Dedicated emergency battery for radio& bilge pump

centerline · Dec 21, 2013

my personal opinion would be to install a manual pump as an emergency bilge pump.... the extra battery is a pain in the butt to maintain and store up and out of the water prone area, and, if you actually DO need it, you will probably need it for a longer time than it will hold out anyway... there are several brands and models that mount in an easy to use location, but are neatly out of the way until needed...

in addition to a more dependable system in an emergency, you will have redundancy in the important part of the system, which is the pump itself, rather than the battery....

Stu Jackson · Dec 21, 2013

Ross Gard said:
1. How do I maintain a battery with charge, above sole boards for emergency use of bilge pump and radio?
2. I need the extra dedicated battery to be connected to main bank for charging, and giving extra power,but able to be automatically isolated if lower batteries are flooded.
3. Is there a switch method to isolate bank, without having to manually turning an isolator switch.

Ross,

1. It is questionable whether you actually "need" this feature. There is really NOT much height difference between the cabin sole and your head, which is about how far the water would have to get. So all you're gaining is another few feet. There are other ways of performing the criteria, like smaller battery packs tied to radios with masthead antenna connections, but if you want another deep cycle battery connected to your house bank, and able to be isolated, so be it.
2. Set up a separate "bank" of a single battery that is switched manually from your house bank, is part of the house bank in normal operation, and is charged properly.
3. If you switch like the separate "start" bank option, that will work for you and you just leave the third "bank" of that single battery switch to be part of the house bank when charging, and at all other times except the emergency.

Basic Battery Wiring Diagrams This is a very good basic primer for boat system wiring: http://c34.org/bbs/index.php/topic,6604.0.html

This is another very good basic primer for boat system wiring: The 1-2-B Switch by Maine Sail (brings together a lot of what this subject is all about)
http://forums.catalina.sailboatowners.com/showthread.php?t=137615

What you will have to do is make sure that your two emergency "uses", i.e., the bilge pumps and the radio, and wired ONLY to that third bank and fused and switched properly.

JK_Boston_Catalina310 · Dec 21, 2013

Another point is pump rate. A good emergency manual bilge pump will be in the 20-30 gallons a minute range (1200-1500 gph). Most electric bilge pumps are 500 gph. Electric bilge pumps are generally for nuisance water not emergencies.

Captn TJ · Dec 21, 2013

Ross Gard said:
Manual pumps work on a centreline pick up. My experience is when healing water is either port or starboard, not centre line. My manual pump is out on stern gunnel, can't see when water is on pick up point. Buckets no good either. Slippery floor, can't hold bucket level and a rolling boat, by the time making rear hatch, water has spilt, not much left to through out. Have rigged port & Stb pumps to cope, just need reliable power to keep them going.

If you're concerned about water pickup when healing - were you then planning on having either a flexible pickup line or two different pumps?

A few thoughts and concerns. If you're shower sumps are plumbed to the outside such as on my 423 you could use the sump as an auxiliary pump by inserting a hose into the sump and the other end into the waterlogged area. This is a well documented process on 423 site.

That aside using either the above approach or another pump - a spare battery won't last long unless it is under continuous charge (engine running).

An option would be to install a mechanical pump connected to the prop shaft with a flexible hose that could be placed on either side.

In any case I would install bilge alarms

Don S/V ILLusion · Dec 21, 2013

Frankly, if water rises that far, one battery connected to one bilge pump will be as useful as rearranging the deck chairs on the Titanic. Isn't this more an academic discussion?

centerline · Dec 21, 2013

Ross Gard said:
Manual pumps work on a centreline pick up. My experience is when healing water is either port or starboard, not centre line. My manual pump is out on stern gunnel, can't see when water is on pick up point.
Buckets no good either. Slippery floor, can't hold bucket level and a rolling boat, by the time making rear hatch, water has spilt, not much left to through out.
Have rigged port & Stb pumps to cope, just need reliable power to keep them going.

the manual pump, as it is installed on your boat may have a fixed suction tube on the boat centerline, but the pump does not care where it gets its water from.... nor does it care where it is mounted.
if you only have one manual pump mounted, it should have a flexible pickup tube long enough to reach the area you would ever need to pump out.... it will remain connected to the pump below decks, stows easily out of the way, and for the small amount of trouble it is to move the tube thru the cabin area to be placed where the water is pooled, is way less trouble than maintaining a completely and fully redundant battery and electric pump system dedicated for emergency use, that would still have to be shifted to where the water is pooled when needed.... and its ultimately more reliable which equals safety in this case

Merlin Clark · Dec 21, 2013

A small electrical pump mounted at the bottom of the bilge for routine pumping and a larger electrical pump mounted higher for emergencies, bilge pumps in 12v are available to at least 3,800 GPH.
If you have water coming in you'll need to find out where and do what you can to stop it. If this isn't possible, prepare to abandon ship while the pumps are still working.
Light off the EPIRB, get your go bag, get everyone in their PFD and survival suits and ready the life raft.

Ralph Johnstone · Dec 21, 2013

I think you're obsessing a little over bilge pump capacity but if you want it ..................... consider using your engine sea water pump as an auxiliary bilge pump (see below). Don't know what size your engine is but it's sea water pump is considerably larger than my 2GM20F @ 7 USGPM.

That should keep your socks dry for those days when the bilge pump just isn't quite enough

.

Calif. Ted · Dec 21, 2013

Actually, I've seen submerged batteries in boats continue to operate bilge pumps. In one case Skipper (another poster) and I awoke to find the powerboat between us sinking. Water was about 3 feet deep in cabin, batteries below that, we flipped on the bilge pump and the thing dewatered itself.

Calif. Ted · Dec 22, 2013

That particular boat took about an hour to empty, and I've seen other instances of short term use. Some people think an AGM might not care if it was submerged. I couldn't swear to more than less than an hour.

Captn TJ · Dec 22, 2013

Calif. Ted said:
That particular boat took about an hour to empty, and I've seen other instances of short term use. Some people think an AGM might not care if it was submerged. I couldn't swear to more than less than an hour.

Looks more like a car to me!

Chief RA · Dec 22, 2013

Calif. Ted: Please be careful about informing our people that batteries perform underwater!
This is NOT generally the case! Chief

Don S/V ILLusion · Dec 22, 2013

Ross Gard said:
Thanks Ted for the insight on submerged batteries. What is your guess for time batteries are active underwater? And before they die.

Excuse me for interjecting but even if a battery could operate under water, I'm having a difficult time imagining ever depending on that scenario to help.

Realistically, once water gets as high as you envision in your original scenario, the best you can hope for is buying time until the inevitable happens. One submerged battery is something no one should ever subject their passengers to which brings me back to my prior comment.

Stu Jackson · Dec 22, 2013

Another way to say it is: if BOTH the + and - battery posts get "connected"...

Blooey.

heritage · Dec 22, 2013

The battery posts are connected while underwater but how good a connection is it. If submerged in distilled water there will be no electrical connection at all. Fresh water will allow ions to flow but not nearly as fast as a copper wire connected between the battery posts. Sea water will provide a better connection but it could take a long time to run the battery down to the point that the radio and bildge pump would stop. How long the battery would last, who knows. Perhaps MaineSail can run some tests for us??

Captn TJ · Dec 22, 2013

heritage said:
The battery posts are connected while underwater but how good a connection is it. If submerged in distilled water there will be no electrical connection at all. Fresh water will allow ions to flow but not nearly as fast as a copper wire connected between the battery posts. Sea water will provide a better connection but it could take a long time to run the battery down to the point that the radio and bildge pump would stop. How long the battery would last, who knows. Perhaps MaineSail can run some tests for us??

Isn't this really an academic discussion since if one is that concerned about the level of flooding either mount the battery at a higher point or have the 'ditch bag' and raft ready to go.

Dedicated emergency battery for radio& bilge pump

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