'Automatic' EV switch

I have experience with both the Coastal and the factory EV mods. I had the Coastal Mod kit and a factory switch and the tech installed both. Back to your question, I find the EV more useful after the ICE has run for a while. It is great for large parking lots and for stop and go traffic in town after getting off the freeway. ( I have a 20 block stretch in Seattle where I am on EV all the way to the parking lot) At startup EV just delays the warm-up cycle and in my experience does not increase MPG. Also in cold climates your windows will fog up as the climate control system seems to be delayed also. If you turn the defrosters on EV is disconnected.

 

Interesting, that's good to know. Thanks for the tip. Not sure which EV kit I will buy, but I will buy one.

 

I use EV and battery power mode more than most here, and I would never want it automatic.
It is just too critical to use it at the right times, so your mpg is helped and not destroyed.
And with the low battery capacity, one button push lasts me about as long as I want the battery discharging anyways.

In general when you push EV the car should go into EV and stay there. When it doesn't it is telling you you should not have used EV in that situation to begin with. So there should not be a need for it to keep re-entering EV automatically.

 

Your "automatic" EV switch is a bad idea for the following reason:

When the Prius starts cold, it wants to avoid heavy engine load if it can. It therefore draws more on the battery for the first minute or so. (Watch your energy arrows.) Since it is inefficient to accelerate on battery power or to use battery power at high speeds, you are much better off letting the engine warm up while you are still at slow speeds.

EV mode is favorable at low, steady speeds when the battery is at a high level of charge, or at very low speeds, such as parking lots.

The problem with your suggestion is that once you hit your faster speeds and the engine is forced to start, you would continue to draw from the battery while the engine warms up. Your battery would therefore be drawn down excessively, and would have to be re-charged from the engine, which is inherently inefficient.

Remember that the Prius is not designed to be gas-or-electric. It's designed to be gas-and-electric, and most of the time it's using both simultaneously, frequently using electricity (at MG2) as it is generated (at MG1) from engine power.

The only time I'd recommend using EV at start-up is if you are going to travel such a short distance that the engine is not needed at all, or if you just want to impress pedestrians by your silence and you don't mind a small loss of efficiency.

There are only very limited situations when forcing EV mode via the switch is favorable, and those require human intelligence. The only "auto" EV you want is (as Evan pointed out above) already in the car.

All that said, I use the Coastal EV switch and like it a lot (for those infrequent times when I consider it favorable - - and to impress pedestrians in parking lots.)

 

I also have been under the impression that the ICE starts up when the car starts to warm up the emissions system. The idea is to get it warm before the ICE is needed for full power because drawing full power when cold greatly increases emissions.

So I wouldn't start the car up in EV all the time if you're doing so for environmental reasons. You'll quite possibly make thing worse.

I tend to see only two good environmental uses for EV mode:

1. If you are going to move the car a short distance and won't ever need ICE on that trip.

2. If you know that you are soon going to be going downhill for longer than necessary to recharge the battery, and so you want to use EV to burn some electricity now that can be recharged on the downhill. That in effect uses energy from regen that would otherwise have been wasted in braking friction while going downhill.

But there are also quality of life uses:

I am starting to use it while pulling into my carport late at night so as not to disturb the neighbors.

When listening to the audio system with the car turned off, it's best to have the hybrid system engaged to avoid draining down the 12V battery. But you don't really want the annoyance of the ICE engine running. So EV mode lets you listen to audio in peace and quiet without danger of running the 12V battery too low.

 

Thanks Evan for clarifying. I stil think the switching should be like it is now.

I could see someone living where EV was good at start up every day, but then everywhere else they stopped it would likely be a bad idea and they'd have to switch out of the mode more often than they need to switch into EV mode.

But I live where it will soon be cold enough EV won't work at start up anyways. Car has to warm up first.

 

There is another:

I often observe the engine remaining on when the system is fully warm, the battery charge is high, and the speed is slow. Under these conditions, if the instantaneous mpg is high, the engine is not burning much gas and all is well. But often, under these conditions, the mpg is low. Then the engine is burning a lot of gas and (presumably) charging an already highly-charged battery.

If I do nothing, the battery will soon be in the green, which is unnecessary unless you are about to hit a long uphill (which I never had when I lived in Fargo).

The EV switch lets me shut off the engine when power requirement is small and the battery is already well charged.

Also, in winter in Fargo, with the heater running, the engine would never shut off. The battery would get fully charged, and I'd be wasting gas. The EV switch allowed me to shut it off, except in the most bitterly-cold weather. I'd still get plenty of heat out of the heater.

Note: My drive in Fargo was usually too short for the car ever to get into Stage 4 operation. I know from reading John's posts that if I had driven farther, the car would eventually warm up properly and operate as we expect. Fargo is just too small. (Which was one of the things I liked about it.)

 

OK, sounds like a one-shot timer is needed to pulse the EV line after x seconds on power up.
Or maybe Norm could add this feature to the Can View that has a built in EV button?

I guess one reason I don't see using this is my driveway goes up hill to the street!
At work I often use EV to get out of the parking lot. So it's simpler for me to remember to push EV when I need it.

 

The only point I can see to the Auto EV is to not miss the window of opportunity to engage EV before ICE starts for warmup.

I sometimes use EV to prevent ICE from starting when I use my air compressor. The system voltage and current is much better in READY mode, but I don't want to warm up ICE just for that.

 

EV already disengages automatically if you exceed the acceleration current limits, or set max speed.