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  • project of mine: 12v panel to charge 8 aa batteries

    I have a 12v 10 watt panel and I wanted to use it to charge AA batteries. I have a 8 AA battery case, and a blocking diode. Is there anything else that I need? This is my first solar project. Has this been done before? Any advice for me? One question that I have is how long should it take to charge the batteries?

  • #2
    Charging AA batteries, you need to either babysit the setup, and disconnect individual cells as they get full, or use a regular battery charger running from a 12V battery, and the PV panel keeps the battery charged.


    Lets figure out what 10 watts gets you. A normal AA battery is 1 Ah of capacity, or 1.2 watt hours (V x A = W ) and (W x Hours = Wh)

    So in theory, a 10W panel could charge 8 batteries in less than 3 hours. In practice, you only get about 50% of label wattage actually usable, delivered into the batteries. You will also find the small 10W panels, the 10 w is like the 300W stereo ads from the 70's, in reality, it's a tenth of that, Small panels seldom meet their power spec. And the panel is 12V, and batteries are 1.22V, so there is a problem there too.

    I'd suggest looking into about a 30w panel, to charge a small AGM (not GEL) 12V battery, via a 12V charge controller (Morningstar makes several good low power controllers). Then use a 12V car power cord to pwer a MAHA AA battery charger (see the model in my .sig) to properly charge the batteries from that.
    spreadsheet based voltage drop calculator:
    http://www.solar-guppy.com/download/...calculator.zip
    http://www.solarpaneltalk.com/showth...oss-calculator

    http://www.mike-burgess.org/PVinfo_2.html

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,
    battery lugs http://tinyurl.com/LMR-BigLug
    Setting up batteries http://tinyurl.com/LMR-NiFe

    gear :
    Powerfab top of pole PV mount | 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

    Comment


    • #3
      Originally posted by natel View Post
      I have a 12v 10 watt panel and I wanted to use it to charge AA batteries. I have a 8 AA battery case, and a blocking diode. Is there anything else that I need? This is my first solar project. Has this been done before? Any advice for me? One question that I have is how long should it take to charge the batteries?
      The previous reply has you covered.

      But you might be interested in this site if you like eletronic hobbies: http://www.solorb.com/elect/solarcir...rge/index.html

      Or this: http://www.evilmadscientist.com/article.php/solar

      David Cook also has a circuit project: http://www.robotroom.com/Solar-Recharging.html

      I haven't tried these projects yet. It's just things I bookmarked.

      Comment


      • #4
        AA charger and solar

        Originally posted by natel View Post
        I have a 12v 10 watt panel and I wanted to use it to charge AA batteries. I have a 8 AA battery case, and a blocking diode. Is there anything else that I need? This is my first solar project. Has this been done before? Any advice for me? One question that I have is how long should it take to charge the batteries?
        Hi

        I have not tried with 8 AA batteries but I would think you should be able to do something.

        They do make AA battery chargers with built in solar panels but the one I have is very slow charging.

        Instead, I simply plug a old 5 watt amorphous panel (came with blocking diode installed) into a AA charger that came with both mains and 12 volt car charger.

        It works fine for 2 or 4 AA batteries for my radio, a LED camping lantern and cameras. I also plug a "torch" with a built in 3 AA battery into the panel and it charges as well....the torch has a wind up generator and mains power charger as well....but I never need to charge from mains.

        The panel sits in a west facing window at home and in summer, starts charging as early as 7 am (country NSW Australia) with the sun on the opposite side of the building. There is a large sloped metal roof next door about the same height that I think is giving me a lot of reflected light.

        In a good summers day, it will charge up to three times....maybe one set of 4 and two sets of 2.
        Now it is getting colder It starts charging later (8 am right now and only one of the red LEDs is on, so it is charging but very little right now with two batteries in it, I just unplugged it and plugged my "torch" in instead ...3 AA battery pack in it and it is charging).

        The 5 watt panel came with two power leads, one with alligator clips and one with a male cigarette lighter plug so I had a short female to female lead made up to plug the car charger lead into the panel.

        The charger I use is branded Hahnel and it says...input DC 12 volt 670mA Output DC 2.8/5.6v 800mA. The panel input is therefore down a bit but it still works fine and the green LED will come on when charged.

        Just occassionaly I think it gives a false charged indicator but I just unplug it and replug it and it is fine.

        Of course, do this at your own risk but i have not had to plug any of my AA chargers in to the mains power for months....actually I did the other night for a camera but was not needed).

        Comment


        • #5
          HI

          I should also say be very careful of using too MUCH solar power.

          I would not put a 2 or 4 AA charger directly on a 10 watt panel.

          It MIGHT be ok (and if shaded may be good) but might be too much as well.

          A self regulating panel to match your AA charger would be the way to go.

          Comment


          • #6
            Originally posted by noone View Post
            ...A self regulating panel to match your AA charger would be the way to go.

            Cool, where did you find a self regulating panel ??
            spreadsheet based voltage drop calculator:
            http://www.solar-guppy.com/download/...calculator.zip
            http://www.solarpaneltalk.com/showth...oss-calculator

            http://www.mike-burgess.org/PVinfo_2.html

            solar: http://tinyurl.com/LMR-Solar
            gen: http://tinyurl.com/LMR-Lister ,
            battery lugs http://tinyurl.com/LMR-BigLug
            Setting up batteries http://tinyurl.com/LMR-NiFe

            gear :
            Powerfab top of pole PV mount | 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

            Comment


            • #7
              Self regulating panel

              Originally posted by Mike90250 View Post
              Cool, where did you find a self regulating panel ??
              Hi

              Just means a panel that does not need a regulator as the voltage
              is only a little above 12 volts instead of the 17 or 18 or so that most are.

              There are lots of small panels around 5 watts or less that are self regulating.
              I would think that a panel around 14 or 15 volts should be ok to plug a AA charger into....depending on the amps.
              Some of those amorphous roll up type panels seem to be sold as self regulating.

              OT I was looking for a much larger self regulating panel for directly powering things for some projects but could not any and got a regular panel and found I did not need it self regulating....after that I found these.

              http://solar-gp.com/types-of-solar-panels.html

              Might be ok for smaller ones but for using in the hot Australian sun, I would think they might be ok to start but get too hot and lose power. (and i could not get an direct answer from an Ebay seller of them).

              Would be good in colder climates I would think.

              I guess I should stick to normal panels and use a longer lead and maybe try and use voltage drop to my advantage....for AA charging though some of these or similar might be ok???

              I just know i am happy with my 10 year old 5 watt amorphous panel plugged directly into a AA charger.

              Comment


              • #8
                not sure on how to go about that...BUT

                Originally posted by natel View Post
                I have a 12v 10 watt panel and I wanted to use it to charge AA batteries. I have a 8 AA battery case, and a blocking diode. Is there anything else that I need? This is my first solar project. Has this been done before? Any advice for me? One question that I have is how long should it take to charge the batteries?
                I'm not sure about that but I have a bunch of rechargeable Eneloops AA &AAA. They come with a 110 charger, I just charge my big 12v battery with 120watt panel then use a small 400watt inverter to charge them. Just make sure you charge them slow 4-6hours, Keep to ohms law and you'll be fine. Some how reduce your charging to 500 or less mamps. 300ma for about 6hrs. Sounds like a fun project.

                Comment


                • #9
                  OK, all funning aside, THERE ARE NO "SELF-REGULATING" panels.

                  Rechargeable batteries need to have a controlled recharge. Hooking up to a panel, and hoping for the best, really means you don't have your face near the batteries when they blow. Sometimes they just vent, sometimes the vent sticks and the cells swell up, and leak, and rarely, they go bang.

                  So do us all a favor, and give some credence to long term posters, and less to newer, unproven members when weighing advice.

                  We moderators, need to at least, give "safe & sane" and mostly code compliant advice. I can say to do what 2 of us do, use a panel, with a 12V charge controller, and a commercial AA battery charger to safely recharge the batteries.

                  Mike

                  Maha C401 aa/aaa Charger 12vdc input, universal wall wart powersupply.
                  spreadsheet based voltage drop calculator:
                  http://www.solar-guppy.com/download/...calculator.zip
                  http://www.solarpaneltalk.com/showth...oss-calculator

                  http://www.mike-burgess.org/PVinfo_2.html

                  solar: http://tinyurl.com/LMR-Solar
                  gen: http://tinyurl.com/LMR-Lister ,
                  battery lugs http://tinyurl.com/LMR-BigLug
                  Setting up batteries http://tinyurl.com/LMR-NiFe

                  gear :
                  Powerfab top of pole PV mount | 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

                  Comment


                  • #10
                    Originally posted by noone View Post
                    Just means a panel that does not need a regulator as the voltage
                    is only a little above 12 volts instead of the 17 or 18 or so that most are.
                    There is no such thing as a self regulating panel. Solar panels are current sources not voltage.

                    Now with that said it is entirely possible to connect a panel to a battery directly and leave it on there without doing any harm if you know what you are doing.

                    The key to doing so is that the battery AH capacity and panel current are matched up to do so with the appropriate voltage of the panel being somewhat higher than the battery it is connected too. The trick is the panel maximum current must be about C/100 or less where C = the AH capacity of the battery. So for example if you had a 100 AH 12 volt battery you can connect a 12 volt 15 watt or less panel directly to it without doing any real harm, unless it just left to sit for very long periods of time. What you are effectively doing is making a trickle charger.

                    Now with that said the panel would be worthless for any real charging as it is not capable of supplying any real meaningful charge current. It can only keep a fully charged battery fully charged. Piss poor way to go about it, but it can be done. In fact if you search the web you can find just such panels made for cars left to be parked for long periods of time that plug into the cigar lighter socket of about 5 to 15 watts. .
                    MSEE, PE

                    Comment


                    • #11
                      I did not invent the term!

                      Originally posted by Mike90250 View Post
                      OK, all funning aside, THERE ARE NO "SELF-REGULATING" panels.

                      Rechargeable batteries need to have a controlled recharge. Hooking up to a panel, and hoping for the best, really means you don't have your face near the batteries when they blow. Sometimes they just vent, sometimes the vent sticks and the cells swell up, and leak, and rarely, they go bang.

                      So do us all a favor, and give some credence to long term posters, and less to newer, unproven members when weighing advice.

                      We moderators, need to at least, give "safe & sane" and mostly code compliant advice. I can say to do what 2 of us do, use a panel, with a 12V charge controller, and a commercial AA battery charger to safely recharge the batteries.

                      Mike

                      Maha C401 aa/aaa Charger 12vdc input, universal wall wart powersupply.
                      Lots of panels are sold as "self regulating"
                      Google it or not...its JUST a term.
                      it just means panels that can be used directly
                      pretty much because the voltage is down to a level that should be fine for 12 volt things.


                      Mostly made by using fewer cells.

                      As I said, I would NOT use a panel with excessive amps. and I said I would not use a 10 watt panel with 2 or 4 battery AA charger (8 AA batteries and if you know what you are doing, you might well find a way of doing it).

                      My 5 watt panel is using a commercially sold AA charger and the input is less from the panel than it would from either a car cigarette socket or a mains charger even in full sun, let alone what it gets most of the time....when I DO use it with a mains charger the batteries get a LOT hotter than they do in the same charger from the solar panel.

                      I also said do this at your own risk.


                      I am not advocating hooking up a 200 watt panel to wire accross a single AA battery!


                      Edit
                      if you want me to say do this only if you know what you are doing, fine! i will.

                      Comment


                      • #12
                        Here is an example of something that does not exist.

                        Shell apparently believe self regulating panels exist...in fact they thought they made them....

                        See pages 3 and 11
                        http://www.physics.arizona.edu/~cron...stallation.pdf



                        I only post this as an example of what they are...I just found this page now when googling "self regulating solar panels"....the linked article is for much bigger panels and batteires than I am talking about.

                        Comment


                        • #13
                          Originally posted by noone View Post
                          Shell apparently believe self regulating panels exist...in fact they thought they made them....

                          See pages 3 and 11
                          http://www.physics.arizona.edu/~cronin/Solar/TEP module spec sheets/shell installation.pdf
                          I assume you are talking about this:

                          OK I read exactly what you are talking about, and like I said earlier you can connect a panel directly to a battery when certain conditions exist, and that is exactly what Shell is telling you. The panels are not self regulating in the sense you are speaking of. They give two examples.

                          ! is as I stated earlier used strictly for a trickle charger. Panels are current sources, not voltage. Providing you select a panel where Imp is roughly C/100 you can connect it directly to a battery using a diode.

                          The second application is a very specific installation again using the panels characteristic Isc ability being a current source. They make a special 50 watt panel with only 33 cells. It has to be connected to a 12 volt 100 AH or larger battery where there is a constant load on the. A 33 cell panel has an open circuit voltage of 16.5 volts and a Imp of 3 amps or C/33 to a 100 AH battery. It will work but is an extremely low rate of charge of not more than a trickle charge.
                          MSEE, PE

                          Comment


                          • #14
                            Just because someone says the moon is made of green cheese, does not mean it's true.

                            Just because some markerter slaps a SELF-REGULATING sticker on a product that has no regulation capability (it's just a panel, not a panel with a charge controller) does not mean it is accurate or adviseable to use.

                            If you match a tiny panel to a battery, like a spike landscape light, that can work, but it has to be designed to limit the power to the batteries. While I am able to to that design and caculation myself, it's not worth it, as anyone who has solar landscape lights finds out after a couple winter months.
                            spreadsheet based voltage drop calculator:
                            http://www.solar-guppy.com/download/...calculator.zip
                            http://www.solarpaneltalk.com/showth...oss-calculator

                            http://www.mike-burgess.org/PVinfo_2.html

                            solar: http://tinyurl.com/LMR-Solar
                            gen: http://tinyurl.com/LMR-Lister ,
                            battery lugs http://tinyurl.com/LMR-BigLug
                            Setting up batteries http://tinyurl.com/LMR-NiFe

                            gear :
                            Powerfab top of pole PV mount | 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

                            Comment


                            • #15
                              Originally posted by Mike90250 View Post
                              Just because someone says the moon is made of green cheese, does not mean it's true.

                              Just because some markerter slaps a SELF-REGULATING sticker on a product that has no regulation capability (it's just a panel, not a panel with a charge controller) does not mean it is accurate or adviseable to use.

                              If you match a tiny panel to a battery, like a spike landscape light, that can work, but it has to be designed to limit the power to the batteries. While I am able to to that design and caculation myself, it's not worth it, as anyone who has solar landscape lights finds out after a couple winter months.
                              Hi

                              I agree on saying just because someone on the internet says something it does not make it true.

                              In this case....it IS however wrong to say that self regulating solar panels do not exist.

                              They DO, it is just the name given to panels designed power things directly and made to work on a lower voltage than normal panels...often voltages below about 15 volts it seems and mostly made by using fewer cells than a normal 12 volt panel.

                              if your argument is that using it is not safe, fine, argue that but to say they do not exist just puts questions back at you.

                              Shell made that panel in the link above and refer to that as self regulating (and it was designed for battery charging....not just trickle charging). That is a 50 watt panel model SM50-H and it typically puts out 14.5 volts.



                              Kyocera make self regulating panels (model Kc35 is a 15 volt 35 watt panel.)

                              Some self regulating panels are sold with a 12 volt cigarette plug to plug 12 volt things in directly to the panel (like my 5 watt panel which as I said, came with both a 12 volt cigarette plug and a set of alligator clips).

                              The Go power self regulating panels are an example of that.

                              Most self regulating panels though are less than 5 watts I think.

                              Those G&P panels linked to earlier are the first I have seen at larger sizes.

                              I want a larger self regulating panle to use for cooking without batteries using a single solar panel and other purely resistive loads....funny thing is i would never use a self regulating solar panel of size to charge a battery without a regulator even if it was possible.


                              Using a small panel with a lower power input than from mains or a car to charge AA batteries in a commercially sold charger designed for a 12 volt power source?? no problem, works well and I can take it anywhere....though again, if you do it it is at your own risk and PLEASE make sure the panel power is not greater than the normal source.

                              Comment

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