I want to keep an open hole of water on a 1-2 acre (approximately 10’ deep) pond for waterfowl. The pond is too remote to have access to electricity. I’m looking for (inexpensive) ideas for a de-icer system that would last for a few days without maintenance (i.e. recharge batteries).
I have “experimented” w/ a trolling motor lower unit attached to a portable metal stand which created a 10’X20’ hole outta’ 4” thick ice by “directing” warmer water to the surface. The problem was the small marine battery only lasted 2-3 hours before runnin’ out of juice.

I’m planning to purchase a couple of large marine deep cycle batteries to provide the system w/ extended longevity, but I don’t know how to properly
wire multiple batteries for this purpose. Also, I think I can double the battery life by using a flasher timer, but don’t have any idea how to set up this system. Any ideas, thoughts, etc. would be appreciated!