A question for our electrical engineer (or just really smart) GTers

Discussion in 'The Okie Corral' started by Calicowboy, Oct 29, 2020.

  1. Calicowboy

    Calicowboy

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    Hi, I just got a little Coleman solar powered trickle charger for one of my vehicle's 12 volt battery, since the vehicle isn't driven very much. The charger is putting out 17.5 volts and 3.5 miliamps in semi weak sunlight. I have another Coleman charger I've been using on a different vehicle for some time, and it always puts out 12.5 to 13 volts, so I don't know if this new one is defective.

    I know a vehicle's alternator usually puts out somewhere around 13.5 to 14.5 volts, but a lot higher amps. Is 17.5 volts at this tiny amperage going to hurt my vehicle's battery? I know a vehicle alternator running that hot would cook a battery. Assuming it won't hurt my battery, do you think it will help (in any meaningful way) with keeping it charged?

    Thanks,

    Calicowboy
     
  2. Mayhem like Me

    Mayhem like Me Semper Paratus

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    1-3 amps is normal trickle charging range
     

  3. Oldschooltube

    Oldschooltube Flux Capacitor Technician

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    I don’t think 3.5 milliamperes could even overcome the natural unloaded drain of a battery.
     
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  4. MrPizza

    MrPizza

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    Its bad. The amperage is way too low and the voltage is high
     
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  5. jimcorbin

    jimcorbin

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  6. RenoF250

    RenoF250

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    I would not be so sure about that, it could have a circuit that is "looking for" a battery. Try connecting it to a battery and see how much current it puts out.

    Regardless it is not going to hurt the battery short term, no way it has enough current. Over the period of days it may try to overcharge it but I doubt it. Keep an eye on it and if the voltage goes too high or you see a lot of acid residue on the top I would be more concerned.
     
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  7. Hef

    Hef

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    Charging voltage is usually 14.4VDC, and high amperage. At 3.5ma, you could charge 1 or 2 phones or tablets, but not a vehicle.
     
  8. Kevinr20

    Kevinr20

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    With such a small wattage panel, it does not need a charge controller. Solar panels normally put out around 17 to 18 volts and my understanding is it will regulate itself down to the battery voltage if connected directly. It won't harm the battery at 3.5ma.
     
  9. Kevinr20

    Kevinr20

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    How do you know the amperage is low without known the wattage of the solar panel? Panels run 17 to 18 watts under no load.
     
  10. Khufu

    Khufu Pharaoh

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    Why would you put a bunch of heavy stuff on solar panel? It seems that is a good way to exceed the fracture limit of the panel?
     
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  11. Simi_gun_guy

    Simi_gun_guy

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    Are these readings with the panel connected to a battery? What is the battery voltage w/on the panel connected? 17.5 v @ 3.5 mA is only 0.06w. There is something wrong with these numbers. Is the panel clean? Cracked? Wires damaged?
    If the above numbers are with the panel attached to a battery and the battery is not below ~11.5v when not charging, then the panel is failed.
    If you’re charging with a ~40W or more panel, charge controller is required. Otherwise you’ll cook the battery. Overcharged is a thing.
    I’ll offer more feedback with more data.


    Ed
     
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  12. .264 magnum

    .264 magnum CLM

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    A. I'm not an engineer
    B. Due to having some very remote water wells, some oil and gas stuff and bad power at my lake house/boat lift I have dozens of 12 and 24v solar + battery sets powering pumps, motors and boat/waverunner lifts.

    Unless I'm missing something you are not going to charge a sex toy with 3.5 milliamps @ 17 volts.........that's roughly 0.0595 watts - let alone a 12 volt car battery. You need something like 100x that much power to charge a car battery reasonably.

    1. Look at the panel and make sure it is 100% clean. No slick looking glaze, no dust, no leaf covering part of the panel etc.

    2. Make 100% sure your readings are accurate.

    3. Some panels more or less don't work at all in weak light.

    4. Even though you won't specifically need a regulator use one.
    A. even crappy ones clean up the power a good bit and decent ones prevent battery discharging.
    B. Decent regulators have nice status/level indicators.
     
  13. .264 magnum

    .264 magnum CLM

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    I was hoping you and or Haldor would jump in......

    Good call on the object battery not being below ~11.5 volts. Below that nothing will happen.
     
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  14. inthefrey

    inthefrey Moved on...

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    Nope! Current way too low. However, that voltage seems to be normal for an "unloaded" circuit to draw down to 14V. Seems like it's not sensing the battery? What is the model of the charger? 2, 6 or 10W?

    However, **FROM THE USER MANUAL**

    The Coleman 6 Watt Solar Battery Trickle Charger Twin Pack is the ideal solution for maintaining 12 Volt batteries for your cars, RVs, tractors, ATVs, electric fences, deer feeders, boats, and more. These units are completely weatherproof and charge in all daylight conditions, even in the shade. The built-in blocking diode protects battery discharge at night. A perfect solution for battery maintenance, these units are completely maintenance free and easy to install. It has a maximum power output of 6 Watt, 400 mAh.

    SO, roughly .5 amps in bright sunlight? *math may be wrong*
     
    Last edited: Oct 29, 2020
  15. Simi_gun_guy

    Simi_gun_guy

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    Not really sure what to make of the manual. If it’s a 6w panel, ~400mA is in the area. But 3.5ma is 0.0035A! Not worth putting in the sunlight.

    Specific questions:
    What is the battery voltage with no load, no charge?
    Did you MEASURE the current from solar panel charging battery? What is that value?
    How did you measure the charging current
    Is the panel clean?
    Is the panel damaged?
    Is the panel wiring damaged?
    Is the panel facing the sun?

    Sorry, need direct answers to these questions to go further.

    Ed

    I have *some knowledge* of solar power …
    My rooftop solar
    1A9AAA6F-C4CD-4DB0-A96F-ABC3FD62937A.jpeg
     
    Last edited: Oct 29, 2020
  16. Calicowboy

    Calicowboy

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    Hi, I appreciate y'all taking the time to help. I have to admit, electricity is akin to The dark arts to me- I don't have a clear understanding of it.

    To answer a few questions: The panel is brand new, clean, and undamaged as far as I know. I tested it when it was not connected to the battery. It connects via the cigarette lighter (which always has power on this vehicle), so it would be difficult to test it while it's connected to the battery.

    This is the panel: https://www.walmart.com/ip/Coleman-...MI4s6YjoLb7AIVsyCtBh02LwpFEAQYASABEgL3HfD_BwE

    I have another one of the exact same charger, and never got a voltage reading so high, which made me wonder if this one is defective. I also never tested the amps on the other one.

    I'm going to put a fresh battery in my multimeter tomorrow and will check both panels' output when the sun is shining, to make sure that an old multimeter battery wasn't the cause of the 17.5 volt reading in the new panel.
     
  17. cougar_ml

    cougar_ml

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    Quick check:

    test battery voltage with charger unplugged.

    plug charger in, come back next day (or just several hours later of bright sunlight)

    If working, battery should be up by at maybe a couple hundreths of a volt over what it was before.


    What are you measuring to get 3.5ma? If you're just putting the meter to the leads and testing that way, it won't be accurate. You have to hook the panel up to an actual load with the tester in series to get an accurate amperage test.

    Once you plug it in, that 17V is going to go down to whatever the battery is, or just slightly above it. The battery is the load in this case, and the internal resistance is going to eat up most of the supplied power. The rest should be just enough to keep the battery from draining (but won't be enough to provide any actual charge unless it's something like a 12V 5 amp battery on a trailer or similar)
     
  18. Simi_gun_guy

    Simi_gun_guy

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    Ok, plug it in, call it good. It “should” work.
    Can’t go any further than that w/o data or being there to evaluate.
    Good luck!


    Ed
     
  19. BobbyS

    BobbyS Truth always sounds like lies to a sinner

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    3ma won't hardly cover the cold weather



    I get more current from the fillings in my teeth
     
  20. Inyo Tim

    Inyo Tim Senior Moment

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    Calicowboy, can you link us to the charger you have on Amazon so we can read the specs?