340 DA battery isolator question

[hmcclard]

I have a 1989 340DA with twin 454's and 2 group 27 batteries on the starboard side and 1 group 27 on the port side. I'm cleaning up the engine compartment while both engines are being rebuilt. I found the Guest battery isolator is dead, doing nothing. It also is wired between the group of 2 and the 1 on the port side. The starboard side has one deep cycle and 1 starting battery hard wired together. It really hasn't been a problem and I never paid attention until now with the engines out but should the isolator be between the deep cycle and the starting battery?? I'm a little confused about whether to replace the isolator or maybe rewire a new one or just put my bliders on and say "whatever" if it ain't broke don't fix it and put one of the newer models in as it is wired.

 

[sbw1]

No expert on this but my understanding is each battery should be isolated from the others so one bad one does not degrade the others. I believe all four of mine are isolated.

 

[Chris-380]

The isolators purpose is to isolate the banks so that they charge equally and discharging bank 1 wouldn't effect bank 2. By the nature of them, you will lose about .6 volts through the diodes in the isolator.

Should not have deep cycle and start battery on the same bank imo. I do not know the design of the 340's especially on the 1989. New to sea ray, but I was under the impression they had a bank for each engine (2) and the house was on one side and the genny was on the other. If you ran one bank down, you could start the genny, and charge the other bank up or just emergency (put all in parallel) start the dead side.

Good luck, whenever you parallel batteries, you want them to be as much alike as possible, so both should be the same style/brand/age ertc.... any difference will likely cause a circulating current trying to balance it out (electrically)

 

[ttmott]

The isolators purpose is to isolate the banks so that they charge equally and discharging bank 1 wouldn't effect bank 2. By the nature of them, you will lose about .6 volts through the diodes in the isolator.

Should not have deep cycle and start battery on the same bank imo. I do not know the design of the 340's especially on the 1989. New to sea ray, but I was under the impression they had a bank for each engine (2) and the house was on one side and the genny was on the other. If you ran one bank down, you could start the genny, and charge the other bank up or just emergency (put all in parallel) start the dead side.

Good luck, whenever you parallel batteries, you want them to be as much alike as possible, so both should be the same style/brand/age ertc.... any difference will likely cause a circulating current trying to balance it out (electrically)

Right on Target!
hmcclard - Interesting that you have in the dual battery bank one cranking and one deep cycle but they are both "Group 27". Group 27 batteries are classified as dual purpose so something awry there. Regardless batteries connected in series or parallel should be the same type and age so they are properly charged and discharged as a unit.
You should consider round filing the old isolator and installing an Automatic Charging Relay (ACR); the 0.6 volt transfer loss will go away.

 

[hmcclard]

Thanks. I did look at the starting battery... it is Group 24... it's a little smaller than the 2 group 27's and don't know why I didn't notice that; the guys that removed them while taking the engines out had them on a pallet out back. I just never really looked at them closely... they weren't a problem... out of sight out of mind... will be more cautious. They were all in the boat since I've had it and it's time to replace them all anyhow. I've found ACR's that the specs appear to better than the old isolator and the cost is really decent.