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12VDC Solar to 1.2VDC Regulator?

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    #16
    Originally posted by CCinPA View Post

    As I ponder all this great information... Is it really true that a24v into a 12v will "boil" the 12v? Then taking this one-step-at-a-time... Would replacing the 12v rechargeable with a 24v rechargeable be a step in the right direction?
    Another way to read this question is 'what happens to the batter when it gets overcharged'? The answer depends upon the battery chemistry. For example, if you overcharge a lithium ion battery, then you can get metallic lithium to plate out...you don't boil the battery but you might ignite it. When you overcharge NiMH then you get electrolysis of water to Hydrogen and Oxygen...NiMH cells are designed with bit of catalyst, so for low rates of overcharge the H2 and O2 simply recombine to make water and heat. At high rates: yes, you boil the battery. Some types of Lead Acid battery will do the same; others will vent flammable gas.

    If you carefully match the source to the battery then you won't have a problem. But if you don't want to use a small solar panel on a relatively large battery, then you need a charge controller.

    -Jon

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      #17
      Originally posted by winnie View Post

      Another way to read this question is 'what happens to the batter when it gets overcharged'? The answer depends upon the battery chemistry. For example, if you overcharge a lithium ion battery, then you can get metallic lithium to plate out...you don't boil the battery but you might ignite it. When you overcharge NiMH then you get electrolysis of water to Hydrogen and Oxygen...NiMH cells are designed with bit of catalyst, so for low rates of overcharge the H2 and O2 simply recombine to make water and heat. At high rates: yes, you boil the battery. Some types of Lead Acid battery will do the same; others will vent flammable gas.

      If you carefully match the source to the battery then you won't have a problem. But if you don't want to use a small solar panel on a relatively large battery, then you need a charge controller.

      -Jon
      To continue with Jon's post, for flooded lead acid batteries, if the charge rate is below a certain percentage of battery amp hour rating, then you don't need a charge controller since the charger will never overcharge the battery. I dont remember the figure, you can probably Google it easily. Think of those motorcycle trickle chargers that you just leave on continuously. They put out about an amp. You can get a small simple chsrge controller from a place that sells solor/off grod equipment like backwoods solar.com.
      Ethan Brush - East West Electric. NY, WA. MA

      "You can't generalize"

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        #18
        Originally posted by synchro View Post
        Also, what is the requirement on ripple or noise on the 1.5V output. For example, if it's for lighting it would be relatively tolerant to noise. But an audio application would not be.
        Dc has no ripple
        John,

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          #19

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          Ebay. Put it in the waterproof box with the battery.
          John,

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            #20
            Or simply dip it in a can of polyurethane after making connections and let drip dry.

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              #21
              As I continue working towards a solution... I want to thank all for your patience with me.

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                #22
                Would this be an appropriate charge-controller?

                https://www.ebay.com/itm/12V-24V-Pro...Condition=1000


                Attached Files

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                  #23
                  Your solar panel is shown as 1.5W, 24V. That gives .063A. If the charge controller draws say 10ma, that is 1/6 of your energy budget. Your energy budget is tight enough with out that. I suspect that others are correct - no charge controller is required. A .063A source is not going to over charge any SLA battery.

                  You did read the specs on the charge controller?
                  Without data you’re just another person with an opinion – Edwards Deming

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                    #24
                    Originally posted by iceworm View Post
                    Your solar panel is shown as 1.5W, 24V. That gives .063A. If the charge controller draws say 10ma, that is 1/6 of your energy budget. Your energy budget is tight enough with out that. I suspect that others are correct - no charge controller is required. A .063A source is not going to over charge any SLA battery.

                    You did read the specs on the charge controller?
                    This is going to sound lazy... But I don't think I'd understand the specs... ?

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                      #25
                      Originally posted by electrofelon View Post

                      To continue with Jon's post, for flooded lead acid batteries, if the charge rate is below a certain percentage of battery amp hour rating, then you don't need a charge controller since the charger will never overcharge the battery. I dont remember the figure, you can probably Google it easily. Think of those motorcycle trickle chargers that you just leave on continuously. They put out about an amp. You can get a small simple chsrge controller from a place that sells solor/off grod equipment like backwoods solar.com.
                      The problem here is that the maximum charge current for a typical Flooded Lead Acid battery is .1 C where C is the 20 hour amp-hour capacity. If you are applying a constant current maximum charge (from an unregulated PV panel) you do not want to exceed .1 C but you need to recharge the battery fully within a roughly 6 hour period of peak sun. That means that you will end up with a large battery that is only partially discharged. But if you size the battery and panel for reliable recharging during winter conditions (maybe 4 solar hours per day when weather is good) then you arel likely to overcharge the battery to some extent in summer unless you have a charge controller that limits the float voltage.
                      Anything else will require that you have a provision for adding water to the battery as needed and recognize that you will lose some battery life.

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                        #26
                        Originally posted by CCinPA View Post
                        I like a challenge(no matter the size), then a solution
                        With all the helpful input... Here is what I came up with. Thoughts?
                        Forget the 24v solar cell you have, forget the big battery and controller idea.
                        These Chinese ornaments usually have an internal solar cell that charges a rechargeable battery internal to it and also acts as a ldr sensor to turn off at night. They require very little current as they use circuitry similar to a jewel theif.

                        Problem is, they have junk solar cells that can't adequately charge the internal lithium battery.

                        Just buy one of these off ebay, or perhaps two, and parallel the outputs.
                        Then wire in place of the original internal solar cell connections.

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                        John,

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                          #27
                          Thanks for all your help... Here is what I put into operation... It may not look pretty... But it works!
                          Attached Files

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