Li-Ion battery charging - Waking sleeping batteries

Discussion in 'The Projects Forum' started by atanumukerji, Mar 28, 2014.

  1. atanumukerji

    Thread Starter New Member

    Apr 1, 2011
    Dear all,

    I have designed a system which uses a 7.4 V, 6,6AH Li-Ion battery pack (18650) in the configuration 2S-3P. It is charged using a uC based software algorithm which is CC till 8.4V and then CV till current falls below 0.05C. I charge the battery using a 12V DC charger or a 15W, 12 V Solar Panel. Obviously there is a buck-converter in between which manages the voltage applied to the battery.

    Recently I came across situations that batteries which go to sleep would not revive using the software charger. I had an earlier version of the same system using a different microcontroller SH4 from Freescale, which would wake up the battery. However the new version uses a different microcontroller MC9S08PA4VWJ which does not work. The only change is I see is the speed of operation - it was 12KHz for the buck converter PWM earlier and now it is around 35KHz.

    Can any one suggest what is wrong or what I should try? Please ask if you need more information.

    Thanks in advance
  2. Dodgydave

    Distinguished Member

    Jun 22, 2012
    a circuit would be helpful.
  3. burger2227


    Feb 3, 2014
    Lithium battery packs require protection circuits to monitor each series battery connection. Parallel series connections can all be monitored with the same board. The protection circuit can also be used in the device to protect batteries from excess discharge, overloading or overheating.

    You can get the boards on Ebay.
  4. atanumukerji

    Thread Starter New Member

    Apr 1, 2011
    Thanks. I will try to cull out the circuit subsection and post it.

    As for the PCM card, it is already there on the battery pack I am using.
  5. ronv

    AAC Fanatic!

    Nov 12, 2008
    Batteries that go to sleep? You mean really low voltage?