Using the Primes 120v Charger at 240 Volts, Cost $20 !!!

That is part of my home turf. But outside of pandemics, I travel many more descents like this, and even in a regular Prius it seems so very wasteful to lack battery capacity to recapture it. So the next car will be a plug-in, Prius or otherwise ...

 

On a 'normal' Prius it fills up with a 600 foot vertical drop compared to 3000 feet in the Prime. For most of the US, 600 foot is very useful. (No part of MS is over 880 feet above sea level, so there simply is no single drop of 600 feet in my state. Eastern TN may have such a drop)

 

Very interesting video jerrymildred. It looks like this driver got 37.8 mpg over this 44 mile trip while at the same time charging the EV battery up to 80%. Am I looking at this correctly? Pretty cool.

 

You are correct. So if John drove on in EV and used up that 80% he'd have gone another 20-25 miles depending on speed and temperature without using any more gas. I'll leave the arithmetic to anyone who want to figure it out. I need to get to work soon.

Indeed. When I had my PiP, I completely filled the battery from almost empty coming down from Clingmans Dome. The Prime would be spectacular there (as it was when we visited Colorado with it.)

 

I'll take a stab at it. If we assume John got another 20 miles on the EV, then I think the effective MPG overall would be (44+20)/(44/37.8) = 55.

This is almost exactly equal to the rated HV mileage of 54 MPG, so is about equivalent to having taken the entire 64 mile drive in HV mode. This seems much better than I would have guessed. Nice job Toyota!

So total fuel use was 44/37.8 = 1.16 gals, and if he instead drove that 44 mile leg in HV he would have only used 0.8 gals, so the penalty for selecting Charge Mode was 1.14 - 0.8 = 0.36 gal. At $2.50/gal this is 90 cents.

Can I assume this 80% figure refers to the portion of the battery allocated to EV, i.e., 6.3kWh? If so, then to charge this same amount at home (80% of 6.3) at out local electricity rate of 10.9 cents/kWh would cost 0.8*6.3*10.9 = 54.9 cents.

So I can see that it is more expensive to charge this way, as mentioned. Still, I like it for the flexibility!

 

Your calculations look about right. And I agree with your conclusion. Charge mode can be useful if you want some EV at the end of a long drive, but unless driving conditions are ideal, it'll cost a little extra. HV mode in the Prime is incredibly efficient.

 

My 'normal' Prius commonly fills in just 300-400 vertical feet, but that is because it starts the descent with a fairly high charge. To go 600 feet requires starting at a low charge level.

Even in the Western U.S., that capacity is still very useful and covers a large majority of the available descents. But from the Rockies to the Pacific coast, my travels do cover a considerable number of other hills where it isn't enough, not even close.

 

Just wanted to report back that I did ultimately purchase one of the cheap Chinese L2 chargers from Amazon (around 200 dollars), and the quality of the Japanese made Toyota OEM charger is so much better. I took apart the car connector ends on each to have a peak at the wiring and the Chinese one is so cheaply made. Thinner conductors, less substantial wire joints, no strain relief, and basically just junk in comparison. The Toyota product looks like it is built for endurance. All wires held firmly in place, protected switch, sealed case. The plastic clip mechanism appears much sturdier as well. I do like the Chinese charger's performance and the fact that it's display shows current, voltage, and total energy flow though. I am considering swapping the long cable and J1772 connector over to the 16 amp box.

So my point is, Toyota makes a very high quality EVSE product just like their cars. Given what I have seen, I would feel slightly more comfortable safety wise operating the Toyota charger at 240V than the Chinese one. But honestly with proper over-current protection on the circuit (20A breaker) neither one worries me because I know the car is in command and determines what to draw from the EVSE box and when.

 

Wouldn't this $19.99 (on Amazon) adapter cord work? tinyurl.com/v3y4zwkn (this one is a 10-30)

 

Nope. It's a 10-30 to 6-50 adapter. You can't plug the 5-15 plug on your EVSE into the 6-50 part of the adapter. Note that the wide and narrow prongs are opposite between the 50A 240V (6-50) and the 15A 125V (5-15) plugs.

 

If you don't mind removing the original 120 V plug from your Toyota charger, the cheapest option by far is to just replace the plug with something like this. This is also a safer approach since there is no need to create a 240 to 120 Frankenstein cord that someone might inadvertently plug something into one day.



If you still want to use your modified charger on 120 occasionally standard adapters back to 120 are readily available.

 

But then there's no thermal sensor in that replacement plug and it's only for 125V anyway. I would think you'd get a fault on the EVSE, but I haven't actually tried it, nor would I. Use a "proper" adapter or get a proper L2 EVSE. Chopping the plug off of an $800 EVSE isn't what I'd call cheap.

 

You're right. I forgot about the temperature sensor. Good point. So perhaps we are trading one risk for another. Of course if the connection to your 240 outlet is getting hot you have more serious problems, and if we build a homemade adapter it will also not have a temperature sensor on the 240 plug. In this case, is the downstream temp sensor in the Toyota plug still helping? I believe the temperature of interest is at physical connection of the plug terminals due to the possibility of poor connection.

As for the "$800 EVSE", is there a market for these?

 

Especially if you installed a 50 Amp breaker, 8 AGW romex, and a 14-50 outlet, none of these are stressed by a 12 Amp load. The thermal concern is with 15 Amp devices doing 5 hours of 12 Amps continuously. IMO

 

Agreed. However, if you are using the outlet only for this EVSE the safest approach is still to use the minimum breaker that meats the demands of the device plus a little overhead. A 20 Amp breaker is the best choice in this case (maybe 15). The code in our area only requires that the wire gauge be at least large enough to cary the current passed by the breaker (in this cage 12 gauge). 8 is fine of course since it is much larger and will run even cooler.

 

If you decide to install a 14-50 outlet using 8 AWG romex, but put a 15 or 20 Amp GFCI breaker; you are sized to protect your Prime* but upgrading to a Full BEV is just swapping out the breaker for a 50 Amp, not rewiring. I would make a Dymo label for the 14-50 outlet saying 20 Amps max. (or 15)

* 15 amp double pole breakers are rare but exist, 20 Amp is very common and cheaply available. If you find a 40 Amp EVSE, a 50 Amp breaker can allow 333% more wattage if the car allows it, (Prius Prime does not) so charging time will be greatly reduced.

 

Yes. I agree the heavier wire provides a simple upgrade path to a higher current EV in the future with the simple swap of the breaker from 20 to 40. However, to go to 50 amps I believe 6 gauge wire is required. Yes, I would label the derated outlet as you mention.

EDIT: I did some searching and some localities do allow running 50 amp circuits using only 8 gauge wire (if in 3-wire runs). However, 6 is frequently used since 50 amps is between gauge maximums according to some charts.

 

At 50 Amps, I believe that the distance of the wire is going to effect the retired gauge, but it has been a lot of years since I had to pass that test.
Local Code is just one reason why you want a licensed electrician to make sure you are safe; all we can do is offer very generic advice.

 

You are fine. Don't worry. If it was installed by an electrician I am sure it meets local code as is. Also, I just found more information from the NEC that the conservative values in the table I posted above are only for low temp wires. You can run 50 amps in 8 Ga (COPPER) wire rated at 75 C or above as shown below (Well, at least as of 2002).

 

I like the phrasing of this common disclaimer:

Legal information is not the same as legal advice -- the application of law to an individual's specific circumstances.

Although general legal information can be very useful, you should consult a lawyer if you want professional assurance that the information presented, and your interpretation of it, is appropriate to your particular situation.

Statutory and case law are constantly changing and vary by jurisdiction. Your lawyer is there to assist you in understanding those changes and taking appropriate action.​

In the above disclaimer, please substitute "electrical" in place of "legal", "engineering principles and code requirements" in place of "law", and "licensed electrician" in place of "lawyer" -- and you will get the gist of what most of the experts posting on this topic to Prius Chat are trying to say.