Bought one from Aldi about 7 years ago for £12.99

It has "revived" several "lead acid" batteries* from the grave since then

It charges 6 & 12 volt batteries

No "digital voltmeter" on it though
Suppose technology has become cheaper since mine was made

I can highly recommend them

And they are way cheaper than the "Opti" brand

*leisure batteries when I lived "off grid"