Hybrid battery and AC

The AC compressor runs off the HV battery, so it'll definitely cause the charge to go down quicker than usual. In my car, without AC there is usually a 2-4amp draw on the HV battery. AC on raises that to 7-13amps.
By low, do you mean low fan speed or a higher temperature?

 

In general, this is basically normal...in winter cold your engine runs to make heat for your comfort, and this tends to keep the HV battery charged in the green bars a lot of the time on our car. In summer, the A/C drains the battery and you engine should come on automatically to keep your battery charged to the lower level. Assuming your system is operating properly, the car will automatically keep the HV battery charged. I never see too many green bars in the summer.

I am not quite sure all the ways to accidentally drain the HV batt (not a good thing to do), but the main way to do this is run out of gas and then keep driving until the HV battery drains. Don't do this however.

 

It's normal for the HV battery to drain somewhat when the aircon is running and the engine is stopped. It shouldn't hurt anything, when the state of charge (SOC) gets down to about 2 bars it will kick the engine off and start recharging it.

If it's draining faster than previously then it could be one of the following:

- The HV battery could be losing some capacity.

- The aircon may not be working as efficiently as it was previously.

- It may just be a perception issue, if for example you're starting out with a lower SOC. This is because the SOC display is very non-linear, with lower bars counting for much less charge than bars 6 and 7.

BTW. What SOC (how many bars) do you typically have before this starts, and roughly how long do they take to drain?

 

How many miles on the car?

 

The Prius A/C is electric, drawing power from the hybrid battery, that way you can run the A/C while going down a hill or sitting at a stoplight without having the ICE turning on. There's nothing wrong with your car like anybody is trying to say. If it's a hot day then the A/C has to work hard to cool the air, which means more power from the battery is required. The fan speed doesn't matter. What matters is how cold you want the air coming in your car to be. When your battery gets low, the ICE turns on to help charge it.

 

The system in the Prius look after the HV battery well except under one condition and that is in neutral. The engine cannot start in neutral but the A/C will continue to discharge the battery so this must be avoided to stop the HV battery being discharged to a point where it cannot start the engine.

John (Britprius)

 

Katia P.... I have a 2nd generation 2004 Prius and have never encountered your problem.
As far as I know, the A/C compressor is powered by a 12 volt electric motor drawing power from the 12 volt system not the high voltage propulsion battery. If anything, the gas engine should run more often to recharge the 12 volt battery.... something I notice happening in hot weather as my mpg drops a couple of miles per gallon when I use the A/C. I live in the Washington DC area, thus my A/C got a good work out last week with the week long 90+ temperature.

 

Not so. The AC compressor is running on ~230VDC HV system power. That is the reason why there is a strong requirement, with any work on the compressor that involves replacement of the oil, to use special high dielectric ND11 oil from Toyota (or equivalent). The engine will come on to recharge the HV battery when it needs it, if siting at a stop with AC running. The OP mentions 15 min, which is quite within specs. In hot weather, it is important to run the AC as that is what also keeps the HV battery cool, by means of the cooling fan air intake on the side of the back seat.

 

Re: The AC compressor is running on ~230VDC HV battery power.
Thank you, As i wrote, I was under the impression that the compressor motor was 12 volt.
BTW... the side vents for cooling must be on later models as my Prius is an early 2004 with cooling for both batteries coming from the front. I learned this when I had a new 12 volt battery installed after 6 years and the mechanic had to remove the vent in order to change the battery.

 

Ok, here's what's happening with your Prius. When you start out on a trip the HV battery gets hammered pretty hard in the first few minutes. This is due to a number of factors.

- It uses EV propulsion in preference to the engine for the first minute or so until the cats are warm.
- It can draw a significant amount of HV power in the first few minutes to recharge the 12V battery.
- The aircon is also working pretty hard to initially cool the cabin.

It seems that, as our HV batteries age, quite a few of us are noticing this issue with SOC dropping fairly rapidly in the first few minutes after starting. The solution that works well for most people is simply to let the engine warm up (idle in "P") for about 40 to 60 seconds before driving off. Try it and see, it really works.

 

Thats normal. If you sit in a drive through with the ac and lights and radio on it will hit purple pretty fast. Same thing in stop & go traffic. See that in mine everyday.

The second the battery goes into purple it will force the engine to run even though its sitting still.

But the car should go from purple to about 2 or 3 bars in about a mile of normal driving. The battery ecu will not let the hybrid battery go to low or to charge to much.

You'll know if somethings not right in battery town if it throws a Hybrid warning on the dash also. Do all you can to keep the interior cool. Don't drive around with the windows down. Keep cabin cool and dry to preserve the Hybrid battery.

Use a window shade you can buy here at the PC SHOP. Its custom fit to cover the Prius windshield and insulated. best cover ever. Mines going on 6+ years old. Don't let the cabin get sweltering while its parked. Your just cooking the Hybrid battery.

 

Yeah my 2007 with 71k does the same thing. Actually when I bought it last year and it only had 54k on it, I noticed that sitting in the drive-thru with my a/c blowing at McD's waiting for my $1 ice tea, lol, would drain the battery pretty quick down to the purple bars.

But it seems to charge back up quickly enough with the ICE running. I just hate driving the car with the battery in the purple, the acceleration sucks. So lately I manually cycle the a/c button when Im in the drive thru to keep it just tolerable in the cabin. Then when I pull away, I leave the a/c on.

 

Yes I try to take it easy on the car when in purple as that puts max strain on the motor to turn mg1. Max load on mg1. I bet the temp really spikes on mg1 during that event. Its all about not drawing a sh*tload of current through the mg windings.
Manually cycling the ac is excellent idea. I keep forgetting to do that. I will do that next time. Thanks.

Just an excellent car though.