Battery Issues

[Stpetelsu64]

Hello everyone! This is been a rough year with no income and then boat repairs and a new seawall to be paid for. But I have a simple (for some of you ) question. I was out of town when my seawall was being built. The guys had to disconnect my electric so they ended up disconnecting my shore power on my dock. So days with no charging the batteries went down. Fast forward 6 months later and some are just plain dead. But I can start the boat and most things work. Only the cabin lighting and bow thrusters do not. A few of the batteries are testing too low of voltage. So that gets me to my questions.

I have 6 batteries. 2 for each engine and 2 for the bow thrusters. My manual says exactly "the main engine cranking batteries consists of 4 31 DCM series 12 volt batteries. And then 2 series 31 12 volt marine batteries connected in a series to create the 24 volts to run the thrusters (which I have only used a few times anyway ) But when I went to purchase the batteries the person told me only 2 are used for cranking or starting the boat. That the other 2 that are paired with the starting battery are house batteries for other different functions which are located on the panel. Now that does make sense. So why would the manual say 4 DCM series batteries and then 2 more 31 series for the bow thruster? I think it should be 4 Deep Cycle batteries and 2 starting batteries. But another question is how to line up the starboard and port batteries side by side and know which is the starting and which are house?

Hope I didnt confuse everyone. But I am pretty sure the manual has an error. And the schematics on paper are hard to see. Any help at all would be appreciated

 

[bbwhitejr]

You have 2 batteries wired in parallel for each engine. These 4-batteries are all cranking batteries that also serve as house batteries. The 2 thruster batteries are wired in series to give you 24 volts. One side of the cranking batteries likely run the “house” and the other side provides power to the 12 accessories on your helm.

Hope this makes sense.

Bennett

 

[Stpetelsu64]

You have 2 batteries wired in parallel for each engine. These 4-batteries are all cranking batteries that also serve as house batteries. The 2 thruster batteries are wired in series to give you 24 volts. One side of the cranking batteries likely run the “house” and the other side provides power to the 12 accessories on your helm.

Hope this makes sense.

Bennett

Yes it does now that I just went out and looked. The pair for each engine is wired in series and of course the thruster ones are wired to get 24 which I did know
So when I see the other 2 pair wired in series I am assuming I can just purchase 6 31 Deep Cycle batteries as long as they are dual purpose? I think you stated it a way I can actually understand now that I looked at it.
So I guess I just purchase 6 of same batteries? Thanks as I think I got it

 

[bobeast]

I'm pretty certain those paired batteries, With the exception of the thruster batteries, are wired in parallel, not series. As such, as Bennett mentioned, they are used both for starting AND house service. So the person who told you otherwise is....confused.

I'll probably take flack for this, but IMO, some good deep-cycle AGMs are more than sufficient for dual purpose, although the purists will likely tell you they have to be "designated" as dual-purpose batteries. My battery advice is always the same. Get the biggest baddest AGMs you can fit and afford, and call it a day.

 

[Stpetelsu64]

I'm pretty certain those paired batteries, With the exception of the thruster batteries, are wired in parallel, not series. As such, as Bennett mentioned, they are used both for starting AND house service. So the person who told you otherwise is....confused.

I'll probably take flack for this, but IMO, some good deep-cycle AGMs are more than sufficient for dual purpose, although the purists will likely tell you they have to be "designated" as dual-purpose batteries. My battery advice is always the same. Get the biggest baddest AGMs you can fit and afford, and call it a day.

Right I meant to say the 4 are 2 pairs wired parallel and the bow thruster ones wired in series.
So any certain batteries you suggest. My budget would be about 250 each appx. Thanks for the help

 

[Sum Escape]

Check out Sam's Club Duracell (East Penn manufacturers them) deep cycle group 31 AGM's. Last time I purchased 4 for our inverter bank (April 2018) they were $155 each.

 

[bobeast]

Right I meant to say the 4 are 2 pairs wired parallel and the bow thruster ones wired in series.
So any certain batteries you suggest. My budget would be about 250 each appx. Thanks for the help

Less expensive batteries are likely to have lower capacity, typically around 75 Ah. These batteries are a bit more expensive than your budget, but provide 110 Ah, so each bank would have 220 Ah. If you spend a lot of weekends on the hook, you might want to consider the higher capacity.

 

[Stpetelsu64]

Less expensive batteries are likely to have lower capacity, typically around 75 Ah. These batteries are a bit more expensive than your budget, but provide 110 Ah, so each bank would have 220 Ah. If you spend a lot of weekends on the hook, you might want to consider the higher capacity.

ON trips we usually are hooked up to shore power as the boat is when behind the house. Day usage we are out on it for about 5 hours a day a few days a week. How about these 2 below. One is Duracel from Sams and the other is Interstate. Looking at both. Plan to get out and purchase today or tomorrow.
Also looking to just get 6 dual purpose. Easier to hook up as far as knowing what goes where

https://www.interstatebatteries.com...=marine&subcategoryKey=&ignorecategoryid=true

https://www.samsclub.com/p/duracell...p-size-31dtmagm/prod3590232?xid=plp_product_1

 

[bobeast]

ON trips we usually are hooked up to shore power as the boat is when behind the house. Day usage we are out on it for about 5 hours a day a few days a week. How about these 2 below. One is Duracel from Sams and the other is Interstate. Looking at both. Plan to get out and purchase today or tomorrow.
Also looking to just get 6 dual purpose. Easier to hook up as far as knowing what goes where

https://www.interstatebatteries.com...=marine&subcategoryKey=&ignorecategoryid=true

https://www.samsclub.com/p/duracell...p-size-31dtmagm/prod3590232?xid=plp_product_1

Either one of those is a fine choice for your stated usage pattern. Between the two, I would lean towards the Duracell.

 

[Stpetelsu64]

Either one of those is a fine choice for your stated usage pattern. Between the two, I would lean towards the Duracell.

Thanks you helped make my decision. Really do appreciate it

 

[bbwhitejr]

ON trips we usually are hooked up to shore power as the boat is when behind the house. Day usage we are out on it for about 5 hours a day a few days a week. How about these 2 below. One is Duracel from Sams and the other is Interstate. Looking at both. Plan to get out and purchase today or tomorrow.
Also looking to just get 6 dual purpose. Easier to hook up as far as knowing what goes where

https://www.interstatebatteries.com...=marine&subcategoryKey=&ignorecategoryid=true

https://www.samsclub.com/p/duracell...p-size-31dtmagm/prod3590232?xid=plp_product_1

Love the Duracells made by East Penn. I am on my 3rd boat with them and they have never let me down....

Bennett

 

[Stpetelsu64]

Ok so another stupid question How do I know which of the 2 batteries for the port and starboard are actually the starting battery and which is the house? Since I see I had all dual purpose in the boat now it isnt a problem. But I purchased 2 starting batteries and 4 deep cycle. So how will I know in what position the starting batteries go? My common sense tells me the wire that leads to the alternator and solenoid indicates that is the correct one.

 

[bbwhitejr]

The only stupid question is the one you do not ask...you do not have separate house and cranking batteries. It is very typical for diesels to have 2-cranking batteries wired in parallel. The 2-batteries also serve as the house batteries. The are not separate...both crank and both serve the house. My 2-port batteries crank the port engine and run the house. My 2-starboard batteries crank the starboard engine and power everything at the helm.

Bennett