ltc4010 won't start charging drained NiMh battery

Hi nesha,

Hope you are doing well,

Since the LTC4010 has a battery present threshold voltage at Vcell of 350 mV , the charger assumes that a deeply Discharged NiMh Battery with <350 mV voltage level is not connected or the battery has shorted cells or is in some way damaged, the charger does not recognize the presence of a battery and no charging will occur. However,  once the battery is "trickle charged" for a short time using external means and the battery voltage has reached the battery present threshold voltage, the battery will be charged correctly.

Attached below is a solution for charging a deeply discharged NiMH battery. The solution shown below provides a "pre-trickle" current (determined by R1) to a deeply discharged battery with a single cell voltage that is less than 350mV. Once the single cell voltage exceeds 350mV, the READY pin pulls low turning on Q1, which turns off Q2 , thus stopping the Pre-trickle charge current and the normal LTC4010 C/5 trickle charge current begins. The C/5 trickle current continues for 1/12th of the total programmed time.

The down side to this solution is that the charger can no longer determine when a battery is not present since this charger will enter the precharge state and then ends with a FAULT because the VCELL voltage did not exceed 900mV at the end of the trickle time period. Connecting a battery will not initiate a charge cycle because the FAULT PIN latches, thus requiring the charger to be reset by removing and reapplying VIN.

Regards,

Siglo

Hi nesha,

Hope you are doing well,

Since the LTC4010 has a battery present threshold voltage at Vcell of 350 mV , the charger assumes that a deeply Discharged NiMh Battery with <350 mV voltage level is not connected or the battery has shorted cells or is in some way damaged, the charger does not recognize the presence of a battery and no charging will occur. However,  once the battery is "trickle charged" for a short time using external means and the battery voltage has reached the battery present threshold voltage, the battery will be charged correctly.

Attached below is a solution for charging a deeply discharged NiMH battery. The solution shown below provides a "pre-trickle" current (determined by R1) to a deeply discharged battery with a single cell voltage that is less than 350mV. Once the single cell voltage exceeds 350mV, the READY pin pulls low turning on Q1, which turns off Q2 , thus stopping the Pre-trickle charge current and the normal LTC4010 C/5 trickle charge current begins. The C/5 trickle current continues for 1/12th of the total programmed time.

The down side to this solution is that the charger can no longer determine when a battery is not present since this charger will enter the precharge state and then ends with a FAULT because the VCELL voltage did not exceed 900mV at the end of the trickle time period. Connecting a battery will not initiate a charge cycle because the FAULT PIN latches, thus requiring the charger to be reset by removing and reapplying VIN.

Regards,

Siglo

Thanks Siglo,

Can you check if the solution picture/diagram is attached?

I just see a link which can't be displayed on ez.analog.com page, neither at my Outlook.

Regards,

Nenad

Hi Nenad,

Yes. The diagram is attached and can be seen on my part.

I have re-uploaded the image here for your use.

regards,

Siglo