LTC4079 random termination

Hey everyone,

I'm using an LTC4079 to charge a set of 4 series connected 18650's. The charge voltage is set to 200 mA and the input voltage is 30V. I don't see any heating on the device nor have I had any issues charging these batteries in the past.

The voltage on the prog pin is around 1V and randomly drops to 0V for a few seconds while the current drops from 0.2A to 0A. The device charges the batteries for about 2 seconds and then it stops again for about 10 seconds and then repeats the 2 second charge cycle. This constantly repeats. I've got no idea what could cause this as the only thing from the datasheet that resembles this is charging high resistance batteries and that doesn't seem to be my case. I'm also not using a timer to terminate the charging, rather I've connected the timer pin to ground. Furthermore the enable pin remains high throughout this constant charge/stop cycle as well as the input remains stable and is currently just a DC bench power supply.

Here's a rough schematic of the configuration:

R91 is actually a  thermistor.

Here's a link to the batteries I'm using where you can find the datasheet:

http://www.mantech.co.za/datasheets/products/LGABB41865-190226A.pdf

http://www.mantech.co.za/ProductInfo.aspx?Item=15M0457

Thanks in advance for any help!

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