Battery capacity?

Awesome. Cool idea to calibrate it. I can probably use Kill-A-Watt on a single phase to calibrate. And looks like my 10% overhead math is not far off at all. Savings on L2 should pay for the used EVSE I bought in about 100 months

 

Last update regarding charging efficiency. Running the OEM at L2, but with the car limited to 8A max takes about 11.8kWh to fully charge the battery. This compares to 11.3kWh at L2 without the 8A limit, so is a bit less efficient.

One of the downsides that I noticed when charging with the 8 amp limit is the LED light bulbs in the house tended to flicker. I suspect the throttling isn't a smooth 8 amps, but rather a chopped up current that averages to about 8 amps. This causes the AC voltage to bounce a bit leading to the light flickering. I've found some LED bulbs are really sensitive to voltage fluctuations.

Due to the flickering and efficiency loss, I think I'll stick with L2 without the 8 amp limit. I doubt there's much of a difference in battery lifespan anyhow.

 

Like several of my higher energy consuming circuits (space heat pumps, heat pump water heater), I have an old utility style KWH meter inserted in my L2 EVSE branch circuit, on a standard meter base, though it reads only to whole kWh units, not fractions. But a variety of other home energy monitors exist that don't require rewiring in this old-style meter. Some monitors merely hook in to your main electric panel, though may need a real electrician to install the current transformer sensors on the wires of the circuits you want to monitor.

For regular home charging, I now have a true J1772 third-party L2 EVSE that can charge at my RAV4's full 6.6 kW rate. It reports energy delivery and other details over WiFi, though I haven't yet tried to check its calibration.

This adapter works with the factory EVSE included with my RAV4 Prime, though beware that all adapters of this sort can't meet any electric or safety codes, because uninformed household members can inadvertently and easily destroy other appliances with it:

Last week, I used a similar NEMA 10-50P adapter to charge my RAV4 from a 240V welding outlet while spending the week at dad's place.

"Efficient" is the wrong word for this context. "Fast" is more descriptive and accurate. The 120V operation is almost as efficient as 240V, but much slower.

Household 240V is split-phase, which is just a center-tapped single phase. 2-phase is different. (One of my college engineering profs had worked on a true 2-phase system, back before it was converted to 3-phase.) The difference matters when metering.

 

Flickering would mean the wiring is arcing somewhere in the house circuit? Or maybe excessive voltage drop causes led bulbs to flicker? I don’t know what setting level 1 120 v to 8 amps has to do with level 2. I am pretty sure it is independent. L2 is like 14.6 amps on each 120 leg at 3.5 kw total. The factory evse is rated 12 amps on the label.

 

Incorrect in this case. The OEM charger takes about 13.5kWh to charge the car when supplied with 120V (L1) and the same charger takes only 11.3kWh when supplied with 240V (L2). You are correct that L2 is faster, but in this case it is also much more efficient. I would have not guessed this, but that is what the data shows and has been confirmed by multiple owners.

 

A few of the LED bulbs I have must not have any AC filtering in them as they flicker with every AC variation. For instance, when our clothes washer direct drive motor agitates back an forth, we can see some bulbs pulse along with it.

I tried the 8 amp max setting on L2 to see how it would affect the charge speed and efficiency. I have not tried the 8 amp max setting on L1, but I suspect it would make things even worse.

I'll need to put an oscilloscope on the AC feeding the charger and see what the noise looks like before I guess too much more. The connections are tight and it's a 60A circuit, so wire size shouldn't be the issue. I'm assuming it actually pulls the full ~12A, but modulates it on and off (PWM) so it averages out to 8 amps. The scope will tell the tale when I get time.

 

I was replying to this specific item (emphasis added):

Please show your math to demonstrate "Toyota 240V EVSE with a proper plug, all signs point to it being at least twice as efficient as 110V".

Your later reply shows a ratio of 13.5 / 11.3 = 1.19, or 19% more efficient. In my math, that is far far short of "twice as efficient". On that scale, 19% much closer to 'almost the same' than 'twice as efficient'.

 

Sorry. I was focusing on your statement, "efficiency is the wrong word for this context." Obviously the math does not support "twice as efficient", but that wasn't a comment I made.

I will state that a 19.47% increase in charge efficiency is rather sizeable in my mind, but to each their own.

 

Half as much "loss", thus the "twice as efficient" comment on my part since the overhead is not experienced for 11 hours, but for 3.5 hours to full charge. I didn't mean that you'll need half as much kWh to charge, just the diff from what goes in the battery and comes out of the wall will be half as big on L2. Like instead of 3kWh overhead on 120 EVSE should be 1.5kWh overhead for 240 EVSE.

13.4kWh out of the wall to fill 10.6kWh battery on L1 vs.
12-ish kWh out of the wall to fill the same 10.6kWh battery on L2, so
2.9kWh overhead vs 1.4kWh overhead, or twice as efficient

 

^ That is not how scientists and engineers express efficiency.

 

I’m surprised that the computer in the car doesn’t track the amount of charge that the battery has accepted afterwards. You would think it wouldn’t be very difficult to integrate since it has an onboard charger and therefore monitor and meter the juice. it would be nice to know, exactly, or relatively how much charge the battery has taken on. The Toyota app is Kentucky Windage at best …

 

@NullDev would you share what difference would it be to use L2 charging vs a dryer 240 V outlet in the US?
You seem to know the electric stuff a lot to share some wisdom. Thanks.

 

You can do L2 charging with a 240V dryer outlet. I chose to wire a L14-30 (240V, 30A, twist-lock) style of outlet because I had most of the parts on hand, but I could have just as easily used a dryer style (10-30R) outlet.