Traction Battery Discharged In A Day?

[Dutchguy]

For three weeks I am now the proud and very happy owner of a new Auris

The other day I was out for a short visit some 8 miles away. coming back from an easy going drive and parking up back home at night I noticed the traction Battery was charged two bars below full, quite normal. The next time we went out about 20 hours later I noticed at start up that the Battery traction Battery has only two bars left from empty. Once driving the battery charged to a normal level again in about 5min.

As far as I can remember nothing special occurred when parking up. No alarms, no beeps. I did not perform the hazard light "trick", but as far as I know this relates to the 12V battery and not the traction one.

The next day driving all seems to be back to "normal".

The dealer (sales person) said he's seen this before, but reckoned it was due to a temperature change.

Googling this I only found one suggestion that this could be due to a recalculation of the SOC of the battery.

Is there something I should be worried about?

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[Chris Dance]

Our Prius goes from full to two bars regularly when only making local runs. If I do a long run the indication is full and stays that way for some time.

I do not think you have anything to worry about, you would have had a warning if something was drastically wrong. Other members may have more knowledge of hybrid electrics.

[Dutchguy]

I have seen the indication going from about 3 or 4 bars to about 1 bar from full during driving, but never over night when the car was standing on the driveway. Does this occur overnight when you're not using the car?

I just realised something. I have used the EV mode for the last 200m on a slight incline before it occured. (Just as a trial). this may have drained the Battery a little. 200m should be possible, right? Maybe the indication is just a little slow?

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[kithmo]

Don't take the SOC meter as gospel, it's only an estimate and it's not an instantaneous readout. As you said in your last sentence there, the refresh rate is slow sometimes. I suspect that if you had turned the car back on straight after turning it off, it could have dropped a bar then.

I've seen mine drop to two bars where the engine should kick in to charge it and the engine kicks in as I accelerate then drops out and into EV as I take my foot off and the SOC hasn't moved, still on two bars. Sometimes first thing in the am when it's on two bars and the engine starts up, it takes a mile or so before the meter moves, other times it goes up after only a few hundred yards.

[Dutchguy]

Thanks guys. This does makes sense.

On another matter, I've never seen the Battery completely full, as in all bars green. Not even after a longish motorway drive. Is this normal?

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[timberwolf]

Yes, it is normal.

You really should try not to worry about the state of charge of the HV Battery.

Theoretically, if you were at the top of a long hill and started to go down that hill, you'd want to start with the HV Battery "empty", so that there was more room to store the energy that is captured during regenerative "braking" (regenerative braking by applying the brake pedal or simply easing off the accelerator pedal to control you speed down hill).

The Hybrid system cannot predict the future so there has to be a compromise, and having the Battery state of charge at either "empty" or "full" is not ideal, it would be better to keep it somewhere in the middle, available if you need a sudden demand for acceleration when the electric motor helps out the petrol engine, or with room to spare should it be need to capture energy through regeneration and reduce the energy waste as heat of friction braking.

[Grumpy Cabbie]

I have seen the indication going from about 3 or 4 bars to about 1 bar from full during driving, but never over night when the car was standing on the driveway. Does this occur overnight when you're not using the car?

I just realised something. I have used the EV mode for the last 200m on a slight incline before it occured. (Just as a trial). this may have drained the battery a little. 200m should be possible, right? Maybe the indication is just a little slow?

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Yes there is a delay and also probably down to temperature.

Don't worry about it, the car will let you know if there's a problem. The HV Battery is never full or empty as the car only uses between 35% & 75%, with 35% being displayed as empty on the screen and 75% being totally and utterly full after a long run down a steep hill. This small area of usage is to allow longevity of the Battery. Remember all those horror stories years ago about hybrid batteries only lasting a couple years before needing replacement as people were comparing it to their mobile phone or cordless drill? Well the reason phones or drills (or garden solar lights) only last a few years is because they're cycled 0%-100%. The Prius Battery would only last a couple thousand 0-100% cycles before packing in too, but if it's cycled between 35%-75% (usually a much narrower band) it can be cycled 100,000's+ number of times, hence lasting the life of the car or 10+ years.

Using EV mode up a steep hill is not really a habit you want to get into as it probably over stresses the battery. It's a petrol car with electric assistance, not an electric car. EV is a gimmick and best used for a little fun or to move the car off the drive etc. You'll be drawing more power out of it quicker and faster than preferable. And as you've seen, there's a small delay in the monitoring.

Anyhow, don't worry about it. You have an 8 year 100,000 mile warranty or upto 10 years unlimited mileage battery warranty if you have a full Toyota service history.

http://priuschat.com/threads/why-is-my-battery-never-full-or-empty.139653/

[Dutchguy]

Thanks Grumpy Cabbie.

It's good to know the system will keep it all under control and warn me if there is something wrong.

I did use the EV mode just for fun and forgot I had used it.

It is surely not very powerful in EV mode. Like others have posted, you will hold up normal traffic when accelerating from zero this way. Nowhere near the 60kW what is quoted. I guess power delivery is reduced in this mode and full power is only delivered when it's supplementing power to the ICE when needed?

Cheers

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[Grumpy Cabbie]

There is power in the EV side of things but it is often held back to protect the Battery.

Drive down a long steep hill and don't put the car in B mode to ensure the HV Battery is filled as much as possible. First you'll find that the Battery indicator goes totally full, next you'll find the brakes go funny as they switch to normal friction braking and the regen is switched off (which shows how much difference regen makes all the time - you'll be surprised how weak normal friction only braking is), then if you keep going down this steep hill you'll find the engine starts to rev and rev louder and louder, but using no petrol. This is the car trying to burn off the energy it's receiving but doesn't now need or want. At this point you'll likely be at the bottom of the hill. Now try driving the car and you'll find it'll accelerate rather nicely but won't switch the engine on until halfway up the power bar. The car will run like a BEV keeping up with traffic etc, but it will be reducing the battery levels quickly and the acceleration on electric starts to return to normal. After about a mile or so the car has returned to normal.

So it gives a small glimpse of what power is there in the electric side of things. Such hills are not great for a hybrid if you have to drive down one every day unless you use B mode. Once or twice a week will be fine as the car will look after itself and the above description shows how.

[Dutchguy]

Interesting. I will try it when I encounter such a hill. The hills we have around here are not long and steep enough to fully fill the Battery.

Thanks

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[Cyker]

Does it get quite cold overnight? Cold tends to depress the voltage in chemical batteries, and most Battery level indicators are really just glorified voltmeters so that would likely account for the apparent overnight loss if there is quite a big temperature differential where you are.

The thing about why it doesn't fully charge has been answered pretty comprehensibly by everyone else :)

I think the brakes on a Prius are as small or smaller than the ones on my Yaris and you really don't want to rely on them for harsh braking from speed, so it's desirable to hold a reserve for the regen brakes!

[Grumpy Cabbie]

Significant warm to cold temperature changes can knock 2 bars off a normal charged Battery, but this owner has gone right down to 2 bars/empty.

It definitely sounds like driving the car up a slope on EV (which will seriously and quickly deplete the battery) together with the delay in the update of the screen. It's about every 15-30 seconds or so. A perfect storm to reduce the Battery level quickly.

And not to worry. Mine does it too, though to worry everyone, mine only started to do it as it got more worn out and higher mileage. It used to be a smooth drop from 6/8 to 5/8 bars, 4, 3, to 2/8. Now it goes 6/8, 6/8, 6/8, 5/8, 2/8 :( and it doesn't go quite as far on EV mode like it once did. Still, it passed it's Battery test so I'm not worried.

The op has nothing to worry about. My HV battery has taken a hammering with town traffic. It's still hanging in there fine. If someone uses their car privately, then the battery will be good for the life of the car.

[Dutchguy]

It has not been very cold overnight. About 9C while daytime temperature was about 12C. That's why I was surprised initially. I think the fact I used the EV mode for the last 200m may have caused it. However saying that, I usually seem to drive with the EV light on (usually in eco mode) for that last stretch in my residential area and have not seen the issue. Just wondering, is there a difference between the forced EV mode and the "automatic" EV mode?

Grumpy Cabbie already put my mind at rest, just being curious. Sorry if this is a newbie question.

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[Grumpy Cabbie]

Yes there's a difference between EV MODE and electric running in normal mode. EV Mode allows a faster acceleration but also further pedal travel - generally. Not sure what screen the Auris has but the gen3 Prius has a hybrid gauge that shows the levels and times the engine will come on etc. EV mode doubles the level of electric running upto a preset limit of 31 mph displayed (about 28 mph actual).

But the car has so many variables depending on so many factors that it's a feat of programming. Just enjoy it. It fascinating and appeals to the inner nerd in us all.

[Dutchguy]

Does it show :)

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[Peter2673]

Suggestion: Just go to display settings and TURN OFF the left hand section of the dashboard display. It took me five years of ownership to realise, but sparing yourself the cognitive effort of monitoring what the car is up to is really liberating. Furthermore, and really surprisingly, my fuel economy improved fractionally.

Pete