Building a solar charger for USB devices (iPhone 5)

Discussion in 'The Projects Forum' started by Cornall159, Jun 4, 2013.

  1. Cornall159

    Thread Starter New Member

    Jun 4, 2013

    I know that there are similar projects about but I want to run this specific setup by everyone.

    I have a 12v solar panel (i think either 5/10w - i cant remember) that is designed to be used as a trickle charger for a car battery, it has either a male cigarette lighter plug or crocodile clips to connect to a car/leisure battery. Essentially what I plan to do is buy a 12v lead acid battery, a fairly small one similar to the type used in some RC cars and boats, connect the solar charger to the battery then wire a cigarette lighter to USB charger to the battery to then connect the USB charging cable to charge my phone.

    Would this work?

    Is there anyway this setup could damage my phone?

    Is it likely to work well as a charging solution?

    Will the battery last with this sort of treatment or will the slow charging kill the battery?

    Do I need to wire in any sort of regulators or anything to prevent over/undercharging?

    Thanks in advance for any help you can give.

  2. wayneh


    Sep 9, 2010
    In my opinion, yes, it probably will. I do wonder if the phone will get enough current to initiate charging.
    I don't think there is any more risk than using the same USB adapter normally.
    I think it depends on the USB adapter. If it's a DC-DC converter with decent efficiency - and it probably is - I think a PV panel of that size should work in full sun. Grey area is whether it will work under clouds, in the evening, etc.
    Slow charging is great for batteries. A bigger risk is protecting your 12V battery from too deep a discharge.
    IMHO, no. Oh wait, I was talking about the iPhone. You may indeed need to worry about overcharging the lead battery and as mentioned, you need to watch against deep discharging it. Does your PV panel not have a charger circuit built in? It should at least have a blocking diode to prevent discharge during darkness.
  3. Cornall159

    Thread Starter New Member

    Jun 4, 2013
    The solar panel has a blocking diode I believe. Is there anything I can wire in to prevent full discharge? Or could I avoid this by ensuring I have a big enough battery that it is unlikely?
    I was looking at a 12v 12ah deep cycle battery. Is deep cycle best, and is this a lot?
    What about using 8 1.5v rechargeable batteries (maybe d's) would this be any better regarding current or risk of complete discharge?