We had a long discussion about the $ 6 Harbor Freight chargers a while back.  A big problem with them is they don't let you know what is going on....the red light is on all the time.  You have no idea if they are working or not....or if they ever do shut off....or just keep pumping a small amount of current into the battery all the time.

My mother uses Harbor Freights ones on her garden tractor and another one on her pickup truck in the winter.  I have stopped using mine and bought better ones that let me know what they are doing.  I like seeing that the battery gets charged....and then they shut off for a while.

You get what you pay for.
That's a lie.
Ask the folks who bought a certain bridge.
You Will, however, pay for what you get.