• Mobile App For Android Now Online!

    Download it here. The app is searchable in the Google Play Store under Sailboat Owners.

    Sorry iPhone/iPad users, we are still waiting on Apple. :(

    Click the X in the upper right corner to make this go away

Preventing Battery Freeze

Sep 20, 2015
111
Navigator 4200 Classic New Bern, NC
Is there a good method for preventing battery freezing? In an earlier thread, we talked about the slight bulge my batteries developed after what we are guessing was a freeze event. I have four battery boxes with eight golfcart batteries and three group 27 starter batteries in them. The boxes are wooden with closing tops. I will normally place a small 120V oil-filled space heater in the bilge to keep the engine area warm, but the batteries are in a different section of the space and, apparently, don't get enough heat. The boat live in North Carolina and isn't subject to continuous bitter cold, but we get a few snaps of teens or single digit temps.

Is there a heating device I can put inside the boxes (maybe even a 12V device) that can keep the boxes warm without compromising safety or should I construct a blanket cover for the boxes? Although, now that I think about the second one... it would not allow off-gassing... probably a bad idea)

Thanks in advance!
 

TomY

Alden Forum Moderator
Jun 22, 2004
1,972
Alden 38' Challenger yawl Rockport Harbor
There is! Charge them fully and check the electrolyte levels, then disconnect and totally forget they exist. :) You're protected to 50F below zero for the winter. Charge them in the spring, you'll find they may have lost 10 or 20% of their full charge, if that.
 
Oct 22, 2014
10,822
CAL 35 Cruiser Portland OR, moored EVERETT WA
we talked about the slight bulge my batteries developed after what we are guessing was a freeze event.
More likely the event was an over charging event. The battery overheated and thus the bulge.

Unless the batteries were fully discharged charged and the temps dropped below zero for an extended period. A healthy battery when fully charged is approximately 25% sulfuric Acid and 75% water. Thus you have built in freeze protection. The electrolyte mixture has the freezing protection as indicated by @TomY when fully charged.

Partial charge state moves the mixture towards more water less acid. Less freeze protection.

Follow TomY's model and you should be fine in NC. Unless we get a massive Polar Vortex out of the Arctic sweep across the country. Then all bets are off. Head to the waters south of the Caribbean for survival.
 
Jan 11, 2014
4,466
Sabre 362 113 Fair Haven, NY
What @TomY said. Make sure they are fully charged, the water levels and electrolytes are good, and disconnect them.

What you do not want to do is keep them warm. Warm batteries self-discharge at a faster rate than cold batteries.
 
Sep 20, 2015
111
Navigator 4200 Classic New Bern, NC
There is! Charge them fully and check the electrolyte levels, then disconnect and totally forget they exist. :) You're protected to 50F below zero for the winter. Charge them in the spring, you'll find they may have lost 10 or 20% of their full charge, if that.
That isn't an option as we use the boat most of the winter as a "condo" and even take it out on those odd warm winter days.
 
  • Like
Likes: rgranger
Oct 22, 2014
10,822
CAL 35 Cruiser Portland OR, moored EVERETT WA
The Sterling unit is a very good unit. When set up with the Temp sensor it is designed to reduce the chance of an overcharge event when the heat of the battery exceeds a set temp. All things working to spec.

Are you saying that you have the charger running all winter? The Temp sensor is on the battery all winter?
 
Jan 11, 2014
4,466
Sabre 362 113 Fair Haven, NY
That isn't an option as we use the boat most of the winter as a "condo" and even take it out on those odd warm winter days.
If you are connected to shore power, leave the charger on.

Disconnecting the battery is what we northerners do because there is no charging source over the winter and there are parasitic drains on the battery. In your case, make sure everything except the bilge pump is turned off.

Since the boat is in the water, freezing the battery is not an issue. It will not get cold enough in NC for the batteries to freeze. Assuming the batteries start off the winter in good shape, i.e, fully charged and with the proper specific gravity it would take an extended time (weeks) of extremely cold weather (well below 0° F) to freeze the batteries. There is a tremendous amount of heat in the water surrounding the boat that will keep the boat's innards warm enough to prevent freezing. The worst case scenario is some parasitic drain and self-discharge leaving the boat in a partial state of charge.

Do you winterize your engine and water systems?
 
  • Like
Likes: captcoho
Sep 20, 2015
111
Navigator 4200 Classic New Bern, NC
The Sterling unit is a very good unit. When set up with the Temp sensor it is designed to reduce the chance of an overcharge event when the heat of the battery exceeds a set temp. All things working to spec.

Are you saying that you have the charger running all winter? The Temp sensor is on the battery all winter?
Yes. That is the case. That charger (with a temperature sensor) has been on that bank since it was new.
 
Sep 20, 2015
111
Navigator 4200 Classic New Bern, NC
If you are connected to shore power, leave the charger on.

Disconnecting the battery is what we northerners do because there is no charging source over the winter and there are parasitic drains on the battery. In your case, make sure everything except the bilge pump is turned off.

Since the boat is in the water, freezing the battery is not an issue. It will not get cold enough in NC for the batteries to freeze. Assuming the batteries start off the winter in good shape, i.e, fully charged and with the proper specific gravity it would take an extended time (weeks) of extremely cold weather (well below 0° F) to freeze the batteries. There is a tremendous amount of heat in the water surrounding the boat that will keep the boat's innards warm enough to prevent freezing. The worst case scenario is some parasitic drain and self-discharge leaving the boat in a partial state of charge.

Do you winterize your engine and water systems?
I believe you. There just seems to be little else that could have caused the bulging (it was a possibility lofted by MaineSail in the other thread). But to answer your question... No... I do not winterize the engine and water systems, but do run heaters throughout the winter in the cabin and one in the engine room.
 
Sep 11, 2017
186
Beneteau 373 Cape Cod
There is! Charge them fully and check the electrolyte levels, then disconnect and totally forget they exist. :) You're protected to 50F below zero for the winter. Charge them in the spring, you'll find they may have lost 10 or 20% of their full charge, if that.
I live about 500 miles north of North Carolina, in Massachusetts. We have notably colder winters than NC.... and I do exactly as @TomY said. Charge them to maximum, then disconnect them from everything (not just switched off, but cables PHYSICALLY removed from posts on batteries). Then completely forget about them until spring, reconnect, and top off. Would it be better if I topped 'em off once a month during winter? Probably, yes. but that would require hours of driving each time to where my boat is stored, and that's not an option for me. Seems to work pretty well up here, so I'd imagine that would work fine in N.C.. While there's some loss there, I have to imagine that trusting them hooked up to an unattended automatic charger for months at a time poses at least as much threat to the battery's well-being as what I do. I'm admittedly no electrical engineer though... just a guy with a frozen boat who sleeps well at night, and seems to have plenty of amp-hours after a quick top-off each spring. YMMV.
 
  • Like
Likes: TomY
Jan 11, 2014
4,466
Sabre 362 113 Fair Haven, NY
I believe you. There just seems to be little else that could have caused the bulging (it was a possibility lofted by MaineSail in the other thread). But to answer your question... No... I do not winterize the engine and water systems, but do run heaters throughout the winter in the cabin and one in the engine room.
If you don't have to winterize your engine, then you don't have to worry about freezing the battery. A battery is a lot cheaper than an engine block or heat exchanger.
 
  • Like
Likes: TomY
Oct 22, 2014
10,822
CAL 35 Cruiser Portland OR, moored EVERETT WA
Here you go Gonzo MaineSails article on winter care for batteries.
When I set up my system I spoke with him and he suggested I remove the temp sensor during the winter as it does not work well with air temps near freezing. Not clear on this. I suspect it has something to do with the sensor wire/cold temps/ and accurate voltage transmitted to the charger.
 
Oct 22, 2014
10,822
CAL 35 Cruiser Portland OR, moored EVERETT WA
Gonzo, I hear you use the boat as a Condo during the winter.

One of your advantages with the Sterling is the availability of DC power when turned on and yet not attached to any battery. This could enable you to disconnect batteries for winter and still turn on DC powered appliances on the boat while the Sterling charger is running.
 
Dec 15, 2006
201
Catalina Catlina 310 Campbell River BC
When I was in Alberta -40c in the winter was normal did not have frozen batteries. Now if you feel you need the protection go to NAPA and get battery warmers and plug them in, they are used in the cars up north like Yellowknife.
 
  • Like
Likes: captcoho
May 23, 2016
159
O'Day 1984 23 Island Park, NY
As stated above, disable the temp sensor if leaving on the charger in cold weather... Same temp compensation circuit that drops the charge voltage in hot weather raises it in the cold, to the point where the electrolyte can boil like it's doing an equalization... I don't know why charger companies don't build in a Max compensation to avoid this. Wouldn't cost enough money to warrant leaving it out.

In many cases the sensor can be disabled by pulling out of the charger the telephone style plug that connects the sensor