Trouble installing Catalina OS due to very slow internet speed

I've been trying to install the new OS on my mac. I've had problems because I'm trying to install 8 GB on a speed of 2 mbps. The download speed is super slow. I've tried leaving my mac overnight, when I woke up around 3 to check it up. I downloaded 6 gb already. I slept again and woke up devastated to find that my mac had no battery anymore and the installation was cancelled. I tried to find a way to resume it but couldn't find out how. Do you guys know any other methods? My os version is sierra 10.12.6