Do Not Sell My Personal Information Jump to content


Regenerative Braking Issue


Recommended Posts

Had my RX400h for 18months now and still love it, however I have one niggle with the braking system and want reassurance it is normal.

When braking gently especially going down hill the car will slow (as you would expect) and the needle on the power meter drops into the blue.

However after a short time the regenerative braking ceases, power meter needle jumps up out of the blue, the car lunges forward and you have to press the brake pedal harder to slow down again.

When I got the car I asked my local Lexus dealer about this and they said it is a normal characteristic of Hybrid cars and I would get used to it, I haven't and it still takes my by surprise sometimes.

I have driven a CT200 and IS300h and neither of these had this characteristic.

A good example is a hill I go down every day, it is approx 1/4 mile long and at the same place near the bottom every time the regen braking stops and I have to press the brake pedal further.

It doesn't make any difference if car is cold or warm or if Battery level is in blue or green.

Anyone else have this issue or is it just me ????

Link to comment
Share on other sites


Yes my 400h is the same, I had a prius before this, and it was exactly the same. I think it is the power generated by braking that gives a surge of electricity, a bit annoying at times. But yes they're all the same

Link to comment
Share on other sites


Thanks for the feedback, so it appears that this is norm in all 400h.

I can't seem to find anything regarding a software update as described by Boxbrownie.

However doing a bit of digging it looks like Lexus have had quite a few complaints on safety grounds on this issue !!!!

Take a look at the following website.

www.carproblemzoo.com/lexus/rx400h/service-brakes-problems.php

Not sure if I am relieved to hear it is not just me that has this issue or having seen the above website should I be worried !!!!!!

Link to comment
Share on other sites

Hello, if I am going down quite a steep hill I always use the B (engine braking) position as it saves wearing the brake pads out. If you don't use that , the car can tend to run away with you due to is size.

I can't say I have noticed what you mention though.

Link to comment
Share on other sites

This is normal. If the regen braking has to stop (e.g. if Battery full, Battery temp. too high) then it will switch to mechanical braking.

This doesn't alway happen smoothly and the regen lets go before the mechanical fully cuts in which gives you an acceleration feeling (actually is just less deceleration). You shouldn't have to press the pedal harder, you just naturally do it when you sense it occurring.

You get the same issue sometimes when going over a bump and a wheel loses traction.

This is mainly corrected on generation three hybrid systems so it isn't a problem on the Prius MKIII, Auris (a.k.a Lexus CT200), IS300h etc.

Shame Toyota/Lexus haven't just corrected this for the 400h, a firmware update is really all that is needed.

  • Like 1
Link to comment
Share on other sites

http://news.bbc.co.uk/1/hi/8497471.stm

Apparently the Mk3 Prius still seems to be affected, although despite anecdotal evidence on the internet forums and in the press Toyota UK say no problems have been reported.....a typical reaction.

I am sure this is the same "feeling" that drivers of Lexus experience but being a much smaller production sample little if anything will be admitted to or corrected.

This is the same issue I read about quite a few years ago, I just cannot seem to find the info now.

Link to comment
Share on other sites

my 450h does not do this. It may be only affecting the 400h's

Well yes, one would have hoped Lexus/Toyota may have cured this "characteristic" on the newer models.

Link to comment
Share on other sites

As mentionned by others, switch the gearbox to "B". It will prevent the car from gathering speed as you go downhill without having to keep your foot on the brakes.

Don't forget the change it back though... otherwise your petrol consumption will go through the roof!

Link to comment
Share on other sites


  • 4 years later...
On 04/03/2014 at 9:47 PM, Woody123 said:

A good example is a hill I go down every day, it is approx 1/4 mile long and at the same place near the bottom every time the regen braking stops and I have to press the brake pedal further.

Hi All, I'd like to cross reference this to my regen braking thread here:

 

As you can see, my issue is similar, in that I initially get regen braking and the needle drops below 0.  Then deceleration is reduced and the needle rises.  But, I find that this behaviour repeats (oscillates) many times during the same manoeuvre (e.g. long descent).  

Are you all saying that the cycle of initial regen, then no regen happens only once during a braking manoeuvre, or happens repeatedly like for me?

Link to comment
Share on other sites

I have a IS300h so there's no 'B' option on mine, but you can use the flappy paddles to 'select' a lower gear, which I've only ever used a couple of times but it maintained the speed without using my actual brakes.

Lexus will have the system set up so 0% and 100% Battery on the display are actually only say 20% and 80% in reality, this would save you running your Battery completely flat and when full gives you extra 'space' for a bit more charge.

So here is the thing, when you are regenerating into the Battery, you will go past 100% as far as the display is concerned but there will be still be a limit when then Battery is actually full, now when this happens, you have still got to dump the excess electricity being generated somewhere, what the system does is to use this electricity by spinning the secondary electric motor which causes the petrol engine to turn, thus using the petrol engine as a load to keep the system happy.

 

I'm surmising that its this transition to spinning the petrol engine where the actual braking diminishes even temporarily, you would sense this as a surge in acceleration due to gravity.

I've watched several videos on YouTube showing how the hybrid system works, and in one of the Weber videos, they actually mention this effect where the engine will spin to create extra load, just like conventional engine braking would.

 

Vince

  • Like 1
Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

 Share



×
×
  • Create New...