Power breakers’ panel and battery

[puncta2000]

First with the easy question.. my engine wet 8D batteries are showing under 12V. I am thinking of replacing them with AGMs. Any recommendations? I found a solid marine AGM on Amazon but it is a deep cycle. I see West marine has a dual purpose ones? This is the first time that I am replacing the engine batts so not sure which direction to go.

My next question is, why would the previous owner change one of the shore lines to 120V from 240V. I have 2 STBD shore inlets one is a 120V 30A, the other is same. But on the power panel one line is 120V and the other was factory labeled as 240V but now a label covers the 240 with a 120V label. Maybe his Marina only had 30amp pedestal power?. The gen is 240V 50Amp.

Any ideas would be much appreciated.

Puncta

[Pete7]

Puncta, when you say "engine start batteries" they seem very big for starting engines. Do you have other batteries for running the house loads?

Also is this a motor boat, perhaps with two engines?

Don't buy anything until we get to the bottom of what you need, but do give those batteries a really good charge and also record the lowest voltage the batteries drop to in use and what they are being charged at. Is there any battery monitoring devices?

Finally what make and type are the 8Ds and how old are they? there is probably a date or code on them to Google and say when they were made.

Pete

[ranger58sb]

Originally Posted by puncta2000

I found a solid marine AGM on Amazon but it is a deep cycle.

What brand/type/size/model number was that?

There aren't all that many AGM deep cycle options. Some AGM batteries labeled "deep cycle" are really dual-purpose.

A pair of G31s will usually start an engine that was starting on an 8D. You can compare engine required minimum cranking amps to battery maker's cranking amp specs. Lifting each individual G31 won't hurt you as much as lifting an 8D.

-Chris

[puncta2000]

Thank you very much ranger42c and Pete7 for the input.

There are 5 batteries on the boat.. all 8D. The engine starting are 2 wet 8D Interstate.. no code or manufacturing date unfortunately. They show 10.5-11volts. 2 AGMs for bow thrusters and house. 1 AGM for stern thruster. No code on any of them.

Engines are Caterpillars 3208 375hp. They do start easily so far but I wanted to start fresh this season with good batteries. I like the G31 idea very much. I am researching the engine starting requirements.. another good tip. Thank you both

Puncta

[ranger58sb]

Originally Posted by puncta2000

2 AGMs for bow thrusters and house. 1 AGM for stern thruster. No code on any of them.

It's not uncommon for thruster installers to use Odyssey 31M-PC2150 AGMs. If that's what you've got, they're very good batteries, especially for that purpose (very high cranking amps), and not inexpensive. I'd describe as sort of a hybrid between dual-purpose and true deep cycle...

Two of these would make a very decent pair for starting engines.

Repeat: not inexpensive.

-Chris

[boatpoker]

"Dual Purpose" is marketing BS.
They are either or, not both.

[ranger58sb]

Originally Posted by boatpoker

"Dual Purpose" is marketing BS.
They are either or, not both.

If you meant that as response to my comment about Odyssey batteries, you can look at their actual specs (cranking amps and potential cycles) and decide for yourself what you'd call them.

-Chris

[puncta2000]

Thank you for the input. Setting aside the 2 wet 8D starting batteries. The 3 other batteries are the typical Fullriver blue AGMs. They list the AH rating similar to deep-cycle batteries. I will look into the Odyssey batteries, I can handle Grp31.. 8D batts would be very challenging on my own. Cannot ask for help at the moment. There is room for 2 x 31s. I may just disconnect the starting 8Ds and connect new 31s. Take the 8Ds out this summer.

On a totally different topic, as I was checking things in the ER I found several ballast weights on the floor. I heard of a special 3M tape that is typically used to reattach them. I know 3M tapes have numbers. Any thoughts which tape that might be?

[FAST FRED]

The engine starting are 2 wet 8D Interstate.. no code or manufacturing date unfortunately. They show 10.5-11volts.

When is the voltage 10.5 to 11V?

Just sitting , cranking the engine , or with a battery charger working?

Sounds like the 8D may be OK, just some load like a bilge pump or blower or fuel pump operating.

Disconnect the 8D and read the voltage on each.

[puncta2000]

Thank you all for the input. Sorry for the delay in responding. The boat is in Seattle and we stayed away for a couple of weeks.. we are back now and staying at home on the boat.

The batts show 10.5-11v before I start the engines. Even after Idling for 10min, voltage is still around the same range. 30min later it starts to creep up slowly to 11.5v. I have not taken the boat on a longish run is a few weeks. Potentially a factor.

I will try to take it on a run this coming week and see if they charge up. If they need changing, I may look at grp31 instead.. I don’t think I want to deal with the weight of 8D batteries.
Thank you

[ranger58sb]

Originally Posted by puncta2000

The batts show 10.5-11v before I start the engines. Even after Idling for 10min, voltage is still around the same range. 30min later it starts to creep up slowly to 11.5v. I have not taken the boat on a longish run is a few weeks. Potentially a factor.

Are the 8D 10.5-11.0V batteries not on a charger serviced by shore power?

Generally voltage consistently under 11.8V or something like that is a dead battery. Should be at near 12.7V or 12.8V for a brand new 12V battery...

If yours have usually been on a charger then yours are due for replacement or maybe something else is wrong, perhaps with the charger. OTOH, if yours have just been sitting there for a long period of time, not on a charger, or maybe you have no charger... then charging with the alternator -- for maybe 24 hours or so? -- might help. Check water levels first, etc.

-Chris