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    dwill207 Junior Member

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    My hybrid battery has been running low the past few days. This has never happened before, but it has been around 90 degrees out during the same few days. I noticed it this morning as I left for work. It was down to two bars when pulling out of the garage. I was getting pretty nervous, but at least the ICE was charging it. Although, it never fully charged the system, as I live pretty close to work. On the way home, I tried to drive around for a mile or so to see if I could get the battery fully charged.. The best I could do was four bars. Is this typical of the hybrid system in warm weather? Should I be worried about it? Also, the system has a fan, why doesn't it come on if the hybrid battery is so temp sensitive?

    Thanks...
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    cnschult Active Member

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    you're gonna want to wait for Seilerts on this one but I want you to prepare yourself for some bad news.

    I truly hope Seilerts says nothing major is wrong. But while we're waiting for Seilerts to see this thread, why don't you give him some more information:
    when was the 12V battery replaced and was it DENSO or Optima?
    how long does the car sit at work and what time do you get out of work?
    what is the air temp when you leave work and how short is your drive home?
    what is the air temp in the morning and what time do you leave for work?

    and the most important piece of information we need is Does the gas engine (ICE) turn off at a stop light after it has been given enough time to warm up?

    I didn't ask if any warning lights were on cause I am under the assumption that if they were you would have mentioned it in your original post, so just confirm that there are no triangles of death or christmas lights on your dash.
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    dwill207 Junior Member

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    I just replaced the 12v a month ago, and it's OEM. Not sure if it's Denso, but it was from the dealer.

    The following info is for the shift I worked today:

    The car sat for a little more than 8 hours. I left work a little after 3pm.

    The air temp when leaving work has been 83 and my commute is very short. Barely a mile.

    The air temp in the morning has been in the mid 60s and I leave to work about 6:15am.

    The ICE does shut off at lights after warming up, and/or stays on long enough for the battery to reach 3 to 4 bars, then shuts off.

    I did use the AC on max continuously.



    On Friday, (the day before the noticeable drain in the morning), I worked 10am to 6:30pm

    When leaving to work the temp was about 75. The car sat for 8 hours in the parking garage. When leaving work the temp was over 80, not sure of exact temp. I used the AC on max. Also, the car sits in the garage at home upon arrival and overnight.

    Also, no warning lights of any kind on my dash. Thanks for the quick reply.
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    KK6PD _ . _ . / _ _ . _

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    Well considering you run the AC full, no wonder your battery is run down. I can sit in the line at In and Out for 10 minutes and it sucks my battery to purple! Turn the AC off, you will be amazed how much gas you will save.
    Also with only a one mile commute, I don't see why you just don't walk! The car will waste gas warming itself up only to be driven a mile and parked. Not much time there for a charge! What do you get for MPG anyway??
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    dwill207 Junior Member

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    I know... Everyone tells me I should walk. And I would but I never wake up early enough. I didn't buy the car for my work commute. My gf lives 62 miles away, (one way). I usually get 40mpg. On one fill-up on a trip to Southern California, I managed 50.

    Before writing this reply, I checked the battery and it was at 4 bars. I ran the heater to let the ICE run for a bit, and it charged it up to 6 bars. I took the car out on a 10 mile loop, (with the AC off), and was able to get it to 9 bars...? That's what I'm used to, but it IS cooler at this time of night. It seems like the battery is only "almost dead" in the heat with the AC on, on really short drives. I'll check it again in the morning before work and see how it looks.

    I have to state again, I've never seen the battery that low before, which is why I'm wondering if something is wrong. It's always held up pretty well with my short trips, and the AC being on.
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    cnschult Active Member

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    With having a garage and with such a short commute and your need to run the a/c on max I highly recommend figuring out a way to permanently install a trickle charger on your 12V battery, especially since it is a DENSO and not an Optima. I think the 12V runs your a/c, then your HV battery drains to charge the 12V, hence the drained HV battery. The trickle charger will greatly extend the life of both your expensive HV and cheap 12V batteries. In addition you will see a large improvement in fuel economy, which I'm guess you are in the low 40s or possibly high 30's.
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    dwill207 Junior Member

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    I don't have the slightest clue how I would attempt to hook up a trickle charger to the HV battery.

    I checked the battery Monday morning and it was at 9 bars before I pulled out of my garage. It seems to be back to normal now. So, I think the problem I was having was definitely heat related. It will be hot again this weekend, so I'm anticipating the issue will return. I'm wondering how the car will do on 100+ degree days in the summer. Just out of curiosity, is there a manual way to get the hybrid fan to turn on?
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    cnschult Active Member

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    no you misunderstood me i am recommending you install the trickle charger on the 12V battery which runs accessories such as the a/c. I am not a battery expert like seilets but I think this would keep your HV battery with more bars and improve your mpg greatly.

    touching your HV battery is suicidal WALK AWAY FROM THE LIGHT!!!
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    edthefox5 Senior Member

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    AC compressor runs off a 200 volt power supply from Inverter.
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    edthefox5 Senior Member

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    You answered your own question. Driving a Prius such short distances routinely is hard on the Hybrid/Traction battery as it will never see a full charge. And its very hard on the 12 volt battery too which is why you see recommendations to trickle charge the 12 volt battery. Both batteries will never see a full charge.


    Not sure why your nevervous at 2 bars as you will see that alot anyway. It will turn on the ICE and make it run and charge the battery. I see 1 purple bar alot sitting in a drive through. 1/2 mile down the road I'm back up to 4 bars.

    Outside temp is not that hard on the Hybrid battery just sitting there if you have a good tint job. If no tint that will be a hot car unless you use a good windshield cover. The cover they sell here on PC SHOP is excellent. Custom fit and mine is 4+ years old and in still excellent shape. That really helps keep cabin temp down.

    I wish I was only a mile to work. I would walk it at least 3 times a week. Fast walk it. Leave your work shoes at work and wear sneakers to & from.
    1 people like this.
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    qbee42 My other car is a boat

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    Where did anyone get the idea that the hybrid system is ever supposed to fully charge the HV battery? Under normal operation, the HV battery should not fully charge. Only special cases, such as long downhills or cold weather, cause the battery display to go up near the top.

    If the OP has a low speed run coming into his driveway, he will almost always end up with a low SOC as a function of normal operation.

    Tom
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    cnschult Active Member

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    you are absolutely correct, I only recommended the trickle charger due to his short one mile commute and need to run the a/c on max. I feel this will extend the life of his Denso since he didn't buy an optima and it will also improve his FE with that higher initial surface charge on the 12V
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    seilerts Battery Curmudgeon

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    The car has a built-in trickle charger: MG1. Turn on the car and let it idle until shutoff. That is sufficient to charge the HV battery for a couple of months.

    If it has been a California car all its life, then it is covered under CARB warranty 10 years/150,000 miles. Don't worry about the battery if it is still under warranty.
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    dwill207 Junior Member

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    Don't worry... I wouldn't even think of messing with the HV battery. haha
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    dwill207 Junior Member

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    I guess I misspoke. I didn't mean 'fully charged'. What I meant to say was, it didn't charge back up to where it normally is. In my car, that's usually 9 bars.
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    dwill207 Junior Member

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    Thanks for the info. I just wanted to know if there was anything to worry about. I'm not used to the battery getting into the purple range. That rarely happens with my car. But I guess it will be frequent with hotter temps and MAX AC use, coupled with short trips.

    I do a lot of walking at work. I have a pretty physical job, so the last thing I want to do is walk home. (It's at a steady incline.) : )
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    edthefox5 Senior Member

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    Your welcome. I have a physical job too so walking to work would not be fun.
    Good luck!!
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    uart Senior Member

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    There are only 8 bars. If either one or two bars are displaying then they are purple. If three through to six bars are showing then they're blue, and if seven or eight are showing then it's green. Normal operation is 5 or 6 bars.

    I guess you must be counting the white spaces between the bars as well. Just count the colored bars (1 through to eight) otherwise you'll confuse people.
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    Asmodeus2112 Junior Member

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    Dwill, it's not you or how you operate your car. I have the same problem with my 2006. Works fine as long as the weather isn't in the 80's and sunny. But leave it in the sun in hot weather and a minute or two into driving the battery bars drop and ICE is constantly on charging the battery and the car drives like poop. There are some others that have cars with this problem too. I'm trying to figure it out right now as summer is coming and it's starting to happen again.

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