charge daily or when needed?

My EVSE draws about .3-.4W when not charging. For me, that equates to less than 50 cents per year, given that it's plugged in 24/7/365. (and not accounting for the time it's actually charging) Seems like it's not worth the hassle of plugging/unplugging.

Honestly, if your 12v battery is getting to the point where its charge state is impacting normal operation, either you have a bad battery, or there is something wrong with your charging system. The DC-DC charge from the HV battery is much more capable than a typical alternator setup, and should always keep you with an acceptable charge (albeit maybe not MAX possible). Given that you don't need to use the 12v to start the engine (which is a huge power draw on most vehicles), I wouldn't be concerned at all. On the other hand, if it makes you happy to use a battery charger periodically, there's no reason not to.

 

That doesn't apply to the AUX (12-volt) battery either.

The originating comment was about short-distance travel being too brief to top off. With longer drives, it's a non-issue. We have many years of data from countless owners confirming that already.

 

No harm in attaching an automatic battery charger or maintainer, but I've seen trickle-charging eventually destroy a battery. I also agree, there seems to be no point in doing so under normal circumstances. The aux battery isn't harmed or degraded in any way if it's not completely charged when you park the car. Charging doesn't improve it's condition in any way, when it's not quite charged to capacity.

 

Since post #12, this has been about the 12v aux battery. If it were really a case of the aux battery requiring a bump-charge every time it was parked, that would certainly be a problem, particularly on a long-distance trip in winter. If the aux battery were gradually losing charge, the headlights, the heater and eventually the car itself might stop working.

 

It's does use a fair bit extra electricity to leave the cord plugged in all the time. I used a Kill-a-watt meter for the first several months and noticed that the difference between the Kill-a-watt meter and the car meter was almost 20% more on the K-a-w meter. I tried for about a month with unplugging the cord from the outlet when not charging and the difference was much closer. I assume there is a transformer in the square black box on the cord and it must use a fair bit of kwh, even when not charging. Has anyone else checked this? I am actually looking at putting a switch on the outlet where I charge from, because it is a hassle to plug and unplug every time I charge.

 

Kill-a-watt measures at the wall. PiP measure at battery discharge. There is about 15% charging loss into the PHV battery.

Not sure why you saw 20% difference.

 

Is it fair to assume that since all rechargeable batteries discharge internally to some degree, that the topping-up process would continue to consume power, in addition to the circuitry that monitors the battery level?

(Note: we are now talking about the EV battery.)

 

But the charging light turns off once it is full. I don't think there is any topping off since it won't start again until the timer triggers it or you replug it.

 

That's good to know. If I leave on a 1-year vacation, leaving my PiP plugged in, my charger won't monitor my battery and keep it charged? Sounds like a design flaw.

 

But doesn't the inverter's 12V output take over powering all the accessories? My understanding is the 12V battery is really there just for system boot and (limited) driving of 12V accessories when not in READY mode.

 

The 12V system powers most of the accessories, but it doesn't come directly off the battery. The voltage converter feeds a constant voltage to the system when it's running. When it's not running, the battery feeds the system.

 

A bit more detail: the loss is in the charging system in the car, not the external EVSE (the block on the power cord). The charging system has voltage converters, fans, and such, and there is loss in the charging chemical reaction in the battery itself. As mentioned earlier, the power consumed by the EVSE is miniscule. It is only a few simple logic circuits to handle the J1772 protocol, and a relay to turn the power on and off to the car.

 

oh yes it does!

 

That's only correct if the car is in Ready mode. When the car is off, there are a host of drains off of the 12V Aux Battery:
1) Smart Key System (SKS). The computer controlling the SKS is almost always on. Once that is finished talking to your key fob it then kicks off a series of other charges.
2) If the doors are locked, the sensors on the front doors and the hatch are energized. If the doors are unlocked the sensor for the locks are energized.
3) Lights come one in the interior as you approach the car.
4) When you open the door, footwell lights turn on.
5) When you open the tailgate lights are enabled (not by the SKS obviously but by a switch).
6) If you have a Homelink rearview mirror that is on.
7) If you leave your headlights on the car will turn them off after 30 seconds.
8) The power windows are enabled for up to 10 seconds after you turn the car off.
9) Brake lights are always enabled as are internal door locks.

There's a nice little startup tutorial that shows even before you hit the power button, the Prius is drawing about 2 amps. Granted it shows the drainage for a Gen II, but the PiP is not too much unlike the startup.
Prius Startup Current

 

That's not the case. When I fire up the remote A/C via my phone (using Entune), the system will indeed begin recharging automatically afterward. I can see (using ChargePoint) electricity being drawn again, even though it had already stopped prior to that.

 

Perhaps, but I don't think Li-ion self discharge is that bad. I doubt a full PHV battery will not go flat in one year.

The 12 volts lead acid battery will go but that's the intended design. Every car will do this.

 

That's the greenest thing you can do.

Many people tries to get as many EV miles as possible (even giving up gas economy) instead of thinking outside the box and move closer.

I now walk to grocery shopping and to get a hair cut.

 

Talk to the guy from Pakistan, who ordered a PiP from Japan, which arrived with a dead battery and wouldn't take a charge. Would you like to risk leaving your hybrid for a year without charging? The Tesla had a scandal about this a few years ago. They recommend leaving it plugged in while you're away for long periods of time.