Efficient way of driving 10w LED with a 12v SLA battery?
The LED could take 1A at a terminal voltage of 9V according to the specification. This means you need to drop 3V at 1A to guarantee it operates successfully from a 12V power supply. That's probably more like a 4 watt resistor. But your LED is throwing away (as heat) about 7 watts so another 3 watts isn't that big a deal.

However, you can use something like this: -



It will take as few as two LEDs in series - it is an active switching current limiting circuit and will have an efficiency of about 90%. The above is just an example - try searching for "boost current limiter for LED string".

Here's another one: -