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Worry about Batteries for no reason?

Discussion in 'Gen 3 Prius Main Forum' started by David Beale, Dec 24, 2014.

  1. David Beale

    David Beale Senior Member

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    Should listen to myself more often. ;)
    The weather here has been so nice this month I decided to start driving the Prius again instead of the guzzling FJ Cruiser (even though they are practically giving the fuel away).

    So this morning I disconnected the Battery Tender and drove Pearl S to the mall for my walk. When I shut her down two and a half months ago the battery indicator was at about half full. This morning when I put her in "ready" it was one bar from the top. So much for consistency.
    Of course with the Battery Tender on during that down time the 12V system was just fine.
    Tyres were also fine (I did put a few extra pounds in them just before it got cold to compensate).

    In short, once you take care of the 12V battery, don't worry about the car.
     
  2. irrational

    irrational Member

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    Are the 12v batteries in the Prius that sensitive that there is need for a battery tender for only 2 months of inactivity?

    I've used diehards is most of my vehicles, and I've let them sit for 6 months before without issues. Just puzzled, as 2 months doesn't seem that long to leave a car parked.
     
  3. fotomoto

    fotomoto Senior Member

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    Yup. Hybrid 12v batteries don't need to "crank" start the engine like non-hybrid cars so it's much smaller than the batteries in those too. The 12v brings the car online and opens the relay to bring the 300v traction battery online.
     
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  4. irrational

    irrational Member

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    Interesting. So, if I understand; Because they're smaller, they're more sensitive to being left idle.

    Thanks.
     
  5. bisco

    bisco cookie crumbler

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    it's more a matter of battery health. if you know that you're car came in and the battery was never run down to empty before you purchased it, and you've never run it down by leaving a light on or a door partly open, then your fine for two months. but the design of these batteries does not allow for deep discharge without damage. so, one incident, and you may be on a tender for any longer term idleness. i have never had an issue for up to 6 weeks in the middle of winter and batteries no older than 4 years.

    on the other hand, my 9 year old dodge dakota with oem battery sits idle for months at a time, and cranks like a champ. uh-oh, i shouldn't have said that.(n)
     
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  6. loansum

    loansum Junior Member

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    Good info. At a shopping center the other day, a guy walked in my direction holding up jumper cables. I avoided him, since my trunk was full and thought that the tiny Prius battery probably doesn't have much cranking power. My 2010's V's battery is like 5 years old. When should it be replaced for good preventive maintenance?
     
  7. bisco

    bisco cookie crumbler

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    anytime now would be a good conservative time. and you were smart not to offer a jump.
     
  8. Mendel Leisk

    Mendel Leisk Senior Member

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    I just scanned the Prius Owners Manual, and didn't see any specific caution against using the Prius to jump-start another vehicle. That, said, our previous Honda Civic Hybrid Owner's Manual did have such a caution. I'd say the Prius is in the same league, has a very small 12 volt battery, best not used for jump-starts.

    All that aside, that guy should just talk to mall staff, they likely have a jump start station, one of those high capacity contraptions, on wheels.

    If you're letting the car sit for a couple of months I'd go further than a few extra pounds in the tires. For sure bring them up to max pressure indicated on the sidewall. Or better, if you can: jack up the whole car slightly and put in jackstands. So that the tires are still touching, but with little pressure.

    Also, just to clarify: you're charging the 12 volt, and it's the hybrid battery indicator that went from half to nearly full, right?
     
    #8 Mendel Leisk, Dec 24, 2014
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  9. bisco

    bisco cookie crumbler

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    maybe the 12 volt charged the hv battery.:p
     
  10. fuzzy1

    fuzzy1 Senior Member

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    You don't need to worry about avoiding them. If asked, you have an extremely solid excuse to decline, because your Prius MUST NOT TRY TO JUMPSTART ANY TRADITIONAL VEHICLE. In addition to the battery being too small and not intended for crank starting, it also puts you at high risk of a high-four-figure repair bill for blown out electronics.

    Given no other choice, it will be far cheaper for you to pay for their service call, out of your own pocket, than to allow your Prius provide a jumpstart.

    A Prius should be able to safely jumpstart another Prius, but make absolutely sure you know what you are doing first. Done wrong, the combined repair bill could reach into five figures.

    Did those vehicles have 'phantom' electrical loads that still pull current even when the vehicle is off? Examples include SKS proximity sensors, engine immobilizer (or at least the flashing light for it), car alarms, etc.

    These always-on loads can significantly shorten the time a car can sit unused without battery failure, compared to old fashioned rigs that were truly 'off' when the key was removed.
     
    #10 fuzzy1, Dec 24, 2014
    Last edited: Jan 4, 2015
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  11. Mendel Leisk

    Mendel Leisk Senior Member

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    There was a caution in the Owners Manual, to not use the under hood connection, hook up directly to the battery, when jump starting the Prius.
     
  12. Tideland Prius

    Tideland Prius Moderator of the North
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    It's the opposite, not? Pg 544. You can use the under hood connections to jump start the Prius but you should connect to the 12V battery directly if you're jump starting another vehicle.

    Also, that warning/suggestion is gone from the Gen 3 manual. In the Gen 2 manual, it recommends against jump starting another car.
     
  13. Mendel Leisk

    Mendel Leisk Senior Member

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    You're absolutely correct regarding the hook-up, lol. Hey, I was only 180 degrees away...

    I suppose you could use the posts, but no need. Actually, 8 oclock day one with our car I was watching the service dept do just that. They finally caved and gave us a new 12 volt.

    And yeah, it only says don't use the underhood for jump starting another vehicle, kinda leaves you hanging, regarding the question of whether it's permissible. I'd be inclined to not.

    Capture.JPG
     
  14. Tideland Prius

    Tideland Prius Moderator of the North
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    I've always wondered about buying a hybrid off the lot. The dealer knows about maintenance of 12V batteries (esp. having 100s of cars sitting out on the lot at -20°C in the prairies. Do they actually maintain those batteries if the cars aren't sold?). Would they bother to maintain that many hybrid batteries as well?
     
  15. Mendel Leisk

    Mendel Leisk Senior Member

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    Ours was manufactured Aug '09, looked pretty dust/neglected when we spotted in behind a bunch of other cars, November '10. The 12 volt was completely toast. The hybrid battery has been champion to date.
     
  16. irrational

    irrational Member

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    In regards to the 12v battery, I'd assume it has at least a 12 month warranty (if not covered by the full bumper-to-bumper warranty)... at least most do. The HV battery shouldn't be of concern due to the 8 year warranty.
     
    #16 irrational, Dec 24, 2014
    Last edited: Dec 24, 2014
  17. Easy Rider 2

    Easy Rider 2 Senior Member

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    Yes, no, maybe.

    It depends in large part on how fully it is charged when parked and how healthy it is overall.
    One that is inadvertently down to 70% or less might not survive.
    Likewise, one that is about at the end of it's useful life might fail too even if fully charged.

    IF everything is up to snuff, then NO. But you have virtually no way of actually knowing that with any certainty.
     
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  18. Tideland Prius

    Tideland Prius Moderator of the North
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    It'll be under the bumper-to-bumper warranty but a drained battery won't show the problems until about year 4 or 5.

    Again, it's not so much the warranty but the hassle of a vehicle that is out of commission down the road due to the (possible) neglect of a dealership. Most owners report no issue with leaving the car parked for a month but cars on the lot can sometimes spend more than a month there. A 12V battery is easy to replace in any vehicle, the HV is a bit more labour intensive.
     
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  19. David Beale

    David Beale Senior Member

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    I don't use the Battery Tender to prevent the 12V battery from not working, I use it to prevent the 12V battery from deteriorating excessively. If allowed to discharge too much lead acid batteries suffer damage. It may not show up after you recharge them, but it will after "a while", that being from a month to a few years.
    I took care of Pearl's battery (2007) this way, and it is still working in the car today (I added water to it at year 3 to extend its life). Though I think one cell is shorted. The current owner has it parked in his garage with a Battery Tender connected. He uses his PU truck in the winter. We'll see in the Spring if he can still use it. I suspect he will be purchasing a new one.

    The "traction battery" in the "standard Prius" (not the PIP) is NiMH. They don't suffer "damage" from self discharge, even if they self discharge so much they can't start the engine (a running engine is the only way -most- owners can charge that battery). The problem here is the only way -most- owners could charge it back up if it can't start the engine would be to get the Toyota regional service guy and charger sent in (from Vancouver, I suspect for us Canadians). I would expect a rather surprising bill for that. It appears that self discharge is not an issue for time periods of 6 months or so. This battery is -fully- disconnected when the car is shut off.

    Not so for the 12V. There are "parasitic loads" on it, namely the what, 7 microprocessors in the Prius. And as we all know, without removing the battery NO "computer" is ever fully off.

    The reason I was worried (well, I wasn't really worried, but perhaps a bit concerned - not listening to myself again) was the charge state indicator was at half when I shut Pearl S down a few months ago. As implied if not stated, in many posts on this forum, the charge state indicator is NOT a "precision instrument". The reading you see is NOT reality, it is a "best guess". And as shown in this case, the guess is pretty wild! Nothing to complain about, the car did take care of itself well, even if it didn't communicate that to me as well. I suspect, from years of experience with NiCd and NiMH cells, that the -real and actual- charge state is unknowable, and a "best guess" is the best you can expect in the "real world". :)

    Please don't ask me to comment on the PIP battery. I have so little experience with lithium batteries they are still "black boxes" to me, mysterious and magical. ;)
     
  20. Easy Rider 2

    Easy Rider 2 Senior Member

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    Well it depends.......on how LOW it is drained, how often that happens and how long it STAYS discharged.

    Many owners here have had trouble at much less than 4 years.