Trickle Charger for 12V

Discussion in 'Gen 2 Prius Main Forum' started by rogerthat, Mar 24, 2020.

  1. rogerthat

    rogerthat Member

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    Just an additional note that I've been running a dashcam that is plugged into the cigarette lighter outlet (not hardwired). Funnily enough, I posted a thread a few months ago asking if a dashcam could affect the battery - the consensus was that it would not. Out of interest, does the dashcam run off the 12V or the hybrid battery? How about the radio? If the battery is depleted and the radio and dashcam are constantly on, could this possibly hinder 12V recharging while driving?
     
  2. fuzzy1

    fuzzy1 Senior Member

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    All those run off the 12V bus/battery, not the hybrid. They are very small loads and will not hinder battery recharging while driving unless something else is seriously going wrong with the 12V bus.
     
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  3. davecook89t

    davecook89t Active Member

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    The only accessory that uses hybrid battery power is the A/C compressor, everything else runs off the 12 V system. The headlights will put a significant load on the 12 V, anything else should have a very minor draw. Our Gen 2 does not have Daytime Running Lights (which I would like to have for safety reasons), so we just leave the regular lights switched on all the time and our 4 year old battery is still close to fully charged after the car has been driven for more than a few minutes. We also have a dash cam plugged into the cigarette lighter port, so I think your accessories are not significantly drawing down your 12 V as the car is running. I'm assuming you don't have any 3rd party accessories (alarm systems mainly) that are always drawing power and may draw down your battery if they are not functioning properly.
     
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  4. Mendel Leisk

    Mendel Leisk 'Orrible Oracle

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    If anything is drawing power when the car's not "ready" (aka completely on), it's drawing the 12 volt battery down. How much and how fast depends on the component, but considering the diminutive battery, I wouldn't run anything.

    I keep the hatch and dome lights off too. There's more, that don't have switches, haven't messed with those.
     
  5. rogerthat

    rogerthat Member

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    Well its been about 2 hours charging and the charger is showing 14.7V with 1 bar from fully charged on the display. The 14.7V doesn't make too much sense to me, but I'll keep it going until fully charged.
     
  6. davecook89t

    davecook89t Active Member

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    Is it staying at that value or bouncing around some? When charging my battery it may get that high briefly but then comes back down to the 13 - 14 V range. Maybe it is not getting any feedback from your battery saying it is near fully charged. Just a guess, but that could be an indication that the battery is shot.
     
  7. rogerthat

    rogerthat Member

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    It was steady for the minute or two I observed it, but I just went back and it is now bouncing back and forth within the 12-13 V range and showing 1 to 2 bars.
     
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  8. davecook89t

    davecook89t Active Member

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    That sounds like what I believe is the "absorption" stage. There may be some hope for that battery yet.;)
     
  9. bisco

    bisco cookie crumbler

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    after you get the final reading, if the car will start, you might be good to go. check the voltage every morning until you're comfortable that it is holding
     
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  10. rogerthat

    rogerthat Member

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    Yeah, that's exactly what I plan to do... daily checks in the AM for at least a week. Charging is about 5 hours in and the charger display is currently bouncing between 13.5 and 13.9V and 3 to 4 bars (out of 5).

    Any danger in taking the car out for a drive immediately after the charge is complete, or should one wait for battery to cool?
     
  11. bisco

    bisco cookie crumbler

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    no harm at all. just don't shut down until you're back home
     
  12. rogerthat

    rogerthat Member

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    Green light on charger came on after about 6-7 hours total - fully charged and reading 12.6V same as you stated for yours Davecook. I've disconnected charger and will check in the AM - hopefully it doesn't drop too much.
     
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  13. dolj

    dolj Senior Member

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    It makes perfect sense.

    Did your charger come with a manual that explains what is happening at the various stages? If so read it and become familiar with what it does, so you know what to expect.
    Quick charging is not a good sign for a fully discharged battery. At 4 A, it will (should) take in excess of 20 hours to fully charge from empty.

    So, we'll see.

    One last thing, with battery charging, the saying, "a watched pot never boils," comes to mind. As it is fully automatic, just set it and forget it.
     
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  14. rogerthat

    rogerthat Member

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    Almost 12 hrs since completed charge and multimeter reading shows 12.7V. It was12.6V on the charger display on completion of charge and 12.8V (multimeter) last night post charge. Cautiously optimistic.
     
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  15. sam spade 2

    sam spade 2 Senior Member

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    OK. THAT can make a difference. :)
     
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  16. sam spade 2

    sam spade 2 Senior Member

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    13.4 is a "float" voltage and usually indicates that the charger thinks it is done charging.
    If you leave it connected, that likely is it's "normal" maintenance voltage.
     
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  17. rogerthat

    rogerthat Member

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    Well, I may not be out of the woods yet. My last reading after the car sat 12+ hours, was only 12.46 V. I've had no issues starting the car since fully charging, nor have I seen the red triangle. I'll keep monitoring and perhaps use the trickle charger weekly. If I noticed the battery continue to degrade, I'll likely replace at my next oil change.

    Davecook... how often do you use your charger?
     
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  18. Mendel Leisk

    Mendel Leisk 'Orrible Oracle

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    Yeah, a freshly charged battery reading only 12.6 is not good. Dropping to 12.46 in 12 hours, again not good. I'd suspect it's failing, unable to hold a charge.

    Have it it checked with an electronic load tester (at a store or dealership), or DIY with something like Solar BA9. I'd suspect it's Cold Cranking Amps (which these devices can test) will be around 250 or lower. Spec of the OEM battery is 310~325 IIRC, and a new battery will typically display WELL above, that, say 375~400.
     
    #58 Mendel Leisk, Mar 28, 2020
    Last edited: Mar 28, 2020
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  19. davecook89t

    davecook89t Active Member

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    Now that we don't go out much, I put it on every couple of days. 12.4 V is what I normally see on the LCD when plugging the charger in after not having used the car for that length of time. I suppose some owners would replace their battery if they were seeing what I am seeing, given that a weak 12V is thought to negatively impact MPG, but the car has 286k miles and even a $150 - $200 outlay is too much for us at this point. We expect to be staying close to home for the next few months, so I'll just keep doing what I've been doing until we finally retire the car.
     
  20. sam spade 2

    sam spade 2 Senior Member

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    You seem to be stuck on that......but if the battery will not hold it's voltage with NO LOAD (or a tiny little load) there is NO NEED for any additional testing.
     
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