Bilge Pump Power Source

[Sailboat.Sequoyah]

I've searched for this question but haven't found it anywhere in specific (which may be due to the searcher rather than the archived content):

Sequoyah has what I believe to be the usual battery array for a Hunter 340: Bank 1 consisting of a single high output battery is the starter, Bank 2 of two deep cycle batteries in parallel is the house. It has come to my attention the bilge pump is wired to the starter, not to the house bank as appears to be typically recommended by most boaters.

Does anyone know if for some reason Hunter did that as the standard setup for this boat, or would it be more likely it didn't leave the yard that way when it was built and so was altered by a previous owner? What are the advantages & disadvantages of each, i.e. what's gained and lost by wiring to B1 or to B2?

 

[Scott T-Bird]

As you are probably aware, you will want your bilge pump float switch wired directly to a battery so that it runs on a float switch even when the battery switch is turned off. Most of us also have a manual bilge pump switch wired to the DC panel so that we can turn it on when we want to.

It doesn't really matter which bank it is wired too if your float switch is rarely called into use. But, you don't really want it on the start battery if the start battery doesn't have very much capacity in amp-hours. Usually, sailors have it wired to the house bank because the deep cycle batteries have more capacity, and it might not matter so much if the house batteries become discharged as long as the start battery can get you started and the alternator can charge the batteries.

Also, often the house bank is recharged with solar, so the bilge pump is far less likely to run a battery down anyway.

It usually comes down to your own preference.

 

[dlochner]

This is one of those issues where it doesn't make a difference until it really makes a difference.

For nuisance water on a boat that is always plugged into shore power or used frequently, either battery will work. However, once away from shore power or a constant charging source or for a boat that is used less frequently a connection to the larger power source is a better option as the pump can pump longer before it kills the battery and sinks the boat.

As @Scott T-Bird said, it should be connected to an always on circuit that can't be accidentally shut off.

 

[Sailboat.Sequoyah]

Thanks, fellows. Yes, the pump is continuously powered, and there is the normal momentary trigger switch. I've replaced the old float-operated pump with a new sensor model, eliminating that mechanical switch. It was in the process of doing so I discovered it runs off Bank 1.

Everything I've read says you're spot on with this. I'll change it to the house bank in the next few days, soon as I get past a project now underway.

 

[Gunni]

And what happens when your boat is sinking, and your house battery is dead? Your start battery is your emergency battery, used only in an emergency to start the motor and get critical items power and pumps running. If you follow MaineSail’s advice it is kept charged by the house battery with a relay charger. In all cases it should be isolated from your house. Your start battery is always fully charged, who knows the state of your house battery when the Kimchee hits the fan. Leave your bilge pump on the starter battery. If you have a emergency you want that engine to come on and your bilge pump to be connected to a charged battery.

 

[Richard19068]

And what happens when your boat is sinking, and your house battery is dead? If you follow MaineSail’s advice it is kept charged by the house battery with a relay charger. .

I may be wrong but the relay between the house bank and the start battery doesn't allow the house bank to charge the start battery unless the alternator is putting out over a certain amount of voltage so a resting house bank isn't going to be charging a depleting start battery unless the engine is running or your on shore power. If I'm wrong on that then forget the rest of this post.

I would connect the bilge pump to the house bank.

If you are plugged in or your engine is on in there shouldn't be an issue either way.

If you are not plugged in and your house bank gets depleted you start your engine with the "emergency start battery" and the alternator will send power to the house bank and the bilge pump will start/keep working.

If you are not plugged in and not on board to start the engine the battery you have chosen will run the pump until the battery is drained. Which would you want running the pump, a low amp hour start battery or your high amp hour house bank?

 

[Sailboat.Sequoyah]

Gunni sez: "If you have a emergency you want that engine to come on and your bilge pump to be connected to a charged battery."

I'd want the engine to come on, anyway. Once it does the bilge pump works. I think I'd rather save that juice for the cranking.

 

[Gunni]

I always find it curious when boat owners decide that they know how to wire a boat better than the boat designer. Good luck.

 

[Sailboat.Sequoyah]

So far as I know, the way it's hooked up now probably wasn't how it left the yard. I haven't been able to get a confirmation of it, but the standard apparently being to connect to house I suspect it was changed at some point in the twenty years this boat's been out here.