What we have not worked out is why they do this, as not every one does. The 12V charger spec is different on the 2 different chargers the Twizy has been supplied with, however both appear to be able to supply more amps than the battery can take with out issues and swelling.
Therefore it has to be with load, or a batch of faulty batteries. We are not going to have enough information on the swelled batteries as most get binned. Mine had not swelled at 6 years so I Swapped it just in case and still have it as there is nothing wrong with it.
These little batteries are not that powerful and a large load will flatten then quickly, but then the on board charger should assist with that load by supplying power from the traction battery. I wonder if additional load on the 12V side causes all the power go into the battery and the high current damages the battery causing it to get hot gas and expand.
Those who’s battery as expanded can you say what loads you have on?
Parrot, or Radio/Audio