Why is it so hard to keep the level of charge in the battery?

100% factually incorrect and would defeat the purpose of a hybrid vehicle entirely. The only way to keep a constant charge in a battery pack is to not use it. The car uses it as it wants to. It will maintain it between 40% and 80% automatically. 40% = 1 bar, 80% = all full bars.

DO NOT try to use the traction battery as much as possible. That will hurt your mileage except if you have a plug in conversion installed. All battery charge comes from the gas engine, and the less you use the batteries the better. You want the gas engine to accelerate you to speed, and then just glide with no arrows on the energy monitor which uses the battery just to run all the accessories with the engine off. This will yield the best mpg over the largest range of terrain and speeds under 50mph-ish.

Your car is acting normal, and you are actually making your miles per gallon worse then it could be by trying to hard.

 

This idea may come from the idea that the car has a favorite spot for the battery level (around 60%). It will be more likely to use charge if above that level and more likely to store it if below.

 

I agree with all the above about keeping the battery at a constant charge.

Actually, I am amazed the Prius battery management is so effective. I never worry about it; never try to circumvent it's usage or charging. It is a small battery, and appears to be exactly where the designers wanted it within the design criteria. It appears to be in near perfect balance with the ICE, MG1 and 2, weight, long life expectancy, tire and wind drag ........ and 50 mpg.

The design criteria did not dictate a 150 mph vehicle; or 0-60 in 5 seconds; or extended EV range ... to name just a few. Change any of the design criteria, and the current Prius is no longer a "balanced design." Competition will eventually cause the design criteria tio change .... such changes will dictate changes in the ICE, MG's and battery .... and etc.

I am absolutely convinced ... and comfortable, with the thought that the G3 Prius is not the "ultimate" design. It is not the "final," "end-all" design. There is still room for evolution of the Prius; and the G4 will be as big an imporvement on the G3 as the G3 was over the G2.

 

I agree that the battery management is very efficient. When my wife uses the car, she always brings it back with a full battery, she doesn't understand the concept of coasting ....

 

The actual energy expenditures are similar. The display of that info is not. In the G3, there is very little hysteresis whereas the G2 has a much larger hysteresis. Meaning it shows no energy transfer for values +/- X in the G2 versus +/- Y in the G3 where X >>> Y.

While driving on electric only during your glide will up your instantaneous mpg, as explained above it is not beneficial unless you are trying to deplete the pack because you expect to replenish it immediately after with a long regen period. Trying not to use it is still the best policy.

The Japanese (namely Honda and Toyota) have been experimenting with supplemental GPS based engine management systems. So your Gen Whatever will know you are climbing a hill of a mountain and in 0.25km you will reach the crest and then descend 1km or something like that. So it will automatically deplete the pack around the crest, in anticipation of it filling back up.

 

Ignore the arrow display on the Gen III. Switch to the HSI screen and stay within the 1/8th of the left side of the ECO bar for gliding. See http://priuschat.com/forums/gen-iii-2010-prius-main-forum/89230-pulse-elusive-glide.html

 

On GenIII, ditch the arrow screen. Use the HSI screen, where a 'perfect' glide is very easy.

Perfection on the arrow screen probably requires something like 0.001% accuracy, which is absurdly unnecessary. The HSI screen uses much more reasonable rounding to get close enough.

 

Yeah.. it is so difficult to hypermile on the G3.

Btw, the maximum charge that I have managed on the hybrid battery is 6 bars and not 8 bars. Is that normal?

Thanks.

 

Actually i think the Toyota reccomendation (ease off, and then reapply to stay in stealth) makes sense. I ran some quick (and estimated) numbers. here are my suppositions:

Below about 10kw of power (12hp or so) the prius ICE is about 20% efficient.
Above 10kw the prius ICE is 35% efficienct
A gallon of gas hold 36.6kwh of energy
Driving in town requires less than 10kw of power.
Power coming from MG1 through the inverter is 90% efficient.
Power is stored in the battery with 90% efficiency.
Power is extracted from the battery with 90% efficiency.

This model says using the ICE in town (just 36.6kwh*20%) gets you 7.32kwh from your gallon of gas. If however you rely on the battery (and when the car recharges the total power coming out of the ICE [for charging and your current driving] is over 10kw) the formula is 36.6kwh*35%ICE efficiency*90%inverter loss*90%battery store loss*90%battery retrieve loss gets you 9.34kwh from your gallon of gas.

OK, it's a very simple model, and i'm sure there's some better data available for the various losses, but it makes me believe that Toyota are right, and that if you can drive in stealth, you should. the exception here is pulse and glide, where you can just use 35% efficient ICE for powerful pulses, and then glide. that's not always possible or practical though, and passengers don't tend to like it.

 

If your terrain is flat, and you don't have any glides down exit ramps of high speed highways, then that would be normal.

We usually need mountain descents to get 8 bars. On flat land, I sometimes see 7 bars during cold weather warmup. Your weather never gets that cold.

 

But if you are driving slowly enough to where stealth mode is better, then you aren't driving at > 10kwh to get the 35%. You would need to drive hard to recharge the pack back up so that you could drive slowly again in stealth. And this sounds an awful lot like pulse-n-glide.

 

I believe that if you're doing 30mph in stealth, and run down to 2 bars (ow whatever the setpoint is) the engine will come on to push you at 30mph -and- charge the battery, and that the power output will be over 10kw. Someone with a scangauge would need to confirm that.

And yes, it is like pulse and glide, but you're storing the energy in the battery rather than in your momentum. The Sonata hybrid behaves in this way on purpose, even at highway speeds.