EV Mod

Your last question suggests that you might have a (commonly held) misconception about the value of the switch. Assuming your goal is to improve fuel economy, it should not routinely be used for propulsion.

The only time I use it for propulsion is for low speed, low power-demand situations over short distances, like moving around a parking lot or through my driveway. I do make liberal use of it to shut the ICE down while coasting, gliding, or braking during the car's warmup cycle when the ICE will not shut down by itself, and I have demonstrated a substantial fuel savings for my driving conditions. YMMV.

You are correct that the car aborts EV mode spontaneously when power demand exceeds a certain level (hills or otherwise), among other circumstances. The car is very protective of the battery and it limits the amount of current draw.

I have the home-grown version using a Radio Shack switch. It's considerably cheaper ($5 or so for the switch & wire) than the Coastal version, with better functionality (no delay). And you're not dependent on Coastal's spotty (to be polite) customer service. I'm not mechanically inclined, but I don't consider it a difficult installation.

See these threads for my fuel economy testing and installation details:

http://priuschat.com/forums/gen-ii-...on/50270-virtues-electric-vehicle-switch.html

http://priuschat.com/forums/gen-ii-prius-modifications/32831-finally-added-electric-vehicle-mod.html

 

+1 on what JimboK says.

The best use for the "EV Mode" switch is to suppress the ICE coming on
when you've got lots of juice in the HV battery and a flattish, low speed
section of road ahead, or downhill for higher speeds.

Other than that, it takes a whole lot of self control not to use the switch
to get into EV mode and incur a HV power deficit that is costly in MPGs
to overcome with the ICE recharging the HV battery.

I have the Coastal switch. In my daily "winter commute," often by
means of trickery and careful planning, I find myself at the bottom of a
long downhill at a stoplight with SOC between 68 - 72% full by
ScanGauge. Right after the light I go into a school entrance road to
drop off my passenger. After that there is a slight down hill, low speed
run to the freeway entrance about 1/2 mile distant.

Only in this one very special individual case, locking into EV mode is a
good deal for me...
but only if I don't run the HV battery below 65% which is about the HSD
wants to get max FE on the following 50 MPH highway section. That half
mile section coming after 6 miles on the road can raise my MPGs from
42 to 50 on the way to 55+ at the parking garage some 9 miles further on.
Interestingly, if I let SOC get much above 72%, the HSD won't let me get
into EV mode at all.

The EV switch is a real challenge to use well, which as Jimbo says is
usually none or hardly at all.

YMMV, and by a large amount if you're not really, really careful.

 

I can't really assess a benefit of the EV switch other than to run around parking lots in quiet mode in a normal Prius. Further, the EV mode is often "locked out" for me due to the HV battery pack hitting 114oF. Actually, it really irritates me that about 50% of the time I'm disallowed EV because of this temperature limit.

That being said, I have a 4kWh plug in battery pack that I feel the EV switch is pretty essential for getting the most fuel economy out of the PHEV system. I can't wait for Miami winter so I can have access to EV most of the time.

 

I also support Jimbo's post.

I followed Evan Fusco's excellent description, and while a bit nerve-wracking whenever touching wiring and ECU's, it is actually not that difficult. The toughest part was actually fishing the wire behind the dash to use one of the open slots next to the dimmer. I am no mechanic by any means, but consider myself a quick learner and generally do basic car maintenance (tire rotations, oil changes, spark plugs, etc.).

As for actual usefulness of the EV button, it is mostly novelty. I use it mostly for moving the car from one parking spot to another, rarely in day-to-day driving. As others mentioned, using it wrongly can easily *increase* your fuel consumption, so be careful.

Thinking of also doing the anytime camera mod at some point as well, for no other reason than to have another neat button to push.

Good luck!