Schooner

Schooner

Tuesday, December 3, 2013

To be technical.....

   On the topic of batteries...

On the hunt for lowest cost per AH battery? I think I have a winner.
The Interstate SRM-4D.

First some numbers. 116#, 390AH at 25 amp rate, 6 month free, 30 month pro-rated, cost $200 plus tax.

Why do I think this is a true deep cycle?

1: In speaking with a dealer of interstate, he has mentioned he has taken them apart, and the plates are only thinner compared to the 6-volt industrial batteries he sells. He also said they are nothing like the starting 4D, as those plates are very thin.

2: The weight of a standard 4D battery is 99.20#, VS 116.8# for the SRM-4D. 20# of extra lead? sounds about right.....
The SRM-4D is actually smaller in physical size, about 3%

3: Tife. I just replaced a completely abused SRM-4D from 2008. when I say abused, I mean run to 0% many times, left sitting dead, left sitting uncharged for 8+ months at anchor....
5 years of punishment. much harder then a 50% DOD, daily.

4: The dealer quoted a realistic life. he said 6-10 years, with 10 year being a well maintained, no more then 50% DOD (depth of discharge) this is the life he sees in the cores that come back.

So I would say, if your looking for a nice, heavy, long life, cheap battery, this is the unit for you.

 

   On the topic of bilge pumps.

We have a diaphragm type pump. Its made by PAR.
The other type is centrifugal.
This is the more common type, and unless you know that you have a  diaphragm pump, this is what you have.
Each has pluses and minuses.

The centrifugal pumps are quiet, low power, move a lot of water (in the larger units), and are cheap. 

On the dark side, they do not last long, are prone to burn out, cannot be heard when running. How would you know when they stop running if you have no high water alarm. Cannot get all the water out, the best leave about 1" of water, and if they need replaced, your reaching into a bilge full of water, and trying to work in there.

The diaphragm pumps are noisy, use a lot of power, flow less water, cost much more.
They will outlast a centrifugal pup by about 20 years (vs 1-3 years).
Are not prone to burn out, as the motor is out of the water and cooled by air.
They are 100% rebuildable, as all the moving parts can be replaced.
They are outside the bilge, can be repaired without getting wet.
They are mounted forever. No re-gluing.
You can carry almost every part of the pump with you.
They can remove all the water from the bilge, leaving the bilge only wet.

So what is the optimal, safe, ideal setup for a cruiser?
Its a multi-phase approach. 

First, you need a diaphragm pump. You connect this to a float switch on the bilge floor.
This will be your primary pump. This will do the lions share of the work, and if everything is working correctly, this is the only pump that you will ever need. This is wired to a momentary on - off - auto switch.

Second you need a float switch, wired to an alarm. This will be your high water alarm (VS 3" of water on the cabin floor) This float will be mounted to kick on 1-2" above the kick on point of the primary pump float switch. This will be wired to an on-off switch.

Third, you need an emergency pump. This unit will be mounted barely above the primary pump's kick on point, on the float switch. The float switch of this will be mounted to kick on 1/2" above the high water alarm float switch kick on point.
I recommend 1000GPH of actual flow per 10' of boat.
These are sold as GPH with no hose attached. Not realistic, and this is also false advertisement.
Look further into the specs. Find the numbers for 6' of head. This is what you base the 1000GPH on.
For our boat this is 4500GPH@6'. we will need an 8000GPH unit.
The switch for this will be on - off - auto. The reason for the ON and not momentary ON is because if this unit is used, it will be used for one of two reasons. Either the primary pump is broken or not working, or because your leaking, very badly.
I hope you never use this pump. BUT if you ever have to you will be glad you can turn it on, and leave it on, while you see to getting the leak stopped.
The final setup will be, dewatering pump, alarm, emergency pump.
Make sure they all have their own connection to the battery, and their own circuit breaker.







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