Battery placement

Time to relocate and wire batteries. I am presently rethinking the DC system in a 36 ft gulfstar. Presently the vessel has 2 D4 batteries, one for each engine, a couple 36 series deep cycle batteries as the house bank and a separate battery to start the 5 kw genset. The first issue is location of the batteries. When the 35 gal waste tank was added the vessel started to list. It is my opinion that the listing is due to excessive weight located on one side. Mounting of various components like batteries, waste tank, and hot water heater is located on a shelf at about waterline and gunnel area. This means the weight of a D4 battery is relatively high and on outer edge. Not sure why they use a separate D4 for each engine when one good starting battery should be enough to start the engines (64 hp Perkins). I am thinking of trying to locate the batteries on a platform I would build that would place the battery weight closer to keel center and lower in the hull. I would suspect this would reduce hull tendency to roll in beam sea as well as reduce listing especially if weight is balanced. Any thoughts, or suggestions as to battery and switch / charger set up. The vessel presently has 65 amp smart charges as well as associated manual switches and isolators.

Ken

Two separate engine starting batteries gives you some redundancy, but with a genset and a separate genset starting battery which can be used to charge up a dead battery, I think you will be ok with one.


So eliminate one of the 4-Ds and even replace one with a lighter Group 31 which is plenty to start your Perkins.


It is impossible to cover all of the different wiring permutations with battery switches, isolators, combiners, ACRs, etc. in a posting.


You will probably get dozens of wiring suggestions to your OP and you will have no way to sort them out, so get a good book on the subject. Nigel Calder's is a good one.


David

Greetings,
Mr. kp. If your waste tank (35 gallons ~ 350lbs full) was mounted off center it will be difficult to trim permanently.

Perhaps it won't work in your particular situation, but I trim the boat by moving (pumping) fuel from one side of the boat to the other, depending on the tankage. So, consider installing that capability if you can.

djmarchand said:

You will probably get dozens of wiring suggestions to your OP and you will have no way to sort them out, so get a good book on the subject. Nigel Calder's is a good one.


David

Click to expand...

This.

From a trim issue, it should be simple enough to place the right amount of weight where you want to move the batteries to, or disconnect the batteries and put them on the floor about where you'd move them to. See how it affects the trim.

djmarchand is right, for the electrical knowledge, get the book and start there. Lots of factors involved, all covered in detail.

djmarchand said:

Two separate engine starting batteries gives you some redundancy, but with a genset and a separate genset starting battery which can be used to charge up a dead battery, I think you will be ok with one.


So eliminate one of the 4-Ds and even replace one with a lighter Group 31 which is plenty to start your Perkins

Click to expand...

He has two main engines I believe.

So I would stick with a starting battery for each engine. Just step down to a group 31 for each.

As to reducing roll by moving the batteries around, forget that. Move them around for other reasons if you want. But it's not going to help with the roll.

Does the boat list when the tank is empty?

Yes it seems to list when empty. This just started when I moved the D4 back to its original location before mounting the tank. When tank was installed the D4 was moved to central position. I do not remember the vessel listing. The new location was very was not good. It was on the gas tank and i did not like haveing the weight of a D4 in that location so I moved things around so I could put D4 back in original position. Originally the vessel may have listed when in that location I did not have vessel long before tank was installed and d4 moved. The listing side has waste tank, D4 battery, 27 series Battery, and two 31 series batteries as well as all of the galley appliances. When I repositioned the D4 I also removed two air conditioners. A heavy one was on the presently high side. regarding starting batteries, I am thinking of installing a good deepcycle as the starting battery to handle both engines. It will allow further draw down and still maintain CCA fo 600 to 800. Just a though I am playing around with. I have oredered the electrical book.


Ken

Ken, If you do relocate the batteries below the water line I would install a small additional
battery above the water line. This would allow you to call for assistance if your bilge was flooded with 25 watts.

John

Greetings,
Mr. kp. Deep cycles are not good starting batteries. Better to buy a purpose built starting battery.

A 4D battery only weighs about 120 pounds. Kind of odd that is would make much of a difference in the attitude of the vessel. Does the boat list when a small person stands on one side or the other?

Deep cycle batteries will work as starting batteries just fine.

Capt Bill, Not only does it seem starange that the simple placement of the battery would cause this, I agree with you, but I would think the placement of a person small or large would change something and doesn't seem to. Again boat is new to me but I do know when it was bought it did not seem to list. When tank was put in and battery moved to center, again i do not remember listing. This started this season as soon as vessel was put in water. over winter I removed two air conditioners, most of the air wiring, plumbing, and air handlers, moved the waste tamk back three feet and relocated the D4 back to the position it was in when we bought the vessel. I would think it has to be a weight issue unless someone has another answer.


Ken

Capt.Bill11 said:

A 4D battery only weighs about 120 pounds. Kind of odd that is would make much of a difference in the attitude of the vessel. Does the boat list when a small person stands on one side or the other?

Deep cycle batteries will work as starting batteries just fine.

Click to expand...

But you could be effectively moving 240lbs since you are removing it from one side and adding it to another. And the arm of the weight obviousy would have a lot to do with it. 240lbs will cause a listing moment on a smallish boat....especially older Gulfstars that have round bilges.

PS....I added about 200 pounds of chain to my chain locker on my boat and you can definitely see the nose down moment.

Do your engines require a lot of cranking before they will start? I used to have some that had glow plugs and required a lot of cranking. My battery regime then was 2 8D primary house, 2 4D secondary house, 1 4D Start, for twins and a genset. I still have the single 4D to start 3 engines, but it never gets a workout, as all 3 start with only a second or 2 of cranking. I replaced my house batteries last year after 10 yrs, because they had started to take a little too long to recharge. The start 4D is now 11 years old and still going strong, so seems to never get overtaxed.

You can certainly downsize your start bank to a single, appropriately sized battery.

Baker said:

But you could be effectively moving 240lbs since you are removing it from one side and adding it to another. And the arm of the weight obviousy would have a lot to do with it. 240lbs will cause a listing moment on a smallish boat....especially older Gulfstars that have round bilges.

PS....I added about 200 pounds of chain to my chain locker on my boat and you can definitely see the nose down moment.

Click to expand...

I was never great with math, so you'll have to explain to me how the mass of and object can double by moving it laterally 12-15ft?

I understand the arm/leverage effect but I was thinking the new postion of the battery would be approximately the same as the old.

The bow of your boat has less buoyancy do to its shape so I can see how 200 more pounds up there might have that effect.

Greetings,
Mr. 11 is correct. I retract my statement in post #10. Apologies.

RT Firefly said:

Greetings,
Mr. kp. Deep cycles are not good starting batteries. Better to buy a purpose built starting battery.

Click to expand...

Four group 31 deep cycle wet batts in parallel are!