it kind of depends on what battery you are running.

like agm would be slightly different than a standard wet cell battery.

I used to like batery tender brand, but found that when they don't work the company charges you to send it in and back to yourself under warranty work.

so I switched to schumaker brand.

for agm battery I use ctek brand chargers for that kind of battery.

but it is 20 to 30 for the shumaker brand and 100 for the ctek.