salimshah

One of the problem with electricity is that it needs to be put away (stored) or used.

Here is a hypothetical situation ... traction battery is fully charged. [it can't take more charge]. Now when you press the brake pedal there is no place to dump the electricity that is generated due to braking and thus there should not be any regen braking.

I have been trying to test this but I still see charge meter drop even when the battery is full .. leading me to think it never gets full.

Salim

NateJG

The energy is used (read: wasted) by spinning-up the ICE (similar to downshifting into a lower gear while braking in a “regular” vehicle).

salimshah

I get that ... but that is if there is any place to go.

If the tank is full you can put more fuel in it.
Similarly if the battery is fully charged you can't charge it any more. You can sustain the charge by adding what is being consumed (lights radio etc) but not enough to divert to slow down.

I am unable to get to the point where I can claim the traction battery is fully charge .. indicators show it is full, but on braking the gauge still defects as if it is charging.

Maybe there is a dummy load that just produces heat.

Salim

ukrkoz

Nate is correct. Energy surplus is dumped via ICE.
Salim, you making two mistakes.
1. Believing that battery can be fully charged
2. trusting gauges in the car.
For starters, I have battery showing as fully charged quite often. Yet, from numerous discussions on this topic at TN forum, we figured that battery has a safeguard NOT allowing it to be fully charged to say 100%. We think it gets to about 85-90%, what shows as 8 full bars on display/green light, but in reality, dumping mechanism is involved. That battery is very much so protected from overcharge/overheat by various watchdogs.
We also figured that vehicle gauges are more of entertaining gizmos for owners, that reality representation. Simple example. I am cruising at 20mph, gauge shows battery is charging, I gently feather accelerator pedal and speed starts increasing - while gauge still shows battery is being charged. I did this many times.
So maybe just take it easy and let it be? Maybe, instead, explore B mode? My all time favorite feature of Toyota hybrids. Love it!
If you want to have absolute truth about this and that, connect TSI and watch life stream of what's going on.

salimshah

Ah .. "engine breaking"! ... where the engine compression strokes are used to fight the wheels that are turning.


Thanks.

Salim

MellonC00

I feel the same way. On my daily commute I have a quite steep drop from 2000 ft to about 600 ft. The graphics says my battery is topped up (or close to it) by the time I reach about 1000 ft. The rest is just gone to waste, I guess......

I don't how the KERS system works exactly, but something that keeps the motion in kinetic energy form in case the battery tops out would be ideal to bring back to forward momentum when the battery is low.......

ukrkoz

Yes, Salim jan. B mode. Fantastic tool. Fuel supply is cut off to the ICE but it's spun by MG. VVT-I control engine resistance by bleeding air out of cylinders. So ICE mass and hydraulic resistance is used to slow down the vehicle. Also, charging amperage is 3 times higher than simple braking regen. 0.5 mile 12% downhill in B mode can easily do "100%" battery charge. If you were to start at 6 bars.

riredale

A conventional ICE at idle is really just a big vacuum pump, which is why a hybrid design exists in the first place--to keep the ICE out of that mode as much as possible. But when the system needs to bleed off excess energy, it spins up that big vacuum pump under the hood.

In a way it's using the ICE much as a "Jake Brake" does on a truck diesel.

Buzzer479

Hey guys,
It's a bit off topic but I think I might get some help here:
I just bought a 2015 RX450H with 100K kilometers. Its a bit on a high side for mileage but the price was good.
I have questions, is it normal that when in traffic the engine charges the battery quite often and the overall fuel consumption skyrockets ?
I was in bumper to bumper traffic and was watching my average consumption go from 8.7L/100km to 10.5L/100km and the "after full" go to 13.5.
It went down afterwards to 11.5

Any help or advice would be appreciated.

Best,

ukrkoz

Hybrid shines bright in slow creeping traffic. I once had almost entire display covered in 60mpg bars. Especially if you were on mild decline and can roll down in traffic.
But that's primarily on FWY. City stop and go you will not have this.

Buzzer479

Thanks for the reply Ukrkoz,
Is 25mpg something that I have to settle for with my car ?

salimshah

The answer to the question is pretty complicated.

Obvious things are that the MPG = 0 if the internal combustion engine runs and the wheels do not move. And a few zeroes plummets the average.

Another obvious fact is that as long there is stored energy in the traction battery is present and the vehicle does not move or crawls with the traction battery [ICE does not run] the zeroes do not come up.

When the traction battery gets depleted (or drops below the min threshold) the ICE is fired up. At this stage the ICE not only provides the crawl energy, + the charging energy + what ever the loads are [indirectly AC etc].

Now the complication ... If the stored energy was enough [from previously conserved energy] then your MPG will benefit, but if the stored energy was less then ICE has to make up for it + Losses in the conversion {Laws of conservation of Energy applies}.

In the long run with the hybrid you will gain by harnessing a portion of wasted energy (braking) as compared to a non-hybrid. On top of that you gain when the ICE does not run. In your case the ICE kicked in while the vehicle was not moving and the during that time, the hybrid consumed more energy then the non-hybrid.

Salim

PS: I would not be hung up on number like 25mog you mentioned. The important thing to remember is that you are harnessing a potion of energy that would have been lost and not consuming energy idling. It is very likely that without the hybrid you would be doing 21mpg. 4/25 is not an insignificant number.

ukrkoz

No, by gods, no. You do have hybrid, right? Unless you live in Alaska and have heavy led foot, you should be doing better than that. I mentioned before, I live in Seattle area, which is VERY hypermiling unfriendly terrain, and I average around 30mpg. But I do very little city driving and have developed very good hypermiling driving style. Also, I drive basically alone. But even when I did use my car as a truck, I was still solid over 28 mpg.
So no, you should do better than that

ukrkoz

Buzzer, start here. principles are identical across entire hybrid lineup.

Buzzer479

Guys,
Thanks a lot for your replies.
Ukrkoz, I checked the video, it was very helpful since it is my first hybrid car.
Here is my latest experience:
After reading more and more on the forum I realized that mpg is way more common measuring unit here. So, I decided to change my unit to mpg. After I did this my after refueling ave became 29 mpg and average became 31.9 mpg. I was happy and confused at the same time. I switched it back to L/100km and it read 9.9L/100km and 8.8L/100km.
Then I figured that my mpg were in imperial gallons... In US gallons it is around 24 and 26.6 mpg. Today I decided to drive the car all day the way I drive my V6 Acura type s.
The average went down to 25.3. Now I am asking my self if I am too concerned about mpg and gas saving and should I just drive it as a regular car ? I would like to see 30+ mpg but so far not very close.