Prime Loses Charge Sitting Unplugged

No, this is not normal.

When you say it is starting as if the battery is empty - how long did the charge take when you plugged it back in, and what was the indicated battery percent when you turned the car on prior to charging (or did you do this)?

 

Are you certain it was full? I have have had occasions where there was a timed charge in the future and I forgot to override it to "charge now." Did you turn on the car and see the battery at 100% or were the blue dash lights off and that led to conclusion that it was full?

This would be highly unusual to lose a full charge in 10 days of idle time. Any chance somebody at the house took it out for a drive while you were gone?

One note - if you are leaving town for a week, it is best to leave the battery at a low state of charge and then charge just prior to your next use. Per the owner manual:

●Leave a low level of charge in the hybrid battery (traction battery) when leaving the vehicle undriven for a long period of time. After confirming that EV mode has switched to HV mode, turn the power switch off.

●Use the charging timer function as much as possible in order to fully charge the hybrid battery (traction battery) immediately before starting off.​

 

We have taken a number of trips over the past 2 years where one or both of our Prime sat unused for a week. That hasn't ever happened. It's basically at the same level afterward we left it.

I would seriously question whether you actually charged up before unplugging, especially since there are a number of "it didn't charge" threads. It's likely something prevented the charging that you haven't noticed or encountered yet.

 

@jb in NE beat me to it.

In READY mode, I'd expect the battery to hold up with no A/C or other high power loads running for at least a week or more before the ICE starts.It's quite easy to leave any Prius is READY and forget to shut it off. You cannot charge it, though when in READY, so that's my guess.

With the car off, the traction battery should hold its charge for many weeks, although that's not good for it as quoted above in the owner's manual.

 

It's easy to overlook message differences. The notify could have been charging interrupted.

 

What climate control event would occur if the car were turned off and unplugged?

 

I've noticed sometimes the battery declines in mine, but it's sneaky about it. If I let it sit for more than a day without charging the percent remaining is usually about the same next time I start it. But when I start driving it declines more quickly than usual. I don't have much experience with leaving it for a week, but I don't think that would drain the battery. I'd estimate it might lose less than 10%.

When it's off the battery is physically disconnected by relays, so there's nothing that can cause a drain. Changes in temperature might have some effect on it. But thinking about other lithium batteries it doesn't make sense for them to lose more than a few percent in a week.

 

I’m in Houston now and left our Prime at the airport at 50%.

We’ll see where it is upon return but my suspicion is it will be at 50%.

 

I left mine for five days at 1.6 miles (didn't note the %) and it was 1.6 miles when I got back.

 

actually - all batteries self discharge ........

Elevating Self-discharge - Battery University

The rate of lithium discharge turns on how high they are charged, as well as their surrounding temperatures surrounding, their age etc, and then there's also the possibility of parasitic loss turning on what kind of devices are drawing small amounts 24/7 (extreme heat/cold thermal management, cellular/wifi connectivity etc)
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They all self-discharge (a small amount), but losing a full charge (6+ KWh) in a week is not normal.

 

folks shouldn't bet their bottom dollar that it's not normal .... sometimes

Prius left on all night | PriusChat
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To fully discharge a 6.6 KWh battery in a week (168 hours) requires a constant 39.2 watt discharge for the duration. Self-discharge isn't going to do that.

I suspect that the OP (as others of us have done) did not charge the car at the start.

 

perhaps meant to say 39.2Wh? .... if so - could that possibly fall w/in parameters of climate control occasionally cycling on/off the whole 168hrs? don't know what climate temp setting /surrounding temps would cause more oe less power drain.
or .... yea - just not charged after all
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No. A Wh is a unit of energy, a watt is a rate of use of energy. If it were 39.2 Wh, that would be about 0.6 percent of a full charge, essentially not noticeable.

 

that's right - and 39.2Wh's per HOUR, used over 168 hrs .... yields 6.5kWh's & change used.
sorry if the prior post wasn't clear in that regard
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