How can I get a replacement battery?

Doubt parts are available. Its the usual story of cheapo generic far eastern junk getting a (half) respectable badge and being sold cheap.

There's a manual available here: http://www.lidl-service.com/static/11707901/66765_EN.pdf which may give some contacts, but it looks like these got to just bit of Lidl, who don't actually make anything, just badge it up and sell it.

You'll probably have to get a new one so aim for a proper known brand and check availability of support BEFORE you commit to buy. Check out Bosch deals etc., at, say , Screwfix.

X
July 2015

Try Lidl customer services - they will know

Good luck...
July 2015