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12V charging while HV charging

Discussion in 'Gen 1 Prius Plug-in 2012-2015' started by jerrymildred, Jul 23, 2018.

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  1. jerrymildred

    jerrymildred Senior Member

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    I haven't seen any thread about this, but there have been occasional questions about the PiP's 12V battery being charged while the HV battery is charging from the wall. So, the other day, I checked the voltage of my 12V after it sat for about 14 hours and right before plugging in the EVSE. Then I checked it while it was charging. For good measure, I checked it again right after the HV battery finished charging.

    IMG_8565.JPG
    12.63 VDC before charging and with EVSE disconnected.

    IMG_8566.JPG
    13.51 VDC during charging.

    IMG_8568.JPG
    12.86 VDC after charging and with EVSE disconnected.
     
    #1 jerrymildred, Jul 23, 2018
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  2. Pluggo

    Pluggo Senior Member

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    ...and that is why you can swap out the 12v battery while you are plugged in and not lose any settings.
     
    #2 Pluggo, Jul 23, 2018
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  3. bisco

    bisco cookie crumbler

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    oh jerry, that's so 2012.:p
     
    #3 bisco, Jul 23, 2018
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  4. bisco

    bisco cookie crumbler

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    thanks! i never thought of this. if i ever need a new 12v, i'll give it a shot.
     
    #4 bisco, Jul 23, 2018
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  5. jerrymildred

    jerrymildred Senior Member

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    I figured you "old timers" must have gone over this, but my searches came up empty. So I did my own confirmation. :)
     
    #5 jerrymildred, Jul 24, 2018
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  6. bisco

    bisco cookie crumbler

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    a question was asked in a prime thread, 'what if you had a charger/maintainer on the 12v at the same time the car was plugged in and charging?'
     
    #6 bisco, Jul 24, 2018
  7. jerrymildred

    jerrymildred Senior Member

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    I remember that and that's what moved me to do my own test. I didn't put it in that thread because I didn't want to butt in with PiP data that may or may not apply to a Prime.
     
    #7 jerrymildred, Jul 24, 2018
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  8. bisco

    bisco cookie crumbler

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    so that is similar to batteries in parallel v series?
     
    #8 bisco, Jul 24, 2018
  9. jerrymildred

    jerrymildred Senior Member

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    I guess I'm a little addled today. Not sure I get what you're asking. I'm working on building a new website from scratch using a new theme and I think I fried my brain. LOL!
     
    #9 jerrymildred, Jul 24, 2018
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  10. bisco

    bisco cookie crumbler

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    no worries, my brain is always addled. i'm thinking your are putting 12+v in from two different sources, but it is not 24+v, just more power.
     
    #10 bisco, Jul 24, 2018
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  11. jerrymildred

    jerrymildred Senior Member

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    Now I get it. More power is always more gooder. ;)
     
    #11 jerrymildred, Jul 24, 2018
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  12. Jerry Liebler

    Jerry Liebler Member

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    I do believe the statement should not just say "plugged in" but "actually charging while plugged in". If you listen, you will hear the contact or s close after you plug in and charging begins OTOH you will also hear a click as they open when the HV batt is fully charged and charging ends. The 12 volt battery's charger is part of the inverter in the front of the car. The car's high voltage system must be "hot" for charging of the 12 volt battery to occur.
     
    #12 Jerry Liebler, Jul 25, 2018
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  13. jerrymildred

    jerrymildred Senior Member

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    Good clarification! Yes, that's what I observed with my meter. 12V battery read the same unplugged as plugged in and not charging.
     
    #13 jerrymildred, Jul 26, 2018
  14. bisco

    bisco cookie crumbler

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    there are a lot of people who still think if the car is plugged in, the evse is monitoring the hybrid battery and keeping it topped up.
     
    #14 bisco, Jul 26, 2018
  15. jerrymildred

    jerrymildred Senior Member

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    I can double check that tonight, but I'm pretty sure that the 12V reads the same plugged in and not charging as plugged in. One indication I can give right now is that the current draw on my meter is 0.02 amps whether the EVSE is connected to the car or not. If it was charging the 12V there would be a change in current when I connect it to the charging port..
     
    #15 jerrymildred, Jul 26, 2018
  16. bisco

    bisco cookie crumbler

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    mine read above 13 when charging, and 12.7 a few hours after charging while still plugged in, last time i tested it.
     
    #16 bisco, Jul 26, 2018
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  17. jerrymildred

    jerrymildred Senior Member

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    Have you measured it before plugging in, set the timer so it wouldn't charge right away, plugged it in, and then checked the voltage? I think I'll try that tomorrow unless you've already done it. If my theory is right, it would be the same.
     
    #17 jerrymildred, Jul 26, 2018
  18. bisco

    bisco cookie crumbler

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    i've never used the timer.:oops:
     
    #18 bisco, Jul 26, 2018
  19. jerrymildred

    jerrymildred Senior Member

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    Well then, I'll let ya know how it goes tomorrow. (y)
     
    #19 jerrymildred, Jul 26, 2018
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  20. bisco

    bisco cookie crumbler

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    it might depend on how long you have the car off before you measure it, then how long you wait after it finishes charging.
    if the time is similar, surface charge shouldn't be too different.

    if the battery is very healthy, they may be similar or same. but an older battery might measure a little higher after a fresh charge than before, not counting surface charge.
     
    #20 bisco, Jul 26, 2018
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