge/degrade.

Maxz · June 4

Plot thickens. Lexus Parts Direct Swindon advise they are sure their warranty is only 12 months on a 12v auxiliary Battery, whereas both Sidcup Lexus Service and Parts teams advised me independently that they offer 3 years if purchased part only or fitted. If there is a marginal difference in pricing based on a Lexus Parts Direct discount or using your forum Gold membership, after confirming directly with your local dealership in regards to 3 years warranty, any saving on price (or in my case trying to save a long return walk to the Sidcup dealership as Lexus Parts Direct delivered, carrying a 12v Battery as my original factory one would no longer boot the car) should be carefully considered versus my situation where it fails in the 2nd or 3rd year and you are not covered.

I will now have to attempt to make a warranty claim on the Battery at Sidcup, based on an invoice from Lexus Swindon where as highlighted my vehicle details and mileage were not requested or added to the invoice. This is another consideration when not buying the Battery from your local dealership. This is because from what I was advised today, a warranty is also only upheld on a 12v if there is evidence of your vehicle covering at least 6k miles a year (unfortunately I cannot find this detailed on the Terms of Business on the reverse of the invoice as shown). If this detail is not included, how can the 6k per year be proved on the paperwork and terms Lexus appear to rigidly enforce but not clearly communicate at the point of sale?

My vehicle is booked in next Friday for a Battery assessment but given all the messy paperwork trail above and the conflicting warranty terms across different Lexus Dealerships, I will be popping in person to Sidcup this Friday ahead to avoid any disputes on the day of the test. I am hoping this is not a 3rd overly complex and difficult experience with Lexus, as TBH I am now very much leaning away from this brand despite my historic employment with Toyota. This is less to do with the vehicles or employees themselves who are excellent, more the over bureaucratic terms and conditions when it comes to issues, that to be frank are not contributing to my customer experience, despite going through legitimate Lexus dealerships for all parts and servicing.

I'll update on how this ends and if ultimately a nicely written letter to head office is required, about consolidating warranty terms across dealerships and ensuring all relevant details are obtained from the customer when selling items where a warranty and its very specific terms apply.

DBIZO · June 4

If you already have problems with starting up the hybrid, that's way overdue replacement, whatever the age. That's minimal power compared to cranking the engine.

Be mindful that these are not full-sized 12V car batteries, but smaller ones because, again, all it needs to do is power up the hybrid system, and it's the NiMH traction Battery that cranks the engine. Toyota/Lexus chose these to save space and weight. However, this means that the 12V holds less charge (45Ah vs. typical 60-70Ah) and may wear out faster (VRLA does not like deep discharge, for example, when sitting long), especially if your mileage is irregular/low.

Also, your 10 years in the Skoda, isn't that rather exceptional? VRLA technology tends to last 10 years only in ideal conditions, which means always fully charged, never too warm. A car rarely provides ideal conditions.

If your warranty is disputed ('computer says no'' situation), your best chance is always a letter to the dealer head office, appealing to an expectation of higher standards. Good luck!

Maxz · June 5

Finally cleared up after speaking to Lexus head office. Lexus Parts Direct are correct in their confirmation that a replacement 12v Battery purchased from a Lexus Dearlership has a 12 month warranty only and there is an annual mileage stipulation.

Your 12v Battery only is under a 3year less than 25k mileage warranty, if it is the original factory fitted Battery and is within these time and mileage terms (plus I assume you may also have to have done the minimum 6k miles per year, so at 1 year 6k on the clock, at least 12k at 2 years and 18k at 3 years if claiming for a fault).

As with most of these warranty scenarios, devil is in the detail.

Notamech · June 5

I think people should stop buying the original Battery if thwy dont drive regularly. Sounds like there are several reports on this forum of issues if not driven regularly. I have a Yuasa sealed silver calcium Battery that im sure is cheaper than the original and i also use my car infrequently ie just about 30-40 mins 3 days a week and have not had these issues(touch wood). Ive gone on holiday and left the car standing with the Battery connected for close to a month without issues. The wifes jazz also has a yuasa and its been 6 years now no issues.

Maxz · June 5

7 hours ago, Notamech said:

I think people should stop buying the original battery if thwy dont drive regularly. Sounds like there are several reports on this forum of issues if not driven regularly. I have a Yuasa sealed silver calcium battery that im sure is cheaper than the original and i also use my car infrequently ie just about 30-40 mins 3 days a week and have not had these issues(touch wood). Ive gone on holiday and left the car standing with the battery connected for close to a month without issues. The wifes jazz also has a yuasa and its been 6 years now no issues.

Sounds like I could do with one of those, as at £296.89 fitted, then at only 2 years old requiring replacement, Toyota AGM batteries dont't seem like a worthwhile choice. Would you be so kind to share the exact model / specification of the Yuasa so I can look into possibly doing the same? 👍

I have Yuasa's fitted in my house alarm and as you mention my first went for 6 years no issues before requiring replacement.

Notamech · June 6

12 hours ago, Maxz said:

Sounds like I could do with one of those, as at £296.89 fitted, then at only 2 years old requiring replacement, Toyota AGM batteries dont't seem like a worthwhile choice. Would you be so kind to share the exact model / specification of the Yuasa so I can look into possibly doing the same? 👍

I have Yuasa's fitted in my house alarm and as you mention my first went for 6 years no issues before requiring replacement.

Sure thing. Il double check when i go to the car next but am pretty sure its this one https://www.yuasa.co.uk/ybx3053.html. Looks like its less than half the price and it fits and works perfectly.

Notamech · June 6

Confirming the Battery linked above is the one I have. One thing though is the vent tube doesnt fit it probably needs an adapter or something maybe it came with one but the used car dealerthat fitted the Battery probably didn't bother. I have heard of people calling up yuasa and being sent an adapter free. I have just left mine disconnected for now.

Maxz · June 7

On 6/6/2024 at 11:36 AM, Notamech said:

Sure thing. Il double check when i go to the car next but am pretty sure its this one https://www.yuasa.co.uk/ybx3053.html. Looks like its less than half the price and it fits and works perfectly.

Amazing, thank you for this.

DBIZO · June 7

On 6/5/2024 at 12:08 PM, Maxz said:

Finally cleared up after speaking to Lexus head office. Lexus Parts Direct are correct in their confirmation that a replacement 12v battery purchased from a Lexus Dearlership has a 12 month warranty only and there is an annual mileage stipulation.

Your 12v battery only is under a 3year less than 25k mileage warranty, if it is the original factory fitted battery and is within these time and mileage terms (plus I assume you may also have to have done the minimum 6k miles per year, so at 1 year 6k on the clock, at least 12k at 2 years and 18k at 3 years if claiming for a fault).

As with most of these warranty scenarios, devil is in the detail.

Thanks, good to know. For a critical single-point of failure component that should last 4-5 years, a 12 month warranty is very poor indeed.

Maxz · June 7

4 hours ago, DBIZO said:

Thanks, good to know. For a critical single-point of failure component that should last 4-5 years, a 12 month warranty is very poor indeed.

They got wise to the frequency of Battery issues early on most likely. I think I may have lucked out for now as after several days on a Ctek 800xs, the voltage seems to be back up (12.7v) in Accessory mode without dropping off rapidly anymore. I am closely monitoring and intend to put the trickle charger on as often as possible.

The instructions state negative on a metal body part and positive on the Battery terminal. When charging in the boot, which bit of bodywork are people using, or is it safe to simply clip both negative and positive terminals directly? At the moment I am charging on the metal rail on the engine (negative) and the positive terminal in the fuse box. Setting up is a bit of a faff, so looking for a quicker plug and go option.

Maxz · June 8

This is what is concerning me about charging the Battery from the boot per the charger instructions attached. Positive terminal can connect directly which is easy, but the negative not sure where to safely connect it.

IS300FSPORT · June 8

Does your charger have a fuse to protect voltage overload & spark protection feature?

I have connected the Positive cable directly to the Battery & negative directly to the Battery countless times never had an issue. Connect the cables first then switch on your charger. Just be careful with the positive cable being close to the jack maybe cover it with a cloth.

For info I'm using the Noco Genius 5 I was connecting the crocodile clips directly to the Battery. Now I have the quick connect lead permanently connected to the Battery terminals literally plug and recharge once every couple of months don't need to remove the Battery cover anymore either.

CTEK sell a quick connect lead

Here's my setup if it helps