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  • Home made solar battery charger

    I apologize if this has been answered before, but I searched and couldn't find the answers. Also apologize for my ignorance on the subject matter, but I'm not stupid and am trying to learn lol

    I use battery operated lanterns that take 3 D batteries apiece. I use rechargeable batteries and a solar charger I bought on amazon: "Solar powered battery charger charges 4 D, C, AA and AAA batteries", for $39.

    I love the charger, but it only charges 4 D batteries at a time. I'm planning on buying more lanterns and would like to build a charger that charges at least 12 D batteries at once.

    Although I've been studying electric circuits and solar stuff, I still am very undereducated in the subjects and need a lot of help.

    Specifically, what do I need to make such a charger? What are all the components, the size of panel, etc? I shop on amazon a lot, so if you could throw me a few links of the components on amazon, I'd be most appreciative.

    Thanks for reading this!

  • #2
    The best bet, would be to get a conventional battery charger that can manage as many cells as you need. Getting the design right to properly charge sealed rechargeable batteries is very tricky. I would not even attempt it myself.

    SO - I suggest this one:
    http://www.thomasdistributing.com/MA...ger_p_244.html
    a MAHA brand charger, 8 channels, 8 D cells, full charge in 5 hours @ 2A rate for D NiMH cells

    But it's going to take some serious power to do this, 3V @ 2A x 8 cells = 50 watts going into the batteries, that's likely 100w going into the charger to run all the control circuits. You can set things back to lower rates, but then you need more time (10 hours) to charge cells, and you don't have 10 hrs of sun in a day.

    How I would do it (if I needed to charge 12 batteries daily.

    2 of the Maha MH-C808M chargers $85 ea

    2, 200w PV panels (they only put out 80% of nameplate for 1 hr a day) $400

    Morningstar Sunsaver MPPT isa bit undersized, at 15A @ 12V, so you may burn it out. or not. maybe. $200
    http://www.morningstarcorp.com/products/sunsaver-mppt/
    -or-
    Rogue Power 20A MPPT, should be OK
    http://www.roguepowertech.com/produc...pt/mpt2024.htm $250

    12V generic deep cycle marine battery 80ah, 40 lb, used as buffer for the solar/inverter/charger.

    Bummer, have to add an inverter to get 120V AC for the D battery charger. Maha makes some smaller chargers that
    have a 12V power cord, but you'd never get 12D's done in a day without using 12 of the chargers

    12V 300 pure sine inverter (several models around, I like the morningstar SureSine 300) $200-300

    So, it's not going to be cheap, but it will work if you get 5 good sunny hours. Maybe won't get that much in winter, I've only have 1 sunny day in the last 3 weeks, lots of generator time here.
    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


    • #3
      Wow, that sounds like something I don't want to tackle. I truly appreciate your help, thanks for going to all that trouble to help me. Maybe I should just go ahead and buy some more of those chargers off amazon.

      I figured, since the solar panel they used isn't very big and it charges 4, then I wouldn't need one very much bigger to charge 3 times as many.

      Thanks again, and I'm off to amazon!

      Have a great day!

      Comment


      • #4
        Originally posted by jackx View Post
        ...
        I figured, since the solar panel they used isn't very big and it charges 4, then I wouldn't need one very much bigger to charge 3 times as many. ....
        I hope Amazon will tell you how many hours (Days actually) it will take that small panel to charge 4 D NiMH batteries.

        My guess is 2 days to charge 1 dead battery . They want to sell you stuff. I want you to have something that works, but it will cost. power is not free, and 12 dead D batteries will require a lot of power to recharge.
        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


        • #5
          They make lanterns that will recharge themselves with solar.

          Comment


          • #6
            Originally posted by jimindenver View Post
            They make lanterns that will recharge themselves with solar.
            Most of those small lanterns have a very small solar cell. Unless they get some really good sunlight it can take days to fully charge it back to 100%.

            Read the fine print and you will see they may give the amount of charge time in "hours" but when you do the math it comes down to 2 1/2 days of good sunlight.

            Comment


            • #7
              You are probably right although there are plenty on the RV forums that swear by them. We have a 30 year old twin tube florescent lantern that takes 4 6v batteries, we change them out every few seasons needed or not. Those batteries have gotten so expensive that this next go around I will spend less replacing it with a LED lantern if I can find one bright enough.

              Comment


              • #8
                Originally posted by jimindenver View Post
                You are probably right although there are plenty on the RV forums that swear by them.
                Forums perpetuate more BS than one can imagine - we try to keep it to a minimum here but many sites don't bother.
                [SIGPIC][/SIGPIC]

                Comment


                • #9
                  Originally posted by jimindenver View Post
                  You are probably right although there are plenty on the RV forums that swear by them. We have a 30 year old twin tube florescent lantern that takes 4 6v batteries, we change them out every few seasons needed or not. Those batteries have gotten so expensive that this next go around I will spend less replacing it with a LED lantern if I can find one bright enough.
                  Most of those little solar charging pv lights are cute and are fun to talk about but have not longevity due to poor battery design and very small solar panels.

                  I have one of those twin tube florescent lanterns using D size batteries. It has worked well but I think when it dies it would be hard to find a lantern using those older florescent lamps. More than likely the new ones are all LED style.

                  I have recently replaced about 95% of the old 12v 6w incandescent lights with 2w LED type in my RV. They seem to put out as much or more light as the incandescent did with much whiter light. So far I am happy with them.

                  LED lights and lamps keep coming way down in price so I would expect the florescent and incandescent ones to slowly disappear from the market.

                  Comment


                  • #10
                    for charging nicads/nimh, i use an rc charger. I bought a triton2 charger on ebay for 30 dollars. This charger charges everything, lipo/nicads/nimh/lead acid. It charges at max 7 amps but for nicads/nimh , i never charge above 1.5 amps.
                    The beauty of this charger it uses any 12 volt battery as the power source, which you can use a solar panel to keep charged up. and it will easily charge 12 batteries at one time if you connect them in series. i use it to charge my harbor freight 18 volt nicad packs for my power tools. (according to the box it can charge up to 24 nicads at one time). at first i was a little sceptical about how this charger could charge an 18 volt pack when the input power of the charger was only 12 volts, but the LCD screen does show the charge voltage was over 20 volts. At 1.5 amps my harbor freight 18 volt pack takes less than an hour to charge. Thats good enough for me.
                    The original wall plug that comes with these harbor freight tools are trickle chargers with no cutoff, the directions even say never leave charger connected for more than 3 hours or it will ruin the batteries. With the triton it will peak charge them and shutoff when they are done. The lcd screen will tell you at a glance the status of the batteries, how much mah you have charge them and beeps when its done.
                    i recently bought another triton for 20 dollars this is the original model 1 which only charges at 5 amps max. For charging nicads these cant be beat, i also use them to charge my 12 volt 17 ah jump start pack.
                    The newer rc chargers can put out more amperage but the prices are much higher.

                    Comment


                    • #11
                      Originally posted by jony101 View Post
                      for charging nicads/nimh, i use an rc charger. I bought a triton2 charger on ebay for 30 dollars. This charger charges everything, lipo/nicads/nimh/lead acid. It charges at max 7 amps but for nicads/nimh , i never charge above 1.5 amps.
                      I use an iCharger 306B myself for much the same duties. Unless you are a battery fanatic, rc chargers can do more harm than good if not set up properly. One problem I see with your nicad setup is charging all the batteries in series without any sort of balancing circuit - or do you make use of that with your own custom balancing harness?

                      But as Mike points out, at the end of the day, one still needs to properly solar charge the 12-24v battery bank you are using as a source for the chargers. It can be done, but only the battery-fanatic (yes, I'm one), or rc modeling mindset will go to that extreme. For more normal folk, this isn't really practical.

                      Comment


                      • #12
                        Originally posted by jackx View Post
                        Specifically, what do I need to make such a charger? What are all the components, the size of panel, etc? I shop on amazon a lot, so if you could throw me a few links of the components on amazon, I'd be most appreciative.
                        Jack - to keep things simple, solar and lanterns have moved well beyond the D-cell setups. As you've seen, cobbling all the pieces together to do it *right* is a pain and costly. I've done it.

                        What I'd suggest is looking into rechargeable lithium powered lanterns that have a 5v usb charging port to recharge with. I've seen quite a few on Amazon.

                        But to charge them, simply use an Anker 14 watt foldable solar panel. It has a 5v usb smart charge output, and I've measured 1.7A under best conditions from them at the 5v output. That would charge most lithium-powered lanterns in about 4 hours or less from a heavy discharge.

                        To verify charging, I like to use 5v usb voltmeters similar to this one:
                        http://www.amazon.com/BESTOPE-Detail...+usb+voltmeter

                        This keeps things fun, simple, and interesting while reading up on how to power your 2kw solar arrray for the offgrid cabin.

                        Comment


                        • #13
                          Originally posted by PNjunction View Post
                          Jack - to keep things simple, solar and lanterns have moved well beyond the D-cell setups. As you've seen, cobbling all the pieces together to do it *right* is a pain and costly. I've done it.

                          What I'd suggest is looking into rechargeable lithium powered lanterns that have a 5v usb charging port to recharge with. I've seen quite a few on Amazon.

                          But to charge them, simply use an Anker 14 watt foldable solar panel. It has a 5v usb smart charge output, and I've measured 1.7A under best conditions from them at the 5v output. That would charge most lithium-powered lanterns in about 4 hours or less from a heavy discharge.

                          To verify charging, I like to use 5v usb voltmeters similar to this one:
                          http://www.amazon.com/BESTOPE-Detail...+usb+voltmeter

                          This keeps things fun, simple, and interesting while reading up on how to power your 2kw solar arrray for the offgrid cabin.
                          That looks like a neat little USB meter. Based on that low price how accurate would you say it is?

                          Comment

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