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How to make cig. outlet always hot?

Discussion in 'Gen 2 Prius Main Forum' started by Bunce, Mar 23, 2020.

  1. Bunce

    Bunce Active Member

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    Hi guys.

    Does anyone know how to make the cigarette lighter outlet always hot?

    I don't drive the white prius, and to keep the old struggling 12v battery topped up I wanted to plug in a small solar panel I have.
     
  2. SFO

    SFO Senior Member

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    #2 SFO, Mar 23, 2020
    Last edited: Mar 23, 2020
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  3. sam spade 2

    sam spade 2 Senior Member

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    Better to visit an auto parts store and get some SAE battery connectors with pigtails.
    Connect one to the battery.....or jump points.....and the other to your solar panel.

    P.S. Small solar panels usually have a really small capacity.
    That might not be enough to keep the "old struggling" battery alive.
     
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  4. Bunce

    Bunce Active Member

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    Ya, that's what I'm looking to do. I'll be DIYing though since I have wire, taps, add-a-fuse, connectors etc. I was just hoping to find a tutorial or write up.
    It looks simple enough but it's always nice to read about someone that has already accomplished it.
     
  5. Mendel Leisk

    Mendel Leisk Senior Member

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    IMG_2128.JPG There's an always-on lead going to the obd port, maybe you could tap into that. I have a memory saver cable with an obd connector, and here's what pins it has. I believe it's the solitary pin in the corner that's 12 volt positive, testing for continuity.
     
    #5 Mendel Leisk, Mar 23, 2020
    Last edited: Mar 23, 2020
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  6. davecook89t

    davecook89t Senior Member

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    This has worked well for me. 5 watts is not so much that you need a charge controller, but enough to keep a good charge on the battery, if it is under direct sunlight for even part of the day. I have never tried to use the cigarette lighter port, the battery clamps have a cord that detaches from the solar panel. On our Gen 4, I just leave the clamps permanently attached to the battery under the hood, tuck away the cord and remove the solar panel from the hood of the car if I'm going to drive it. Since the positive jump point on the Gen 2 is under the fuse box cover, you would need to remove that clamp and just wrap the wire that was attached to it around that terminal. The wire is thin enough that the fuse box cover should close almost completely, even with the wire running under it.

    At one point, I had the solar panel sitting on the dash of our Gen 2, while it was parked at an airport parking lot for a couple of weeks. I was able to keep it attached to the jump points by sticking the wire between the door and the door frame and then running it through the opening at the top of the hood. I was not sure I would get enough sunlight through the windshield to keep the battery charged, but it worked fine, and I was able to verify that by measuring the voltage from the solar panel (~ 21 V) while it was sitting on the dash.
     
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  7. sam spade 2

    sam spade 2 Senior Member

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    Maybe, maybe not. It depends on the specific panel in use.

    5 W at 12 V gives you about .4 amps, max.
    IF that doesn't result in about 13.2 Volts or more at the battery during max. sun exposure, you are just wasting your time.

    In most cases, a "charging" voltage of less that 13.2 won't overcome the battery's internal resistance and no useful current will flow.

    EDIT: Then.....after reviewing your post again, you might get away with applying 21 volts to your battery for a relatively short period of time if the source is current limited, but for long term storage, that will NOT be good........for the same reasons that a "dumb" trickle charger isn't good.
     
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  8. davecook89t

    davecook89t Senior Member

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    Yes, certainly not ideal. We are usually separated from one of our cars for months at a time, spending long stretches in either Florida or New York (also Washington state for a few months in the summer, but we don't have any hybrid vehicles there). The first few times with our Gen 2, I disconnected the negative terminal from the battery in the back (also not ideal, as I've come to understand from reading posts on this forum because of the sparking, but I just thought it was easier than fighting with the plastic tabs on the positive terminal).

    Leaving solar panels always connected instead of losing all the car's radio and navigation settings every time is kind of an experiment. I didn't think leaving the battery disconnected with no cycling for months at a time was the best either. So far, the battery in the Gen 2 is still OK after almost 4 years of doing that and the battery in the Gen 4 has had 2 1/2 years without failure. A few hours of direct sunlight per day might be just enough to keep either the AGM in the Gen 2 or the regular lead-acid in the Gen 4 happy. I will update this post (if I remember) when one of them fails.
     
  9. Mendel Leisk

    Mendel Leisk Senior Member

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  10. davecook89t

    davecook89t Senior Member

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    The panel he used from Canadian Tire looks exactly like the ones I bought from Harbor Freight, but eventually gave up on. (Reading through the thread, it seems that others had similar experiences). I bought 4 in total for our 2 hybrids, because it seemed that 1.5 W might not be enough to keep the batteries fully charged. 2 of the 4 failed, mainly because the connections were so poorly soldered, I believe. I've had better luck with 2 of the slightly more expensive ones from Amazon that I linked above.
     
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  11. Mendel Leisk

    Mendel Leisk Senior Member

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    Yeah have no clue about the panels, mostly found his attention to detail interesting.
     
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  12. Bunce

    Bunce Active Member

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    The panel I have, I believe to be the same as this. https://amzn.to/2QIRzKH
    After reading dome of the posts you guys and kindly shared, I think I might just run a wire direct to battery since I have most of the rear interior out from working on the hybrid battery. I can install a quick disconnect at the dash end. This will enable me to get the maximum power from the little panel to the battery.
    One thing that has come up is that it doesn't sound like there's a diode on this panel. I'm not sure if that's an issue since it sounds like most people leave them connected. Does a solar panel use power at night time somehow?
     
  13. davecook89t

    davecook89t Senior Member

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    The description on the one you linked does say it has a "built-in blocking diode", and even the cheap Harbor Freight ones claimed that. I never had a problem with them draining my battery, eventually 2 of them just stopped charging it.

    I'm not sure if a permanent 7 W without a charge controller is still OK. I saw several opinions saying 5 W would be. YMMV.
     
  14. fuzzy1

    fuzzy1 Senior Member

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    Without a blocking diode, solar panels have some reverse current leakage. It depends on the panel and on the battery voltage it is hooked up to. In some cases, it can leak more in the dark than it replaces during the day. Especially when it gets parked in a garage or elsewhere out of sunlight.

    While we call it reverse current on the PV module, electrically it is actually forward current through the long stack of diodes that make up the PV cell stack. ** This current should be small because the forward voltage per diode junction is small, lower than the what we consider to be a normal diode drop. But when not accounted for in the design, or with leaky devices, it can become insidiously large.

    ** Silicon PV cells are effectively diodes, run with so much light-derived forward current that the forward voltage builds up, and we can connect to and harvest much of it.
     
    #14 fuzzy1, Mar 24, 2020
    Last edited: Mar 24, 2020
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  15. Bunce

    Bunce Active Member

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    So I looked in the controller box, perhaps mine is an old version as there was no diode.

    From some parts I had, I cobbled together a direct to battery cig. outlet and an extension. It's currently parked with the solar panel on the dash. I had just taken the battery off the charger so I'll wait until tonight to get a V reading and then check it over the next few days. The forecast is spring showers so we may get some sunny spells.
    I'll report back with my findings.
     
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  16. Bunce

    Bunce Active Member

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    Update: I think my battery might be too far gone to be able to "maintain" with a small solar panel. Here's the data.

    Date hrs V
    03.24.2020 19.15 12.44
    03.25.2020 12.00 12.45
    03.25.2020 13.45 12.45
    03.26.2020 12.20 12.39
    03.27.2020 11.00 12.31
    03.28.2020 13.15 12.28
    04.03.2020 14.00 12.09

    There hasn't been much sun around the last few days. I'm currently reconditioned the hybrid battery and have the 12v on a trickle charger, perhaps after a few days on that it'll perform better, if not it might be new 12v battery time.
    I'll still continue to tinker with the 12v solar charging though, especially as we won't we driving any time soon.
     
  17. davecook89t

    davecook89t Senior Member

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    Have you tried measuring the Voltage and Amperage coming from your solar panel under various lighting conditions? Even the cheap Harbor Freight ones I had were showing 21 V under cloudy skies in the middle of the day. As long as they were functioning, they were fine. Unless you have some serious parasitic drain, I would think a 7 Watt panel functioning properly should keep your 12 V fully charged under almost any weather conditions.
     
  18. Bunce

    Bunce Active Member

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    If it was a healthy battery I'd say it probably would, but I suspect it sat for a while before I bought it and thusly damaged the battery.

    Those readings are at the battery, with the panel hooked up to it. Could the battery have been absorbing some volts and not showing them? It should have been showing the same as the V output of the panel right?
     
  19. davecook89t

    davecook89t Senior Member

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    I was measuring the 21 V from the panel without it being connected to the battery. If measuring the battery with the panel connected, I would think you should see somewhere around 14 V, and I believe you would see that even if the battery is weak. The difference between a good battery and a weak one would be observed after a few hours. The good battery would hold its charge, whereas the weak one would soon register a very marginal voltage, < 12.5 V. That's why I am suspecting your solar panel is not doing its job. If it is still connected during the midday times you listed, I would expect to see about 14 V on your battery.
     
  20. Minima Domum

    Minima Domum Member

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    I've had a solar panel permanently mounted on every car I've owned for many years now and it's great, never have to worry about a flat battery, even if I leave the radio or a light on.

    I use much bigger panels (100w+) but a 20w with a small charge controller mounted close to the battery shouldnt cost much and will give you pretty much unlimited storage capacity even if the weather is bad, I wouldn't bother with anything smaller than that, or running without a charge controller.

    As for the actual thread topic, I used a spare fuse slot under the dash and just plugged in an "add a fuse" then replaced the positive lead on the back of my factory cigarette lighter.
     
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