Safe to Leave Dead Batteries on Board for the Winter?

Tom J

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Sep 30, 2008
2,301
Catalina 310 Quincy, MA
The owner of the boat next to me at my yacht club was happy that he had left his bilge plump on. After he had launched the boat at the beginning of the season, and then gone home, I noticed that his bilge pump was cycling continuously through the day. I called him and he came down to the boat and found that he had forgotten to reinstall the raw water intake hose that he had removed during the winter.
I leave my bilge pump on 24/7, but it feeds off the house bank, which feeds off solar panels, and would take a long time to deplete, and that still leaves the engine start bank to get things going again.
 
Jul 7, 2004
8,402
Hunter 30T Cheney, KS
To Benny's point - "The best argument that I have heard for powering bilge pumps 24/7 is "If they can save the boat or not; what do I have to loose" and my answer is "the battery bank".
This logic says you would rather lose the boat than some consumable batteries??
A sticking float is pretty rare I would think.
 

dLj

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Mar 23, 2017
3,370
Belliure 41 Sailing back to the Chesapeake
To Benny's point - "The best argument that I have heard for powering bilge pumps 24/7 is "If they can save the boat or not; what do I have to loose" and my answer is "the battery bank".
A complete discharge of a battery, once, does not destroy it. It's not good for it, but it does not destroy it. If you can charge it fully, run a good equalization step on it, it will still be in decent shape. Now, you don't want to keep repeating this or you will destroy that battery.

But from my perspective, I'd rather take the statistically small probability risk on a one-time dead battery due to a malfunction of the circuit and keep the security of the bilge pump turned on helping against water ingress that protects my boat, it's interior etc. I think the statistical probability of me forgetting to close a window, a seal getting something stuck in it allowing a leak, a through hull that's decided to start leaking, a hose connection that is starting to weep, etc. etc. is far greater than the bilge pump circuit going crazy and draining my battery.

The statistical probabilities surrounding the number of potential failure modes are far greater in the scenario of not having the bilge pump turned on than the essentially single failure mode of the bilge pump circuit failing, and discharging a battery....

Of course, neither of these fully protect you from some sort of catastrophic failure. However, keeping the bilge pump on does provide a greater level of security than keeping it off.

This logic says you would rather lose the boat than some consumable batteries??
A sticking float is pretty rare I would think.
I've found two main failure modes for pump float switches, they stop turning on, or ther float can get stuck on - meaning the float came up high enough due to water ingress, something made it stick in the up position and then you can run down your battery.

In the first case, since the boat is a dry boat, who cares? In the second case - well - you just found out your boat isn't as dry as it should be.

I can't see a solid logic to not keep your automatic bilge pump turned on, especially if you have one in place. If you don't have one, and you have to go through the expense of installing one, then I could see arguments supporting not do that as viable.

dj
 
Jul 27, 2011
4,988
Bavaria 38E Alamitos Bay
It would probably take only a few hours to threaten sinkage of a boat having water ingress at a rate that most bilge pumps might keep up with if turned on. That is, if your ingress is, say, 20 gal/hr, and the pump is off, it would take 20 gal/hr x 8 lb/gal x 10 hr to gain 1600# of water weight. At 15 hr, you’re adding over a ton, etc. My point—I think most electric bilge pumps at their worst, even intermittently, can manage 20 gal/hr discharge. So, it would not be the case that a pump would have to meet the ingress rate in real time, continuous operation, or be useless in saving the boat, etc. There is a clear need to have it on all of the time IMO.

As far as the dead battery component, if the boat is not plugged in or connected to solar, then—yes—the battery might die, the boat might flood, and then sink. A bilge alarm that sounds off in high water might buy a lot of time, maybe several hours to a day. I’d rather have these stop-gap measures in place than to say “What the hell? S..t happens!” :doh:

As far as float switches sticking, don’t buy the lever arm (Rule) type. Test them/inspect routinely, say monthly.
 
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