This maintainer is capable of only about an amp. I suppose you could actually charge a battery with it if you had a lot of time. But battery maintenance is really what this is designed for.
When batteries just “sit”, that’s not a good thing at all.
My two units arrived quickly and were placed into service straightaway.
So far so good . . . appear to be working as advertised.
Deal remains available as I write this. No regrets. I can use these things but was unwilling to pay the higher prices elsewhere.
ETA
Sad to report there is a HUGE problem with these maintainers which I’ve only just confirmed:
These things are ginormous generators of EMI, sometimes also called RFI. That aspect does not interfere with their ability to maintain a battery. In fact, if you never listen to AM radio this is not even an issue for you.
I operate four Sangean PR-D5 radios in various rooms around my home. The PR-D5 model is noteworthy for its ability to pull in distant radio stations and sadly, as well, EMI from battery chargers like those in the OP.
I’m guessing now these maintainers are completely unsuppressed where EMI is concerned. Maybe that contributes to the low price.
Try a Faraday cage. DIY by lining a box with aluminum foil to cover the mainainer. If maintainer gets warm/hot, may need to make a few holes in the cage.
Unfortunately these maintainers plug into the wall, in addition to having leads which latch onto the battery terminals. Both of those are antennas. But I imagine most of the EMI is coming straight into the house through house wiring.
EMI is a real PITA. Decades ago I spent weeks alone inside a huge Faraday cage, taking measurements in process of trying to find a way to suppress certain DC motors. The room was also an anechoic chamber. You could become lonely in there. It was not a happy or rewarding experience.
I might try throwing a cap across the outlet where the maintainers are plugged in. But that probably would not work satisfactorily. More likely I will simply not leave them plugged in.