My boat is in indoor (unheated) storage all winter. I have access to electricity. I was thinking of plugging my shorepower into the wall and letting the smart-charger on the boat keep my batteries charged all winter. Is this a bad idea?

My boats shrink wrapped outside and I have my shore power run to an outlet that a can turn on or off. I usually turn it on to operate my on board charger the first weekend of the month. Let it charge for 24 hours. I've been doing this for 4 years now and no problems.
The Smart chargers are not supposed to over charge or "boil out" the electrolite. I would think it should be ok.
They're also very popular with the antique and collector car crowd since they sit for months at a time too.

Make sure your charger is a 3-stage electronic chargerwith full shutoff after float cycle, not a trickle charger.

Also need to use a hygrometer and verify that you don't have any lame cells, otherwise the charger (even a top notch one) will cause the remaining cells to outgass which will corrode everything within 10 feet of the batteries if in an enclosed hatch or under a cover.

Once you are ok on both counts, go for it. I've been doing that for years.

Thanks for the input. My on-board charger charges at 14 volts (according to the guage) then automatically shuts off. After reading your replies, I think I will plug it in for a few hours, once a month throughout the winter. This way too, there will not be an electrical cord dangling from my boat. I don't want the mice to find a way into my boat

I have shore power on my hustler with the charger and leave it pluged up year round. you still need to ck th water. it still lose water even being fully automatic.i also leave 100 watt bulb on durring the winter just for the hell of it.

stringer,

if they're still losing water, then your float voltage is too high. Call your charger mfr and see if the float voltage is internally adjustable. I'd drop it in small increments until you stop losing water. This is due to simple overcharging.

(I've got a pack of 5 group 31 batteries that are hooked to a Newmar 40 amp SmartCharger. They went in on May 2000. The charger has been "on" 100% of the time since then - boat is on genset when unplugged. I have added less than 6 ounces of TOTAL water to the five batteries - and I only added it cause I was determined to; they didn't need it.)

There not losing that much water . I do run them down with all the stereo equ,