Experience in HEAVY traffic

Shutting the air off would help that, but I realize in some locations that really isn't a practical option. I know I'm not gonna sweat on my new seats! Perhaps manualy setting it to low and at a temp closer to the outside temp would make some difference.

When I was a kid my first car used to overheat in traffic and I'd have to put the heat on. It would be like 98 out and I'd be cranking the heat. Holy crap I haven't thought about that in ages.

It sounds like you spent more time in "stopped" than "go" traffic.

 

... wow... If the Prius is getting only 5-10 mpg in that kind of traffic, I wonder what a normal car manages for such conditions. Don't even want to think what a gas guzzler would average here.

 

I have a friend who rented an '04 Prius in Seattle this weekend, and drove himself and his family (4 total) down to Portland and back on I-5.

He ran into the same traffic you did, and also similar MPG -- 50 MPG total. He was extremely impressed, because he (and his teenage son) were not "driving the Prius way" -- they were just driving normally.

 

I was recently stuck on the Richmond-San Rafael Bridge for about an hour, going 0-5 mph most of the time. So this is the first time I used neutral while driving. The low speed made pretty safe, and it gave me something to do since I was bored. So ... I would stay stopped as long as I thought I could without making my fellow traffic victims unhappy. When I had maybe 3 car lengths then I'd take my foot off the brake and pick up speed to about 4 mph, and then shift to neutral and coast. My goal was to coast to a stop but I didn't manage that except once. Still, since you can't regen at 5mph (top speed) I figured the more coasting in neutral and the smallest total number of stops and starts would conserve my battery power the best ... of course trying to postpone that pink bars, ICE runs to recharge the battery as long as possible.

I hope I'm expressing this clearly. I'll be interested to hear any suggestions or comments on driving technique in stop & extremely slow go traffic. For the bored and mileage obsessed of course ...

 

Hadn't actually considered MPG maximizing technique in traffic jams, not a situation I face often. However, delrey's technique makes a bunch of sense. Much easier than feathering the accerelator peddle constantly, for that particular situation.

 

I have had similar experiences on the DanRyan. When travel times get over 50 minutes from the circle to 95th, the batteries run down to the pink bars, the ICE runs a lot and I get bad mileage till I get the batteries back.

What I've tried a couple of times is to hit the gas enough to charge the battery but not drain it, get some speed up (even if just a few car lengths) and use the brakes to help charge the battery. This seems to be about the best way to get the batteries charged again in stop and go.

By using neutral trying to save juice, I think you're just extending the ICE running time for recharge. When you're that low you've got to recharge, not keep trying to extend what little is left.

 

I wasn't that low when I started, the battery was pretty fully charged. I just knew that eventually I'd empty it and have to run the ice. (Road construction & closed lane across bridge == 1 hour). So I was trying to figure out how to get the most miles per amp, I guess, given that it was so slow I couldn't speed up past 8 mph.

I only tried to sneak up above 8 mph and get some regen when I thought I'd have more than a couple car lengths ... figuring that there is more loss in speeding up and using the momentum to regen than just running ICE to charge the battery directly, once it became necessary. I may be wrong there.

Obviously this is not something that comes up very much (usually even if I'm "stuck in traffic" I can go faster than 8 mph!). I'm just posting about this because I enjoyed trying to apply what I've learned here to a new (for me) situation. It was great to know already that there is no regen happening below a certain speed, my thanks to whoever I learned that from on PC.

 

As far as the regenerative braking goes, they recovery rate of the kinetic energy is somewhere in the mid 30% range. So it is actually more efficient to charge the traction batteries off of the ICE rather than using the ICE to gain momentum and then converting it back to electricity.

 

just a note, if your running the A/C and using neutral be advised that your not recharging the HV battery. The power for the A/C has to come from some where and if you pull the HV BSOC down you'll have to run the ICE longer to get it back up. The best is to leave it in drive and if you see the BSOC dropping just put it in to B That will fire the ICE and start the recharging of the HV battery if your stopped as MG2 is stopped and the ICE is driving MG1 which has to put the output some where and that is the battery.

 

I think that it is ok if the only time the Prius is in neutral is when delray is actually coasting in behind the next car if otherwise left in "D" the ICE will kick in when needed and charge the battery.

 

Good point. I probably should have said that I turned off the A/C ... good thing about being stuck near/on the bridge is that there is a nice breeze!

I didn't stay in neutral that much, but I was in Park quite a bit and of course in Drive as well.

I don't think I would shift to B to force the battery to get charged though, as long as you are in D or P then ICE starts and charges the battery when it gets low ...

 

I could easily have forgotten about needing to avoid staying in N too long, since it was so easy to shift from D to N, coast down until I had to brake, and then sit in N with the brakes on. Usually I just put it back in drive so I was ready for the next start.

 

Doesn't the manual say to avoid using Neutral as much as possible? Also, is it a good idea to be using Park so often? Does the hybrid system do something once shifted into Park, like that liquid pumping thing that happens when you shutdown?

 

It seems to me that the only real problem with shifting into neutral is forgetting that you did it and thus leaving the transmission there until the battery is discharged. If you are not so forgetful, it's ok to coast in N for a while in order to gain speed going downhill or to shift into N at a stop light in order to hold the car still with minimum or no brake force. In fact, for all practical reasons the car shifts into N by itself when coasting will all arrows off.

 

This is true. "B" is for "engine Brake", not "forced Battery recharge". The only use for B is on long downhill stretches, to avoid wear on the brake pads. (I know that delrey knows this; some others appear not to.)

 

B really has two modes, as some of the Japanese Drivers first pointed out.

Above 20 MPH, it does do 'engine braking' by spinning the ICE

Below 20 MPH it simulates engine braking by increasing the regenerative resistance, and does not spin the engine.

This does in fact result in more regeneration than you get using the brake pedal.

The Japanese Power Drivers strive to use B mode for slowing below 20 MPH whenever possible.

The drawback is that your brake lights don't come on and you have to make sure no one is tailgating or you may get bumped.

 

So Tempus, at speed between 8 mph and 20 mph there is a component of the friction brakes used as well? I thought it was all regen braking unless going for a very hard stop above 8 mph, but if what you say is true then there must be friction as well as regen braking going on, or am I mistaken.

 

Depends on how hard you push. There CAN be friction brakes at any speed. Using B, you know there are no friction brakes being used, and thus wasting energy that would be available for regeneration.

 

Uhh, so once the traction battery is fully charged, where would the regeneration braking energy go? Is there a resistor bank somewhere?