Battery drains while parked under the hot sun

It's too soon to tell if anything is wrong with your car. It's still in the break in period. The battery does not normally show a full charge unless you have extended periods of downhill driving. Next time you decide to drive to Las Vegas, you'll have an opportunity to see it fully charged on the downhill drives.

Your car is warrantied for 3 years/36000 miles. I say give it more time, get used to it a bit and then see if you still notice something different.

 

Seems like you should be able to show better mpg than 40. Keep driving, and you should see it improve.

 

Is the ignition really Off?

Not an issue. Flatlanders may never see it. The car's aimpoint is 6 bars (75%), which is also close to the best for battery longevity. It will go higher with braking regeneration, and you will need a reasonably steep descent to get it full. I sometimes fill it with a 400 foot descent in 2 miles, but not always. The several thousand foot descents on 5% grades always fill it.

Newbies should drive 'normally' for a few tanks to get a baseline MPG before trying for better results. But by 2100 miles, you should already have that.

Next: Fuel economy complaints/queries? Please copy, paste & answer these questions, esp. if you're new

 

Further, do keep in mind the battery charge indicator is a guess at best. The value shown will change with battery temperature. In short, it's just a "bells and whistles" thing. It doesn't really tell you anything useful. In fact, it lies all the time. For example, 100% is actually around 80% and 0% is actually around 30%. The HSD controls the battery charge level. You can -influence- it but you can't control it.

As mentioned above, do be careful that you actually turn the car off when you leave it. You can tell if you did because it will give you an audible warning (close any door with no fob in the car and the car in "Ready" and it will ding a couple of times).

So relax and watch the blinking lights.

 

Bump those tires up a bit over 40 psi. That will help mpg's. Mine are upper 40's when I get to drive my car.

I'd like to say I also have noticed my HV battery level dropping from using the solar vent but I would have to check it out again this season to verify. It's been many many months since I even sat in my car

Mike

 

Well, if either of you are implying that somehow the battery is being drained by the fan please explain how that would be possible, given that the relay in the traction battery pack is -open-, and it opens -both- the positive and negative leads. There is no connection between the traction battery and the car. Zero, none.

I can think of only three possibilities as causes to this -indicated- battery charge level drop, in order of probability -
1. The battery temperature has changed enough that the system -thinks- the charge level has changed (temperature change causes battery voltage to change).
2.You left the car in "Ready".
3.Somehow the change in temperature has caused expansion of the battery pack and that has caused an electrical leak inside. I have never heard of this happening, but it's -possible- (barely). Given that in use the pack temperature gets much higher than any ambient temperature we are, hopefully, likely to ever see!

You might want to check the battery vent inlet to make sure it's clear. If it's blocked the battery will operate hot, and that will increase the operating vs non-used temperature difference. And that will increase the difference the system will think there is in charge level.

 

I've noticed that drop in battery level as well. I parked outside in 80 degree bright sun for almost 9 hours and I usually come back to my car with the fan running and when I start the car, the battery level is down to 2 or 3 bars. I know for sure that when I get out of the car in the morning my battery level is a shade under the full mark.

 

This is starting to sound way more familiar to me now that I think of it. I know for a fact there is zero wrong with my car. It has fifteen hundred (1500) miles on it. It is brand new yet. Not a chance the interior vent would be covered with anything as nobody or nothing ever gets put back there
As far as leaving it in ready, impossible for me to do that. I fully understand how the car operates other than some of the particulars like how the software & hardware are running this solar vent roof or getting Entune to operate correct every time I hop in the car but that boot up/power up button, piece-o-cake
I will run some tests when I get to take it out this season. It's still in storage.

Mike

 

It is time!!!!!

 

Mine doesn't do this. I drive my car daily and it's around 1,400 miles now. I haven't noticed the battery being lower when I leave work than when I got here. I'll pay closer attention to this though and see what I can determine. Tomorrow is supposed to be 92 so I'll check it out.

 

why should it drop at all? maybe one bar because it was just over the edge, but i can't see more than that unless the heat has something to do with it. but i parked my '04 and '08 in full sun in 90 degree weather for 8-10 hours for years and never experienced that.

 

I have a feeling there is more electricity being used than the solar panel puts out.

Mike

 

But where is it coming from? The traction battery is supposed to be disconnected by a relay when the ignition is off.

 

According to this, heat will lower the voltage of a battery. We already know that the Prius uses coulomb counting while operating to track the battery voltage, augmented by adjustments (probably mostly based off of voltage) that happen when you turn the car on, which corrects any error that may have accumulated during the coulomb counting.

So you park the car, the battery gets nice and toasty, and the voltage drops as a result. When you turn the car back on, it sees that the voltage is lower, so it shows the battery SoC as lower, although the total stored energy is probably still the same.

So here's your next experiment - if you find that you can reproduce it reliably, try parking in a location where it happens, but leave the car until nighttime, or something like that. Or, possibly, turn it on (for a few seconds) when it's hot to check the battery level, then again at nighttime when it has had a chance to cool off for a few hours. In either case, maybe you will find that when the battery has had a chance to cool off again, the SoC displayed has recovered to what it was when you first parked the car.

 

Good question. Seems there are always new things learned about these cars. Really wish a Toyota engineer could tell us here what is going on. Maybe someone here will dig into it and figure out what the car is really doing when that solar fan is activated. Seems like there is more than just the solar panel and that switch on the dash to the solar vent system.

Mike

 

The only problem with -thinking- because it's parked in the hot sun the battery temp. is higher is that the battery -operates- at a high temp. Probably higher than afternoon ambient. And because the battery is tucked away -out- of the sun and -out- of the interior air (it's under the floor), it will probably be closer to ambient temp than interior cabin temp.

You need to -measure- the battery temp to really know what it is and to even have a chance to figure out what is happening. You can probably get the battery internal temp from a Scangauge or other system scanner.

Oh, and as posted by others and me, the battery is -completely- disconnected from the car by the relay. The battery computer is still connected, but the battery is not.