Tip for when your EV range is almost, but not quite enough

This long post is for those who'd like to basically extend their EV range just a few more miles once it's run out. Those of the "just drive the car" school should probably skip this

This is a tip/observation I found to basically be able to use (mostly) EV still -- even once the EV range has depleted and HV has come on -- if you only have a few miles left (say 8 miles or less).

Coming home from where I occasionally work, if there's no traffic, the EV range runs out between 1/2 way to 2/3rds of the way, and the rest of the way has to be in HV. However during rush hour -- because it's start and stop (and I employ things like "B" in start-and-stop EV driving) the EV range gets extended to ALMOST enough to get home -- but never quite enough.

This post is for situations like this -- where you just have a few miles left after the EV range runs out. It's not really effective if it's more than say 8 miles, but for something like 8 miles or less, it seems to work pretty well.

In general, if you were to drive steady in HV mode, you can say there's two ways to drive (without cruise control). You can (#1) always keep your foot slightly on the pedal and never really take it off, or (#2) keep your foot on the pedal for a bit, then lift it up for a second, then put it back down for a bit, then lift it up for a second, then put it back down for a bit, etc. Whether one is "right" or "wrong" isn't the point -- but the car reacts differently to these two different methods. And if your EV range has run out only a few miles from home -- and you only have a few miles left to go, driving in the (#2) style above will let you cheat and basically "extend" the EV usage of the car somewhat even after your EV range has run out and HV has come on, giving you really great MPG for those last few miles (because most of it will still be in EV instead of gas) -- much better than if you just drove "normally."

For instance, today I had 5.3 miles left when my EV range depleted (4.3 left on the freeway, then 1 more mile on streets). I immediately reset the trip odometer at that point (to see the MPG I would get for the last 5.3 miles) and by driving "#2" style above, my MPG was 110.1 when I got home -- in HV -- for those last 5.3 miles (4.3 freeway, 1 mile streets) -- because I nudged the car to keep using mostly the EV battery even after the EV range officially ran out.

The reason for this is, as you know, in HV mode, the car will switch back and forth between using gas, and (temporarily) just using the traction battery. If you drive like (#1) above (keeping your foot down and never really lifting it up), it will indeed go back and forth -- but will take a long time before (and between) switching back and forth.

However, when driving in HV, lifting your foot off the gas pedal, immediately puts the car into "temporary EV" mode -- and even if you immediately lightly press on the gas pedal again to keep up your speed, the car will still usually be in temporary EV mode for about 10-15 seconds. Then as soon as the gas comes back on again, simply lift your foot up again to trigger the temporary EV mode again for another 10-15 seconds... and when the gas comes back on again, keep repeating the same procedure.

That's how you "suck" even more EV range out of the car, even once the EV range has depleted and even though you're in "HV".

The reason this doesn't work for longer distances is, of course, that doing this keeps using more of the EV battery and eats into the buffer area. You can do it to a point (maybe up to 7 or 8 miles) but after too long, the car will refuse to go into temporary EV mode again until it's had a chance to recharge the battery back to the baseline level (at which point there's no reason to do it). But I've found it works well if you just have a few miles left.

So though this may not be a good way to drive "normally" (though it's good to know that lifting up the gas pedal for a moment always triggers the temporary EV mode unless the battery is way below where it should be), it IS a great way to extend and use more EV once the official EV range has run out, as long as you only have a few miles left. Once home, your charging time will take a little longer (since the battery level will be a bit lower than the baseline), but if you're someone who finds themselves running out of their EV charge just a couple miles from home/work, doing the above is a way to keep going on (mostly) EV for a few miles longer.

Again, doing the above today for the last 5.3 miles on HV after the EV ran out (4.3 on fwy, 1 mile on streets), I got 110.1 MPG instead of probably something like 55MPG.

Edit: Note: I've done this a few times now, but the times I've tried it have all been during slower (rush hour) traffic. It may not last as long if you're going 75mph. This latest time, the 4.3 freeway miles were heavy but not stopped traffic, 40-55mph, and the last street mile I kept under 45mph.

 

Yes, exactly, I dip into the HV reserve, though I've found it works for well over 2 miles, at least during rush hour times (I decided to finally post after doing it once again yesterday, when I had 5.3 miles left). For the 4.3 miles left on the freeway, speeds were between about 40-55mph (congested but not stopped traffic) and then the last street mile or so I tried not to go above 45mph. If one is going 75mph on a Sunday morning, it may well only be 2 miles, I don't know, the times I've tried it have all been during slower traffic. I added an edit to the original post to address this, thanks.

 

Right, but when your EV range is gone and you have 6 miles left to go, unless you want to walk home, the ICE has to come on. The trick though, is to use as little of that gas as possible at that point for those last few miles, by basically "tricking" the car into dipping into the reserve and still doing mostly EV (again, you can only do it for so long until the car won't let you do it anymore before charging the battery -- but for just a handful of miles, it always works ok for me).

As far as efficiency, all I can tell you is what I've observed. Obviously nothing (exact speed and conditions) can be exactly duplicated multiple times in the real world unless you want to cause a traffic accident, but all I can tell you is, I've tried it numerous times -- both just driving "normal HV", and numerous times using this trick for the last few miles -- and the difference in MPG is substantial. By driving "normal", the MPG might be 55-65 at those speeds. By doing the trick though, I've been able to get over 100MPG (yesterday, 110.1MPG, by tricking it to draw more from the battery than gas). Also, the highest I've EVER been able to get for "real" (ie, going for at least 5 miles, and not just going down some steep hill) HV mileage has been 74MPG (city driving once). So the 110MPG is quite a bit more than that.

YYMV of course, and as I stated, it's good only if you're a few miles short (otherwise charging will start to occur) but thought I'd post it for others who might face the same situation as me, as on rush hour days, the EV range always seems to deplete just a few miles from home. If the conditions are right, and there's just a few miles left, I do it, and it works great. Any way to burn less gas and exhaust out of the tailpipe is good for me..

 

Interesting. The Prime is the first Prius I've owned (had a Honda hybrid before this) so didn't know about it. Figured I'd post it in case there were others who might not have known this trick, if they often find themselves in the same situation (ie, running out of EV with just a couple miles left).