The charger will be fine. Only thing with the Riva 1100 mAH batteries is only use the wall charger. Never charge them on a PC.
Now there's some advice I have never thought about and now that I have, it makes a lot of sense!
Talk about teaching an old dog some new tricks!
I have a Go Go with propitiatory 1300 Mah batteries and I'm sure it needs to be charged the same way.
Thanks DeXTeR