LTC4020 -- The system can not recover when disconnect and reconnect battery .

Dear sir/Madam 
I use LTC4020 with your evaluation board DC2134a .(for charging 2x12V 20Ah lead acid batteries) 

there is a big problem : 
in stage 1 and 2 of charging  cycle (Constant current charging and also absorption phase), if we disconnect the battery and reconnect it again , it is IMPOSSIBLE to system come back to continue charging . the output voltage of the board will be about 25.5 (the voltage of batteries) and the charging current will be about 0.4 . 
Just we must disconnect the board's input voltage and reconnect again , to system goes to continue charging batteries normally with correct current and voltage . (for example 6.3A and voltage goes up to 28.8) 

can u help me ? it is so important for a battery charger system to recover after disconnect and reconnecting the batteries .

Best Regards

  • Mohsen

    Did you ever resolved your problem with the battery connect and disconnect?  I am seeing the same problem in our system.   Regards

  • Hi Jihermo . 

    No . It seems that it can not be solve by hardware changes . It seems there is a problem it the IC design algorithm .

    In our systems , we never disconnect battery from charge in the middle of charging . Battery always connected to charger . But I meet this problem in my tests . 

    Anyway , I think think LTC4020 is best solution for lead acid battery chargers . however I saw another terrible problem it this system (2 or 3 times ) , But I think it is the best choice .

    thank u . 

  • Mohsen

    Thank you very much to confirm our suspicions.  We actually found this problem in our own prototype board and were concerned it might have been layout.

    You also mention "another terrible problem" in your system.  It seems that id we remove the battery and put it back in Absorption mode, one of the FETS and the Controller IC get damage.  Did you see any damage to the components? 


  • Hi Jihermo 

    EXACTLY ...

    But We found that if we use a fan to cool the IC and FETs , this problem will occur rarely . how ever not solve completely and we observe it also with fan.

    about this case I even observed that D6 (B360A) , FETs and IC burned just when system started to absorption mode :-o (not disconnect and reconnecting the battery)  . battery was connected to board and every thing was fine and system started to charge batteries normally . there was no problem in stage 1 . but when it goes to stage 2 , the FETs burn with flame and also IC and D6 burned . 

    Note that I meet this case just 2 times and I think the problem starts by burning D6 (when system start to increase the charging current to maximum current that set by resistors)  and when D6 burns , then FETs Burn and then IC ... I think B360A not strong enough for this purpose , so we decided to use stronger diode instead of B360A and also we decided to install D5 (that it is optional in LTC4020 datasheet and evaluation board ) 

    Do u ask about this case and its solution from Engineer Zone ? 

  • Thank you Mohsen

    We have not contacted Engineer Zone yet. I saw your questions and they are similar to the problems we are experiencing.  I will contact them though.  Thanks 

  • thank u Jihermo . 

    would u please also send me a message or mention me  when u build a ticket about this case in Engineer Zone ? 

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