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A little basic help please

Discussion in 'Renewable Energy' started by browningbuck, Dec 1, 2009.

  1. browningbuck

    browningbuck New Member

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    kinda new to some of this, so please educate me.

    now im use to charging a battery with a matched Voltage charger ie. 12v battery 12v charger.

    how ever i have a LiPoFe4(4 A123 cells in series creating 12v), can this be wired in to a 3v solar panel thats creating 130ma? or would i need 4 panels to create 12v 130ma? charge rate is not an issue (hence the LOW mah)

    anyway thank you for all your help in advance.
     
  2. browningbuck

    browningbuck New Member

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    really, i thought this would have been an easy answer.... can anyone help me out?
     
  3. Pommie

    Pommie Well-Known Member Most Helpful Member

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    Your knowledge of Lipos is none existent and so no one bothered to reply. Try googleing and then come back with a question that isn't a simple search.

    Mike.
     
  4. dave

    Dave New Member

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  5. browningbuck

    browningbuck New Member

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    wow that time you took to insult me could have been spent on the simple answer (which probably would have been shorter)

    okay, let me try and restate my original question with a little more information.
    the A123 cell is much more forgiving than a standard Lipo "Not sensitive to straying outside recommended voltages (2-3.6)"

    so would this work?

    [​IMG]
     
  6. tcmtech

    tcmtech Well-Known Member Most Helpful Member

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    No. it will only charge the cell at the negative end.
     
  7. magickaldan

    magickaldan New Member

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    Either physically disconnect the series connection when charging or add a switches between the batteries. It will charge them but with 1/4 of the 130ma for each battery. So each battery would get ~32.5ma. Or create a voltage booster to boost the 3v to 12v, and accept the losses in conversion.

    What size batteries are they? 1100? or 2300ma? Gonna take 40+hrs to charge 1100ma batteries and 70+hrs for 2300ma. But if you had 4 solar cells it would take ~17hrs for 2300ma.
     
  8. spindrah

    spindrah New Member

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    really??

    you think you can connect the positive terminal to ground without popping them??
     
  9. browningbuck

    browningbuck New Member

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    what is it with people shooting there mouth off like this? is it cause your on the internet that you think you can talk to someone that way? revised my drawing to better explain what was in my head



    thank you magickaldan for actually having custructive comments. i agree that the time would actually be really long to recharge the full unit (they are 2300), but at the same time the most draw on this would be 500mah for maybe an hour a day. but time isnt that big of an issue.

    i also got to thinking about the solar cell as well, but correct me if i am wrong, but would i need to actually reverse the polarity to recharge the system?

    [​IMG]
     
    Last edited: Dec 2, 2009
  10. Pommie

    Pommie Well-Known Member Most Helpful Member

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    Of course it won't work. You are shorting the solar panel.

    Mike.
     

    Attached Files:

  11. magickaldan

    magickaldan New Member

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    If you add switches then it won't short out.
     

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  12. mneary

    mneary New Member

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    With two diodes in series with each 3V cell, you'll be wasting a significant amount of charging power. And with the necessary switches shown by magickaldan, it means you can't charge while using the 12V output.

    Either rewire the solar for 12V (you'll actually need more than 12V to meet the charging requirement of the batteries) or build a 3V->12V boost converter. They aren't that difficult at low power levels.
     
  13. spindrah

    spindrah New Member

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    Not that difficult? for you maybe, but for someone with so little electronics knowledge, you will need to give him step by step instructions.
     
  14. magickaldan

    magickaldan New Member

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  15. browningbuck

    browningbuck New Member

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    okay guys, that step up converter is really the best idea so far, how ever i think that i will still at least need 1 more solar cell due to the lack of mah. i couldnt figure out how much i would lose converting 3 to 12, so what i think is i run two solars in parallel and just boost my mah a bit. thanks a ton guys

    and spindrah please dont underestimate people. i can build something that is already drawn, it was coming up with an idea that was out side the box. sorry that this thread was such a bothersome ordeal for you, but since you are on a forum there is some common edequate that your mom should have tought you "if you dont have nothing nice to say, dont say anything at all"...
     
    Last edited: Dec 3, 2009
  16. tcmtech

    tcmtech Well-Known Member Most Helpful Member

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    Some people are just naturally grouchy thats all. Dont concern yourself with others manors and be thankful for the ones you have! :)
     
  17. browningbuck

    browningbuck New Member

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    okay, not to try and go back and fight (rather learn the flaw in my theroy) why wouldnt the revised system above work? (i see that the resistance from the diodes would make it ineffiecent...so thats why i wouldnt use it) but it was said that i am shorting the panel, but isnt that how you run a solar panel(not shorted of coarse since it SUPPLIES electricity) but still it has to close the loop?

    anyway so revised revised drawing with now 12V supply would be done like so correct?
    (i know it looks backwards but please think this through with me)(or would this actually just increase voltage and never charge the battery?)
    [​IMG]


    if wired like this, you would never actually recharge the battery rather you would run as much power as you could supply from the solar cell, then the rest would be drawn from the battery (but then again, if there is no draw, the access power would then be stored back to the battery)
    [​IMG]
     
    Last edited: Dec 3, 2009
  18. summitville

    summitville Member

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    Browningbuck, If you redraw your original diagram slightly differently you will reveal the electrical flaw. Move the top diodes slightly left and the bottom diodes slightly right to show each Diode connected to the middle of the wire between the batteries. Now you will plainly see the current from your solar cell (+) will flow into the top diode and then directly out the bottom diode back to the solar cell (-). The Top Left Diode does nothing and the bottom right diode does nothing. The middle three pairs of Series Diodes are Parallel connected and will each pair fight for current to make the BEST 1.4 Volt Short-Circuit on your Solar Cell. That is not what you wanted. I am sorry but no current will flow through the batteries.

    IF you decide to Series Charge your batteries you need to boost your Solar Cells Voltage to well ABOVE 12 Volts. It appears that the A123's need to be CHARGED to 3.6 Volts MAX. That may be tricky to manage on each battery in a Series Circuit. Each battery can/will have a different Charge Voltage because of different internal resistances. So, your absolute MAXIMUM Charge Voltage for your Boost Circuit is 4 x 3.6V = 14.4 Volts. (3.3v x 4) = 13.2 Volts is your NOMINAL Battery Voltage not 12V. Do not allow any one battery to go above 4.2V for any length of time or damage to that battery will result.

    I am not exactly sure what you should do when your battery pack hits 14.4 Volts. Typcially, a fast charger then goes into Slow Charge and drops the current to a lower level to add a ""finish" slow charge and then eventually stops charging all together. You can hold a CHARGED Battery pack at 13.2 Volts forever without over-charging (assuing each battery is at 3.3V).

    You are probably designing a "Slow" charger so I would think you need to stop charging when you hit 14.4 Volts and then back down to 13.2V to HOLD the charge.

    Does this info help?


    Properly recharging batteries (especially in series) without damage is not as simple as one might think.
     
    Last edited: Dec 3, 2009
  19. browningbuck

    browningbuck New Member

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    well it seem like the idea i thought was correct is
    [​IMG]

    so now i would need to get a 1N5400 to handle the 2300mah of the cells corret?
     
    Last edited: Dec 3, 2009
  20. summitville

    summitville Member

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    Browningbuck, In you latest schematic / bottom drawing, in your case it will work if only you have 15.1 Volts from your Solar Panel. You need 14.4 Volts to Charge the A123 Battery Pack plus the 0.7 Volts for the diode drop. 15.1v = 14.4v + 0.7v

    In your first drawng you showed Solar cell as 3 Volts
    and in a following drawing you showed Solar Cell as 12V.
    What is the actual output voltage of your Solar Panel?

    Also, this latest drawing you picked is for
    3 series connected 1.2Volt NiMh batteries
    and a 4.5v Solar cell - you don't have that do you?
     
    Last edited: Dec 3, 2009
  21. browningbuck

    browningbuck New Member

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    the drawings with the NiMh was just to illustrate that the solar panel is to by wired in parallel, rather than in series. not really anything pertaining to the NiMh cells just verifying theory.anyway i found a stupid solar cell at Cabels that should help me out, its a 12V system (i need to check the specs and see if the unit already has the correct sized diode in it) anyway thanks summit. i appologize for the confusion the last attachment added to this already convoluted thread :)
     

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