House batteries connection

[Boby_Hunter33]

I have 3 batteries.
All grouds are connected.
Two are connected together through a doide to the main 12v bus. And the third is connected to the same bus directly.
Is there a need for the diode?
Thanks

 

[Don S/V ILLusion]

You might want to look more closely as what you describe makes no sense, e.g., the diode which is a primitive and poor way of isolating and undercharging batteries. What you describe also doesn't include mention of a charger. Try to diagram the electric circuits and repost if you want some advice.

 

[Monty VM]

photos?

 

[Boby_Hunter33]

Atached is a photo.
1a-the common 12v bus, the small wire is not connected to anything.
1b- 2 thick cables coming from two batteries connecter together.
The voltage between 1b to 1a is 0.8v. The voltage 1a to ground is 11.5 and from 1b to ground 12.3.
2- connected to the common 12v bus comes from the wind gen controlle
3-the main 12v bus, the cable going right is connected to the third battery and the one going left goes to the boat 12v main fuse and from there to the battery charger and the rest of the boat.
4-goes to the 12v to 110 converter. Although it is connected on top of something that looks like a diode there is no voltage difference between the top connection and the main 12v bus.
To summarize it, i have two out of the three house batteries connected behind a diode tgat drops the voltage by 0.8v thus not giving me the full capacity of those two. My question is: shuold all batteries connected in parallel without any diode or should i add diodes to all three and separate them?
Thanks

 

[Don S/V ILLusion]

I'm still confused but to answer your question, the isolator serves to separate batteries for a specific purpose which you don't have with this setup. Regardless of what you are trying to accomplish with your power, get rid of the isolator as other devices, e.g., a battery relay or combiner will work better avoiding the voltage drop.

What are you trying to end up with - separate battery banks or one bank consisting of three batteries?

 

[Boby_Hunter33]

This is how i got the boat.
The previous owner bought her new from hunter. He omstalled the solar panels and the wind gen (which i replaced with a modern one).
The guy who is an experianced sailor did some modification that are smart, but he knew nothing about electricity. So i am trying to figure out if this type of installation has a reason or just ignorance led to this type of connection. If there is some logic there, why not connect all three 'behind' diodes. If there is no good reason then maybe the best thing is tp get rid of that diode.

 

[Boby_Hunter33]

Took a closer look at the little box i thought it is a diode. Actually it is a fuse. I understand why pne would like to have a fuse. But why the voltage drop? Now that the sun came out and charged a bit the voltage gap on the fuse was reduced to 0.4 volts. Attached is a pic of the fuse.

 

[Don S/V ILLusion]

I'd like to help but this sounds like you need to go back to basics, figure out what you want rather than try guessing what you have and that is better done on the boat with someone who understands boat electrical systems rather than me or anyone guessing.

 

[Boby_Hunter33]

I would like to reduce the voltage drop.
So, i will have a fuse for each battery, this will reduce the voltage drop by half.
Maybe it would be better to have fuses with lower resistance resulting in lower voltage drop.
Does anyone have experiance with other fuses then buss?
Thanks.

 

[LeslieTroyer]

I personally like the MRBF (marine rated battery fuse) but som installs can’t take the extra height. As an alternative the ANL style works well.

I purchase them at waytekwire.com

 

[jssailem]

connected on top of something that looks like a diode

Boby, that is not a Diode. It is a Fuse. It appears to be a 100 or maybe a 300 amp fuse (too dirty to decipher the writing). It serves to protect the wires from being over heated and burning up. Perhaps to protect your boat from a fiery ending.
It is what is known as an MRBF fuse, as @LeslieTroyer has described above. It is a good type of fuse for your boat and it appears to fit.

I understand your concern with "Voltage drop". My opinion, your focus on the connections is directed to the wrong location. Voltage drop most often occurs due to undersized wires, and dirty connections. Less frequently at or near the battery.

I would draw a plan of your wiring, the sizes of all the wires on the plan and what appliance each of the lines feeds along with their amperage demand.

This way you can get a clear understanding of why the systems are the way they were installed. Then you can better judge if they need repair, replacement or just cleaning and left to do their job.

 

[Boby_Hunter33]

Thanks.
Measured the voltage drop and it is over the fuse.
Maybe fuse needs replacement.
But now i know the direction to go.