Onboard Charger – Winter??

I checked past posts to be sure, but no one really answered or gave their experiences. I just bought and installed a Minnkota 315D 3 bank charger in my boat. It says in the manual that it also acts as a maintainer for the batteries with a “long-term maintenance” mode for extended periods of it being plugged in. My question is: what about winter time? I store the boat in a garage (not heated) off-site but not close to my house, either. Do you leave yours plugged in all winter or just charge them periodically?

I leave mine plugged in all winter in my driveway. No issues. Except I would never buy a minnkota charger again. Mine lost a bank twice now. Had nothing to do with leaving it plugged in. Once under warranty, now I just use it with one less bank. These chargers are well known for this.

I leave mine on all winter in my pole barn. It does a great job. I have a three bank Minnkota…. 305??? I think. Its probably 12 – 15 yrs old and never gave me a bit of trouble. Just make sure you keep the water level up in the cells. Always use distilled water.

Leave mine plugged in all winter as well.

No issues on mine yet, 315D. I’ve followed biggills posts on repeated failures and know he had a different model.

Regardless of what they say, I’ve learned not to trust them entirely. Always check your water levels come Spring.

My batteries stay right in the boat plugged-in to the onboard charger. If I stored my boat outside in the extreme climate, I’d probably think twice about this strategy. My boat stays in an insulated (but unheated) attached garage that rarely drops below ~40 degrees. My starting battery in the back of the boat gets its own battery tender placed on it as it is not connected to the onboard charger.

This has not left me sitting yet come Spring. I do swap out my starting battery every 3rd year though as I am paranoid about having a fairly new one that charges easily and holds a charge over time. I know some guys run their starting batteries until failure, but I like the peace of mind associated with a newer battery.

What type of batteries are you using? Some don’t need to be on a maintenance charger.

ClownColor wrote:

What type of batteries are you using? Some don’t need to be on a maintenance charger.

Thanks for the replies. These are typical deep cycle lead acid.

Dealer told me today to plug in overnight once a month (outside cold storage )

Thousands of boats all across the northern states and Canada are stored in unheated buildings or outdoors without access to electricity. Leaving batteries in the boat all winter is not a problem if you do it right. Batteries work by a chemical reaction. Chemical reactions slow down as temperature drops. Nothing bad will happen to a good, fully charged battery in the winter.

1. Make sure the water level in the batteries is at the indicator.
2. Charge the batteries fully.
3. Disconnect all the positive terminals to prevent accidental discharge and secure them where they will not contact the post. (I disconnect the negatives also; that way I make sure I clean all the terminals in the spring.)
4. After a day or so, check the voltage with a digital multimeter. If a battery is low, pull it out. You don’t want a bad battery freezing and bursting in the boat over winter.

Below is a chart I’ve kept before and after storage for the last few years.

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If you have the charger and electricity where you store, leave it plugged in all winter. It may not be a requirement for your batteries, but it will improve their life.