Improved VW solar charger


VW has been shipping their cars to the US with small solar panels inside to keep the batteries from going dead during shipment. Dick Streefland picked one up and added a small monitor circuit to monitor and charge his battery. Batwatch is based on the Atmel ATtiny13V and measures the voltage on two sides of a resister to determine the voltage of the battery while the solar panel is charging the system.


  1. BronzeG3 says:

    I would use that solar panel to power a fan to circulate air during the summer. Other then that, nice hack.

  2. ahh this should quell some disidents on the quality of the hacks. It has led, circuits, and is simple.

    This is brilliant. I wonder if you could do this without the pannel attached.

  3. Steven Thomas says:

    I think this kind of thing would be a good aftermarket kit for hybrid cars. My hybrid has a sun roof, and I thought a perfect place for the panel would be between the interior shade and the glass. The space is about 18″ x 24″, so it’s peak power should be about 50 Watts. (I estimated using this panel

  4. Nate says:

    This is an awsome hack. I was looking into some of these panels to give away as door prizes for the VW bus festivals I go to.

    clean, simple and well executed.

    Thank you

  5. roy says:

    Can someone manufacture this under $50 and put it on ebay? I need one. I don’t have the time to make it.

  6. mike says:

    nate: what kind of bus do you drive?


    Fuel Injected 77 Riviera with a 78 engine so I get hydro lifters as well :).

    Of note, go westy sells a similar panel here ( ) for 40 dollars that clips directly to your battery, although they are currently sold out.

  7. PaulH says:

    mike, I had a ’77. After it caught fire, I bought a ’70 westie.

  8. mike says:

    yay for replacing all the fuel lines right after i bought it! i almost passed out driving that thing 80 miles home with a broken gas cap and a leaky fuel line. ive been told the best thing to do is upgrade to metal aircraft fuel lines, as they dont melt when it gets really hot, althought i havnt done that yet.

  9. steve says:

    next hack pleas

  10. #2 – no it doesn’t look like you could use it without the panel. the panel provides the power to the voltage regulator to run the micro. so, you would have to provide a power source for it, and that power source also would be attempting to charge the battery.

  11. bird603568 says:

    die kthanks. steve do you want my atx led lamp?

  12. andrew says:

    cool ;)

  13. turdmoe says:

    thats an interesting device, simple and useful.

  14. mahder pwned says:

    lets all get together and make hackaday like Counter Strike.
    i’ll start:
    voteban steve (the dumb one)

  15. steve says:

    i have a better idea lets make hackaday like a proper website and bann all you idiots and then lets go one step further and put some proper hacks on OH MY GOD THEY UNTHINKABUL PROPER HACKS NEVER LOVE THE TROLL

  16. shiznannigan says:

    Trouble is, most newer cars won’t allow voltage IN to the 12v outlets. These solar devices do nothing for your battery.

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