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Solar panel trickle charger for Prius.

Discussion in 'Gen 2 Prius Main Forum' started by Kaptainkid1, May 3, 2021.

  1. Kaptainkid1

    Kaptainkid1 Active Member

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    Vehicle:
    2009 Prius
    Model:
    III
    Since my Prius is parked on the street outside in the sun I would find my Prius 12 volt battery would be too dead to start my car.

    Here is the parts list.

    Look at this on eBay
    100A Solar Panel Charge Controller 12V 24V Regulator Auto Mppt Battery Dual USB | eBay

    Look at this on eBay
    30W 18V Outdoor USB Monocrystalline Solar Panel Battery Charger Motorhome | eBay

    These parts added up to about $40 and now is part of my solar power trickle charger keeping my 12 volt power full and healthy.
    The PWM controller can handle up to 200 watt solar panel and keep my ARB fridge running all day when I'm out for a long weekend camping.
    It was easy to install and has many features to maintain battery of all types lithium, Lead Acid and AGM. It also has two usb ports for charging devices.

    I will upload photos of my set up and show you various ways for the small panel location.
     
    #1 Kaptainkid1, May 3, 2021
    Last edited: May 3, 2021
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  2. Kaptainkid1

    Kaptainkid1 Active Member

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    Here are the photos. 20210503_124426.jpg 20210503_124202.jpg 20210503_124015.jpg 20210502_172201.jpg 20210502_171927.jpg
     
    #2 Kaptainkid1, May 3, 2021
    Last edited: May 3, 2021
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  3. Kaptainkid1

    Kaptainkid1 Active Member

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    More photos. 20210503_141553.jpg 20210503_141542.jpg 20210503_141443.jpg

    SM-J737T1 ?
     
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  4. edthefox5

    edthefox5 Senior Member

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    Nice!

    Thanks for the links!
     
  5. bisco

    bisco cookie crumbler

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    looks good, well done!(y)
     
  6. AzusaPrius

    AzusaPrius Senior Member

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  7. pasadena_commut

    pasadena_commut Senior Member

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    Can it keep up? Good question.

    How big is that panel, maybe 12 cm x 30 cm? Solar power (total from the Sun at the Earth) is around 1KW per square meter, and solar panel efficiency is around 20% (.2). So the power from a panel like that, is at most 1000 * .12 * .3 * .2 = 7W. Assuming the electronics are 100% efficient, the corresponding current is 7W/12V = 583 mA. So, under ideal circumstances, that is more than enough to offset the 15-20 mA car off current, even though that off current is 24 h/day whereas the charging current is more like 10 h/day.

    The thing is, that panel is not likely to be in ideal conditions unless the owner moves it around during the day. The rule of thumb is, I believe, that panels which have indirect sunlight put out about half as much power as those in direct sunlight. If the panel is not built well a dark shadow (neither direct nor indirect light) falling on just one part could drop the output to next to nothing. This is because no current flows in these devices unless they are in light. The poorly made ones just put a bunch of solar cells in series, and if any one cell sees no light it shuts off current flow through the whole chain. Better made ones use diodes to shunt current from still working cells around the ones which are off. Those just lose power more or less as a function of the area which is shaded, it isn't all or nothing. There are also geometry issues - the calculation above only applies if the light is parallel to the panel's normal vector. There is likely a loss factor of somewhere between .5 and .7 because of this. The glass will also block some of the light, so maybe another factor of .5?

    Rough calculations, but it suggests that a small panel like that, if it is of high quality, could keep the 12V charged as long as the car was parked in a reasonably sunny location.
     
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