Battery controller stops functioning

When about 8 months old (refurbished from Apple store) the battery controller seemed to disconnect. No display of battery charge was possible, even with other battery Apps.

There is a buzzing noise from the left back side, near the charging cable connector.

The battery charging cable plug also doesn't show the status light.

The WiFi turning off is the best indicator I noticed of the battery being very low on charge.

Carrying it around, particularly when traveling seems to bring on this problem.

I've found the best solution is to let it it totally discharge, then it returns to normal.

I've had it into the Apple store 3 times, they fiddle with it, but the problem returns after several charge cycles.

Fortunately I bought the Apple extended warranty, but I'm here because Apple techs have failed to do a repair of this problem.

I love this Mac for portable use, but it is failing me.

TIA for any suggestions.