I am thinking of buying a solar trickle charger as I have occasionally had a flat vehicle battery after it has been stood for a week or so. Does anyone have any experience of these or recommendations i.e. "they're rubbish" or get such and such a type or model? There are some small, cheap ones available but they only have an output of 1.5W and I am not sure if these will be adequate particularly as the vehicle has an alarm and I have been unable to find out how much power it consumes. Any advice welcome.