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Not being able to understand simple LM317 lead acid battery charger

Discussion in 'General Electronics Chat' started by Willen, Nov 25, 2015.

  1. Nikolai Petrenko

    Nikolai Petrenko Member

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    I alway standby charge 12V 45Ah battery 1 time a month with 14V 5A source, it well ?
     
  2. chemelec

    chemelec Well-Known Member

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    Charging Just One Time a Month is a Cyclic Charge.
     
  3. Nikolai Petrenko

    Nikolai Petrenko Member

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    oh, my bad! Thanks
     
  4. dave

    Dave New Member

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  5. maxs

    maxs New Member

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    this is what ive been looking for but im going to change it up a bit to charge single cell 2vdc lead acid deep cycle cells or make it an adjustable voltage charger...thanks for posting...
     
  6. bountyhunter

    bountyhunter Well-Known Member

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    Your post just made my day.....
     
  7. bountyhunter

    bountyhunter Well-Known Member

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    Then you might want to start a thread about building a bench supply. Start with what voltage and current it has to provide, how many outputs, etc. And BTW: using chips like LM317 is a poor way to build a bench supply. It is not that difficult to build one with adjustable voltage and current using cheap op-amps and transistors.
     
  8. MikeMl

    MikeMl Well-Known Member Most Helpful Member

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    Oh Yeah???
     
  9. crutschow

    crutschow Well-Known Member Most Helpful Member

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    Why do you think it's a poor way? :confused:
    Certainly building one with op amps and transistors is significantly more complicated.
    An LM317 regulator is cheap, has a built-in reference, current limit, and over-temperature limit -- it's near bullet proof.
    The only limitation is that it won't go below 1.2V but not many applications require a voltage below that level.
     
  10. chemelec

    chemelec Well-Known Member

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    Crutschow, I Agree and if all you need is a Simple Battery Charger, Why get complicated.
     
  11. bountyhunter

    bountyhunter Well-Known Member

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    1) The LM317 won't adjust down to zero V.

    2) It doesn't have easily adjustable current limiting.

    It's just a really crappy way to go. For the time it takes to build it, I would do a better design.
     
  12. bountyhunter

    bountyhunter Well-Known Member

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    Here is the post I replied to:

    Willen said:
    I am going to make a bench power supply so that current is not fixed.

    My reply to that post:

    "LM317 is a poor way to build a bench supply."

    and I still say it. I was talking about a bench supply, something you will use a million times in your career. Don't build a piece of junk.
     
    Last edited: Apr 16, 2016
  13. bountyhunter

    bountyhunter Well-Known Member

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    Please see post ten in the thread. Building a lab supply is not that complicated. The design I posted has a lot of features which can be omitted, but the basics of voltage control loop and current control is shown.
     
    Last edited: Apr 16, 2016
  14. crutschow

    crutschow Well-Known Member Most Helpful Member

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    What post ten? :confused:
     
  15. tvtech

    tvtech Well-Known Member Most Helpful Member

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    Carl..you there?
     
  16. chemelec

    chemelec Well-Known Member

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  17. MikeMl

    MikeMl Well-Known Member Most Helpful Member

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    ...and then, when the circuit doesn't work, you can enter it into the simulator so that it can show you why it doesn't work...
     
  18. crutschow

    crutschow Well-Known Member Most Helpful Member

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    It's interesting the number of simulator Luddites on these forums. :rolleyes:
    A simulator is just a tool. If you don't want to use one fine, but why act like those who do are somehow wasting time? :confused:
    I seems apparent that you simulate a circuit so that you have a good shot that it will work in the real world.
    The chances are very high that if the circuit won't work in simulation then it won't work when you build it.
    And I've trouble-shot enough circuits to know that finding the problem in a simulator is a lot easier than finding it in a (non) working circuit.
     
  19. chemelec

    chemelec Well-Known Member

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    And I have found that some circuits that Simulate correctly, don't work in real life.
    And Visa Versa.

    However I am Fortunate that I already have All the parts, so no need to Buy any for playing.

    Crutschow Wrote: And I've trouble-shot enough circuits to know that finding the problem in a simulator is a lot easier than finding it in a (non) working circuit.
    This Just Depends on your SKILLS
     
  20. crutschow

    crutschow Well-Known Member Most Helpful Member

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    Yes some circuits will simulate but not work when built, but it's rare for a circuit to not simulate correctly (other than simulator problems such as convergence issues) but still work in practice.

    Of course trouble-shooting depends upon your skills. That's obvious.
    But in the simulation you can readily look at all the node voltages and branch currents to see what's happening.
    That's not possible in the actual circuit where it's difficult to look at more than two (or perhaps four if you happen to have a 4-channel scope) node voltages, and impossible to easily look at most branch currents.
    It's also easy to modify component values to see their effect on circuit operation.

    An example: I was given an op amp circuit at work that was exhibiting instabilities and I was asked to trouble-shoot it.
    I couldn't determine any obvious problems by probing the circuit so I simulated the circuit.
    Initially it worked fine but when I added in the estimated stray capacitance at the op amp input from the coax input line the instability was seen.
    So the circuit design was modified, and simulated to optimize the fix before the mod was done to the circuit.
    The circuit worked fine after that.
    If I hadn't simulated the circuit, it likely would have taken me much longer to determine the cause of the problem as well as what the best fix would be.
     
  21. bountyhunter

    bountyhunter Well-Known Member

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