I'm sure this one will get answered with a one word reply, search didn't show anything I could use without 4 hours of reading.

I have a rechargeable battery with 18.8v, can I use this for an Mr16 10w bulb to build a light? The light I have works fine with 10 AA rechargeable batteries, but only lasts an hour or so and I thought this bigger battery would last longer.
I don't know much about electrical theory, but am handy with some strippers and tape