I don't think it's draining the battery, but using engine braking to replicate the same deceleration character that occurs from regen when the battery is not full.

 

oh that makes sense. Engine breaking in lieu of regen when battery is full.

 

I would have agreed with the theories above, except recently during a cold spell it happened to us after a long period of not experiencing it. I know the battery was not full at that time. I say cold spell because from what observed was that it happened for a short while into the drive, during which time we were calling for heat in the cabin. It was all country roads so there was no stopping. 5-10 minutes into the drive it wasn't doing it anymore.

 

Pure EV mode wouldn't help if going down a hill. The car would still try to give more charge. If going up a hill or on flat ground, stepping on the gas should use up some of the charge. I wonder if they could figure out a way for the computer to bypass regen when the battery is full or before it starts the engine revs?

 

I'm sure they could "figure out a way." They chose a different way. Its current behavior is by design. It's a feature, not a bug, as many are treating it.

 

If it is a feature, what is it trying to accomplish? How come RAV4 hybrid does not do this?

 

The feature is that it prevents the traction battery from over charging and shortening it's life span.

 

I believe they are trying to keep the same deceleration profile whether the battery is full or not.

The RAV4 is a good deal lighter than the RX. It may not need it, or they may not implement it because it's a different model.

 

I have not observed this behaviour on a flat surface. I can't think of any logic why it would.

This probably does not help but it does happen to me downhill and only if I am on cruise control. I expect this to be the correct behaviour. As per the below image, I believe that it is engine breaking to try and maintain the 85km/h speed (note the over 4K RPM). Off topic, but one other observation here is that the wheel is charging the batteries. I have always though that the "engine" like icon on the right is the engine but note that there is no energy flow to the wheels or to the batteries. This to me implies that that icon is the transaxle, not the engine. From my research, the engine drives one of the motors in the transaxle which makes the transaxle behave like "CVT". I am no expert so I could be completely wrong.

 

My previous RX 450 did not do this either.

Totally bizarre for a hybrid to do this. I think it is a bug as it is random, unpredictable, and pointless. If you don’t want to charge the traction, throw a relay.

I bet a dollar to a donut a software update is coming. This is simply not what a Lexus should drive like.

 

Drives exactly the way I want it to drive.

 

I have a 2023 RX350h. On rare occasions, when I take my foot off the gas, it seems like the engine makes a very loud noise as if the rpm was still very high. This stops when I brake and come to a stop. It may occur and then not repeat for a several weeks. Any idea what is going on? I just had it in for my 10,000 mile service and the service rep blew it off as regenerative braking

 

There is a thread on this already. I believe it is the hybrid system using engine braking due to the battery being full or otherwise not being able to accept charge. This keeps the deceleration character constant, whether regen is available or not.

https://www.clublexus.com/forums/hybrid-technology/1017180-extremely-high-revving-when-foot-is-off-gas-in-rx350h.html

 

Thanks. I have read through this thread and just want to add that it has definitely occurred on flat roads.

 

Flat road or hill doesn't really matter if the battery can't accept charge from regen..