I have a Sears 10 amp charger with regular and deep cycle modes, 2 and 10 amp settings.
How should I charge my starting battery? Trolling motor battery?
2Amp... set it on low, and let it trickle charge..... should take anywhere from 12-36 hours or so. I have deep cycle battery, and just use regular setting... should be more than fine.
Put it on the 10 amp setting and forget the 2 amp setting. 2 amps is for lawn mowers and motorcycles. The longer your battery is discharged the more damage that will be done. Now tell us what type charger it is. Is it a smart or automatic charger? If it is then watch the guage and after it drops to zero leave it for a couple more hours and then turn it off and disconnect.
Think about the batteries you have and how they are charged.
Example My boat has a group 24 starting battery and a group 24 deep cycle they are both charged with a 65 amp alternator thru a battery isolator on my I/O.
My cars have 100 amp alternators and my truck has a 130 amp alternator.
I have never had any battery that did not last at least 6 years.
Good alternators and smart or automatic battery chargers will control the voltage put out. Most will charge in the 13.8 to 14.8 volt range. Then the battery it self will determine how many amps it takes.
In the case of a 10 amp automatic charger or smart charger on a discharged battery it will start out near 10 amps. As the battery charges the current will continue to drop and most after 2 hours will be 5 amps or less. Even with a 10 amp automatic charger on a group 27 trolling motor battery after a day of fishing it will take more than 12 hours to charge.
If the charger is a manual charger then really need a volt meter to monitor it with.
Manual charger and most trickle charger will over charge because they have no voltage regulater and the voltage can clime way over 14.8 volts.