Connect with us

12V 3Amp monitor - can I use a 12V 4.5 Amp battery? Help please

Discussion in 'Electronic Repair' started by David D, Apr 26, 2007.

Scroll to continue with content
  1. David D

    David D Guest

    I don't want to fry my security monitor, but I want to hook up a 12V
    4.5A rechargeable battery to it. Since the monitor on the back says
    "12V 3amp", would the monitor fry or would it just take what it needs
    and be ok with this amperage?

    Thanks
     
  2. Meat Plow

    Meat Plow Guest

    It will just use what it needs.

    --
    #1 Offishul Ruiner of Usenet, March 2007
    #1 Usenet Asshole, March 2007
    #1 Bartlo Pset, March 13-24 2007
    #10 Most hated Usenetizen of all time
    Pierre Salinger Memorial Hook, Line & Sinker, June 2004
    COOSN-266-06-25794
     
  3. Ryan Weihl

    Ryan Weihl Guest

    In this case the question should be:
    "how long can I use the monitor before I have to recharge the
    battery?"

    --
     
  4. Gary Tait

    Gary Tait Guest

    A little over an hour.Maybe more if you are lucky.
     
  5. Make sure the polarity (+ and -) are correct and you'll be fine.
     
  6. Guest

    Guest Guest

    beware, as the battery discharges, the voltage will drop. as that happens
    the monitor will attempt to compensate for the loss of voltage and may (
    may) cause internal power regulating components to overheat or fail.

    these things require a steady 12v level to attain good design performance
    (give or take a volt or two). if you are lucky it will just slowly dimm and
    become uselesss, then u know its time to recharge the batt, or it may just
    turn itself off due to voltages it will not accept,

    it depends on the manufacturer and just how much design thought they have
    invested in the monitor

    some may be very forgiving, some may give u poor performance as the battery
    volts drops.

    if it starts to smoke, you know what to expect.

    be very attentive during the first time you use the battery setup, smell,
    feel and even use a voltage meter DVM to track the voltage value of the
    battery power.
     
  7. Guest

    Ï/Ç David D Ýãñáøå:
    I 'm from greece and i don't know so much english. Yes you can use
    this battery the problem is in Volts. If you have a batterry with up
    of 12V don't try to use it with this monitor because you burn this
    monitor. The 4.5 Amperes of battery say how much current you can use
    from battery and if you have a monitor with up of 4.5A and conected
    with this battery you burn the battery and maybe this can make the
    battery to BOOOOOOOOM. You Understand?
     
  8. David D

    David D Guest


    'thanks for the replies.
    Right now, I am interested in getting 12V battery with a 4.5
    amperage. The only problem is I am doing it DIY and trying to make it
    on the cheap - therefore I am stuck with finding a way to RECHARGE the
    battery. Of course without LED lights and levels, I won't know know
    if it is charged or not. And yes, I don't want to blow a $100.00
    monitor either. My main purpose for this is to create a portable
    monitor system. I went to Canadian Tire to find the 12V cordless
    drill batteries, but they only pump out 1.5 Amp, so it is getting
    harder then I thought...
     
  9. DaveM

    DaveM Guest


    'thanks for the replies.
    Right now, I am interested in getting 12V battery with a 4.5
    amperage. The only problem is I am doing it DIY and trying to make it
    on the cheap - therefore I am stuck with finding a way to RECHARGE the
    battery. Of course without LED lights and levels, I won't know know
    if it is charged or not. And yes, I don't want to blow a $100.00
    monitor either. My main purpose for this is to create a portable
    monitor system. I went to Canadian Tire to find the 12V cordless
    drill batteries, but they only pump out 1.5 Amp, so it is getting
    harder then I thought...


    Well, now we're getting to the root of the problem. The answers that other
    posters have given are correct, for the most part. The issue now is.. how long
    do you need to operate the monitor on battery? The ampere-hour (AH) rating of a
    battery is useful in determining how long the battery can supply power. The
    load current is a major factor in determining this time. The chemistry of the
    battery is also a major factor in this calculation.

    A fairly good tutorial on batteries, AH ratings, Loads and recharging is at
    http://homepages.which.net/~paul.hills/Batteries/BatteriesBody.html. I suggest
    that you read that with great attention and you will get a better understanding
    of your situation.

    For your portable application, I suggest that you look primarily at sealed
    lead-acid (SLA) batteries to start. Newer chemistries such as Lithium-Ion and
    others typically used in laptop computers have a higher energy/weight ratio, but
    are significantly more expensive.

    --
    Dave M
    MasonDG44 at comcast dot net (Just substitute the appropriate characters in the
    address)

    Life is like a roll of toilet paper; the closer to the end, the faster it goes.
     
  10. David D

    David D Guest

    Yes, you are right. I am going to a local electronic store - bringing
    the monitor with me - to see what they say. It would be nice to use
    the monitor for 3-4 hours at a time, longer would be a bonus. I will
    also ask about SLA batteries, thanks for that.
     
  11. There's problem one. Don't go to Canadian Slime.
     
  12. David D

    David D Guest

    Ha, I do like their return policy though.

    Ok, I found a battery - $24.00 - 12V 4.5amp so therefore I am going
    to only get 1.5 hours out of the monitor, right? Ok, I also picked up
    a female sleeve for a 12V lighter - but it is called "VDC 12V", is
    that the same?
    I guess I am going to have to spend more money to get a larger battery
    with more Amps, right?
     
  13. DaveM

    DaveM Guest

    Yep... that's what I'd suggest as a starter. You still need to do the math and
    figure just how long you need to operate the monitor from battery. It's the
    single most important piece of information you need to have. Next, use the
    charts on that web site that I posted for you to calculate the approximate run
    time for a given AH rating.
    Generally speaking, the higher the AH rating, the longer your monitor will run.
    Charging the battery is another question altogether. If you don't feel
    comfortable constructing your own charger (and from your previous questions, I
    gather that you don't), I suggest that you look for a charger that has normal
    charging with automatic switchover to float charging. Use Google.. search for
    SLA battery charger.
    --
    Dave M
    MasonDG44 at comcast dot net (Just substitute the appropriate characters in the
    address)

    Life is like a roll of toilet paper; the closer to the end, the faster it goes.
     
  14. Guest


    There seem to be some misunderstandings here.

    Firstly there is no such a thing as a 4.5A battery, what you have is a
    4.5Ah battery. This tells nothing about what current it will supply,
    but rather its capacity.

    2nd, you wont get 1.5hrs from a 4.5Ah battery on 3A, for 2 reasons:
    a) Ah capacities are only correct for 20 hour discharge. High
    discharge rates will reduce capacity considerably.
    b) If you discharge a lead acid battery until flat it wont last long.
    You need to stay above 20% charge at least.

    For 4 hours of run time, if we momentarily ignore the 2 above issues:
    4x3 = 12Ah
    Add 50% (guessed) for a short run time -> 18Ah
    Add 25% to permit discharge down to 20%: 22.5Ah

    So really you want a 25Ah or more battery to do what you want.

    There is one last issue. Is the monitor 12 real volts or 12 battery
    volts? What are known as 12v batteries arent really 12v. This is fine
    if the monitor is designed to run off car supplies, but if it needs a
    12v regulated supply it might be unfine - or it might be ok. Would be
    wisest to check first.


    NT
     
  15. David D

    David D Guest

    You are probably right, I don;t have the battery in front of me to
    check.
    that is probably a good start.
    How do I check? The monitor did not come with instructions and the
    specs I am detailing are from the back of the monitor, so I cannot
    really tell the voltage it needs. IS there a way to check this
    reliably?

    Thank you for the interest.
     
  16. Ryan Weihl

    Ryan Weihl Guest

    I wish you people would get your terminology right.
    Nowhere do I see anybody talking about Ah (amphours/Battery capacity)
    A battery does not produce Amps, what you mean the battery
    produces 12V(DC) at 4.5Ah for 1 hour (amp hours). Thats 12V for 4.5
    hours at 1Amp load. If the monitor needs 1.5A, the you take the 4.5 Ah
    from the battery and divide this by 1.5A load from the monitor and it
    will tell you how long the monitor will run.
    rw

    --
     
  17. Guest

    Simple way is to determine what it expects to run off, large wall
    wart, stabilised psu or battery. One giveaway would be a dotted equals
    sign, meaning rectified ac, which would mean it expects to see
    unregulated supply, hence a battery would be fine.

    ____
    .....
    (works in non-proportional font)

    However there's no guarantee that there will be anything on it to tell
    you one way or the other.


    NT
     
  18. Guest

    No, this is a common mistake. My post explains why.


    NT
     
Ask a Question
Want to reply to this thread or ask your own question?
You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.
Electronics Point Logo
Continue to site
Quote of the day

-