Different Radon Monitors

I currently rent Femto-Tech 510 radon monitors. I’m looking to purchase several used monitors to cut down on my monthly expenses. I’ve looked at Sun Nuclear, and I like there machines, but what I don’t like is that they have to be plugged in, and I would worry about the batteries dying if I couldn’t plug them in. I’m looking for feed back on that. I also looked at Radstar, could anyone give me feedback on there machine? I do like the fact that the femto tech machine does not need to be plugged in, and I like there reports as well. Any info that could be shared would be appreciated.
Thanks,
Frank

www.nachi.org/radalink

Thanks Nick