Battery Drain - Hot Weather?

I was waiting for my wife at the airport the other day in 95F weather. I had the AC on and the car in Ready. I noticed that the battery would drop to about 2 bars each time before the ICE kicked in and recharged the HV battery.

I think what you saw was normal and that the car will take care of charging the battery properly. You do want to keep the AC running in this type of weather since the cabin temperature is what goes to cool the batteries, through the vent by the right rear passenger seat.

You are correct though that heat does have a negative affect on batteries.

 

If the battery goes down to 2 bars, the engine will start up and recharge the battery until it has 4 (if I remember correctly).
Continue using the A/C as you please - don't need to worry - the Prius can take care of itself

 

Welcome to Prius Chat! I have both a 2004 and a 2010, the A/C on both is powered from the battery.

When you were creeping along in traffic, you were probably on battery power for propelling the vehicle. Once you sped up, the ICE (that's Prius talk for your gasoline engine, for Internal Combustion Engine) propelled the Prius and began charging the battery.

I think the worse thing that would happen is that your fuel economy might suffer a bit. I've only driven in 100 degrees for 3 days last year in my 2004, that was the first time we had 3 100+ degree days in a row in recorded history in Seattle.

 

The Prius pretty much takes care of itself, it isn't going to let the traction battery get so low that it can't start the ICE. Just leave it in Ready and you are OK as long as you have gas in the tank. If you run out of gas get off the road and shut it down sooner rather than later.

The small 12V battery is a different matter, if you are in the Accessory mode or the ON mode you can definitely run that down to the point the car won't go to the Ready mode. Because the 12 Volt battery isn't used to start the engine as it is on non-HSD vehicles it is not very big (about the size of a garden tractor battery) and will run down in a hurry if you leave an interior light on or sit listening to the audio system for to long. Fortunately the 12V battery can be jumped to get the car into ready, instructions in the owner's manual.

 

This is my first summer with a Prius too. I have noticed in hot city driving that the SOC (state of charge) indicator drops lower in bars than in cooler weather. But like our members here have said, the system will take care of itself even though it's a bit unnerving to see the bars drop so low. Your mileage will drop a bit too - it's expected in very hot climates.

 

You don't do anything - just drive and it will take care of itself. The ICE will come on as needed to recharge the battery.

Tom

 

i drove up on i-80 from salt lake to cheyenne today in 100 degree heat and had much the same experience. tooling along at 70 mph and 8000 feet the poor little battery just went down to the last purple bar of death and i was chewing nails. but as everybody has said the little sturdy just kept plugging away and it did recharge. i'm glad for the forum which makes me feel a lot more confident.

 

I'm driving my 2010 for a year now and for the first time all my bars were displayed in the battery icon. Normally the top one stays out but yesterday the last one lit up at the top. In my car manual it says that the battery can't be totaly empty (what i noticed) or full. Anyone else experienced this ?

 

I had a strange one the last couple of days. It's been rather hot and driving round heavy traffic braking and crawling along, I've noticed that the battery will almost get to the top (one bar from full) and then start doing strange things!

It won't allow you to select EV, will run normally but won't ever drain the battery from the second to top bar however much you crawl in traffic on ev, yet won't allow it to fully charge if going down steep hills. It has also switched the engine on from time to time when in this state of almost full charge when stationary with the a/c on full blast. It's almost as if it is too hot but no warning lights are displayed.

I keep the cabin temp pretty cool at around 19c/20c and the battery vent isn't blocked. Is this the sign of a failing HV battery or is it normal when it gets warm?

When I opened the hatch and felt above where the battery is housed it was quite warm to the touch. If I take the car out of town or pull over for a few mins the car returns to 'normal' and all is well again.

The above has happened twice in two days (outside temp 28c), surprisingly just after I got it back from the dealers when the attempted to fix my squeaky front seat.

Any ideas?

 

Yes I see the top bar light up fairly often when driving in the mountains. When using regen braking coming down a long grade the energy will go into the battery until the computer determines it is at its maximum permitted charge, which is less than 100% of it's capacity, the top bar will have been on for a little while when that happens. At that point there no more regeneration is allowed and the engine turns over (just like in the B Mode) to help with braking.

There are some old posts in the Gen2 threads that tell approximately what % of charge each bar represents. Here is one of them: http://priuschat.com/forums/gen-ii-prius-technical-discussion/40109-article-prius-battery.html

 

Everybody relax - the system takes care of itself, as noted by a number of people. The gasoline engine comes on to recharge the traction battery as and when necessary....period.

Drive the car like you would any other - I refuse to get caught up in this occasional hand-wringing over the "technology". For this spot in our garage, the competition was the VW group's diesels. I treat this car, and drive it, just like I would one of those, with no more thought about what's going on with all those computers than I would expend in any modern car.

If the battery display gives you an anxiety attack, look away. Or switch to one of the displays that shows how the juice is flowing, if you want to be reassured.

The AC will work as long as there's fuel in the tank....just like everything else in the car.

 

Having completed 25k miles in 8 months spending 10 hours a day in the car I am fairly familiar with how the car normally works. My concern is that it did something odd - odd in that it has never done it before and has now done it a few times over two days.

I know the engine switches on when in warm up mode and also when the HV battery is low. My concern is that the battery stopped charging when the display showed almost full, but the engine came on and ran for a good 5 or 10 minutes revving quite hard. This happened a number of times over two days.

Perhaps I should just let the car get on with it as no warning lights illuminated. Alternatively I would like to ask for advice from members on here before i visit the dealers. If the car is acting normally then fine, but I would hate the above to be the early signs of a failing HV battery or blocked fan or similar and have Toyota turn down any future warranty claim because I ignored the symptoms.

If you don't ask you don't find out.

 

I have about 25K miles on mine also and I have never seen that type of behavior. If it were mine I would take it in and have it checked, better safe than sorry. Having it checked out will also create a record of your concerns.

 

Interesting behaviour. How hot was the weather when this happened?

If the temperature is really high, then the batteries cannot work too well (hence the fan for the battery pack), probably to a point that they are not used anymore to avoid heating them further by drawing current or charging them (the battery behaves in a way as a big resistor, that heats up the pack when current flows through it).

So if the car was driven, say, downhill and the battery got almost full, and it was hot, it might be that the engine was let running (as if in "B") to avoid charging further the battery and let the engine dissipate the energy, before the battery was completely charged (preventive action).

If you were instead standing at a traffic light, and the engine was happily running with the battery not clearly charging, then I would start worrying...and take it to the dealer.

 

It had been a hot (for here! 28c) and humid day with the a/c on high and I had been working the car quite hard - busy day with lots of fast town driving - quick acceleration followed by quick braking.

Wondering if a combination of all things maybe got the battery hot and it went into the preventive state? Am going to the dealers Monday to get them to check something else so will get them to look at this too.

Fuel economy has been good and the car has fun completely normally since. Was still worrying though.

 

I think you're on the right track, but you're missing something; charging and discharging will both heat up the battery, and if you're standing still, especially with the A/C cranking away, you can easily be drawing over 1500 Watts (7.5 amps or so). My guess is that the battery hit its maximum operating temperature, so the car cranked on the engine, using it to generate electricity to power the A/C and other power draws directly, allowing the battery to remain at close to 0 amps and cool off for a bit.

 

happens to me all the time. I leave work and get stuck in hellish traffic, ac on. The battery empties to only two bars (once it went down to only one). I would get panicked at first but now I learned to trust the car. The only thing that bugs me is that when the bbattery drops, then the car will turn the engine on to glide just 3 meters

 

It is normal for the car to kick the engine on when the battery drops to 2 bars. My concern was that mine did this with 7 bars lit!

I took the car in to the dealers on Monday and they checked it on their computer and it turns out that Macman408 is correct. The battery went into a 'safe mode' or similar as it was getting too hot with the a/c drain and hard city driving for about 5 hours.

The garage weren't overly concerned as the Prius is designed to protect the battery, so at the moment I'm happy again.