While checking voltage and polarity I discovered that the output sat firmly at 24 volts. Seems kind of right but I know that you need typically 13.8 volts in order to bring a 12 volt battery to full charge so 27.6 Volts at least should be available for a 24 volt setup. After a bit of to and fro'ing I managed to get the seller to go back to his supplier/manufacturer who indicated that this must be a faulty batch. Although I suspect they simply specified a 24v power supply in ignorance. I got my money back and suggested that the seller contacts anyone else who purchased this item as I could envisage mobility scooters running out of juice all over the place. Whether he will is debatable.
Don't suppose anyone else bought one?
CS