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  • Solar cell phone battery questions

    Hi all,

    I am trying to find the best solar cell phone charger for my cell phone. The phone battery is 3.8v 5.45wh and 1,440 mAh. I'm a little new to the solar sphere, and want to get a solar charger that has the right specifications, but I don't want to overpay for unnecessary storage/battery. I'd like to be able to fully charge my phone in 4 hours. Could you tell me the solar wattage necessary to do so, and the size/ specifications of the battery I would need? Any calculations would also be really helpful- I'm trying to figure this out!

    Thanks so much in advance!

    Mary

  • #2
    Hi Mary - Welcome to Solar Panel Talk!

    Please just post questions in one forum.

    Russ
    [SIGPIC][/SIGPIC]

    Comment


    • #3
      Originally posted by SolarMary View Post
      Hi all,

      I am trying to find the best solar cell phone charger for my cell phone. The phone battery is 3.8v 5.45wh and 1,440 mAh. I'm a little new to the solar sphere, and want to get a solar charger that has the right specifications, but I don't want to overpay for unnecessary storage/battery. I'd like to be able to fully charge my phone in 4 hours. Could you tell me the solar wattage necessary to do so, and the size/ specifications of the battery I would need? Any calculations would also be really helpful- I'm trying to figure this out!

      Thanks so much in advance!

      Mary
      So, I'll assume you have a dead battery and want to charge it to full in 4 hours. So you would have to harvest about 6 watt hours, and allow for some losses along the way. 6/4=1.5watts per hour - round up to 2 watts to make the math easier. I'll assume that you have 4 GOOD hours of solar charging power (in winter, many places do not, so you need a larger panel)
      So, a 3 watt panel, with the right charge controller and battery adapter, could do the job. Since I don't know of any that actually do, you may need to have a 5 watt panel, eat the losses converting the voltage to the cell phone, but a 5w panel, in full sun for 4 hours will get that battery charged.
      Powerfab top of pole PV mount (2) | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
      || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
      || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

      solar: http://tinyurl.com/LMR-Solar
      gen: http://tinyurl.com/LMR-Lister

      Comment


      • #4
        The panel would have to have excellent sun and orientation for the charging period.
        [SIGPIC][/SIGPIC]

        Comment


        • #5
          Hi all,

          Thanks for your responses! This is exactly what I needed.

          Adding another step, I'd like to charge a lead acid battery with the panel to store the energy for after dark/a cloudy day.

          Do you know the voltage/mAh of a lead acid battery I would need if I wanted to fully charge using the 3 or 5 watt panel, store that energy, and then use it to charge my phone with the aforementioned qualities?

          I would assume it needs to be at least as large as the 3.8v phone battery, but I've heard that only half of the energy from a lead acid battery is harvestable?

          Thanks again, this is such a great help.

          Kindly,
          Mary

          Comment


          • #6
            This is a solar battery charger for phones.
            Check it out at….http://www.amazon.com/Levin-trade-Ra...attery+charger

            Rick
            3.6 kw PV, Classic 150, Radian GS4048A, LFP 195A

            Comment


            • #7
              Originally posted by SolarMary View Post
              Do you know the voltage/mAh of a lead acid battery I would need if I wanted to fully charge using the 3 or 5 watt panel,
              There is no lead acid battery that small, and if there were would be pretty much useless. You can find some 12 volt 7 to 10 AH lead acid batteries, but they would require a 15 to 20 watt panel. Most new cell phones today use USB 3 charging which is 20 watts. Some of the tablets require 100 watts.
              MSEE, PE

              Comment


              • #8
                Hello Mary!

                First, forget carrying around a little sealed-lead acid agm. Not practical and not necessary these days.

                There is a lot of this stuff out there as commodity items, and I'll be very up front and say that as a battery fanatic, Anker tops my list and I have a few.

                Since the phone itself limits the maximum current charge you can use, about the easiest way to charge is to get close to maximum allowed, and that can be done easily by an Anker 14 watt folding panel. I normally get about 1.5 - 1.75a from it, which is pretty fast for a cellphone battery. The "smart IQ" port helps make sure that the cable I grab from the drawer will be configured for the fastest charge. In the old days, I had to hack these cables myself to do that, as some would artificially limit the charge current.

                Of course, you actually have to have decent solar-insolation, and this time of year that can be hard to find for many hours. For now, just go with the largest panel that gets close to the phone's own current-limitations.

                While I recommend the 14watt panel, they do make a smaller 8 watt panel. But if you don't mind the extra folds, having 14 watts available is going to help when solar conditions are poor, and especially when you just lay it flat, rather than angle it periodically during the day as you might have to do with the 8 watt panel.

                While you can charge the phone directly, you might want to opt for an external battery. I'm pretty glued to Anker, so again, something in the Anker Astro external battery line would be good. BUT, don't be tempted to get a large brick! Because you don't NEED to charge to full with these batteries, you can get a smaller unit for boosting, rather than full-charging.

                I hate to post links that look like pure salesmanship, especially this time of year. Anker is good, but there are others that are worthy. Just avoid the toys. They have charts and whatnot that show how many times you can charge depending on the phone you are using which might be easier than pulling out the slide-rule.
                http://www.ianker.com/

                Personally, for convenience, my ideal is a 6000ah Anker Astro Slim3. Pretty much covers most stuff, even though I also have one of their bigger (and less convenient) bricks. No cord to lose, yadda yadda. A small(ish) battery that is actually with you instead of a big brick in a drawer, is much more valuable. Of course, the 14 watt panels charges this just fine too.

                Just remember that these units typically only have about 500 full cycles in them. I have a friend doing a total charge / discharge to hers every single day, which only means that she'll be buying one every year despite my warnings.

                Comment


                • #9
                  Originally posted by Sunking View Post
                  .... Most new cell phones today use USB 3 charging which is 20 watts. Some of the tablets require 100 watts.
                  Actually, I think the high charge rates are "allowed" if the charger responds with the right handshake, otherwise it reverts to the USB1.1 half amp standard, for a much longer time. Just because they CAN fast charge, does not mean they HAVE to.
                  Powerfab top of pole PV mount (2) | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
                  || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
                  || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

                  solar: http://tinyurl.com/LMR-Solar
                  gen: http://tinyurl.com/LMR-Lister

                  Comment


                  • #10
                    Originally posted by Mike90250 View Post
                    Actually, I think the high charge rates are "allowed" if the charger responds with the right handshake, otherwise it reverts to the USB1.1 half amp standard, for a much longer time. Just because they CAN fast charge, does not mean they HAVE to.
                    I think you are right.
                    MSEE, PE

                    Comment


                    • #11
                      That's what I like about the Anker's "IQ" charge ports on the chargers and solar panels. They seem to get it right so that a fast charge can happen without me hacking or finding custom cables.

                      I do verify with an inline 5v usb ammeter-voltmeter do-hicky from amazon as well. All's good in the toy world.

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