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need 100% recharging of battery or is 67% ok?

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by priusunum, Dec 26, 2014.

  1. priusunum

    priusunum priusunum

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    In 2010 I replaced my original battery with an elearnaid Optima D51 yellow top. I have had no problems with it, but this morning discovered I had left my driver door slightly open two days ago and hadn't driven the car since.Of course the battery was dead. I have been charging it on and off all day with a Schumacher charger at 2Amps setting. The battery is now at 67% charged and 12.4 volts. An hour ago, it was at 60% and 12.1 volts. So an hour ago I unhooked the charger and tried to start it. It started up just fine and showed "ready" on the dashboard. I drove it for 15 minutes with no problems and hooked it up again to the charger. After the drive, it showed 67% charged and 12.4 volts. But of course at 2Amps, it's now charging very very slowly.

    Here's my question: Does it need to be charged to 100%? Or can I assume it's sufficiently charged so I can unhook the charger and close my garage door overnight, and be ok to drive it tomorrow morning without further charging? I don't want to leave it on the charger overnight because I'm afraid of hydrogen buildup if I close the garage door overnight as I want to do. My garage is part of my house so I must close it overnight. I should add that I only drive short distances, typically two to four miles each time I drive it.
    Thanks for any knowledgeable advice!
     
  2. bisco

    bisco cookie crumbler

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    you'll be fine, but when you have a chance, you should top it all the way up so it's at peak performance. good thing it's a yellow top, the drain shouldn't affect it's lifespan compared to an oem. shut the door!:p
     
  3. nh7o

    nh7o Off grid since 1980

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    Yes, charge it up all the way. No worries about hydrogen build up. It is the last thing to build up anywhere, having the ability to escape just about any container. The battery, at a slow 2 amps charge rate, will not off gas enough to be any concern. So close the door, charge away. At 2 amps, it will take a while. You should see 14.8 volts while the charger is on, when completely full. If it doesn't get there, it might have a shorted cell.
     
    #3 nh7o, Dec 26, 2014
    Last edited: Dec 26, 2014
  4. edthefox5

    edthefox5 Senior Member

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    In my opinion its toast due to the excellent deep discharge it got. These little batteries sulphate pretty quick.
    But I guess you can keep charging it and see how it does. Look for a bright red triangle on the dash that only shows up at boot up for one second. Thats to alert you the battery is has now dropped below 11.5 volts. That particular light is the only lamp not used for bulb check on the dash when you boot the car so its hard to miss when thrown although many posters with bad batteries seem to miss it. Pretty noticeable to me.

    And once in a while turn the headlights on at night before you start the car and see if they dim when its booting up. If you ever see a dim when booting the battery is done.

    Btw, a sulphated 12 battery is very hard on the Inverter to charge and your mileage will suffer.
     
  5. priusunum

    priusunum priusunum

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    Here's an update: I just checked my charger: in the hour and a half since I first posted my thread, the battery charge has gone from 67% to 88% and the voltage has also greatly increased. I watched the charger readout for about a minute just now, and it varied quite a bit for voltage, between 14.2% and 15.1%. I am very surprised since I had read in the charger instructions that the higher the battery charge %, the longer it would take for it to continue to increase. If it keeps up as it's doing, maybe I'll reach 100% in the next hour?
    Thanks for all who responded!
     
  6. bisco

    bisco cookie crumbler

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    pleasure, all the best(y)
     
  7. mikefocke

    mikefocke Prius v Three 2012, Avalon 2011

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    Lots depends on the "charger".

    Late model expensive ones switch depending on voltage to a maintainer mode so they don't overcharge. Then they wake up every so often and query the battery and only turn the charge function on if the voltage has dropped. Some even have a specific desulficating cycle. And an AGM setting for your Optima.

    If you are getting such precise readings, you may have a smart charger.

    Optimas are good stuff, sounds like you are on the road to recovery.
     
  8. Easy Rider 2

    Easy Rider 2 Senior Member

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    This. ^^^^
    Given your stated useage patterns, you NEED an automatic tender-type charger that you can connect once a week or so overnight to keep your battery up near 100%.
     
  9. edthefox5

    edthefox5 Senior Member

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    Be aware doesn't really matter if it charges up its how well it can hold a charge over time.
    Check battery voltage on jump points at night and then again when u go to use it the next day. See how it does over just 9 hours.
     
  10. priusunum

    priusunum priusunum

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    second update: last night I got the battery to 100% at which time the voltage on the charger readout was 14.4%. This morning, 9 hours later, with a voltage meter applied to the charge point in the engine area, it read the voltage as 12.4%. That seems ok for the car being turned off for nine hours. Do you agree?
    I then drove the car a few times this morning and it ran perfectly. I'm guessing I'm ok now and will try to remember not to leave a door ajar!
     
  11. bisco

    bisco cookie crumbler

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    i think you're good to go.(y)
     
  12. Mendel Leisk

    Mendel Leisk EGR Fanatic

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    Just to verify, should "12.4%" read "12.4 volts"?

    If you've just charged a 12 volt battery, not applied any loads to it, and few hours later it reads 12.4 volts, that seems kinda low. A freshly charged battery in good shape should be reading abnormally high, due to surface charge, maybe 12.8~1.9 volts. Then, after a few days later, having had some loads applied, it should be in the neighbourhood of 12.5~12.6 volts.
     
  13. Easy Rider 2

    Easy Rider 2 Senior Member

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    Sorry ED but it does matter.
    A lead acid battery sulphates less the higher the charge IS.
    It is best to keep it as near to "full" as possible, especially when not in use.
     
  14. Easy Rider 2

    Easy Rider 2 Senior Member

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    OK, maybe, but not really good.

    IF.....you did not have the doors open or otherwise have anything turned on before you made that measurement, it is a bit low.
    Nominal is 12.6 for flooded cell and 12.8 for AGM.
    It may last for many months like that but it bears watching.

    Did you catch what I said about getting an automatic charger ?
    The one you have now either is not automatic OR you didn't leave it connected quite long enough because the "float" voltage at full charge usually is about 13.4.
     
  15. edthefox5

    edthefox5 Senior Member

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    That's great.
    Too bad its already sulphated.
     
  16. GregP507

    GregP507 Senior Member

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    If you want battery longevity, aside from avoiding high temperatures, don't deepen the charge-cycles any more than necessary. Deep-cycling alters the physio-chemistry of the electrodes, shortening the life of the battery. Some batteries are better-designed to withstand this, but in general, the less intense the charge-cycling, the longer a battery will last.