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Old 03-09-2014, 06:34   #1
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solar for float charge over the winter

I will be putting my new to me boat on the hard for the winter in a week. Considering the largest boat I owned before was a Catalina 22, many things about the winterizing process are a bit mysterious to me. That I will be away from the boat for three months just adds to my anxiety.

I have a bank of 2 8G batteries, giving me, I think, just over 500 amps. Calculating a .3% float need, it seems I should have the batteries on a 15-25 watt panel over the winter. I also believe I can wire that panel directly to the batteries without a controller.

Am I correct in these calculations and assumptions? Any additional advice?

Fwiw, the boat will be stored in St Marys, Georgia.
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Old 03-09-2014, 06:58   #2
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Re: solar for float charge over the winter

Honestly,
Aside from the PITA part about lifting them, if you can manage it, you'd be as well to take your batteries home for the winter. It'll keep them out of the cold (freezing at times), & you can keep a closer eye on things. Plus it'll be one less concern to have about the boat during the off season.

If you go this route, you can pull everything but the starting battery off of the boat prior to heading for the travel lift. That way you're not pressed for time, nor do you have to mess with unloading batteries 12 vertical feet once your boat's on the hard. Ugh!
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Old 03-09-2014, 07:05   #3
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Re: solar for float charge over the winter

+1, freeze kills batteries
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Old 03-09-2014, 07:12   #4
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I cannot see any way of lifting them out. They must weigh about 150lbs each. I put one in with a mechanic this spring. It was all we could manage to get it on the boat and in the lazarette.

I am sure freezing is not good for the batteries. But the previous owner left them on in Connecticut and only had to replace them every 5 years or so. I can live with that.

However, I will ask the yard if they have the ability to take them put and store them and at what cost.

But does anyone have an answer to my original question?
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Old 03-09-2014, 07:39   #5
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Re: solar for float charge over the winter

Quote:
Originally Posted by Scot McPherson View Post
+1, freeze kills batteries
Hmm well over 30 years of storing batteries on boats and never once seen one properly charged before decommissioning freeze. It would take close to -70F for a charged battery to freeze. Oh I was also born and lived in Alaska.. Fairbanks gets pretty darn cold and they use the same type of batteries we do...

Effect of Cold Weather on Self Discharge

For the OP you will want a controller but personally I don't like to see any unattended charging when you are not there. Too much to potentially go wrong.. I have numerous customers beyond 10 years here in Maine with their batteries and all have been stored on-board for the winter, fully charged then 100% disconnected from the vessel. The vast majority of my customers store their batteries on-board, charged then disconnected in Maine, all winter...

Boat yards have convinced folks they need to remove them because they MAKE MONEY ON IT...... Save your back....

In regards to solar I had a bank of 6V batteries destroyed last winter by a 10W unregulated panel... The self discharge will be extremely low and you can eventually cook the batteries..

Do I Need A Solar Controller?
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Old 03-09-2014, 13:26   #6
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Re: solar for float charge over the winter

Your idea is probably good without going over the math of discharge/charge rate. There are a ton of cheap solar chargers on Ebay. Think I'd use one of those just to be sure. An overcharged battery that explodes creates one hell of a mess, btdt.

If you use solar, whose going to sweep the snow off it so it will 'see' the weak winter sun.
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Old 03-09-2014, 15:53   #7
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Re: solar for float charge over the winter

St Mary's is like 100 yds from Florida... Freezing temps are rare, and never for more than a few days. Not enough to worry about freezing a "charged" battery. Lots of time on the hook in Chucktown and Savannah and never had a problem with freezing batteries. Not even here on the Chesapeake with a proper charge.

I might suggest moving up in the wattage on the panel however. Not because your calculations are incorrect, but rather because the economics of scale means the lower the panel wattage, the higher the cost per watt.

For example, because I am limited on space to mount a permanent panel, I had to go with a 100W unit at about $2.00 / watt. If I had room, I could get a panel with almost twice the output for the same price.

Controllers are cheap if you are not looking for the latest high tech, sexy, I got the most expensive, etc... With the 100W panel I added a 30A controller (simple PWM) with digital readout for 50 bucks. Oversized for future expansion and from the US panel manufacturer, not an overseas knockoff.

Think about it... a few extra bucks now, might pay off in less shore power time or generator time down the road as well as take care of your immediate needs...

If you happen to want the specs and supplier for the above referenced system, drop me a PM... Don't want to be accused of touting a supplier.

Just sayin'
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Old 03-09-2014, 16:33   #8
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Re: solar for float charge over the winter

I missed the Georgia part. Don't worry about it, charge em and leave em...unhooked. Don't need a vampire slowly sucking them dry.
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Old 03-09-2014, 16:54   #9
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Re: solar for float charge over the winter

Can you not get power to the boat and use a battery tender?
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