DIY Ultrasonic bath?

[Nick]

Given that Old PP9 batteries appear a bit thin on the ground and mine won't be flat for about a year, i was wondering if I could use my wireless charger to power a small ultrasonic bath for cleaning jewelry watch bracelets etc when the radio is not being charged. Power out put is around 5 W at 30KHz but how to transform this into agitated water etc?

A decent tank is about 25W/litre, i.e. my 4lt tank has 2 x 50W transducers welded to it... its a UD100SH-4L - common as muck on eBay

Circuit is not too complex - no exotics there but there are a couple of xfrms - seems to be a basic oscillator (40kHz) with control stuff (timer, temperature settings etc.) + PP driver for each transducer and a relay to turn on/off the heater.

You can buy the transducers on their own from eBay, e.g. http://www.ebay.co.uk/itm/150607443329 or the complete board + transducer as a package, e.g. http://www.ebay.co.uk/itm/160754562847 - the board looks pretty basic - not as nice as the EUmax UD100SH one... - there may be cheaper versions out there but I haven't looked...