Be wary of RING. For many years then had a great reputation with vehicle bulbs, but five years ago I purchased a 3500 inverter for our boat. It went kaput within twelve months. Unrepairable. I had to read the riot act to get it replaced, and then only by travelling to Leeds for the new one. Total shambles. Make sure you read some good reviews from users before buying.Ring are advertising a trickle charger which plugs into your 12v socket, anyone have any experience of these. Seems a cheap option at around 19 quid !!