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LTC4011 top-off charge time isn't constant.

Question asked by Hiroyuki.D on Apr 11, 2018
Latest reply on Apr 26, 2018 by Zack

Hi

 

Regarding LTC4011, when RTIMER is equal to 100kohm, the tmax=100k*30^(-6)=3h which is the fast charge time and the top-off charge time is tmax/3=1h.

But top-off charge time of NiMH battery (4cells) isn’t constant at the customer side. It takes about 1h as the first time of the top-off charge, but after discharge, it takes about 1h25m as the top-off charge. The time is sometimes 1h again repeating the charge and the discharge.

The customer says that the top-off charge time of NiMH battery (3cells) is always 1h and wants to know the reason why the top-off charge time of 4cells isn’t constant.

Could you have any idea of this phenomenon? LTC4011 works correctly?

 

Fig.1 The NiMH battery characteristics

Fig.2 Measurement data by the customer (Vertical:Voltage, Horizontal:Time)

Regards,

Hiroyuki

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