1. Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.
    Dismiss Notice

What does the specification 12V 12AH /" /2HR" actually mean?

Discussion in 'General Electronics Chat' started by netfreak, Mar 7, 2012.

  1. ronv

    ronv Well-Known Member Most Helpful Member

    Joined:
    May 30, 2010
    Messages:
    4,725
    Likes:
    488
    Location:
    Tucson, AZ. USA
  2. audioguru

    audioguru Well-Known Member Most Helpful Member

    Joined:
    Mar 16, 2004
    Messages:
    32,445
    Likes:
    937
    Location:
    Canada, of course!
    Your battery label says, "... Charge: Maximum initial current <2.1A".
    But the WRONG charger has an output of 3A which might cause the battery to boil or be damaged.
     
  3. netfreak

    netfreak New Member

    Joined:
    May 31, 2010
    Messages:
    36
    Likes:
    0
    @ronv, thanku man

    @audiogoru
    oh okay sir, thankyou with that ofcourse :) that was a point which i had completely let unnoticed
     
  4. dave

    Dave New Member

    Joined:
    Jan 12, 1997
    Messages:
    -
    Likes:
    0


     
  5. netfreak

    netfreak New Member

    Joined:
    May 31, 2010
    Messages:
    36
    Likes:
    0

    @ audiogoru
    generally the voltage level of a battery can be checked by placing the dmm right? and getting to know whether the battery is fully charged or not right?
    They say that normally whenever battery is charged up so it should be left for like 30mins-60 mins off the charger and then measured by a DMM to know the appropriate voltage level present on the battery

    My question is that while having the battery on charging, how can one get to know that the battery is charged now? so it would be safe to get the charger off ? assume this all for the same 12V 12Ah/2Hr battery
     
  6. audioguru

    audioguru Well-Known Member Most Helpful Member

    Joined:
    Mar 16, 2004
    Messages:
    32,445
    Likes:
    937
    Location:
    Canada, of course!
    I have never ever used an old lead-acid battery for powering an electronic circuit. It starts my car engine for 5 years then it is replaced. The battery in my car is 6 years old and it still starts the engine fine. I might replace the battery or replace the car next year.

    The measured voltage of a battery depends on its internal resistance. A dead battery has a high internal resistance.
    A "dead" battery without a load measures pretty good but a dead battery with a load measures a very low voltage because its high internal rersistance is part of a voltage divider wirh the load resistance.

    It is difficult to see if a charging old lead-acid battery is fully charged by measuring its charging voltage. If you let it sit for one hour then its dropped voltage might tell you roughly its amount of charge.
     
  7. netfreak

    netfreak New Member

    Joined:
    May 31, 2010
    Messages:
    36
    Likes:
    0
    @ audiogoru
    ahm :/ okay:/ so means the only way to get to know whether my battery is fully charged or not is to charge it for like 15 to 20 mins and then let it rest for an hour :/ and if not charged fully so i may charge that again :/
     
  8. audioguru

    audioguru Well-Known Member Most Helpful Member

    Joined:
    Mar 16, 2004
    Messages:
    32,445
    Likes:
    937
    Location:
    Canada, of course!
    No.
    Use a charger that is designed for your battery, not one that might destroy it. Charge the battery for 14 hours or more. Let it sit for 1 hour then measure its voltage. It should be 13.6V to 13.8V. If it is 12.6V or less then the battery is no good.
     
  9. tvtech

    tvtech Well-Known Member Most Helpful Member

    Joined:
    Mar 27, 2010
    Messages:
    3,166
    Likes:
    348
    Location:
    South Africa
    Depends how flat the battery is when you start to charge it.

    Completely flat takes longer than a battery with some charge left when charging starts...this is going nowhere :(

    netfreak needs to learn the basics of everything Electronic wise....@ netfreak start here:

    http://www.learningelectronics.net/vol_1/index.html

    New site that will help you to understand all the basics...

    Explore, learn and think....come back and surprise us all. I dare you kid :D

    Read all on there and understand all and I will help you to the best of my ability......

    Outa here

    TV Tech
     
    Last edited: Mar 8, 2012
  10. Mr RB

    Mr RB Well-Known Member

    Joined:
    Jul 22, 2008
    Messages:
    4,716
    Likes:
    194
    Location:
    Out there
    I've bought those sealed glass lead acid batteries form a few sources, generally the Ah rating is specced at 20 hour discharge rate. They get a lot less efficient as discharge current rises.

    Also some brands are LIGHTER than others even in the same size casing and same printed Ah rate, so beware of "Chinese honesty" in the specs labelling. :eek:
     
  11. nsaspook

    nsaspook Well-Known Member

    Joined:
    Mar 24, 2010
    Messages:
    1,141
    Likes:
    219
    Location:
    Fairview, Or
    Last edited: Mar 9, 2012
  12. audioguru

    audioguru Well-Known Member Most Helpful Member

    Joined:
    Mar 16, 2004
    Messages:
    32,445
    Likes:
    937
    Location:
    Canada, of course!
    I have never bought a cheap Chinese lead-acid battery because it would be dead by the time the boat gets here.
    Cheap Chinese alkaline battery cells are dead and they leak in their packages in The Dollar Store.
     

Share This Page