battery charge NEVER gets to the top

The arrows don't show the magnitude of the current, only direction, and they are also just a snapshot. The real current flow changes more quickly. At equilibrium, the current bounces back and forth quickly, but at very low levels.

As for acceleration, think of it like this: you want to use the engine as efficiently as possible, so you need to accelerate in such a way as to put the engine at the ideal load and speed. You can approximate this by accelerating briskly, but not so hard to induce wide open throttle.

Tom

 

Seriously. Engines are most efficient near their maximum output. It's a little hard to judge that point without a scan tool, but roughly, if you're accelerating faster than most other cars that's about right. Flooring the gas pedal is too much, and if everyone else is accelerating faster than you it's too little.

The control system is constantly trying to trade off minimum engine emissions, optimal battery charge, and the amount of power needed to maintain speed and run the accessories at that moment (even when the road looks flat it often isn't, and the wind is usually varying). Thus the sloshing of energy.

 

That all makes sense, thanks!

 

After the first 5 min, Prius becomes efficient( Ready in Summer) In Winter it might take 2-3 bars, probably in very cold temps (32F or less) Prius may never be efficient as far as MPG goes. The easiest way to get either all green, partial green or medium blue is easy AFTER the car is warmed up. Brisk acceleration to 40 or 50, let battery continue to charge while letting off gas to 40MPG. At 40 MPG lightly touch the accelerator pedal, for a stealth glide, (no arrows) If there is a stop sign or a red traffic light stop using the gas pedal, always coast or glide to light. with foot lightly on brake pedal for an increased regen rate. Let everyone else rush up to the red light before it turns green. They know not what they do. The trick is to always induce some kind of charging to the HV perhaps a ratio of 3: 1, That is three times as much non use of the HV to one part of battery and engine use.. However if, your drive is only 5 minutes, you will never get there ( green battery) I would sugest that you never take a direct route always take side roads and go 15-20 miles out of your way and use the above procedures. Never take the freeway. Nuts, right? Some people do, do that. Edited 18/12

 

I don't know if anyone mentioned it yet, but the REASON that you will seldom see 100% full bars is that Toyota discovered that the batteries last much longer if they maintain something like an 80% state of charge. If you're seeing all green a lot, you may be on your way to replacing your $2,000 batteries (it's rare that anyone has to do that, but it would be more likely if you had a full charge a lot).

 

This isn't quite right. The batteries would do just fine if you kept them at 100% charge, but then what good would they be if you couldn't use them? The real reason that the batteries are not normally fully charged is that you need somewhere to store regenerated energy. When the Prius uses regenerative braking, it needs room in the battery to save the regenerated energy. If you are driving around with a full battery there is no room for it.

Perhaps what boulder_bum is really driving at is the fact that it is not good for batteries to be fully discharged. The range from zero bars to full green bars represents only a portion of the actual battery capacity. The Prius tries to keep the batteries in this restricted range of charge to extend battery life.

Tom

 

No, that's not quite right. The display is NOT showing 0-100% charge. The display is from 40-45% of actual charge with no bars to 80-85% of charge with all the bars filled. (I've seen these numbers quoted a few times with slight variations.) The controller will keep you in this range. It won't allow further charging or discharging outside of the display range. The green and pink/purple are outside of the target SOC's, but not outside of the safe operating range. The display is also not linear. More SOC is contained in the bars right around the control point.

High discharge/charge rates are detrimental to the battery as well, but they aren't discussed much. Again the controller is limiting some of this (turning on the ICE) and the regeneration rate is somewhat limited too. In normal driving we don't appear to be pulling hard with the electric motor.

Battery temperature is another factor. As I understand it when the battery gets warm enough its ventilation fan will turn on and transfers (or at least regeneration) will be limited until the temp is back in range. This is more of a factor in summer heat with hills/stop and go. I don't know what happens on the low temp. side...and I probably should research that with temps here reaching 0 F recently. I tend to make short runs without cabin heating (from the garage which runs about 40-45 F in sub freezing weather.)

Probably some of the most severe battery cycles are in mountain terrain where the battery can be drawn down to minimum charge at a high discharge rate, then fully charged to double green bars during regeneration down the other side. Even though the controller will keep the battery in the nominally safe range, it is reasonable to expect that the wider/deeper average cycle would shorten the life. There is some heat generated in charging/discharging as well but since we don't have a battery temp display I don't know how to account for it.