Got a question about boat battery charge. If I charge a battery to 100% and then it sets for a few days, should I expect some drainage on the charge or should it remain close to 100%.

Thanks in advance

All batteries self discharge, cheaper batteries more so others.  A few days should not be enough to notice.  30 days, you might want to top it off.  If it's not stored on a maintainer, it should be topped off every six to eight weeks.  

The cooler the area it's stored in helps minimize the self discharge.  Sitting on a cool concrete floor or a cool shaded spot is better than sitting in the boat. 

Note, even with chargers that trickle charge/maintain some recommend leaving them on all the time, some don’t. 

 

Minn Kota says not to leave it connected while my Dual Pro said to keep it connected. 

I charge my batteries and then disconnect the charger.  I will top them off before going fishing.  After two weeks,  when topping them off,  the trolling motor batteries will show a full charge in less than five minutes.  The cranking battery might take 15 minutes due to power drain caused by electronics in the outboard.

Only battery I have is a 75AH deep cycle for the TM and Sonar. I'll toss it on the charger the night before I'm going out - after unplugging everything. The West Marine charger I have has auto cycle, so I COULD leave it on the battery all the time, but it's not necessary.

You should have a on/off battery switch for the cranking battery to isolate the battery when charging.

Do you know how to tell if the battery is 100% charged?

Tom

Few days? Your good. 

I use to worry about this as well. I fished a tournament (7+- hours) then fished two more days of 6+ hours (without recharging) and it was still kicking well. This is just the TM battery btw. 

Weeds and fishing line WILL kill your batteries quick however. 

Always check that first. Check to make sure the terminals are very tight as well. That’s #2. 

A little bit of Vaseline in the terminals and where the TM connects cuts down on corrosion and gets a better ‘bite’ from the battery as well.

good luck