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Stabilizing Voltage

  1. Nov 25, 2016 #1
    Hi guys,

    I'm new here and I was looking for a little help with a project I'm working on. I'm trying to build a saltwater battery that will connect to a phone via usb and charge the phone. However, it doesn't seem like I can connect the battery to the phone directly because the voltage and current aren't very stable. I've read online that plugging in a source with unstable voltage to a phone can mess up the phone. Is there anything I could use to get a stable voltage so I can plug in the phone safely? I was thinking of using a voltage regulator in a breadboard I have. Thanks a lot.
  2. jcsd
  3. Nov 25, 2016 #2


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    Staff: Mentor

    Hi Sean D. :welcome:

    Sounds like a novel idea! Can you give some details of your battery design so we can see whether you'd have enough power there to try to stabilise.

    I'm not even sure that one can, in practice, trickle charge a standard phone, either.
  4. Nov 27, 2016 #3


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    Gold Member

    Some phones will charge at different rates depending on resistors connected to the USB lines to various voltages (or not charge at all if the right conditions are not met). The minimum is often 0.5A or more. To use a high impedance source you will likely need to slow charge an intermediate battery with a dedicated circuit then charge the phone with that.

  5. Nov 27, 2016 #4
    Thanks everyone. I am using 4 aluminum and copper cells connected in series which will then be connected to a USB. The saltwater will be a maximum concentration
    solution. Ideally, I'd like to get around 5V and 1A, but I'm not sure how plausible that is because I haven't been able to test the design yet.

    I've seen people online use an intermediate battery. The point of my design is to offer a more environmentally friendly alternative to a Li-ion battery so connecting an intermediate battery would defeat the purpose. That being said if that ended up being the only way I could do it I would use the intermediate.
  6. Nov 28, 2016 #5
    Break this into parts -
    Make the Battery
    Charge a Capacitor as the initial load and test the battery.
    Develop a Voltage controller ( regulator) based on the typical voltage you can get on the capacitor. There are many ways to set up a charger for a cell phone, but the first piece of info you need is what are the capabilities of the source.
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