Dick
Yes to leaving the bilge pump on. Indeed we had to do this as we had to winterise in the water 3 months before the boat was hauled. We overcame this by disconnecting 80% of the battery bank completely and leaving a sacrificial 20% connected and plugged into shore power. In Greenland we had no reliable caretaker despite best endeavours and upon our return discovered that The yard had hauled in late November as the sea froze but NEVER connected the shore power cable.

When we returned in June (after a 9 month layup) the voltage in our disconnected AGM’s was 12.7v. Sadly I had reconnected to SHOREPOWER before checking the voltage in the ‘sacrificial’ batteries.

In Lewisporte the power for the yard is switched off from November to March and so in-boat top up is not possible for us.

Our starting battery is our only flooded battery and we do remove this and place in a heated shed. Our’s currently resides in Bryan’s office!

In Iceland we did things differently as we overwintering both times in the water with a reliable and cheap electricity supply. Our charger is pretty smart and does periodic top up automatically. We were able to visit Iceland several times during both winters and we were able to stay on the boat with all systems (including dehumidifier and frost protection) working. This practice does not appear to have been detrimental to our battery bank which is now 6 years old. Of course it is lightly used when compared to a live aboard.

We might have an unpleasant shock (because of these various practices) when we return to Lewisporte in June but my financial controller ( Sally) is braced for it! I will let you know (here on the Forum) how it goes when we recommission.
Simon

Hi Simon,
My understanding:
Flooded batteries are most vulnerable to freezing over the winter: in part because their electrolyte is more liquid, but mostly because they lose their charge far more rapidly that gel or AGM and the lost charge makes it more vulnerable. My experience is with gels primarily.
I try, and have always succeeded, in always having a “caretaker” for Alchemy over a winter’s storage. Often this is a fellow cruiser who will be in the area, sometimes a yard worker, sometimes a retired person familiar with boats. Their job varies but is primarily to charge the batteries at the schedule I set up ahead of time. I make things as simple as possible: usually the work is to just plug the shore power cord in (I never leave the boat plugged in 24/7).
If I think it is unlikely that there will be a hard freeze, I am comfortable leaving my gels fully charged for a few months unattended, but since I am looking at a 4-5-month lay-up, I usually have the batteries charged for a few hours on a monthly basis.
Removing your battery bank has always seemed to me a boat yard’s ploy to make a lot of money. Possibly it makes sense (in the old days) for flooded batteries in very cold climate where one is unable to find reliable caretaking. But then, you have to find someone reliable to watch over them (a bit) wherever they end up being stored. (I would not recommend attaching to a “trickle” charger and forgetting for the winter: a practice I suspect many boatyards indulge in: charge and then leave for a period and checking the voltage periodically). Over decades of storing boats in the company of many others, I do not remember anyone removing their batteries.
I do not disconnect my battery bank completely, although if leaving the boat unattended in a warmish climate and the batteries are not flooded, this may make sense as there are always small draws that eventually will bring batteries down. With reliable caretaking, I do not see disconnecting the batteries as necessary. I also like to have the bilge pump active as water will get in, in rainy climates, through the mast and then accumulate with the anti-freeze I have left sloshed in the bilge and can be then pumped out.
AGM’s sound like the battery to have in very cold weather. What was the resting v reading on your AGM’s after a winter on the hard in Greenland (or Iceland)? I am not sure gel’s are that robust with respect to cold and flooded batteries certainly are not.
I am sure I left something out: come back with questions/comments.
My best, Dick Stevenson, s/v Alchemy

Dick
This is very much a Forum initiative and I think Phil is only using Facebook as a way of drawing in a wider group of OCC contributors.

Dick what do you do with batteries in the extreme cold for the winter? The conventional wisdom is that they should be removed but we have never done this and have had no problems. We just make sure they are fully charged then we physically disconnect them. Our AGM’s don’t freeze until -87 according to the manufacturer and, to date, everything has survived.

Hi Phil,
I have over-wintered Alchemy in many places, cold and warm, and both in water and on the hard, and am happy to participate. Can the Forum be "home base" for this project where all the data/suggestions etc. migrates for those of us who do not do FB?
Thanks, Dick Stevenson, s/v Alchemy

Simon
OK - since we can draw on the collective knowledge of members I will post a request on the facebook page for people to contribute om all three conditions and ask for any variations that are specific to in the water or on the hard?
Phil

Phil
Thank you. I will do ‘Very Cold’ and would really appreciate you doing warmer zones as that’s the way we are heading.
Simon

I know it is more work, but how about three lay-up themes, say for up to 6 months: Very Cold Climate, Temperate Climate and Tropical Climate - that would be very useful for a very wide range of members. I would be glad to help. Cheers

In order to remember the lessons we have learned in recent years I would like to write a ‘best practice’ article on preparing a boat to overwinter (unattended) in very cold climates. It would be great to use this thread to collate the experiences of others.
Simon