Thread: Is my Dual bank charger killing my TM batteries?????

It was the charger or so they thought. They did not test it. They replaced 2 of the batteries....good enough

Charging the new ones now and hopefully fishing in the early morning to beat the heat

glad it worked out.

KAG ... keep us informed as to the outcome of your new setup. I'm asking because I have a MK220 on-board charger, and due to circumstances beyond my control I have to keep charger & batteries in my apt (or else use a 10A regular charger on each battery, one at a time). In my situation, having the on-board charger IN the boat would only be necessary for trips where I'd have the boat in a marina slip for more than one day ... and that only happens once or twice a year, max. And it's simply a matter of replacing the on-board charger back into it's former spot & securing it with screws, for those few occasions.

My concern is whether or not leaving it plugged in will/could overcharge the batteries ... vs ... charging them after use, then unplugging the 120V cord, but leaving the leads connected to the battery posts & having the unit draw/leak current back out of the batteries. The MK220 came with the boat, and the former owner left it plugged in all the time ... my tester showed the batteries to be overcharged, and the fluid levels were high enough that it was obvious that fluids had been added (making me suspect that the constant charging had boiled the fluid levels low enough to warrant the adding of additional fluid). Both of those batteries would drop their charge levels down to around the 75% mark, if left off a charging system for more than a week or so ... which prompted me to exchange them for new ones. The prior owner had purchased the batteries two years before selling me the boat, but had not used the boat for more than a handful of times during that period.

... cp

Been using onboard chargers for years now.....have used two kinds Dual-Pro and MinnKota....Am using MinnKota at present time. I always leave them plugged up.....never had a problem with over chargeing or boil over as you call it. I have had long battery life and no problems.

"...never had a problem with over charging or boil over as you call it. I have had long battery life and no problems."
I use a Pro Mariner Pro Mite 5 5 3 always plugged in when home

Opinions are like holes everybody has one. Me too.
I had poor luck with the OEM Interstates that came in my boat. In fact both were toast in 2 or 3 years.
I was on my 4th and 5th year of WalMart Maxx batteries coupled with a 3 bank onboard charger (until 1 shot craps this week). My on-board charger does NOT drain my batteries when it is unplugged from 110V. Batteries naturally lose a percentage of their charge every month (5%?) that increases in rate of loss as the battery is discharged further...
All that said, I would replace the dead batteries with non-Interstates AND replace the charger with a ProMariner or other brand...keep it plugged in most of the time. Big advantage of the newer smart on board chargers is that the batteries do NOT ever need water added to them. Old timers say it is good to boil a battery with and old charger but all that accomplishes is to get the battery hot, and heat kills batteries. I about blew up a battery last night...trying to charge a battery with a dead cell is a bad thing, very very bad thing.

Simple test, park your boat in say Oct. or Nov. like around here when it snow's and don't plug that charger in until say mid April when it thaws out like around here then see how those batteries and charger work out. Yep everyone does have opinion's and belive me I hear them every day when they try to tell me what's wrong with thier boat but can't seem to fix the problem.

Originally Posted by Archerguy1

Simple test, park your boat in say Oct. or Nov. like around here when it snow's and don't plug that charger in until say mid April when it thaws out like around here then see how those batteries and charger work out. Yep everyone does have opinion's and belive me I hear them every day when they try to tell me what's wrong with thier boat but can't seem to fix the problem.

In conditions like that you will most definitely have battery problems come spring. Its not the charger causing the problem, its the fact that the batteries are not being maintained in that cold weather. Google "maintaining boat batteries in cold weather".