I saw this in the Kitplanes September 2016 issue. These are lithium batteries and weigh quite a bit less then other dry-cell batteries like the Odyssey that are typically used in aircraft. For example the Odessy PC1200 weighs around 39lbs while the EarthX ETX1200 only weighs about 8lbs, both have around 600CCA. They’re a bit pricey though, around $700 for the ETX1200 (above). Aircraft Spruce sells them and also found them at Battery Mart. I will need to do some more research on them and what size battery I would need for the Sling. It might be a good option if weight is an issue, though since the tech is still a bit new I’m sure there are problems.
Here’s a comparison (at the bottom of the page) between Odyssey and EarthX (it was done by EarthX) so it’s a bit biased.