Powerpack to power a 5" smartphone while traveling.

Discussion in 'The Projects Forum' started by Fruit bicycle spaceship, Jan 27, 2015.

  1. Fruit bicycle spaceship

    Thread Starter New Member

    Jan 26, 2015
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    0
    I have been riding a bicycle and drifting from place to place and I keep hanging out at places with outlets to charge my phone.

    I have been living at a friends house for a few months now but will be heading out again in a few weeks.

    Last time I was out I used a Solar Joos Orange http://solarjoos.com/products .The unit has a 6"x6" solarpanel and a 20watthour battery built in, and a 5v usb output. It charged my little Lg L34C smartphone in slow charging mode. It had just enough power for my little 3.5" Lg L34c phone, but I will be ordering a 5" phone like a samsung galaxy s4 or s5. Now I used this solar joos orange in Kona Hawaii where it only rains 15 inches a year and is 19 degrees north of the equator, and I left the solar joos out in the sun at my camp all day and then came back to my camp at night and even with all that sun it sometimes was not charged all the way.

    What I am thinking of now as an upgrade would be a powerpack that charges off conventional outlets found around the world, I would want it to be large capacity such as 100watthours. I envision it as two 3.7v 13,500mah lithium ion cells in series to yield a 7.4v 13,500 mah batterypack. And I would want it to charge as quickly as possible since I would be hanging out at an outlet in a library or a coffee shop to charge it and leave asap. They already sell power packs of this size for charging cell phones but none I have seen charge much faster than 7 hours. I know laptop computers charge in 2 hours, since they have large 65watt chargers, but the designers of these cell phone powerpacks seem to think a 5V 2A charger is adequate for charging a powerpack and it would be if I plugged it in in a hotel room and left it over night, but I like to sleep in the woods. Now a 65watt laptop charger is big and heavy, but it has alot of filters to eliminate interference and deliver smooth power to a laptop, charging a battery that is not connected to a computer does not need the purest power, in fact it can be quite noisy. I've heard lithium ions will charge off high voltage as long as you limit the current, so now I am wondering how compact the charger can be. Switched mode power supplies like laptop chargers usually have 19 volt output, so I would need to find one around 10 volts 7 amps limited current, my guess is I could connect that to the battery terminals and charge it till I see a certain voltage, but I don't have much experience charging lithium ions and I read they need a control circuit. I'm more experienced with lead acid and checking them with a hydrometer.

    I've taken the 18650 cylindrical li ion cells out of old laptop packs and charged them with 5v phone chargers before, I disconnect the charger, wait a while, then test the voltage and I stop charging when I see around 3.7v.

    Then I just need a regulator that takes the batteries 7.4 volts and regulates it down to 5v for the phone. I would like a small lcd voltage readout on the powerpack, but how do cell phones and laptops know how charged their batteries are? Is it based on voltage or measuring current in current out etc?

    Any advice on a fast charging 100watthour powerpack?
     
  2. Fruit bicycle spaceship

    Thread Starter New Member

    Jan 26, 2015
    3
    0
    I took the solar joos apart and it had a 3.7 volt pack inside, there is also an mppt circuit for the solar panel. It has a circuit that boosts the 3.7 up to 5v for the output to the usb but only a few hundred mA since my phone said "slow charging". I haven't looked for regulators to output 5v, but I would want the most compact and efficient, seems like it would be more efficient to downstep 7.4 to 5v than to upstep 3.7 to 5v. Any advice?
     
  3. KJ6EAD

    Senior Member

    Apr 30, 2011
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  4. Fruit bicycle spaceship

    Thread Starter New Member

    Jan 26, 2015
    3
    0
    3-4 hours is still pretty long, there has got to be some batteries I can order that charge most of the way in about an hour, even if they dont come in a housing with a 5v regulator, i can add a regulator to any battery.
     
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