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QUERIES on my beautiful newly acquired RX400h


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Good afternoon folks,

My car is a 57 reg, with 89,000 miles, and we love it - it's our first hybrid, so we're still learning.   It's not as fast as our beloved automatic Saab 9-5 Aero Estate but hopefully in these times our rocketing petrol prices, it will be more economical... Anyway, I'd very much appreciate some information that is not clear in the Owner's Manual, and believe me - I have read it IN DETAIL from cover to cover.

1.But having read the 

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Sorry - I hadn't finished - the tab key ENTERED it.   As I was saying :

1.   What is the actual benefit of the Brake mode if it can use more petrol, and can wear out brake pads more quickly?

2.  The manual only has illustrations in black & white.   What do the 4 coloured arrows on the INFO screen (ie Navigation model) mean - ie blue, orange, red & yellow as the book doesn't even mention them?

3. Can I force battery only mode on short journeys around town - eg 5 miles to golf & back, or in traffic jams to avoid pumping out exhaust fumes - and if so, how?

4.  The manual says that putting the car in N for Neutral can drain the battery, but surely when sitting at traffic lights, that what you are meant to do!

as you can see , I'm confused and look forward to some kind person or persons putting me straight ..... PLEASE!

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6 minutes ago, Tony Friedlander said:

4.  The manual says that putting the car in N for Neutral can drain the battery, but surely when sitting at traffic lights, that what you are meant to do!

Either leave in D or put in Park as in N the battery is not charging.

I don't believe there is any downside in leaving in D when you are stopped for a prolonged period, the engine will cut out anyway once warm.

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11 minutes ago, Tony Friedlander said:

1.   What is the actual benefit of the Brake mode if it can use more petrol, and can wear out brake pads more quickly?

I've never had a car with 'B' mode so I may be wrong but, as far as I know, it's not to do with actual braking but more to do with engine braking. When doing a long downhill stretch you can put it into 'B' to do two things; (a) to give the proper brakes a rest, but more importantly, (b) to dump some of the excess electricity generated if the traction battery is full and can't accept any more charge.

Normally, MG1 is used as the generator but if the traction battery is full then MG1 reverts to being a motor and it spins the petrol engine without fuel or spark, so it just acts as a big load to use the excess energy. I think this is what happens when you put the gear selector in 'B'.

22 minutes ago, Tony Friedlander said:

2.  The manual only has illustrations in black & white.   What do the 4 coloured arrows on the INFO screen (ie Navigation model) mean - ie blue, orange, red & yellow as the book doesn't even mention them?

Again, not completely sure because I've never had a 400h but I assume you're talking of the energy screen. The different coloured arrows show the flow of energy and power at any given moment. For instance, the blue arrows may show flow of power from traction battery to the wheels; the yellow arrows may show when the petrol engine is powering the wheels and so on. I'm sure the manual will tell you or if not then Google should. You should see something like this:


Lexus RX 400h Review--Slideshow


 

30 minutes ago, Tony Friedlander said:

3. Can I force battery only mode on short journeys around town - eg 5 miles to golf & back, or in traffic jams to avoid pumping out exhaust fumes - and if so, how?

No. They aren't electric cars and if you tried to go battery only I bet you wouldn't get more than two miles before the traction battery was flat. In traffic jams, if the car is stationary then the hybrid system will shut off the petrol engine anyway and will start it again as and when needed. For instance, the engine is the only source of cabin heat so on a cold day, if you have the heater on, the engine will fire up more often than it would on a hot day.

Hybrids don't have starter motors or alternators, and anything normally driven by a belt from the engine such as power steering or aircon compressor is powered by electric motors instead. Imagine losing power steering halfway through a turn because the hybrid system decided to shut it off!

Start-up is like this: the 12V battery powers all the computers and gets the car into the READY state (hybrid system up and running) which is the equivalent of a conventional car sat idling. Once in READY mode you can drive away on battery power alone but you won't get far at all before the petrol engine starts up, controlled by the hybrid system. When it wants to run the engine it energises MG1 and uses that to spin up the engine to 1,000rpm before applying fuel and a spark to fire it.

The job of the alternator is done by a device called a DC/DC converter, again controlled by the hybrid system . The traction battery in the RX is about 290V and the converter lowers it to about 14.5V to run all the 12V systems and charge the 12V battery. The converter/inverter assembly also provides for other systems such as 48V for power steering; 500V 3-phase AC for the aircon compressor and so on.

The 12V battery is only small and doesn't like being stood around doing nothing for very long and it's not unknown for it to go flat if not used for a couple of weeks. Either use the car regularly, or keep it on a trickle charger, or carry a jump start battery pack in the car for emergencies. Oh, and never use the hybrid to jump start a conventional car. You can get a jump from one but not the other way round. The traction battery should be alright stood around for months without going flat but if it ever does, you'll need the dealer to come out and sort it, or at least someone with the specialist gear and knowledge to use it. The AA, RAC and so on can't do anything with a 290V battery.

Try to never let it run out of petrol. If it does, you'll need 10litres in it before attempting to restart it and if you have more than 3 unsuccessful attempts, the hybrid system could lock out and need a dealer to reset it.

Wow, sorry, I was on a roll there and never meant to go on for so long.

1 hour ago, Tony Friedlander said:

4.  The manual says that putting the car in N for Neutral can drain the battery, but surely when sitting at traffic lights, that what you are meant to do!

If you think you'll be away within a couple of minutes just leave it in D with your foot on the brake. If you think you may be a while, put it into P and take your foot off the brake. As Andrew says above, the hybrid system doesn't charge the batteries in N. I think most people only use N when they need to roll the car a couple of feet and don't want to start all the systems for that.

Most of all, enjoy your new beastie to the full :laughing::thumbsup:

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42 minutes ago, Herbie said:

I've never had a car with 'B' mode so I may be wrong but, as far as I know, it's not to do with actual braking but more to do with engine braking. When doing a long downhill stretch you can put it into 'B' to do two things; (a) to give the proper brakes a rest, but more importantly, (b) to dump some of the excess electricity generated if the traction battery is full and can't accept any more charge.

Hi Herbie,

I think choosing sport mode (the manual mode with fake gears on the gear box, not sport mode on the drive mode selector rotary switch) in the 4RX (and several other models, e.g. 1NX) and selecting a low gear is the same as selecting B in models that have a B mode (e.g. the CT comes to mind, as well as the RX400h).  In other words, in some vehicles (like 4RX) you can select multiple fake gears.... The earlier vehicles essentially just had one low gear, called B.  It's use is, I think, just as you describe.

Cheers,

Paul

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