I have the Oxford Oximiser 900 and it does the job. The Oximiser 600 charges at a lower rate (0.6 amps) I believe, than the 900 which is 0.9 amps. The difference is the time taken to charge the battery.
If you have a beefy battery to charge as the R1 probably needs to start it, the 900 might be better suited. This is common sense based on limited experience, and am happy to be corrected if someone knows more than I do on the subject!