Battery locations

[Brettles]

Hi,

I have owned my boat for about a year now and am thinking about moving batteries as I'm not sure how they are at the moment is ideal. I currently have 4 120ah batteries, 3 of which are together and one is about 2 metres away. The 3 together are connected by 35mm² cable, the other by 50mm² cable. Layout is shown in the top drawing of the attached picture. I have been advised that this one battery being away from the others is contributing very little, so I am thinking about altering the location. 

I can get it close but not right next to the other 3. Cables used would need to be about twice as long as the ones used to connect the 3 batteries. The arrangement would be as shown in the bottom of the attached picture.

I have a few questions which I hope someone can help me with.

1. Will the new arrangement be better?

2. What size cable should I use for the longer ones? 50mm² as it's further away, or 35mm as that is what connects the other 3?

Many thanks in advance 

[system 4-50]

Do you have an engine?

[Brettles]

Yes. These batteries are just leisure batteries. I have a further battery used for starting the engine.

[Clanky]

Have a read of this

 

http://www.smartgauge.co.uk/batt_con.html?fbclid=IwAR2rYSY4V2uD1Z4a0pqlKCCjsi0cIw6Kc2lucou-ZfWQjYMdjqzOWEJCP1I

[MtB]

15 hours ago, Brettles said:

I have been advised that this one battery being away from the others is contributing very little, so I am thinking about altering the location. 

 

I'd suggest the person giving you the advice is contributing very little, due to their limited understanding. I'd say the remote battery is contributing slightly less but not enough to notice.

 

A lot of alarmist tosh is written and spoken about the different methods of interconnecting sets of batteries. Yours looks better than many I've seen although not ideal. Provided the bigger cables to the remote battery are well made and in good condition I'd say it is contributing plenty. 

 

The differences between different arrangements are marginal in my opinion and I very much doubt you'd notice any practical improvement if you go to a load of trouble and expense of changing the layout, to get that remote battery physically closer to the other three. 

[jonathanA]

definitely the proposed the arrangement is theoretically better than your current setup,  whether the effort required is worthwhile is much more debatable.  for me having long battery cables(you say 2m between batteries) is a more of an issue in terms of them getting damaged /chafed etc and the risks associated with that.  If you can get them physically closer with out too much effort, then I think reducing those long unfused, potentially vulnerable battery leads is the real benefit and 35mm or 50mm will be fine 

[Tracy D'arth]

The difference that the wiring arrangements make is minimal providing the cabling is done properly, probably less than the manufacturing tolerance difference between batteries.