Overcharged Protected Li-Ion?

Discussion in 'The Projects Forum' started by johnyradio, Jan 2, 2014.

  1. johnyradio

    Thread Starter Member

    Oct 26, 2012
    39
    1
    Ok, i know you guys are going to laugh at me for even attmpting to do this, but here goes:

    i purchased this battery. from a us-based vendor.

    http://r.ebay.com/TNTDiK

    i checked the battery voltages on delivery. All were about 3.7 volts. Good sign.

    i peeled away the base of one of the batteries, and indeed there was a little circuit board, with a conductor running up the side of the battery to the top.

    i connected FOUR of these batteries in series. They gave 15.7 volts.

    then i connected a 19 volt wall wart to the ends. after 15 minutes the batteries were warm, not hot. i disconnected, and the pack gave over 17 volts! That's too high-- a 4-pack should max at 16.8 V.

    i checked each battery-- 3 batteries were under 4.2 V, but one battery measured 4.9 volts!

    How could a protected battery charge to 4.9 V?

    thx
     
  2. bountyhunter

    Well-Known Member

    Sep 7, 2009
    2,498
    507
    protection was not working.

    I guess the slave labor in the Pacific Rim is dipping in quality...
     
  3. tindel

    Active Member

    Sep 16, 2012
    568
    193
    I don't know. Failed protection circuitry... if you were using a 19V wall-wart - seems to me that you were trying to over charge them... you probably need a drop resistor to keep them from over charging if you're connecting them directly to the wall wart.

    Could also be cheep knockoff stuff from flea bay - I've never heard of UltraFire brand before.
     
  4. bountyhunter

    Well-Known Member

    Sep 7, 2009
    2,498
    507
    The protect circuit should open the FET to disconnect it if it was working.

    The PCB is inside the cell? never saw that one before.
     
  5. bountyhunter

    Well-Known Member

    Sep 7, 2009
    2,498
    507
    China

    http://www.ultrafire.net/products.asp?enBigClassName=Battery
     
  6. johnyradio

    Thread Starter Member

    Oct 26, 2012
    39
    1
    i don't know if this form-factor is legit, but i don't see why not. question is whether this particular product is legit.

    i found this "false plates without any protection function". They are identical to the plates on the bottoms of these batteries.
    http://bit.ly/1dfEL0K

    ha, the vendor just gave me a full refund, when i asked why it charged past 4.2 v. He said "occasional bad battery!". what the....?
     
    Last edited: Jan 3, 2014
  7. tindel

    Active Member

    Sep 16, 2012
    568
    193
    In other words - "Cheap Chinese Garbage... throw them in the trash..." - seriously johnyradio - you're lucky those things didn't catch fire or explode. Li-Ion is not to be messed with.

    Thanks for the link BH! You confirmed my suspicion - junk.
     
  8. johnyradio

    Thread Starter Member

    Oct 26, 2012
    39
    1
    so how long until Chinese counterfeiters realize they cannot fool American buyers forever? And then what happens?
     
  9. Little Ghostman

    Member

    Jan 1, 2014
    294
    97
    False plates thats mad! makes me wonder how many companies there fit these??? scary stuff! surely in bulk it cant cost much more for the real deal???? so why make and sell false plates, might be me but it just dosnt make any logic
     
  10. bountyhunter

    Well-Known Member

    Sep 7, 2009
    2,498
    507
    What's inetesting is that those tiny PCB's look like they might actually be for real if stuffed with the parts. A "fake" would need some random parts. That board is laid out for a six pin IC, three discrete FEts, and some small caps which is what I would expect the actual circuit to have.

    I wonder if they couldn't get the finished boards and just started shoving the bare PCB's in to sell them?

    The point is, that three of the cells tested (charged) actually did seem to terminate charge at 4.2V per cell so they appear to have protection.
     
  11. Metalmann

    Active Member

    Dec 8, 2012
    700
    223

    Well, all our electronics are made in China.

    All that black, shiny, cheap, plastic; has to come from somewhere.

    Makes me wonder just how many American companies, really use China as their base, but brand it as American.;)
     
  12. alexfreed

    Member

    Oct 8, 2012
    72
    10
    The protection circuit on a LiIon battery is NOT the same as a proper charging circuit even when it is fully functional. The correct way to charge is to supply constant current first till the voltage reaches 4.2V and then supply constant voltage till the current drops to 3% of rated current. And the charger should be accurate to about 2% or either the battery is not fully charged or its lifespan is drastically reduced.
     
  13. bountyhunter

    Well-Known Member

    Sep 7, 2009
    2,498
    507
    We made the internal protection IC that went in the Sony battery pack: the accuracy they demanded for the final voltage was 4.200V +/-0.5%, and that precision was really tough because it requires post package trim. The molded plastic around the IC causes physical stress that will change the set voltage by more than 0.5%, so it has to be zap trimmed after molding.

    Here is a TI part that has a range of devices with OV protection cutting in from 4.225 to 4.550V.

    But some charge schemes rely on it to open the series FET when the battery voltage gets to the high point. It's better if the charger has precision CC/CV charging with accurate final voltage, but the protection should never let it go dangerously high.

    the data I saw from Sony was that a +/- 0.5% variance on the final charge (cell) voltage corresponded to a +/- 30% change in charge in the cell..... hence Sony demanding the 0.5% tolerance.
     
  14. johnyradio

    Thread Starter Member

    Oct 26, 2012
    39
    1
    Question, can that 4.9V cell explode on the shelf?
     
  15. bountyhunter

    Well-Known Member

    Sep 7, 2009
    2,498
    507
    Probably not. The greatest danger is from overheating when it is being overcharged. I think sitting dormant it's not dangerous, but don't bet your life on it.

    Some of the first gen Li-Poly cells would sprout internal shorts sometimes and rapidly heat up and burn the user (it was in US Army night vision goggles) so Li cells always have a potential for burning up.
     
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