Installing a level 2 on my garage. charging question

The Prius Prime manages its battery very thoroughly; no need to fully discharge it periodically or anything like that.

In fact, it’s impossible to full discharge the battery; it will just kick into hybrid mode. Like most (PH)EVs, it maintains 10%ish charge and discharge margins to improve battery life.

So, which charger are you getting? We use a Clipper Creek LCS-30P: very basic and rugged unit, but you can’t use it to gather charging statistics or anything like that. The main reason we chose it is that we had only one available 240V circuit, on a 30A breaker. Code requires 20% margin on such circuits, and the LCS-30 was the only unit I could find rated at 24A.

If it weren’t for that, I probably would have gotten a ChargePoint unit with more monitoring and control features.

Arguably at least, there is value in using a charge timer in the charger rather than using that in the P.Prime. Specifically, if you set up a scheduled charge in your P.Prime, it will always wait for that scheduled time to come up, even if it’s hours later. That’s fine at home, but it’s easy to forget to tell it to “Charge Now” when you plug in at a public charger! So you come back after your grocery trip or whatever and no charge (possibly even fees for hogging the charger without using it!). If you instead schedule your charges in your home charger, it will always default to “Charge Now,” which will be right wherever you charge.

 

As long as you don't let a fully charged car sit for a long time, then yes, there is no harm in charging a partial charge, either charging a partially depleted battery to full or a fully depleted battery to less than full.

 

I definitely agree. It seems to stop letting me charge as much if the battery is kept with too high of a charge for too long. Mine started out fairly consistently at 34ish miles of EV range.

However, 8ish months later, we got into habit of using free-charging opportunities the night before, meaning that the battery stayed charged overnight often for a few weeks. The EV range then dropped in three distinct steps, and has since been fluctuating up and down between 22 and 30 miles since, with no obvious “rhyme or reason.”

BTW, I have verified that the actual, real range is what’s fluctuating not the GOM’s estimates, which have always been pretty accurate for me at least. Last time I checked it, a few days ago, it projected 23.8 miles and it actually got 23.4, so dang-good estimate.

Some other P.Prime owners here have seen this sort of thing, but others seem to keep getting the same 35+mile charge they’ve always had since they bought the car.

 

With your mild weather, constant 35+ miles may be possible. In our climate, I routinely get ~32miles in May-Sep, ~28miles in Oct-Nov and Mar-Apr, but less than 20miles during Dec-Feb. This regardless of how often I charge.

 

That, more or less correlated to climate-control usage?

 

It mostly depends on the ambient temp. I hardly ever use the heatpump (cool and heat) on my car if I am alone. Almost never from Mar-Nov. And for winter months, if it is cold enough to be needing heat in the cabin, I will turn the car to HV mode and use engine heat, so even the winter months EV range is more or less purely on ambient temp correlated, not to the climate-control use.

 

That is what circuit-breakers are for. If you connect more to a line than it can handle, power is automatically cut. Watch what happens when you plug a high-draw device (like a hair-dryer or vacuum) into the same line as your level-1 device while it is being used. The moment you press the on button, overload is detected and power to line halts.

This is why better EVSE (level-2 devices) offer the ability to be adjusted. Our 240-volt lines in the garage are 8-gauge, which provide a maximum capacity of 40-amps. The EVSE itself is rated for 40 amps (that's 20% from a 15-50 NEMA outlet on a 50-amp circuit using 6-gauge wire), but we set it to a maximum of 32 amps. If we had needed to share the same line instead, putting both EVSE on that same circuit, each could have been set to a maximum of 16 amps. Like with any household outlet, you should be aware of sustained usage on the same line. Notice that EVSE are not all hard-wired anymore.

If for some reason our next plug-in vehicles draw more than the common 7.2 kW rate maximum, which is the sustainable draw from our 32-amp capacity, we could pull 6-gauge wire through the metal conduits and replace the 40-amp breakers with 50-amp. Doing that, we could set the maximum for the EVSE back to 40 amps to allow a 10 kW rate.

 

Indeed. If you can get an adjustable charger (actually EVSE) with a timer, and with web monitoring and controls, that’s the best bet. Unfortunately, when I bought ours, I could find no such units. IIRC, a year or so after we installed ours those features came available. Oh well... Probably not big enough an advantage to replace ours, but ... would be nice!

 

Unplugging the charging cord as soon as the charge is completed will reduce the drain of the 12v battery. But more importantly for the longevity of the traction battery, not the 12v battery, Toyota recommends using a charge schedule so that you will drive off the car as soon as the traction battery is full. The point is to reduce the time the car sits with a full traction battery charge. So, if you come home with a partial charge left in the traction battery, but you have no plan to go out again that day, use the charge schedule so that the full charge gets completed just prior to your departure the following day.

 

There isn't just one answer to that. It's not good to leave it plugged in for days and days because that will tend to run down the 12V battery as the car and its charger keep tabs on each other. But if you come home, plug it in, and let it charge at whatever time the schedule is set for, and then don't unplug it for a few hours, that's no problem. Neither I nor the owner's manual recommend leaving it plugged in or fully charged for days on end. It's not a fussy car, but no car wants to be abused.

 

Wait, why would keeping it plugged in drain the 12V? I gather you’re suggesting that the 12V system monitoring the states of the 200V(ish) system consumes a lot of power? Why would you expect that to chew up boatloads of power (sure, a little certainly, but why a lot)? Conceptually , it’s just taking a few readings from ADCs. Also why more while plugged in?

Either way though, according to Prof. Kelly (https://youtube.com/playlist?list=RDCMUCtr07mdKhsUwVJjL8Kw_q5A, ~19:00), at least while charging the traction battery, it also charges the 12V battery, since the traction-battery-cooling fans used during charging are supplied from the 12V battery.

Now, I don’t claim to know whether or not it charges the 12V battery other than when charging the traction battery, but if it can maintain the 12V while charging, it would be a piece’o’cake to do so always while plugged in.

 

I said no such thing or anything close to it. I said:

That's a far cry from "boatloads" unless you refer to the little paper boats that kids made back when kids payed with real stuff.

It came from the owners manual.


As for Professor Kelly's video, it is terrific. But note that the system only maintains the 12V battery while it's charging the traction battery. And it's a lot lower voltage than what the PiP did. I have measured both.

 

Interesting... I’d be surprised if that drain would be significant as long as you’re driving or charging the car at least once every few days. Perhaps it would be an issue if you leave it plugged in for months.

Weird that they don’t maintain the 12V while plugged in, even while not charging. Seems like it would be all-but-free to do so.

 

Someone on PC measured it and I think it was about a 0.1 volt per day drop in the 12V battery to leave it plugged in.

Seems that way doesn't it. My theory is that the energy used in keeping the charger & stuff alive just to trickle charge the 12V might be significant enough that they might think it too energy "extravagant."