Smart Battery Charger

Discussion in 'General Electronics Chat' started by Alex.T, Jun 14, 2012.

  1. Alex.T

    Thread Starter New Member

    May 16, 2012
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    When someone refers to their product as a smart battery charger, what exactly are they implying?

    Is there a standard within the field of electronics as to what a smart battery charger would be capable of?

    Hopefully you guys can help me clear this up.

    Thanks.
     
  2. mhastie1234

    New Member

    Feb 10, 2012
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    My impression of a smart charger is. It will charge the battery until it is charged by determining the resistance of the battery, then it will switch into float mode which will keep your battery charged and not overcharge it. Regular battery chargers with just keep charging.
     
  3. Alex.T

    Thread Starter New Member

    May 16, 2012
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    That's where my inquiry was born, so to speak. I've seen companies call their chargers "smart" chargers based on your definition. The charger will sense the resistance of the battery and determine that it's completely charged and it will just trickle charge to ensure it doesn't reach a low point. But on the other end, other companies call their chargers "smart" because they automatically disconnect from the battery upon full charge.

    Which is the most efficient from the perspective of the battery?

    Also, I've read that these chargers have temperature compensation circuits designed into them. Is this to ensure that the battery is not overcharged? For example on a hot day the charger will charge the battery at a slower rate than on a cold day?

    Thanks!
     
  4. mhastie1234

    New Member

    Feb 10, 2012
    29
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    Keeping the battery fully charged is more beneficial to the battery. The cells will not sulfate if it stays charged. For temperature compensation. During the bulk charge step, the battery can accept most of the current and convert it back to available capacity. Once the battery nears a full charge, excess charge current becomes heat. Small at first, the heat begins to accumulate in the mass of the lead plates. As the heat accumulates, temperature of the battery begins to rise. That means current through the battery begins to double for every [​IMG]F! That means more power is dissipated in the battery which means more heat is generated, which means more current flows, which means more heat, which means ...double trouble! If you're lucky you won't be looking at the battery when the caps lift off into outer space with acid following in close formation! The battery charger will shut off long before the top pop's. I have always assumed that the different chargers IE smart/2 stage/ temperature compensation where all the same. When the battery is fully charged the resistance drops. The charger reduces the voltage to maintain the charged battery.
     
    Last edited: Jun 14, 2012
  5. mhastie1234

    New Member

    Feb 10, 2012
    29
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    The temperature Compensation would be ideal for deep cycle batteries rated at different amp hours. You can't charge a 100 amp hour battery with the same amperage as a 10 amp hour battery. This type of charger would sense if the battery is getting to hot and adjust the voltage witch will lower the current going into the battery.
     
  6. Wendy

    Moderator

    Mar 24, 2008
    20,765
    2,536
    Actually a smart charger will attempt to identify the battery, and using a menu system for the user, match the charge characteristics to the specific battery. There are numerous types, each with its own charge profiles. A smart charger matches the profiles of each battery type.

    The Battery University

    I would qualify the charger I bought from Walmart as a replacement a smart charger. Among the menu options that stood out were SLA gel cell batteries, which require much lower charging currents than a conventional lead acid battery that is used in a car, for example.
     
  7. jwilk13

    Member

    Jun 15, 2011
    228
    12
    From what I've read about different chargers, some common functionality of a smart charger would be 1) Multiple settings for different types of batteries (sometimes set with DIP switches); 2) Multiple settings for whether you want the charger to float or just turn off at the end of its charge (DIP switches as well); 3) Detect battery voltage BEFORE starting charge.

    I'm sure there are some more features than what I listed, but those are a few of the features I know of. Compare this "dumb" charger to this smart charger.
     
  8. Alex.T

    Thread Starter New Member

    May 16, 2012
    12
    0
    Is there such a thing as a smart battery charger which can independently identify the type of battery it's connected to?

    Let's say we are talking in reference to lead acid batteries only.

    A smart lead acid battery charger will do the following:

    1. Measure the voltage of the battery and determine if it needs a charge
    2. Should the battery need a charge, it will begin with the 3 stage charge process, constant-current, topping, and float charges
    3. However, that 3 stage charging process will depend on the ambient temperature

    Is this line of thinking correct?
     
  9. Wendy

    Moderator

    Mar 24, 2008
    20,765
    2,536
    To a limited degree, yes. Different chemistries have different voltage drops. Problem, some very different batteries can have similar chemistries. Things like SLA (Sealed Lead Acid) and Automotive batteries, for example. Even marine batteries, which are modified Automotive batteries, are treated different.

    This is why the users have a menu input on the devices.
     
  10. Alex.T

    Thread Starter New Member

    May 16, 2012
    12
    0
    Sorry for all the questions.

    How does the charger measure the battery level? Does it do this just by measuring the voltage on the terminals? Does it put a load on the battery and measure the drop? When it enters the charging process, will it always start from step 1 and go through it or will it start on a different level depending on it's reading of the battery level?

    Thanks for all your help.
     
  11. Alex.T

    Thread Starter New Member

    May 16, 2012
    12
    0
    Bump.

    Hoping someone could help clear this up for me.
     
  12. DMahalko

    Senior Member

    Oct 5, 2008
    175
    14
    Even the "smartest" chargers have to make some assumptions about the battery state because actual charge state detection isn't really possible for a multi-cell battery (anything over about 2.5v).

    Individual cells can develop their own charge curves over time, and some cells will have more or less capacity, so some will "top-off" sooner than others. You can't really detect this without an individual charger and test circuit per cell.

    A truly proper charge method would be to only continue charging the cells that are not topped off and don't do anything with the ones that are topped off. A generic automotive car battery does not permit this since the inter-terminals between cells are not brought outside the battery shell.

    A truly smart charger would also have per-cell temperature probes embedded within each cell, plus an ambient temp sensor for comparison.
     
  13. dick56

    New Member

    Apr 27, 2011
    23
    3
    It has been my experience with aircraft and marine lead acid batteries that a constant-current charge for many hours is necessary to bring up the specific gravity (SG) of the individual cells-about 1.80 amps for aircraft and 3 amps for automotive and 10 to 20 amps for deep cycle marine batteries dpending on size. The SG of an aircraft battery is slightly lower then an automotive or marine lead acid battery due to the different sulfuric acid that goes in an aircraft battery.

    The cells should all be off-gassing when the SG is over 1.260, if not, then the cells not gassing will probably have low SG and more constant-current charging is needed. If a cell doesn't come up after 24 hours, then it probably is sulfated and will not be good for long.

    A lead acid battery needs to have a SG of at least 1.270 to stay healthy and along with that there needs to be a charging system (alternator or generator) that puts out over 14 volts DC during normal operation. Anything less and the battery will go into a slight decline and eventually start to sulfate. Only constant-current chargers will bring the SG up to 1.270 which keeps the plates from sulfating. Constant voltage chargers only will charge the battery, but will not bring the individual cells up to 1.270 so some of the cells will degrade and the battery will be toast before it needs to be.

    I am going on 11 years on my 25 amp hour aircraft battery and my SG is still over 1.270 on all cells. It happens to be a 24 volt battery and the alternators charge at 28.3 volts. I use my constant-current charger every few months for 24 hours to keep the SG up. Our aircraft batteries cost over $350 each so it pays to keep them in tip top shape. The Mastech model 5003 3 amp constant-current charger is cheap insurance.
     
    Last edited: Jun 25, 2012
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