What is the proper way to charge your batteries. I leave mine on the charger until I use my boat next. That might be one week to one month. Is that bad for the batteries? Friend of mine only charges his the day before he goes. Who's right?

I top mine off when I get home and unplug after they charge. The day before I go back I plug them back in until the morning I leave batteries last along time for me never a problem.

I leave mine plugged in anytime it is at the house. The onboard charger I have fast charges, then floats and maintains them until the next time they are used. The charger is designed to be left on as often as possible.

Depends on quality of your onboard charger. I was just checking out the operating instructions on the dual pro I have and it actually states " We recommend that you leave your system plugged in. This will reduce sulfation on the lead plates of the batteries and allow your PCS charging system to keep your batteries fully maintained and ready to perform at their best."
I personally didn't know this and unplug my charger after they are fully charged.I also plug them in the night before a trip just to ensure full charge. This method has served me well for about 18 years.

Open beer, take a drink, plug in the charger and back to the beer. Works every time.

A big opinion discussion often ensues when discussing battery charging as there are opinions in several camps. One thing that no battery-knowledgeable person would ever do that's quoted about the friend above is: Leave the batteries in a discharged state for any length of time.

For sure:
1. Discharging a battery takes a toll on it, which is why they don't last forever.
2. The deeper a battery is discharged, the shorter its service life will be. This is why higher capacity batteries last longer, assuming all other characteristics are fairly equal.
3. The LONGER a battery stays in a discharged state, the more pronounced the impact of that discharge cycle will be.
4. You give a battery the best chance for a longer service life if you recharge it ASAP after any discharge cycle.

So, the buddy who doesn't charge his batteries until he's ready to fish again is killing those batteries faster. Today's high tech smart chargers have a microprocessor controlled profile that includes a high-frequency desulfation cycle that can help extend battery service. They also have a smart float mode that avoids evaporating excessive amounts of water from the electrolyte. This "boil-off" was a reason that chargers were once not left connected.

I vote for the following with respect to conventional lead-acid batteries:
1. Charge ASAP with a good smart charger.
2. Leave it connected, but keep an eye on it and the condition of the batteries.
3. Check electrolyte level after charging at proper intervals for your level of use; fill properly using only distilled water. You'll have to learn by experience how often your batteries need water replenished.
4. Use a battery cut-off switch for the main battery.
5. Be sure to flip the TM breaker or unplug the TM. (Read TM manual to discover you should do this.)
6. Use an AC supply surge protector with your charger. This step is cheap insurance.

I bought a small 2 outlet surge protector made as a small box. It isn't waterproof, but I can protect it under the deck in a place where rain doesn't get to it if charging outdoors on a trip. IF something funky happens on the AC line, the surge protector makes it less likely that my expensive charger will get fried.

Ever had an extension cord stolen? Use a small shackle padlock to secure the cord to a transom eye of your boat. The padlock lets the cord pass through, but the plug and receptacle on the ends are too large to do so. Stealing the cord would require cutting the lock or cutting the extension cord itself. This could be an adequate deterrent.

For sure:
1. Discharging a battery takes a toll on it, which is why they don't last forever.
2. The deeper a battery is discharged, the shorter its service life will be. This is why higher capacity batteries last longer, assuming all other characteristics are fairly equal.
3. The LONGER a battery stays in a discharged state, the more pronounced the impact of that discharge cycle will be.
4. You give a battery the best chance for a longer service life if you recharge it ASAP after any discharge cycle.

From being in the golf business, dealing with golf car batteries, for the last 40 years, take these statements as battery gospel.

SE Kansas grass grower

I agree with all said here. Also like the pad lock idea.

Thank you for your in depth responses. I have believe my charger has the cut off sensor on them so I should be good leaving them plugged. I love TFF and people who share their insight. Has helped me tremendously over the years.

I was one that left mine connected all the time until I had a battery blow up in my boat. My charger failed and supplied 14 volts to the battery non stop. So make sure you check your batteries often.

You are correct about due care, hence my statement:

2. Leave it connected, but keep an eye on it and the condition of the batteries.

Quite often I take a peek into the battery compartment. I put the back of my hand on the side of the batteries to feel for heat. If overly warm long after the charge cycle should have completed, I worry about a shorted cell prompting the battery to attempt to pull it up, or about a failed charger itself.

A few years ago I had a very catastrophic battery failure in a truck I was starting. The belief is that a plate warped when the high current surge for the starter initiated. This resulted in a significant and rapid "expansion" of the entire case. The terminal posts were blown off and very little of the case sides remained. The top was in several pieces. I think a person a half mile away would have heard it. Being that I was sitting in the driver's seat in silence when I turned the key, it took me quite some time to regain my composure after that event!

Thank you. The padlock idea is my own original idea. I have a couple of epic trips in the works and have been thinking through how to slow down some of the separation of me and my stuff - or at least make it less convenient to take.

My power-poles mount to a plate sandwiched against the transom, so taking the bracket is difficult. But, Power-Pole theft = 4 bolts and snip snip to the hydraulic tubing. I've seen a $100+ solution per pole that's nice but a bit much! I am still working on ideas to slow them down or cause a thief to decide it's too much trouble. One is to add an appropriate hole to the square mounting plate near the edge. Use a good quality armored shackle lock on it (if that fits, need to check). Another is use a proper length "bolt style" trailer coupler latch lock on a hole added to the PP/bracket. The locks can easily be removed before launching for a day of fishing.

Yes this for sure and if you don't have built in battery chargers I HIGHLY suggest charging all batteries equally at the same time. Also on boats I've owned where there was a 24 volt system for the TM and same for the 36 volt systems, I found my batteries lasted longer if I ran the TM using all the batteries and adjusted the speed accordingly. I found if I ran on 12 volt and 24 volt in high stress situations the battery that was taking all the load in the 12 volt mode give up a lot sooner than the others......discharging them evenly really seemed to help with battery life...........

After working 11 years for a battery factory I can tell you that you need to get them on charge as fast as you can or they will develop memory and will show a full charge but will not be at full capacity (this a for the conventional type battery there are a few new styles of batteries out now that I am not familiar with). Also it is not a good idea to leave them on charge very long after they are fully charged unless you have a battery maintainer charging system. And yes you should recharge them the night before you fish just to ensure that there was no kind of discharge which is common with batteries while your boat is sitting in idle. Good luck

This is what I wonder about. I have heard you shouldn't keep the on-board charger plugged in for extended periods but I am guessing there are some 'smart' ones where this is OK to do. My charger is an old Guess 2-bank charger and I think I would be concerned to leave it plugged in for a month or two if I wasn't able to use the boat for a while.