This is only my opinion, take it for what it's worth. I'm 60, been into electronics/ mechanics/ HVAC / two way radio on/ off all my life.
STAY AWAY from cheap, complicated, regulated "battery tender" type units from Chi-asian places like Harbor Freight, unless, of course, you have a good fire insurance agent
I just use "basic" stuff, and on smaller batteries--like bikes and lawn equipment, I simply use a heavy turn signal bulb (1157) IN SERIES with the charging lead to limit the current. This allows use of say, 10A unregulated charger, and if the battery "was" pretty low, you can leave it on overnight. A glance at the bulb shows what's up, too
ALL basic charges without extra bells and "boost" functions are simply a transformer and rectifier. I used to repair them, and other than some come with silicon diodes and some (still use) selenium stacks, they are pretty basic
"Boost" function is indeed an over-advertised lie. It simply is not made to "last" Very low duty cycle.
MANY of the junk that "tries" to smart/ regulative/ protective, ---ain't--- Many of the regulated charges have poorly designed circuits with little thought to protection in case something fails. For example, a GOOD regulated 13.8 supply used on ANY electronics stuff will have overcurrent and overvoltage (crowbar) protection as well as the usual fuses on BOTH output and line. Most these junk chargers have a simple automotive auto--recycling breaker inside. These can allow a LOT of heat when something bad happens--a shorted cell, shorted diode, or even some fault in the transformer.
All that needs to happen in the cheaper regulated units is for the pass transistor to short--and now you have an UN regulated charger, so while you are off somewhere running errands or sleeping, the battery is heating, puking hydrogen and acid all over the building and maybe worse.
MY SOLUTION:
Don't use any of this junk. Learn to take the trouble to charge your battery and then UNHOOK it. If you can't remember (I can't) post a huge gigantic piece of paper on the fridge. If you have a larger charger, use a series bulb for current limiting.
OR spend the money (NOT Harbor Freight) on a good quality "tender" I doubt you can buy one for less than a hundred bucks.
(I know the flaming will start-----I know, I know, "you" have a Harbor Freight that's been on your farm for XXXXXX years and has never skipped a beat. OK, "you" are one. What about the hundreds that DID puke?)
