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Battery Charger Project

Discussion in 'General Electronics' started by Gary Lecomte, Oct 27, 2003.

  1. Gary Lecomte

    Gary Lecomte Guest

    I just posted another battery charger with minimum parts count. Both
    current and voltage regulated, but it is a Non-Isolated design. Can
    be useful in some applications.

    If interested, go to:
    http://www3.telus.net/chemelec/Projects/Projects.htm

    Take care......Gary
     
  2. Bill Bowden

    Bill Bowden Guest

    Do you think there any danger to the diodes if power
    is applied at the peak of the line voltage, say 340 volts?
    The current could be many amps for a short period, but
    maybe only a microsecond or so. I usually use a resistor
    in series, but maybe it's not needed?

    -Bill
     
  3. Gary Lecomte

    Gary Lecomte Guest

    Hi Bill, It shouldn't be a problem. The 1N4005's have a surge current
    of 30 amps and the Capacitors Reactance of the 2.2 ufd cap should
    quite effectively stop any peak currents to a reasonable value.
    However at 340 Volts, you will need to use a Much smaller Capacitor to
    get the 100 Ma. in my circuit
    (About .8 ufd and at least a 400 volt rating)

    Take care.........Gary
    **************************************************************************
     
  4. Yeah, right. "Take care", and you have a project that can be deadly.

    I have a gizmo that's very similar to your circuit, that looks like the
    plug on the end of a power cord, minus the power cord. On one end there
    are the two brass prongs, and on the other end there are the standard
    snap-on clips for a 9V battery. This device was imported from Japan in
    the '60s, and was made for charging these batteries. It was downright
    dangerous, and you won't find such devices nowadays because they _are_
    dangerous. If you build one of these circuits, you should enclose the
    battery under a lid with an interlock switch to shut it off when the lid
    is opened, so that someone can't touch the contacts when it's live.

    BTW, the 470 uF (not MFD) capacitor is of little use in this circuit.
    The battery dowsn't need filtered DC, and the cap can't charge up to
    more than the zener voltage.

    --
    ----------------(from OED Mini-Dictionary)-----------------
    PUNCTUATION - Apostrophe
    Incorrect uses: (i) the apostrophe must not be used with a plural
    where there is no possessive sense, as in ~tea's are served here~;
    (ii) there is no such word as ~her's, our's, their's, your's~.

    Confusions: it's = it is or it has (not 'belonging to it'); correct
    uses are ~it's here~ (= it is here); ~it's gone~ (= it has gone);
    but ~the dog wagged its tail~ (no apostrophe).
    ----------------(For the Apostrophe challenged)----------------
    From a fully deputized officer of the Apostrophe Police!

    <<Spammers use Weapons of Mass Distraction!>>

    I bought some batteries, but they weren't included,
    so I had to buy them again.
    -- Steven Wright

    FOR SALE: Nice parachute: never opened - used once.

    (Problem) Evidence of leak on right main landing gear
    (Solution) Evidence removed

    F
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    m
    s
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    ..
     
  5. It should have a 100 ohmn resistor in series with the line, to make a
    low pass filter. This helps prevent high voltage transients from
    passing thru the capacitor and damaging the rest of the circuit.

    --
    ----------------(from OED Mini-Dictionary)-----------------
    PUNCTUATION - Apostrophe
    Incorrect uses: (i) the apostrophe must not be used with a plural
    where there is no possessive sense, as in ~tea's are served here~;
    (ii) there is no such word as ~her's, our's, their's, your's~.

    Confusions: it's = it is or it has (not 'belonging to it'); correct
    uses are ~it's here~ (= it is here); ~it's gone~ (= it has gone);
    but ~the dog wagged its tail~ (no apostrophe).
    ----------------(For the Apostrophe challenged)----------------
    From a fully deputized officer of the Apostrophe Police!

    <<Spammers use Weapons of Mass Distraction!>>

    I bought some batteries, but they weren't included,
    so I had to buy them again.
    -- Steven Wright

    FOR SALE: Nice parachute: never opened - used once.

    (Problem) Evidence of leak on right main landing gear
    (Solution) Evidence removed

    F
    o
    d
    d
    e
    r

    f
    o
    r

    s
    t
    u
    p
    i
    d
    "
    n
    o
    t

    e
    n
    o
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    g
    h

    i
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    ..
     
  6. default

    default Guest

    Peak of the line voltage for 120 volts is ~170 Volts. Peak to peak is
    340 and a DC rated cap should be 3X higher than the AC line.

    The circuit would probably work and last forever, but I'd go with a
    100 ohm resistor to limit the inrush current all the same. The
    current is only limited by the circuit impedance until the 470 uf
    charges. When the reactance cap is at zero volts, and power applied
    at the peak of the sine wave, the wire inductance and resistance of
    the wire and parts are the only limiting factors.

    A flame proof resistor will also serve to act as a fuse if the
    reactance cap shorts. In that scenario, your zener may vaporize or
    flame and the electrolytic turn into shrapnel. The cost of the
    resistor is a bargain considering the safety it adds.

    Does the circuit really need the electrolytic cap?
     
  7. Bill Bowden

    Bill Bowden Guest

    I'm not sure if the resistor is needed or not. When you turn the
    thing on at the peak of the line (170 volts) the current is limited
    only by the wire resistance, maybe an ohm or so. This means the diode
    current will be 170 amps which falls off with a time constant of
    RC or 2uS. If the time constant is 2uS, the current falls to almost zero
    in 10uS. So, we have an average current of 85 amps for 10uS which
    amounts to 850 microjoules of energy if the diode voltage is 1 volt.
    I don't think a millijoule is much to worry about since some of
    those avalanche MOSFETS are rated at 500 mJ. This is 500 times less,
    so I doubt the diode will blow. But the capacitor could be already
    charged to the full line voltage and switched on at the negative peak
    which would multiply the problem by 4. Still not much at 4 millijoules.
    I think I'll try that circuit using a couple 1N914 diodes back to back
    to see if I can blow them. They should survive.

    -Bill
     
  8. Gary Tait

    Gary Tait Guest

    There is a commercial product, for a cordless power tool, that is a
    charger that is directly connected to the line. The terminals are deep
    inside the unit where the battery is inserted.
     
  9. If it's used as a power supply. But for a dharger, I don't believe
    so.

    I've heard that the pulsating DC ripple knocks some hydrogen bubbles
    off one of the plates, but I don't know if this applies to all
    types of batteries.

    --
    @@[email protected]@[email protected]@@[email protected]@[email protected]@[email protected]@@[email protected]@[email protected]@[email protected]@,@@[email protected]@[email protected],@@[email protected]@[email protected]@[email protected]@
    ###Got a Question about ELECTRONICS? Check HERE First:###
    http://users.pandora.be/educypedia/electronics/databank.htm
    My email address is whitelisted. *All* email sent to it
    goes directly to the trash unless you add NOSPAM in the
    Subject: line with other stuff. alondra101 <at> hotmail.com
    Don't be ripped off by the big book dealers. Go to the URL
    that will give you a choice and save you money(up to half).
    http://www.everybookstore.com You'll be glad you did!
    Just when you thought you had all this figured out, the gov't
    changed it: http://physics.nist.gov/cuu/Units/binary.html
    @@[email protected]@[email protected]@[email protected]@[email protected]@[email protected]@[email protected]@@[email protected]@[email protected]@@[email protected]@[email protected]@[email protected]@[email protected]@[email protected]@[email protected]@@
     
  10. Gary Lecomte

    Gary Lecomte Guest

    A Few Comments:

    Yes this circuit can be dangerous, that is why the warnings in my
    article.

    No the 470 Cap isn't needed if you are only charging a battery, but
    can be helpful if it is also running a circuit at the same time.

    As to uf which I agree is proper abbreviation, but back in the 50's
    when I started in electronics, numerous schematics used various
    definitions and I picked up some bad habits. Sorry if it offends
    anyone, but we all have bad habits.

    Placing a 100 ohm resistor can be a good idea as it will act as a fuse
    in the event of a short, however a standard 1/2 watt resistor will
    constantly fail. If you really want this I suggest a wire wound type
    resistor or even a 250 ma fuse.

    I have used this charger design in a large number of speciality
    industral products that have been in the market place for over 20
    years. These products were all used by "Electric Utility Companies"
    throughout the world. "They are totally isolated from the user with a
    plastic case and knobs". No limiting resistor and no problem. I used
    both Phillips "366 series" and Evox "MMK" caps, both rated at 250
    volts. "None of these chargers have ever failed to date". The only
    thing I did do that is not mentioned in my article was to put a small
    brass heatsink on the zener. Not sure if it was really necessary but
    it does reduce some heating.

    A number of units were also produced for 220/240 volt operation by
    simply putting another cap in the neutral line. They were also as
    reliable.

    This design is "definately not suitable for all charging
    applications", but it can have practical safe applications.

    Take care.....Gary
    *************************************************************************
     
  11. Not a matter of bad habits, but a matter of internationally accepted
    abbreviation standards. The m or M in MFD, by international
    standards, means mega if it's capitalized, or milli if it's lower
    case. So it's a matter of confusion as to what you mean. I and many
    others remember those days, and also picked up those bad habits, but
    we had to change to the new standards. It's time you did so, too.

    --
    @@[email protected]@[email protected]@@[email protected]@[email protected]@[email protected]@@[email protected]@[email protected]@[email protected]@,@@[email protected]@[email protected],@@[email protected]@[email protected]@[email protected]@
    ###Got a Question about ELECTRONICS? Check HERE First:###
    http://users.pandora.be/educypedia/electronics/databank.htm
    My email address is whitelisted. *All* email sent to it
    goes directly to the trash unless you add NOSPAM in the
    Subject: line with other stuff. alondra101 <at> hotmail.com
    Don't be ripped off by the big book dealers. Go to the URL
    that will give you a choice and save you money(up to half).
    http://www.everybookstore.com You'll be glad you did!
    Just when you thought you had all this figured out, the gov't
    changed it: http://physics.nist.gov/cuu/Units/binary.html
    @@[email protected]@[email protected]@[email protected]@[email protected]@[email protected]@[email protected]@@[email protected]@[email protected]@@[email protected]@[email protected]@[email protected]@[email protected]@[email protected]@[email protected]@@
     
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