I had my 12v battery swapped in November, but it died again a week or so ago. Fortunatley for me the local garage has employed a new ze technician.
He told me the twizy has a particular flaw, under the lid for the charging plug, the water concentrates and drips down onto the batterry terminals. This caused the connecting battery terminals to corrode, causing my charging problem. It the battery is rotated 180 degrees, the water won’t drip in the terminals. But the wire’s not long enough to reach, so he created a small extension cable to allow him to turn the battery round.
Hopefully this will be of use and sauve your 12v batterys.