starter battery not holding charge

The demand on a hybrid starter battery is very heavy - much heavier than a standard car. Since the hybrid system turns the engine on and off multiple times when driving the starter battery has to 'start' the engine more than once per journey. If you are making short trips the starter battery may not have enough time to recharge. But if you have recharged the battery and it is not holding a charge then its time for a new battery. A local battery retailer can test the current battery and tell you if it has failed.

I've experienced this very issue with the very same vehicle before. Being a Toyota hybrid, the car has TWO batteries you need to take into consideration. The most important is your hybrid battery - that's the thing under your rear bench seats, and the reason there are air vents under the rear seats - those have nothing to do with your climate control. Chances are, that battery in your vehicle is just fine. The one that's causing problems here is the standard 12-volt battery that's present in any conventionally-powered automobile, and serves here to ORIGINALLY start your vehicle when you turn the key, and that's the one you've been jumping. This battery does NOT start the vehicle after you've turned the key - that's where the big hybrid battery takes over. When we experienced this issue with our RX, the vehicle would loose power when run with the key in the accessory position and the engine off after only about 1-2 minutes. The interior lights would flicker, the navigation display would go awry, and the car usually would not start afterward. Even when we avoided ever putting leaving the key in "accessory" it would often fail to start and require a jump. The dealership couldn't figure out the problem, but when they replaced the battery, everything went back to normal. 35K miles later, the car's running fantastically hasn't had a problem since. Good luck!

I have the very same problem with my 2006 RX400h. It has 65K miles on it so we don't drive it very much, but I have put 6 new batteries in it. This time, I installed a remote start system on it so I can start and idle it for a few minutes each day and I hope this helps. I am desperate and willing to try anything .since I need reliable transportation.

I have a Lexus 2006 RX 400h and a 2013 RX 450h. I have spoken with different Lexus dealerships about the 2006 400h battery and get different answers. I've had to jump my 2006 400h 3x in last 90 days and the battery has checked out fine both times. Bottom line is this- the 2006 400h has a small battery under the hood. Although bigger than a motorcycle battery, that's what come to mind when I first saw it. My 2013 450h has a normal sized battery in the rear (and I used it to jump the 2006 this morning). Note: I am not talking about the expensive hybrid batteries under the seat; those serve a different purpose. Lexus put such a small battery under the hood in the 2006 RX 400h that it does not last. My current Lexus dealer has no clue that the 2006 has tiny starter battery in it. I am replacing the 400h battery under the hood even though it checks out fine (a false positive reading). It's 4 years old, and my old dealer agrees with me that the small 400h battery does not last long. Keep in mind the 2006 400h was a vintage year hybrid for Lexus. I think they solved the problem by 2013 in the 450h with a normal sized stater battery next to the spare tire in the rear. They just didn't get it right in 2006 so be prepared to replace the battery (under the hood) more often. Other than that, it's a great car. In addition, unless your Lexus service writer REALLY knows hybrids, they might not have a clue that the battery is is ill suited to last long in your 2006 RX 400h.

My 2006 Lexus 400RXh has the identical issue as jpsartin. After 10 years, I've only driven 65,000 miles. It's in great condition. Except for the battery. If I don't drive it every other day, it needs to be jumped. And, yes, the battery has been replaced 6 or 7 times now. It is helpful to read that the vintage year of the Lexus RX400h designed the car with a puny battery which does not hold an appropriate charge for starting the car. Had they told me this in the beginning, I would not have spent nearly $70,000 (including finance charges) on the Lexus Lemon. Sorry. It's my opinion. As nice as it was hyped up to be (and the fact I received the coveted Bamboo color in this car) it has turned out to be a big disappointment. I've spent hours and hours driving to and from the dealership, waiting at the dealership, on the phone with the service department troubleshooting issues. The AAA guy who jumped my car a month ago said the battery was at 0%. The dealership could not find any issue. They did not offer to replace my engine battery because "it was not under warranty." I was shown my service records and that it was time for my major tune up. Yes, I shelled out over $900 for this tune up. My AC is still not working, by the way. That will be another, what?, $1000? Three weeks later, the subsequent AAA guy who jumped my car said the battery is dead and is not a good battery. I explained that my service tech said the battery he tested was not under warranty. He went back to the battery and returned to me stating "Oh no, your battery is warranted for 8 years." Really? Seriously? He asked me to recharge it by driving for an hour. Bonus side is that we had Christmas Lights to view. Two weeks later, stopped at the airport to unload a friend's luggage. Kept the back door up. Stayed longer than expected (30 minutes). When pushing the rear door hatch electronic button (this seems it may be a common issue) I was unable to start the car. AGAIN. Really? After sitting for 20 minutes trying to find AAA roadside assistance (which I'm rapidly using up my benefits) I decided to try the car again. Said a quick prayer. The car started. This time I'm driving directly to the dealership. AGAIN My RX400h has been at the dealership for over a week. They have tried to recapture the scenario that I have experienced. They say it's all good and they don't have luck trying to replicate the issue. I am very unhappy. That's putting it at G-rated mildly. So, now I wait to hear the outcome of the latest testing with management supervision. I was sold a lemon. Lemon. Lemon. Why do I need to be told NOW that I need to drive it for at least 15-20 minutes each day to keep the battery in good condition. If I was told that from the beginning, I would have kept my Mercedes Benz 300E which drives beautifully. I bought the AWD for the snow where I moved to. If anyone has any tips on what I can do to replace this car at the dealership's expense since I was never warned about the need to drive constantly, I'm all ears. Thank you.

my '06 400h ,got it 2 1/2 yrs ago,,just turned 100k miles.had always started fine ,until 3 weeks ago. it needed a chg/jump. The 1 yr old rebuilt batt. we thought, needed to be replaced.Wrong...I got another batt. 2 weeks later same thing .. After disconecting the neg. term, and everything off, key out door closed.it sparks every 6- 10 sec.. Something in the elec. sysrem is draining the batt.

I am having the same problem with my 2006 Lexus 400h. I just put my third battery in, under the hood... what could be causing it to drain the battery... which, by the way is fine, once it got a quick charge....

Same thing here. 2006 400h now on third battery in the 2 months. First battery was a 7year Lexus battery that was just 1 year old. 2nd battery was 2 weeks old from local parts store. Brought to lexus 2x now and both times they said it was a bad battery. So we had Lexus put in their battery as suggested.....lasted 2 weeks and car dead again. Just had towed to Lexus for them to try again. My bet is that the battery is not being recharged by the converter. These cars do not have alternators.... Could be the invertor/convertor doo-whoppie that recharges the battery is bad. Will let you know what happens

don't know whether someone has been posted this before, to me I havenot seen such post. feel a necessary to write it down. the day found the battery out of order when I sat in my 2006 rx400h listened radio for half hour, I decided to move chair back to make a little comfort, during the chair movement, suddenly the power went out, radio stopped, then I couldn't start the engineer, got err: "shift to P when starting", so jumped start with help. second day morning, would not start engine, jumped, afternoon it was good to start. third day, same story, so I followed some friend's advice to start the engine, disconnect the 12V battery positive pole connection to see what happen, everything sounded normal without that battery, so I thought the alternator was good to support the engine and car's electricity requirement, after I reconnected the battery, I had three warnings, scary, 1: shift to P when starting 2, check VTC system 3. check hybrid system all of them disappear after I replaced the 12 V battery.

After having my battery replaced in my 2006 RX 400h, now the key fob, and master switch to the windows will not work, is this because I did put a Lexus battery in it?

This is the best explanation of how the battery works in our hybrids. This article helped me make an educated decision on buying a new starter battery. http://www.elearnaid.com/whyis12voban.html Other than the starter battery being replaced over the years (and I live in Florida, which burns thru batteries) and the headlight condensation issue, my RX400h is the BEST car I've ever had. 2006 still going strong.

I've had identical problems with our 2007 RX400h (which is an otherwise fantastic vehicle). Starter battery dies easily (after kids watching DVD in car for 10 minutes, while packing the car with all doors open for 20 minutes etc. - all of which are not a problem on "normal" cars). My solution was this dandy Red Fuel Portable Jump Starter and Battery Charger, which I picked up two weeks ago. It's already saved us twice, and is a charm to use. $40 at Mallwart. http://www.batterychargers.com/sl161/ The odd thing is that the car doesn't "turn over" when you jump it, but rather it just clicks on and the 'ready' icon comes on. The engine doesn't even start running for a few seconds afterwards. Which makes me suspect that the problem is not the battery, but something inherent in the electrical system, wherein the jumping process shocks/resets the car into turning on.

I gave up on my vehicle and bought a new RX. I was never able to solve the battery problem, but still love the Lexus brand.

Everybody seems to be missing the real issue with RX400h flat auxiliary batteries, which is about current drain level when the vehicle is parked. When I changed the battery in mine I noticed that when I reconnected the negative ( earth) clamp to the battery, it produced a small but significant spark. Clearly there is a current drain of at least 300-500 milliamps (guesstimate) which will eventually kill any battery quite repidly. That is what Lexus need to sort, but probably can’t without major cost issues

are you leaving your key in or near the car overnight?

I Have a similar problem, I lost a cell in my 12V battery and had to have it replaced. Now when running in eco mode it discharges the battery gradually. But a good car design should keep the battery charged no matter what mode the engine is in. I think that something is marginal in the car. But I am not sure what. Any ideas?

Hello Fellow 400H sufferers who have been having frustrating 12V Flat Battery problems. Good News- I finally totally solved this problem about 4 years ago, after years of jump starts and unbelievable frustration with Lexus, Lexus Service, etc etc who serviced my car. They checked the car out and said there was no problem with anything, and that there was nothing wrong with anything that might be draining the battery. They told me that my habit of only using the car on a weekly basis was the problem. My usage was apparently not suitable for the car. i.e: Not a car problem at all, but ME. And that I should be prepared to use a 'Car Rescue Service' if I was ever to leave the car at an airport for a couple of weeks. That did not sound a very professional answer. I was told that apparently similar problems with the battery drain also happens with some other top Hybrid brands such as top BMW hybrids. So, I decided to find my own solution that would work 100% for me. I loved the car and would not be beaten by a silly battery problem. Surely, could not be rocket science. I did work out a wonderful solution, which has worked 100% reliably for me ever since. I did post a note on this site about it some 4 years ago. I no longer have any worries about the car failing to start. The basic problem is that the smallish 12v battery under the bonnet of the 400H, is being continually drained of significant amount of continuous energy drain, in just maintaining the electrics/ electronics (inc. computer?) of the car. 24/7, whilst sitting in the garage, going nowhere. One to two weeks of doing nothing can empty the battery! You must not unplug the battery terminals if you are not going to be using the car shortly, because the car then loses all its settings. So, in order to discover what was REALLY happening, I bought, fitted, and fully charged, yet another brand new recommended Bosch battery. (my 3rd in 3 years! Not cheap from Lexus. I then plugged my own DIY current drain meter in series with the Battery circuit- plus a DIY Volt meter in parallel across the battery. I then placed those two meters on the dash board. (Meanwhile, I used my other car, or train, for 2 weeks to go anywhere). I Locked the Lexus doors on the remote key- and waited to see what would happen to the battery readings. Every day, I observed the two meters through the drivers window for 10 days, day which time the battery voltage had dropped day by day, to a useless 7.3 volts. All this time, the car was standing unused. My Findings: Horrors- A huge 2.8 amp current drain for about 15 minutes after locking the doors, followed by significantly continuous current drain thereafter, 24/7, settling to 50 ma for ever and ever until the battery's totally drained down to 7 Volts or below. Over 10 days, The Voltage of the 12 Volt battery under the bonnet, dropped from 12.4V on Day one, to 7.3 volts on Day 9. On a brand New battery! By day 8, it had already plunged to a useless 9.05 volts. That meant that I could only safely leave the car for a week before it won't start. For anyone interested, The actual daily readings were as follows: Day Zero, Time Zero from locking doors (midday). 12.4 V, Current consumption 2.8 Amps for about 15 minutes, then eventually dropping to 60ma. Day 1 12.3V, 60 ma Day 2 12.1V, 60ma Day 3 11.9V, 50 ma Day 4 11.9V. 50ma Day 5, 11.8V, 50ma Day 6, 11.7V, 50ma, Day 7, 11.5V, 50ma Day 8, 9.05V, 50ma Day 9, 7.3V, 40ma Day 14, (was away for weekend), 02.4V ! That low voltage must surely have wrecked the battery for the future? THE ANSWER? What I had discovered during my various attempts at recovering from flat battery occasions, was that it only needed a small amount of Jump start power to bring the car back to life! It did not need great big powerful jump battery like a normal petrol engine, just a token 12 Volt gesture, which I got from my pocket size 12V model boat battery! Amazing. I also used a Rechargeable electric drill battery with great success!! Unlike a normal car which needed a big jump of power to power the starter motor, all that the Lexus needed was enough power to re boot the electrics/ the Hybrid battery under the floor! The 12V battery under the bonnet does NOT turn the engine over- (It has no starter motor as such.). It is the huge master Hybrid battery under the floor that somehow starts the petrol engine. So, my final solution was everso simple- as follows:- I bought a new regular 12v 45ah car battery (£50), and put it in the boot. My local car electrics shop guru Neil (of Creative Car Sounds, N21 2RS) then ran a cable from that battery in parallel to the regular battery under the bonnet, via a switch by the dashboard, near the driver. From that day on, I never worried about silly battery problems again. Now, If the car fails to power up/ start up, all I had to do was to turn my new Dashboard switch, to bring LIFE to the system. The Steering wheel pops out and life is back to normal. INSTANT AND RELIABLE SUCCESS. No waiting, no jump leads, no Opening the bonnet, no phoning the RAC, NO PANIC. And the beauty of it all, is that it only takes a few seconds, of very little power from the auxiliary battery in the boot, to get the car going. Phew! So, the battery in the Boot never gets any big demands from it. All it asks for is to be switched on for a few minutes every few months to keep it nicely topped up. Oh, happy man. David

Hi David, i found your description of the RX400h battery problem very informative. I am going to follow your advice as it makes perfect to overcome this issue by having a charged battery available and already rigged to go. We all know that Lexus know this is an issue, hence why they have fitted a normal size 110AH battery on the RX450h. Anyway I think everyone reading your post would welcome, if you agree to some pictures of your battery solution. In particular would be good to see the thickness of the wires from the battery to the dashboard switch and a picture of the switch. The battery location in the boot and the route the cables are taking in the cab. Are there any in line fuses fitted. Where is the entry point from the cab, through to the bulkhead and then to the battery in the engine compartment. Thanks George

I have a 2002 RX300 and replacing the battery twice a year is the only problem I have had with it in 15 years!! I bought a GooLoo Jump Starter last month, put it on the Lexus, it started right up, then when I took the jumper cables off, it went dead again! I am a senior citizen woman, but I have had to learn a lot about cars and batteries lately!!

I'm an old school automotive fuel and electrical mechanic with a little input for all it is worth. I looked up the battery new here in Canada and $35-$400 seems to be the going price. I had all the codes you were talking about and here was my easy fix. Take off the bracket that holds your battery in place. Clean off the top of your battery with baking soda and water so as not to get any corrosive acid on your hands or use rubber gloves. Peel off the battery sticker and carefully with small pointed object pry out the small circular plugs. What I found is that my battery was quite low on water. 600 milligrams to be precise. ( a water bottle plus). take distilled water and fill each cell until the water is 1/2 inch from the battery top. Now put a charger on your battery until fully charged. Most used batteries won't charge above 90%. Then go for a drive. After 5 minutes of driving all warning lights went out and haven't come back on. I hope this helps the bank-book. Cheers!

Above battery cost $350-$400

I've had my 2008RX400h for over 2 years now, and I was well aware of the 12 battery issues. It's not surprising being so small and lots of thinks running off it when the engine is switched off. I use it regularly so it wasn't an issue, until Covid came. Sure enough, battery was flat (it was a new RAC one when I bought it) but I jump started the car easily with a mini power pack - the battery read 4v on a multimeter. Everyone is right, the little 12v battery is only there to fire up the electrics, the rest is done by the hybrid beast. I was convinced it was wrecked but a half hour drive brought it back to life. Since then it only holds it's charge for 3 days or so. Bear in mind a 12v battery is deemed discharged at 12.1v and fully charged over 12.4v, so anything below 12v and you are in deep .... ! As I'm not using the car in lockdown, I did the trick I used on a rarely used van I once had and hooked up some solar. I didn't want to start making holes in the dash to connect to the battery so I found the easiest solution! Your OBD2 socket (they plug in at service) has a positive and ground pin. Halfords sell a Ring OBD Power Cable for Solar Battery Maintainers for £10! I already had a 10w solar panel so I bought a cheap solar panel charge controller from Amazon for under £10 (so you don't cook the battery and balance the charge rate). The solar panel sits on the dash, and there you go. The battery is always over 13v now, so perfect. It does get loaded all the time, sometimes 12.1v, often 12.4v, rarely 12.9v, but the battery is always 13+v. The controller has a cut off at 13.7v so you can't overcharge, it also has load connections, so you could run something off it. So I sorted the problem for under £20. No need for endless new batteries! I would say, this is ideal if you only use the car occasionally. And it may not look pretty, but it's not fixed and goes in the boot when not used. I don't think a trickle solar charger would keep up with the demands the car makes of the poor 12v battery! Finally, if you do this, NEVER connect the solar to the controller before the battery, you'll fry the controller. Connect, 1 plug in the OBD2 connector (the controller will already be wired in), 2 connect the solar to the controller. Disconnect the opposite, 1. remove solar, 2. move OBD2 connector. Cheers!

Hi Clive, many thanks for the detailed answer and guidance, I will certainly follow up on this approach. In the meantime I have rigged up a permanent second battery to overcome the battery no start scenario. The second battery is wired up via a VSR which has an override switch capability so in the event that the starter battery fails, I flick the switch and the second battery connects and provides enough volts to start the system and allow the hybrid system to kick and start charging the starter battery. Once started then I flick the override switch to off and the VSR takes over allowing the second battery to be charged as part of the normal charge circuit. I have also rigged a solar panel to keep the second battery fully charged as a backup for long standing periods. This approach seems to work so looking to fix permanently with the second battery being in the boot area and routed underneath through a conduit back to the starter battery in the engine bay. The VSR fitted along side the second battery with the small switch cable routed through to the drivers panel ( not decided exactly where the switch will be mounted but it will have 2 volt meters showing the status of both batteries. Will update when I have finished doing the installation. Best George

Hi there. I also have the same problems as above with my Lexus RX 400h (2007). I just changed the battery but will probably be selling the car due to the fact that I do not drive it often enough. However, I need to buy myself some time and that is why I bought a new battery. However, only a couple of days after I installed the new battery my key started acting up and wouldn't open or lock the doors remotely. This is what has normally happened when the battery has been running low. My question is, could it be worth checking whether the generator needs replacing as well? Has anyone looked into this? I know absolutely nothing about cars so this is a huge issue for me while at the same time I love my Lexus and am not in a financial situation right now where I would really like to splash out on a new car... At this point though its causing me too much problems not being able to trust my car. :-(

To be clear the starter battery only fires up the electronics. The engine is started by the main hybrid battery so once the starter battery has switched on the car it is not used. However there is always a drain when parked and it’s a design fault. Lockdown was a nightmare so my easy and cheap fix is a 10w solar panel that sits on the dash when parked up for days. I got an OB2 connector (looks like a scart plug under the dash in the footwell) from Halfords (£10) which connects to a cheap charge controller (£8) on eBay. Always plug in the OB2 before the solar panel when setting up and disconnect the solar panel first when taking it off. I don’t drive with it connected. My battery was down to 4v - basically destroyed, and wouldn’t take a charge from a charger but the solar got it back up. 6 months later and no problems - amazing and cheap... much cheaper than a new battery or car!!

Hi Clive, thank you so much for your reply! Sorry if I'm asking dumb questions but if I understand correctly, the starter battery is only used to start the car but does that mean it doesn't charge when driving but needs to be charged manually regularly? Is there any point in looking at the hybrid battery if that is also too old in my car now? A solar panels solution sounds excellent but problem is I live in Sweden, now looking at 6 months of winter and darkness AND my car is parked in a garage. There's no sun available for the car to pick up unfortunately. Due to all the issues with the battery I'm having a lot of problems with the electronics, now the trunk can only be opened manually and the key fob only works from time to time. Have you had these problems as well and if so, what did you do about that?

Hi all, do you think that a 2008 Lexus RX 400H will be fine if I only intend to use it 2-3 days per week? I read somewhere that it may not be great for the battery. Thanks!!

As an owner of a 2008 Rx400h, I have experienced this battery problem. I have resigned myself to the reality that this car puts a unusually high drain on the 12volt battery I have therefore attempted to counter the issue and would make the following suggestions, which have so far been successful Firstly do not buy a cheap battery because it is much more likely to give up the ghost quite quickly due to the loads imposed The two stage alarm system draws significant current from the 12 volt electrics, so avoid unnecessary use, especially in what I would term “stage two” I have made up a lead to connect the positive and negative 12 volt terminals on the diagnostic OBD2 socket (under the dashboard). This connects to a solar panel which I place on the dashboard when the car is parked An alternative suggested by another responder is to have a slave battery in the boot which can be switched remotely to replace a failed main 12volt battery. As a final observation I think Toyota have failed dismally to respond to this problem. I suspect it/they do not want to admit that the Lexus brand image is not so perfect as promoted. I think the silence on this issue, (throughout the Toyota organisation) speaks volumes

The 'battery in the boot' working a treat now. If the stsrt batt falls below 10v then I throw a simple switch in the cab which connects the battery in the boot via a VSR to the battery in the engine bay. This is a simple slave arrangement which is common on a lot of mobilehomes/campervans. I have rigged up the solar panel to keep the battery in the boot fully chraged when not using the car. Totally agree with the observation that Toyota have failed given that they are considered to be a the top end of quality and customer service.

Geor1234 - great to hear your system is working but a word of warning about when to flip the switch... a 12v battery is considered discharged at 12.1v. It should not be drained below 50% capacity - 10v is dead, it is getting damaged and will shorten its life. I was shocked when I learned this. The link below gives a chart to show (scroll down). Not over discharging your battery is key to it lasting a good while. Cheers! https://www.altestore.com/howto/batteries- measuring-state-of-charge-a81/

My 2006 RX400h has 60,000 miles and suddenly would not start. It displayed a “shift into P to start” but it’s in park! There was a dull clicking sound under the dash, all the information icons lit up, went out and the icon of the engine remained. I don’t drive a lot, but short trips about 4 times a week. I have had to replace the battery twice since I bought it in 2006. We have had below freezing lately but my car is in my attached garage, where the temperature is a pretty steady low 40’s. I’m calling AAA, trying a jump to drive to my mechanic who is less then a mile away. I’m surprised to read this is a known issue with the early hybrids and hope it doesn’t involve much more than a new battery, but reading the previous comments makes me uneasy! At least I’m in good company with what I’ve read. This car has and is a wonderful car! I hope it can be again, with not a huge bill. Thanks Clive for such a detailed description and advise. I enjoy reading a Brit’s words like”in the boot”! I’m an Anglophile, so much appreciated! If a new battery is required, what should I be looking for? I will tell my mechanic about your previous suggestions above.

Evening gents. Are just 3 causes. 1.when car is parked, closed, etc, the consumption should be 0,01— 0,03A/H. You have to open the Hood, close the car, put the alarm and if after 2 minutes, (when car enteres în sleeping mode) the consumption is above upper said 0,01—0,020A/H than you should find an good electrician to dismandle the whole car, pannels, etc etc, and see what( buton even) is not "sleeping". This should take a full working Day but problem should GO out 2. Dash board should be checked well because is the car heart and brain. 3. Sometimes the "brain" is full of garbage (as you have to do an restart to your computer) and needs to be remap. Conclusion; Battery does not have to be drained such fast (more than 0,01—0,03 A/H) and to put solar pannels or whatever other soluționa is not ok. You should find and fix the problem not going to bărbier Shop for beauty