li-ion battery

Discussion in 'The Projects Forum' started by TAHIR AHMAD, Mar 30, 2009.

  1. TAHIR AHMAD

    Thread Starter New Member

    Mar 30, 2009
    3
    0
    i have 6v, 7Ah Li-ion battery. i need to charge it can any body help me...:confused:
     
  2. Externet

    AAC Fanatic!

    Nov 29, 2005
    762
    57
    A 6V Li-ion battery should have two cells in series.

    (+Bat)---------------+cell1-----------+cell2-------------(-)

    Each cell must be charged individually by applying NOT MORE than 4.1000 Volts.
    Connect a 4.1000 volts supply to cell 1 for a few hours; disconnect and connect the supply to cell 2 for the same amount of time. + to + and - to -
    If cell temperature rises warmer than your hand, terminate the charging immediately.
     
  3. peajay

    Well-Known Member

    Dec 10, 2005
    67
    0
    i have 6v, 7Ah Li-ion battery

    Are you sure that's not a lead-acid battery? That's a popular size for lead-acid batteries, and as best I can tell with a few seconds of Google, lithium ion is 3.7 volts per cell, which adds up to 7.4 volts for two cells, which makes a 6 volt lithium ion battery seem unlikely.

    If you are using lithium ion batteries, I'd recommend using batteries with a charge protection circuits built into the battery pack, which help to prevent them from catching fire.

    The best thing to do is to buy a charger for your battery. Every now and then there is news about a laptop or a cell phone bursting into flames because of its battery or charging circuit. When professionally built circuits occasionally burst into flames, you can be sure it's rather easy for an amatuer circuit to do the same. A battery charger is a lot cheaper than a hospital bill.
     
  4. jj_alukkas

    Well-Known Member

    Jan 8, 2009
    751
    5
    A Li-ion makes 3.6-3.7v .. And there are no Li-ion batteries with accurately 7volts.. Confirm it first...
    Second thing, never charge a litium ion battery directly with dc source, u will end up with some problem for sure.. Either buy a charger or build your own from a circuit.. I must be an intelligent charger..
     
  5. TAHIR AHMAD

    Thread Starter New Member

    Mar 30, 2009
    3
    0
    thanks

    the battery is:
    YUASA, NP7-6, 6V 7.0Ah
     
  6. Externet

    AAC Fanatic!

    Nov 29, 2005
    762
    57
    YUASA NP7-6 is NOT a Li-ion battery. :mad:
    Charge it with 7.0 Volts constant voltage.
     
  7. peajay

    Well-Known Member

    Dec 10, 2005
    67
    0
    Here's some information about voltages:

    http://en.wikipedia.org/wiki/Lead-acid_battery#Voltages_for_common_usages

    Since you have a six volt battery, you'll have to divide those voltages by two.

    You absolutely do not want to exceed the gassing voltage, or your battery will emit hydrogen and oxygen, which are quite explosive when mixed in the proportions at which the battery emits them.

    It is a sealed battery, but that simply means that the acid won't spill out. It doesn't mean that it can magically contain high pressures.

    I once worked in a place where some moron (my boss, of course) decided to recharge a similar battery that was lying around on his own. The thing swelled up like a baloon. He said it was just fine, that it wasn't going to explode, and he continued to use it. Every time I saw the thing I covered it up in order to try to protect everyone should the thing decide to start venting acid at high pressure. (Yes, he also never kept the thing right-side up, so that if it did vent, then only gasses would come out.)

    I shall repeat my recommendation of buying an appropriate charger for the battery. If you don't know exactly what you are doing, and the fact that you thought you had a li-ion battery tells me that you don't, then spare yourself and everyone around the risk of injury when your battery charging adventure goes wrong and simply spend $10 on a cheap charger designed for the battery.
     
  8. TAHIR AHMAD

    Thread Starter New Member

    Mar 30, 2009
    3
    0
    ok i'll go for the charger...
     
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