Earman

There is a button allowing to recharge the depleted main battery with the ICE engine while driving.

Does anyone know approximately how much gas is used per 100km recharging the battery?

I am trying to find out if it is worth it to recharge the battery while driving on the highway to get an extra 67 km on pure battery power or if it is counter productive to do so and it is better to wait to be at destination near a plug to recharge.

I searched for this subject but could not find anything on it...

Thanks!

shiftD7

It only allows you to charge up to 80% (not 100%).
​​​I haven't calculated myself but I believe some videos reviews have and it doesn't work out to be economical

On the qualitative side, it also makes the engine run at a higher RPM which creates more noise and I feel saps power when you really need it to pass, so I only do so to get a few KM's for city driving if I am out of EV range.

Earman

Thanks for the reply. That was my guess as well so I had never tried it. I was hoping someone could prove it was a useful option but that was wishful thinking! I am wondering why they did put that option as it does not make much sense if it is not cost effective...

nx450plus

The fuel usage is really high and not worth the resultant modest increase in battery charge, especially with BC fuel costs.

Earman

That makes sense. What does not really makes sense is why Lexus bothered putting that option in the car when it is basically useless... Marketing I guess...

clmk

Some cities have green zones where only EV's are allowed (or cars in EV mode), this provides you the option to charge and drive in EV mode when needed if you don't have enough charge.

I also find it useful as a way to force the petrol motor to run continuously to properly warm it up and give it a run to circulate the fluids and run some petrol through the motor every now and then.

nx450plus

These are the 2 narrow use cases.

Utopiag

It was explained on youtube that this function was there for Japanese culture. They do not want to go home and wake everybody up in the hood at night, so what they charge the battery with fuel before heading home and arrive home in EV mode with minimal sound.

mangust

It also could be useful when a car won't be driven for a while as LiON batteries don't like to be near empty for a long time.
Let's say you're traveling and forget to charge or deplete the traction battery before getting to an airport.
This way you can give it a boost while driving.

CdO

TL;DR - If you use Charge Mode at the right time it could improve your efficiency (if you cannot plug in).

I planned to go into more detail on this in the future; but, I'll try and fail to be brief here.

First consider: in HV mode your are constantly charging and discharging your battery. Obviously, this increases your efficiency over a non-hybrid in most circumstances. So, if you use Charge Mode in similar circumstances why would it be inefficient? Which circumstances? Read on...

Next consider: when the engine (ICE) is propelling the car it is also generating electricity via "Motor/Generator 1" (MG1). That electricity can either be sent to the battery or sent to MG2 (or MGR... aka Rear). In hybrid mode, the car decides where; in Charge Mode, you decide. Why generate electricity if it is not needed? It has to. It is perhaps the sole drawback to the design. If MG1 does not resist the force of the engine, the engine will not propel the car... this is what happens at idle. The speed at which MG1 resists is what determines the "eCVT" gear ratio. *Edit: this is only true at underdrive eCVT gear ratios usually happening upon acceleration and below interstate speeds.

Finally consider: the engine is most efficient at generating power at about 2500 rpm where it can output ~67 hp (~50 kW).

When to use Charge Mode? Not when the engine would normally shut off while in HV mode (e.g. when stopped, when decelerating, descending) and not when it would force the engine significantly over 2500 rpm (e.g. when accelerating, ascending, high speeds, etc.). Don't worry too much about 2500 rpm, the efficiency doesn't change much between 1600 and 3000 rpm.

Anecdotally, my best all ICE no plug in MPG (~43) included something like 50 miles of EV range generated by Charge Mode using the logic above. (465 miles from ~Little Rock, AR to ~Houston, TX with about 50 "city" miles where I used the generated EV range.)

Regarding others' tests/reviews on Charge Mode: They didn't use it under the best conditions and it looks like the HV range estimation drops precipitously with the expectation that you will continue to burn fuel at the higher Charge Mode rate for the remainder of the tank thus overestimating the range loss (i.e. no one has done a scientific test yet).

agavios

Is it normal to have no EV miles when you don't charge the car? My car is new, and I have not been able to charge it. It says 0 EV miles. The charge registers at about 30%.

drox

It is always better to charge from the wall at home. However, I did 3 tests with it because I like putting real numbers on things and a test is worth more than a thousand words.

Here was my testing methodology for all 3 tests:
- I stopped near the highway and turned on the car to get fresh trip data on L/100km usage
- I drove in HV for a very short period until I got on the highway
- When I got to highway speeds >100km/h, I put it in Charge Mode. I drove at highway speeds when the engine would be on 100% of the time anyway. I did not test during stop-and-go rush hour traffic.
- When I got off the highway I put it back in HV until my destination
- At my destination, I recorded the numbers like distance traveled, L/100km and added EV range. While this is a little flawed for using the estimated EV range instead of the actual EV range, it's close enough.

Here are the results:

1) I drove 71km and added 15km of EV range. The trip reported 7.5L/100km so that means I used 5.325L to get 86km of range. That's a real L/100km of 6.19

2) I drove 40km and added 10km of EV range. The car reported 7.7L/100km so that means I used 3.08L to get 50km of range. That's a real L/100km of 6.16.

3) I drove 123km and added 41km of EV range. The car reported 8.2L/100km so that means I used 10.086L to get 164km of range. That's a real L/100km of 6.15.

So using charge mode gave me a very similar L/100km to if I used HV mode only.

drox

The car will not let the state of charge go lower than 30% as reported by the app (The real percentage is closer to 15%)

gamma742

Do you think descending down a mountain pass a good use of charge mode or would it be better to gently ride the regenerative brakes down the mountain?

drox

No, it would be better to be in EV mode. This will keep the engine off and you will regenerate a lot during braking.

The only time charge mode makes sense is when the RPM and Torque are in the high-efficiency zone of this graph at 23:08 -
When going down a mountain the torque demands are very low so it is best to keep the engine off.

The only time charge mode could be worth it is at highway speeds around 2500 RPM (the 39.8% star in the graph) if it means you can keep the engine off in situations where efficiency would be low like stop-and-go traffic where EV driving shines.