Off-Season Float Battery Charging, 2 Batteries

zippinbye1

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Dec 2, 2023
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Hi all - my first post here after being a frequent lurker, I finally signed up. Gotta start with something, so here it is ........

Boat in question is a 1998 Four Winns Horizon 240 with a 7.4 Volvo MPI, but that's not too pertinent, as the electrical layout is rather generic .... could be any number of boats, as it has port and starboard marine batteries with a 4 position switch. I'm trailer-stored under cover at my home. Our "winterization" out here in Southern Nevada is pretty tame compared to many parts of the country, since it rarely gets but a few degrees below freezing and when that happens, it's not more than four to eight hours below. In 30+ years living here, I could have left the boat with fresh water in all jacketed areas and escaped damage all but two or three years. An incandesent light bulb in the engine compartment would probably do the trick, but what I do is a flush with RV antifreeze. It's a practical and flexible non-toxic method that allows me to take a spontaneous run on a clear and warm winter day, if I feel the urge. One test fire at the house to purge the antifreeze, and it's off to the lake or river.

In keeping with that simplicity, as opposed to pulling the batteries and float charging them in my shop, I want to attach a battery maintainer with the batteries in place. Can this be accomplished with a single charger? I have good luck with the very inexpensive Harbor Freight units on all my single battery stored vehicles, so wondering if there's a way to sort it out for the boat? Attach to one battery and select the switch to "Both" in order to share charging to the other side? These are the Cen-Tech brand, and are rated at .5 amps - might be a bit week for the cable gauge and distance, approx. 80 inches between batteries with switch in the middle. Or should I just run two chargers independently, with the switch "off?" BTW, I don't think the boat has any parasitic electrical draws - the stereo has a dedicated power switch and no clock or other obvious "vampires." So I do not expect any downstream competition for electricity utilization of the switch is selected to Both

Open to all ideas. TIA
 

alldodge

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Mar 8, 2009
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Welcome
Bat switch OFF and 2 chargers

Using 1 charger and Bat switch on Both can work if both Bats are in same shape. If one has a problem it will take them both down
 

zippinbye1

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Dec 2, 2023
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Agree. Better plan is off and 2 chargers. If connecting to both, you need a bigger charger.
Thanks guys - you pretty much validated what I was thinking. The chargers I've been using are so inexpensive, it's not really a consideration in the 1 vs. 2 debate. I do have two good batteries; a 8 month old and a few years old & recently been through desulfate cycle and actually topped off a couple of tenths greater voltage than the young one. Just trying to keep them both heathy - in the past I have been lazy, and paid the price in diminished life cycle. Some folks say our environment dooms batteries to 2-3 years max, but I'm seeing at least 2x that on all the batteries that I pay attention to. I got 10 years out of my OEM batts on a Ram diesel truck, so I think it's worth the effort.

Thanks!
 

Lou C

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Nov 10, 2002
Messages
12,226
I like the NOCO Genius 10 I bought last year. Thinking of picking up another.
If you have an old charger, check what voltage it is putting into the battery. I had an old Schumacher that was charging at 16.5V! The NOCO charges at the rate you'd expect.
 

Grub54891

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Jun 17, 2012
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I simply make sure the battery's are charged and disconnect them. Top off in spring and go boating. It get's to -20 up here and I haven't had any issues.
 

QBhoy

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Mar 10, 2016
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Hi. Very common here for most boats to have a marine multi output charger installed. Anything from 2 to half a dozen separate outputs. Proper way to go about it. Be likely not an ideal arrangement to have a charger with one output, trying to charge two different batteries. They will almost certainly be in a different state of condition or health from one another.
 

Dubed

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Sep 3, 2021
Messages
350
I disconnect mine, put them on my workbench for the winter, and hook up a battery tender.
This also kinda forces me to clean all the terminals and connections next season while hooking them up.
 

Lou C

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I charge em and turn the batt switch off; during the winter I’ll open up the cover & charge em every 2/3 months depending on the weather. If they are dead in the spring then you needed to replace them anyway. Keeping them on a maintainer all winter can mask a weak battery that won’t hold a charge.
 

Dubed

Petty Officer 1st Class
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Sep 3, 2021
Messages
350
I charge em and turn the batt switch off; during the winter I’ll open up the cover & charge em every 2/3 months depending on the weather. If they are dead in the spring then you needed to replace them anyway. Keeping them on a maintainer all winter can mask a weak battery that won’t hold a charge.
Really...Hmmm?
Sometimes you think your doing the right thing but...
 

Grub54891

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Jun 17, 2012
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Really...Hmmm?
Sometimes you think your doing the right thing but...
That's how I roll. Charge in the fall fully, disconnect, and go to bed. Chage in the spring and go boating. If the battery is shot in the spring it's time for new. I get a minimum of 8 years on batterys, at that point i get nervous and replace them.
 

Lou C

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Nov 10, 2002
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12,226
That's how I roll. Charge in the fall fully, disconnect, and go to bed. Chage in the spring and go boating. If the battery is shot in the spring it's time for new. I get a minimum of 8 years on batterys, at that point i get nervous and replace them.
same, I seem to average 7 years of good use on my Deka gp 27 dual purpose batteries
 

JASinIL2006

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Feb 10, 2012
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5,609
I keep mine in the boat, on a NOCO maintainer all winter. If a battery is going bad, I'll figure it out soon enough come Spring, and in the meantime I won't have a frozen battery and battery acid in bilge.
 

H20Rat

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Mar 8, 2009
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5,201
Make sure it is charged in the fall (around Oct), disconnect the negative, and don't touch it until late May or so. My winter gets down to -40, and batteries last 7+ years. (I usually pre-emptively replace around the 7 year mark)

I have lost more batteries due to maintainers cooking out the electrolyte than I have from not using one!
 

airshot

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Jul 22, 2008
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That's how I roll. Charge in the fall fully, disconnect, and go to bed. Chage in the spring and go boating. If the battery is shot in the spring it's time for new. I get a minimum of 8 years on batterys, at that point i get nervous and replace them.
I hear ya, when a battery passes 4 years I get nervous ! Depending on what the battery is used for, I have replaced good working batteries many times if I fear being stranded with no way to recover.
 
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