Energy Dump?

[jamarimutt]

Evan:

I don't quite get understand one thing. What can I do driving down a long hill to avoid charging the battery to the point of having the engine cycle on/off when I stop at the red light at the end of the hill? What and how would I use the energy wasted by the on/off ICE cycle.

Ah, coasting down the hill in neutral would avoid excessive charging, but then we get into the argument of whether it's good or bad to coast in neutral. :mrgreen:

[DaveinOlyWA]

a large hill might be better to coast at least part of the way in "B" mode. although toyota does warn that B mode should only be used for short periods at a time.

[efusco]

Originally posted by jamarimutt
Evan:

I don't quite get understand one thing. What can I do driving down a long hill to avoid charging the battery to the point of having the engine cycle on/off when I stop at the red light at the end of the hill? What and how would I use the energy wasted by the on/off ICE cycle.

Ah, coasting down the hill in neutral would avoid excessive charging, but then we get into the argument of whether it's good or bad to coast in neutral.  :mrgreen:

The key is to maximize energy use BEFORE you get to the hill so that there is more 'room' for charging up again as you go down. Extemely long hills/mountains/etc. you're gonna max out no matter what. If, however, the hill is not particularly long/steep you should try 'Gliding'--just depress the gas pedal enough that there are no arrows charging the battery....basically you'll be free-wheeling. You will gain speed and it's tough to exactly hit that no arrows state, but if you find subtle movements change you from regen coasting to hyperstealth driving then you're right where you need to be. If there's a stop at the bottom you're gonna have to stop but many times I avoid the initial regen by gliding, I pick up a bunch of speed, then continue the glide on the flatter section before the stop on a hill I do on my commute. Often I can glide almost to the light without using any gas or electricity and keep my speed at the speed limit. That's almost a mile of no power in or out!!

Again, this is not always achievable and without knowing your exact route I can't say if you can avoid that condition or not. I know I had 2 places that I used to energy dump pretty routinely. Since using more glide and hyperstealth/stealth I don't energy dump at all and haven't for many months.

[DaveinOlyWA]

but what is the no arrows mean??

that mean the car is using power out of thin air?

or is it simply a level of power that sits in the transition area where regen, battery and ICE meet?

obviously the power must come from one of these sources. and you must have some petal pressure on the gas to achieve this so the power is most likely coming from a combination either one depending on whether the power demand is going up or down.

i think the no arrow mode is just a bug in the display.

[Frank Hudon]

if you look at my post about interesting results
http://www.priuschat.com/forums/viewtopic.php?t=3506
you will see when the battery gets to 80% full charge you can't regen any more but if you put it in B mode you get a current draw of 18 amps and the bsoc slowly sinks.

[DaveinOlyWA]

i know the SOC display's range is from 30-70% but i didnt realize that a 100% charge was not possible. i figured to prevent overcharging they would cut it off at a higher level than that like 90-95% i would think.

i know that for charging purposes, exact rates arent possible because to many physical conditions affect the effective charge rate including temperature, humidity, etc. but i would think that they would be able to get closer than that since everything is controlled by the computer, i would think that the computer would monitor outside influences and be able to charge higher in the usually rare cases of a large downhill.

although in another sense, i can see toyota's rationale for not wanting to take chances with overcharging since extremely dry conditions could easily increase the charge rate considerably. i guess they wanted a maximum safe margin in all possible weather situations.

still a slightly larger battery would be nice...(if i keep mentioning this in every post, do you think they will get the hint?)

[Frank Hudon]

no

[aforkosh]

There is not any chance to practice techniques involving the accelerator.

The accelerator is only lightly touched in the tunnel. It is never touched from the tunnel exit until leaving the traffic light at the end of the off-ramp (and even then, just enough to hit the peak of a small rise 50 feet past the signal). There is not much chance to practice anything except holding off on braking. Even then, I am usually braking only for control on the slight curves or to fit in the traffic flow (did I mention the lightly used onramp from another freeway just before my offramp?).

[efusco]

Originally posted by DaveinOlyWA
but what is the no arrows mean??

that mean the car is using power out of thin air?

or is it simply a level of power that sits in the transition area where regen, battery and ICE meet?

obviously the power must come from one of these sources. and you must have some petal pressure on the gas to achieve this so the power is most likely coming from a combination either one depending on whether the power demand is going up or down.

i think the no arrow mode is just a bug in the display.

NO arrows essentially means free wheeling....there is no energy going anywhere except the heat created by the drag of the car going through air and any friction within the mechanics of the car. The thing is that on level or slight downslopes you can maintain speed for quite a long time...when needed a very slight increase in pedal pressure will add just enough 'juice' from the battery to keep speed up. I often can get over small rises with just electric, if carefully applied.

And yes, there definately are conditions where extra Ah of battery could help. There's an ongoing project that I'm not free to discuss doing exactly that with great success so far. I know of at least 3 people who currently have additional battery storage with 4th due in the next couple of weeks. Hilly conditions are a good place...extensive city driving is another place it helps. But even on hwys, for some reason (prob. due to decreased internal battery resistance) they're seeing 10-15% improvements in mileage.

[Frank Hudon]

just a thought on the use of extra battery capacity, if you pull down the larger battery and then have to run the ICE longer to get it changed to the point where the computer will allow the vehicle to go into hybrid mode, you have used the extra fuel to achieve your results of having more capacity. For most usage the current setup seems to be well thought out. There will always be exceptions to this but for the most part and most users I doubt that another 3-4,000 dollars worth of batterys will be justified