Prime charging on a timer

Actually, if there is no schedule at all programmed into the car, it will charge immediately when you plug it in. If there is a scheduled charge, the car will wait for that day and time unless you override it. At least that's the way mine was before I programmed the charging schedule.

 

Ok that’s what I thought, but It’s my understanding that the OP did not have a charge event set up. So the posts stating that no charging event would be triggered by him plugging it in because the default is a timed event seem incorrect to me.

 

Convenience.


Rob43

 

For example, our Saturday routine (before COVID19 lockdowns) consisted of:
* A scheduled morning charge,
* Drive on EV to the rowing club and back,
* “Charge now” at home,
* 2.5 hours later, rather than 5.2 hours, after taking a shower, and grabbing some lunch,
* Drive on EV to the grocery stores we like.

 

You are correct that without scheduled event, PRIME will start charging middle of night upon power being supplied by the wall timer as if it was physically plugged into the wall at that time. I have tested this on my previous PRIME and confirmed that charging starts when wall socket is plugged. As long as the timer is rated for continuous 12A and makes good connection, what OP is planing to do would work. But cost more money and insert another piece of element in between the wall outlet and the plug, making it less safe, IMHO.

 

Is this prime going to be your last car, or last car garaged at this address?

Your next car may get a better benefit from 240V service. Might even require it. Same goes for future owners of this home.

If I needed to bring in the sparkies at all, I'd just have them do the one job for both service types.

I'm with you on wanting to use an external timer. It's cool that the car has its own built in, but I would prefer the simplicity and accessibility of one on the wall next to the receptacle myself.

 

Electronics 101: Current (amps) causes heat. Volts do not. Power is volts times amps, so doubling either doubles power. That's why we can run a 900 HP electric motor at 4,160 volts with about the same size wire (and amps) as we use to run a 100 HP motor at 480 volts. Current is the same, but power increases thanks to the voltage increase. So, as long as the current stays the same, the heat stays the same.

What happens inside the car is where it gets a little more complicated. If I've made any arithmetic or operational errors here, hopefully one of the guys who really know this stuff will set me straight, but here goes.

The charger inside the car needs to push over 351 volts into the battery to charge it since that's the battery's nominal voltage. Being fed by 240 provides more power which the charger can use to increase either voltage or amperage to get energy to the battery faster. I doubt that it would increase voltage by very much due to safety factors, so it's probably more current. Even so, the additional current is very small compared to the currents used in driving.

Keep in mind that if I drive in EV at 60 mph, I'll deplete the battery in well under a half hour. That's four times the rate of energy transfer that you'd get with L2 charging. So, if L2 is bad for the battery, driving the car is REALLY bad. An OBDII adapter and a phone app will show that the car is pulling WAY WAY WAY more than 16 amps from the battery most of the time and pushing almost as much back into the battery when decelerating. I once filled my battery from 10% to 98% going down a mountain in Colorado. It took about 15 minutes. At 98%, the engine started. I suppose that was because the battery got warm and the car stopped charging it.

If I use 6 kWh in 30 minutes, at 350 volts, that an average of over 34 amps. Lots more than the 12-16A pulled from the wall by the charger. My meter shows that my 16A L2 EVSE is using about 3.8 kW while charging. If there were no losses (and there are plenty of losses), at 351V to the battery, that would only be 10.9A going into the battery. In reality, it's probably under 9A. That about a tenth of what the battery handles while accelerating or braking.

Oh! And then there's driving in charge mode. That'll charge the battery to 80% in about a half hour. Almost four times faster than L2.

There is absolutely nothing to fear from L2 other than being able to get back on the road quicker and saving a tiny amount of energy thanks to the shorter time running fans and wasting heat.

 

It's actually only twice as fast. The video I filmed (below) made it to 80% (from 14%) in 37 minutes. Looking at the aftermarket gauge, rate is roughly 7.2 kW... which is still quite modest it terms of what can be pushed to lithium batteries for automotive use. Tier-1 for Tesla goes up to 60 kW. The industry is trying to push well past 150 kW... attempting to double that if cost can be properly addressed. So, a sustained 3.6 kW from a L2 is nothing, especially if you let the pack cold soak for a few hours before starting the charge.

 

I was hoping you'd provide one of your cool videos for illustration.

 

Even nicer is the slew of options available from a Wi-Fi enabled charger. We have 2 JuiceBox Pros. They allow you to set minimum & maximum charges, to set time-of-use scheduling, and to monitor session & lifetime stats.

 

Beauty is in the eye of the beholder. There's something to be said for a basic mechanical timer where you just move a couple of pegs to set the timing events and spin the wheel to set the clock to the current time.

No creating user accounts, no ongoing security/credential management, no device pairing, you never get surprised when your new wifi router uses a new standard and won't let your legacy charger connect, or any of that silly stuff. I can't deny that the technology allows a lot of nice incidental features and I'm certain that some users will appreciate them. Maybe even me, whenever I eventually get a pluggy car.

But sometimes the KISS approach really is the right way, and I like knowing that these cars will still work just fine if this is how the owner wants to use them.

 

Then you would be better off with the "set it and forget it" approach from the car itself.

That mechanical timer (we had that old-school metal box with pegs type in our garage growing up, for the christmas lights) needs to be adjusted if the power ever goes out and twice each year for daylight-savings time.

 

We have yet to use the timer as our electric rates are low and stay the same all hours as far as I know. One reason I'd prefer not to use a timer overnight is if a thunderstorm popped up while I was sleeping, I realize the odds might be low, but I unplug our car when I hear any thunder just to be on the safe side.

 

Electricity is only $.14 a kilowatt where I live. Six cents a kilowatt at night. I don’t use the schedule. That way I can plug the car in anytime I get out. In the evening I plug it in at 10 o’clock when I’m going to bed

 

Mainly efficiency. EV chargers have to meet a minimum efficiency at 240V (I forget what the spec is) but do not have to meet any specific efficiency at 120V. Thus most chargers are significantly less efficient at 120V.

Not significantly. Fast charging means rates above C/2, and by definition a 2 hour charge is C/2. Every battery I have ever seen is designed to charge at this rate.

Also these batteries are designed to deliver 100 or 120KW (depending on year) - that's an 8 to 12C rate. A battery designed to discharge at a 12C rate is not going to have trouble charging at C/2.

For high energy, low discharge rate batteries (i.e. laptops, cellphones, radios etc) that is very true. But high discharge batteries (power tools, EVs, ebikes) it is much less true.

 

I simply program the car to charge during daylight hours. Our electric coop is 100% solar, so we (as a coop owner) pay less for the power that we buy when the sun shines. Also, the solar panels on my roof provide the power I need for the car.
I plug in the car whenever I arrive at home and the OEM charger is enough to keep me running without gasoline.