Trickle , maintainer, tender, charger , holy 12 Volt !! I have found that the companies making them use different names to describe the charger, and they all charge the battery , just in different amps and some are regulated and others just charge untill timed out or manually shut off.
I have all kinds of them from big old one on wheels that you set with a timer to the modern day auto maintainer or is it tender ???
Some of the older small ones were just a charger like the 6amp Allanson shown, it never stopped untill you unplugged it, so chance of overcharging a battery was possible.
The old Forney was a cadillac having 6, 8, 12 volts, yes I said 8 volts which most of you probably never heard of in the auto world , I added a pic of a 8 volt car battery count the fill caps (4). If you can see the toggle switch at right bottom it has high and trickle settings. So trickle meant it just gave low amps thus a slow charge time no auto shut off timer.
The modern Eliminator is a 2 amp intellegent battery charger as said on the box but also it says it is a trickle charger. It senses a low battery and charges untill full and shuts down and won't charge untill the battery is low again thus maintaining the battery at 12+ volts.
Maybe confusing but they all charge , just some are regulated and some are not, so call them what you want.
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