Hybrid battery fail.

[Whiteshark]

This same concern is constantly expressed on Lexus owner’s  websites, really without qualification, and often by those who do not have a hybrid. As stated by Lord Voltemore the hybrid battery is designed to last the life of the vehicle. Who knows what that is except there are many original RX400’s running around perfectly normally with extremely high mileage’s. As always the key to longevity is regular servicing and maintenance and hybrid systems do require periodic adjustment to optimise performance.
Where there have been failures , it is not always the whole hybrid battery that fails, just some of the cells, and as mentioned here there are cheaper 3rd party operators now available at reasonable cost.
I have absolutely no problems owning a hybrid, at the same time it will be changed at 5 years or earlier, so always under warranty, but I also suspect it should hold its value well.

[Lord Voltermore]

If battery life on EV's and hybrids  fall off a cliff  in the foreseeable future there will be lots of people with limited budgets also  looking for a life line. The demand for solutions will be there.   

But I think my cunning plan to recycle disposable vape batteries into EV batteries  is a non starter. 
If someone pinches my idea and makes a fortune I wont mind.  Much.  As long as they dont make private helicopter and private jets flights.

My other idea is to buy up lots of non ULEZ compliant cars cheaply, then corner the market when people are desperate for  alternatives to older  EV's. 

[coldstart]

Honda has been building hybrid vehicules for over 20 years now (remember the "Insight"?).
If there were a significant problem with the batteries it ought to show up in the fora by now.
Remember: If you're satisfied you tell two to three people you like; if you're dissatisfied you tell the rest of the world!

@LV: I like your business plan, maybe you should team up with Jeremy Clarkson (I'll drive combustors till my death) 

[nowster]

But I think my cunning plan to recycle disposable vape batteries into EV batteries  is a non starter. 

Not big enough! Disposable vape batteries tend to be odd shapes and max out at about 1500mAh.

I have one I found in a street gutter (with a cheap Li-Ion charging board and a solar cell) powering my homebrew IoT "shed thermometer".

The ones in a hybrid battery are likely to be standard sizes like 18650 with at least double that capacity.

[Neil Ives]

I'm not sure about posting this here. Today my wife and I drove to a country park. We sat in the car to eat our lunch and listened to an audiobook from my phone via the Jazz audio. We may have spent an hour with the accessory power, (is that what it's called when you press the start button but do not put your foot on the brake) being used. I locked the car and we went for a walk with the dog. When we got back to the car and tried to continue to listen to our book the electrics started to fail and eventually went off completely. I was, of course, not able to start the car. I used the Honda+ app to call Honda Support. An AA man came to us within half an hour. The service battery was jumped and the car started. The AA man suggested that the battery is probably knackered. On the way home I called at Halfords and bought a power pack car starter gizmo. The car is not quite 3 years old. Should I expect the battery to be FUBAR?

[Jazzik]

We sat in the car to eat our lunch and listened to an audiobook from my phone via the Jazz audio. We may have spent an hour with the accessory power, (is that what it's called when you press the start button but do not put your foot on the brake) being used. I locked the car and we went for a walk with the dog. When we got back to the car and tried to continue to listen to our book the electrics started to fail and eventually went off completely. I was, of course, not able to start the car.

This has nothing to do with the hybrid (HV) battery. You "exhausted" the 12 volt battery. You could listen to an audiobook or music, but have your Jazz in ready, your battery will survivive and you will be able to start and drive on without help of the AA...

[John Ratsey]

It's usually the new owners who drain the 12V battery while using accessory mode to explore various vehicle features. It's a small battery but I suspect that too many energy-hungry components are powered up when in that mode while the HV battery remains disconnected and can't provide top-up power.

[Kremmen]

I'm sure there's more to it, but you can run an indoor radio for many hours on a set of 4 AAA batteries but a far larger car battery can be flattened in a few hours just listening to the radio

[ColinB]

I'm not sure about posting this here. Today my wife and I drove to a country park. We sat in the car to eat our lunch and listened to an audiobook from my phone via the Jazz audio. We may have spent an hour with the accessory power, (is that what it's called when you press the start button but do not put your foot on the brake) being used. I locked the car and we went for a walk with the dog. When we got back to the car and tried to continue to listen to our book the electrics started to fail and eventually went off completely. I was, of course, not able to start the car. I used the Honda+ app to call Honda Support. An AA man came to us within half an hour. The service battery was jumped and the car started. The AA man suggested that the battery is probably knackered. On the way home I called at Halfords and bought a power pack car starter gizmo. The car is not quite 3 years old. Should I expect the battery to be FUBAR?

In my Mk3, you don’t need to use Acc mode to listen to the audio, you just push the power button on the unit to turn it on without starting up all the other accessories. Also, the radio will switch off after around 10-15 minutes as a warning that the car is trying to protect the battery. You can override this by turning it back on again, but ignore that at your peril. Does the Mk4 unit not work this way?

[Jazzik]

This is a Mk4 problem. Your Mk3 doesn't seem to be a hybrid...

[5thcivic]

I'm sure there's more to it, but you can run an indoor radio for many hours on a set of 4 AAA batteries but a far larger car battery can be flattened in a few hours just listening to the radio

Depends on the power output and number of speakers. Car speakers tend to be 4 ohm which run on current rather than voltage for loudness, dynamic impedance can even be lower, class A/B amps can run warm at louder volumes, which disspate power, two channels, four speakers, current can easily be many hundreds of mA, maybe amps. It is possible that the 12V voltage will go down to the point where the micros won't start, particularly if the system is not regularly charged by a reasonable run. We don't know a lot about HV charging without alternators in these type cars now.

[Neil Ives]

This morning I took my car into the Honda dealership to have the service battery checked. Unsprisingly the verdict was that the battery is OK. I told them what led up to the flat battery. They said that given that information Honda would not have changed the battery under the cars guarantee. I will have to take care when using the audio system with the car in Aux mode. I now have a compact booster in the boot well.

[ColinS]

This is a Mk4 problem. Your Mk3 doesn't seem to be a hybrid...

Hence ColinB's final comment "Does the Mk4 unit not work this way?"

It does pay to read the whole post

[Kremmen]

With the MK4 just leave it in normal EV driving mode

The engine will cut in and out as needed to keep both batteries charged

If your just listening to audio then the engine will cut in very infrequently in my experience

[ColinB]

This is a Mk4 problem. Your Mk3 doesn't seem to be a hybrid...

Hence ColinB's final comment "Does the Mk4 unit not work this way?"

It does pay to read the whole post

Said it before I could! Every modern car I've  had has turned the audio off after a while if the charger (aka the engine) hasn't been running. Surprised the MK4 doesn't have this safeguard ... unless it was deliberately overridden.