Following this video guide and the step up booster converter from ebay below I’m going to make a Sonos Play:1 battery powered so I can enjoy some lovely music on the balcony over the summer.
http://www.ebay.co.uk/itm/XL6009-DC-DC-Voltage-Step-Up-Boost-Converter-replace-LM2577-3-32v-input-UK-Fast-/400858208676
