The R&D centre at Hong Kong's Automotive Platforms and Applications Systems (APAS) on Thursday warned electric vehicle (EV) owners to be careful when charging their cars on the mainland.

The centre said most EVs in Hong Kong use either Japanese or American charging standards and an adaptor is usually needed to charge them on the mainland.

But such adaptors are hard to find, the centre said, with those that are available coming with a price tag of between several thousand and tens of thousands of dollars.

There's also a lack of standardisation regarding safety when it comes to the adaptors, the centre said.

Chief Executive Officer of the centre Du Yonghai said to help solve these problems, they are developing their own adaptor which they plan to make commercially available.

"We have been actively engaging with several partners so that we can commercialise that product, that solution and make it available to the market," Du said.

As of last month, about 100,000 electronic vehicles were registered in Hong Kong.