2007 Prius Battery Level Indicator

2007 Prius battery level indicator - can you use it?
I was working on a larger post about Prius plug-in conversion kits (come back soon for it) and this mini-rant I wrote up for the post did not quite fit here, so I made a separate post for it.
Here is what the peculiarities are:
The energy screen of the 2007 Prius has a battery charge bar indicator. What annoys me is that the indicator seems to be showing the entire battery’s charge level but the charge controller is designed to keep the battery at least 60-70% full at all times. And at all costs I should add. You may be going uphill and may be needing some extra boost from the electrical motor but the charger draws power from the gasoline engine instead because it’s time to charge. No matter what. So, basically most of the indicator is always static and only top two or three bars get added or deleted. So, if you though you have 70% of battery power remaining and possibly adjusted your driving (road conditions permitting, of course), you’d be wrong because as far as the battery charge controller is concerned, you don’t have any power left in the battery.

So, here is my question for Toyota designers working on 2009 Prius: why don’t you guys calibrate the level so it shows all the power level you have ability to “play” with. If the battery has to hold the same amount of spare power to stay operational longer- that’s fine but I don’t think the level should show that. Just show me what I have control over. After all, is it not what the instruments in a vehicle are for? Simply make 2007 60% ZERO in 2009 model.

22 Responses to “2007 Prius Battery Level Indicator”

  1. David Says:

    I have seen my display (2007) show anywhere from 7 to 2 of the 8 bars. It’s green when there are 7 or 8, blue when there are 3-6, and red (I think) when there are 1 or 2.

    My understanding, from some Prius chat postings that I can’t find now :^), is that the display *does* show only the operating range of the battery, not the absolute range. So I think it does what you are suggesting. I wonder why your indicator never gets down in the lower part of the range.

  2. info Says:

    That’s interesting, David. I should take another look at that. I have specifically tried to get it as low as possible but could not get it any lower than 5 bars.

    I drove around a quiet and flat neighborhood where I could go 15-20MPH without giving people behind me much grief. I was specifically trying to maintain the speed so the ICE would not turn on. Basically, what happened was – I would run in all electric until it turns blue (no pun) and goes down to 5 bars. But after that the ICE would start and would not shut down no matter how slow I go until the bars go up into the green range.

    Considering all that behavior is controlled by the computer onboard, maybe there are some differences in firmware loads (for lack of better term) even though I also drive 2007 Prius. I should have the mechanic look at it when they take it in for a service next time. My feeling is though that they’ll find nothing as they are still a bit shy of electronics there and most they can do is to swap parts. I just can’t think of my dealership upgrading Prius computer’s firmware for me…

  3. Dominick Says:

    I bought a 07 Prius about 3 months ago now and have had the same problem most of the time. I have had the bars down to 2 a couple of times with the car not moving and the air on. I would love to be able to control (stop) the engin turning on in traffic. I’m hoping someone comes up with a way to do this.

  4. Jon Says:

    From what I’ve read on the net, the European and Japan versions of Prius have an extra button that puts in in fully EV mode. The ones the the U.S. don’t have it.

  5. Philip madsen Says:

    Aussie 06 model has the EV switch. EV mode has never gotten me more than 300m before it beeps and starts engine. Tried this from a full 8bars green battery.. same difference. it aint an EV till you convert to PHEV

    You never want to see the battery below 2 bars, or your Engine might never start, also remember the big battery charges the little 12v b.

    sitting in the car in park, but ready with the AC on, will last forever, as long as there is petrol.. About 2 bars the engine comes on for a while and recharges the battery a bit and goes off again, keeping the battery floating at 2 bars. Phil

  6. Bob Says:

    I wonder if the guys writing here know what they are talking about. I have a 2005 Prius and have seen the battery indicator go down to one (red) bar many times while driving up long grades. This happens even when the car is not under a load (such as lights or A/C). I talked to the service pleople at my dealer and they say this is “normal,” and that I do not need to bring the car in to have the battery checked. That comment does not mesh well with the people here saying they have never seen the battery charge indicator below the blue range–and especially does not fit with the remark that the battery level should NEVER be below two bars or the engine might not start.

  7. info Says:

    Bob, I stand corrected.

    Since the original post was written I did have a chance to see the battery indicator down to two magenta bars. I have to admit, I’m not sure exactly how you can make it go any further down (to one red?) because as soon as the indicator hits two bars the engine kicks in and nothing can stop it. The terrain is mostly flat here, no long grades, so this might explain the lack of red.

  8. pjp Says:

    I’ve also never seen lower then 2 magenta bars (2008 American version). The engine does kick in and theres nothing you can really do about it except run out of petrol.

  9. pjp Says:

    Actually I have seen it go all the way down – when getting my windows tinted, the battery meter did hit all the way to zero – however that meter on the display is relative – if you see green, that should be around 70% charge, and if you see nothing, that should be around 40% charge, from what i’ve read. the tinting people, for some reason, insisted on the car being in “accessory” mode throughout the job. That brought the OSD’s battery meter down to full empty, but there was still energy and the car still had no problem starting up after that.

  10. Mike Cohn Says:

    I’ve driven many, many Priuses (don’t ask, don’t tell) and can assure you the slight variety in the battery ranges people experience are normal.

    One person said they are usually in the green while many report they are in the blue. Being in the green all the time, by default is a little unusual, but it does happen with some cars and recalibration results in nothing but wasted time.

    Over time, many of those “always green” cars eventually settle into the blue range anyways.

    As for “bob” who got “red” literally and figuratively, when you go up REALLY steep grades that are REALLY LONG, it will drain the battery to the purple level.

    Even though it’s designed to accomodate that kind of drain/fill cycle, I wouldn’t want to do that DAILY over a 10 year ownership cycle.

    Batteries don’t wear out from occasional spikes, they wear out from extreme and continuous spikes and loads (expend/regen) like sugar levels and pancreases.

    Imagine a fat blob of a man who stuffs face with sugars, fats and starches all day long and keeps taking diabetes and heart disease meds but does nothing to change the diet, lack of exercise or the emotions that keep him in his cycle.

    Even though the meds are helping for now, there will eventually be weaknesses that the meds can’t help and ultimately he will die.

    The same analogy goes for the Prius battery – there are all kinds of checks and balances (meds) already in the vehicle that counteract the negative effects of severe and frequent discharging/recharging.

    But don’t keep doing it just because the manufacturer’s reputation makes you think its ok (like meds). Change your behaviors, your driving routes (if possible) and your emotions behind doing what you do to make your car (or your body) really last.

    If you can’t help but live at the top of a 15% grade that goes on for 2 miles one way, then, well, you’ll have to wait and see and maybe make a change of car. But for the remaining 99.999% of us, this situation won’t occur.

  11. Codemonkey Says:

    Sorry this is a little off topic, but if you run out of gas will the car run as an EV until the batteries run out? Just Curious.


  12. CFL-CTA Says:

    I’ve seen the battery indicator lower than that. Only two bars, and they were purple.

  13. Bill Says:

    I have a new blog. No one has mentioned having an all-yellow display. This morning on a 40 mile trip on a four-lane highway, the battery display went full yellow stripes. I have had the Prius for 3 years and this is a first.

    I have seen the display from full blue stripes to all white background (no stripes). I cannot recall ever seeing green or red.

  14. Doz Says:

    Well my (UK) 2008 T3 Prius gets down to 2 purple bars when I EV it up a hill near my home.

    2 purple bars is the lowest it’ll go.. the ICE kicks in and charges the battery.

  15. Sandy Says:

    The battery state of charge the car tries to maintain is also dependent on altitude. Around sea level, it tries to maintain about 6 out of 8 bars. At around 8,000 feet, it will try to maintain about 3 out of 8 bars. Apparently, the reasoning is that at sea level, there is no reason to maintain a lot of spare room for opportunistic regenerative breaking — there can be no long downhill if you are already at sea level!

    The way the computer manages the battery level under various conditions of acceleration and breaking is far more sophisticated than most people, beginning techies included, could manage. The way most beginners try to use their newly installed EV-mode button, they actually reduce their mileage by unecessarily using the battery path, when direct path for that power level from the engine would have been more efficient. The efficiency gained by the batter is primarily from the recovery of breaking energy, and avoiding using the ICE under very low acceleration power demand. Generally “using” the batter as much as possible otherwise REDUCES mileage.

    Uninformed discussions like some of the comments above are probably judged by Toyota as a potential a “customer relations” problem, and I hope Toyota doesn’t remove the motor energy flow display for that reason. I would not be suprised if they removed the display in a future edition, eliminating all these “frustrations” with how the battery is behaving, and have people just get good mileage instead.

  16. LM Says:

    Everyone above is wrong. I drove a Prius through the Sierra’s, tons of gigantic up and downhills. I mean, really, really, really long up and downhills. The battery will go to no bars at all, and it will fill up to all bars as well.

  17. michilds Says:

    Re: running out of gas. The Prius will run in EV mode after running out of gas. This happened to me, the dash lit up like a Christmas tree, we pulled to the side of the highway, then turned off the ignition. When I turned the ignition back on, I was able to drive to the exit (I was right at the ramp) and up the ramp, across the highway to a gas station. After refilling, all the riot lights eventually went away. I don’t recommend it!!

  18. Dennis Carr Says:

    Try leaving the dome light on like a moron I know!

    One, you ain’t going nowhere and the simply job of connecting a jumper box gets extreme because they have put itty bitty jumper points to attach to! Also, just try and find metal on the front to attach ground to. Better practice this before leaving home.

    Anyway, with the help of the friendly tow truck man, the start is WEIRD! No fuss no muss, cable on and touch the button and your on! Engine of course starts aa soon as the micro-bits settle down and go to work.

  19. Gechab Says:

    I have a 2008 Prius touring. It went from 2 bars in rush our traffic to full in 20 min. I’ve never seen it do that before. Usually, it just stays pegged at just over half full. I called my local Toyota service and they said it’s normal and that unless there’s a big red triangle in your dash display, your battery’s fine.

  20. info Says:

    Thank you for your comment, Gechab. Yes, I agree, there are so many variables that you can never actually know or predict how many battery bars you have. Since Prius does not actually drive on electric power only (not too far anyway), this is not even a very critical information.
    I did want to ask you an additional question though: when I drive in rush hour traffic, it usually drains battery, not recharges like in your case. Even if it’s a very slow downhill traffic which you’d think would not touch the battery ’cause it just rolls downhill by itself, it still usually drains the battery to two-three bars if it’s long enough. So, do you always drive with headlights on? I do and those are HID headlights, so I’m thinking headlights may be “helping” in draining the batteries.

  21. Karen Says:

    Am I worrying for nothing? My 2007 Prius battery bars have recently went to 2 bars. I was just driving a few miles around where I live. I thought “Is it just going to die?” with the battery showing such a low bar. It’s usually 6 blue bars. I goes down fast to 2 bars and then it can go up to 7 green pretty fast.

  22. info Says:

    Unfortunately, it is a cause for concern. But the good news is that it’s possible that it may be fixed. Over time the cells in the battery deteriorate, and not at the same rate. And the charge controller may no longer be able to keep their charge/discharge rates in sync. Although you cannot completely fix it, you can at least re-balance the the individual cells that comprise the battery, and make the controller able to charge them again properly (although it has to be said that, unavoidably, in the 13 years they did loose some of their initial capacity).
    My son in law recently did that procedure – re-balancing the battery – and was able to fix (as in prolong the usable life of) the battery pack on their 2008 Prius. It required a purchase of a special couple-hundred-dollars device and getting access to the battery underneath the backseat. If you feel comfortable doing car electrics (this part is high voltage tho), you may be able to do it yourself. Otherwise I would advise getting it to a car mechanic that is familiar with Prius batteries.