Battery bank conections

[OldPeculier]

Well its been many years since I have posted on here.  I documented my re-fit of Old Spot in the build blog section and have been happily living on and cruising her ever since.  However since I've aquired both a spouse and a dog, I've now moved over to the dark side and purchased an 11 year old 12x55 Viking fat boat. 

 

Its in pretty good nick but as always there are jobs to be done and improvements to be made.  One thing is to fit a battery state of charge meter.  All prety straight forward as I fitted one to Old Spot.  The thing is, when I took a close look at the battery bank (4x 110ah +starter) I noticed that there are several conections both pos and neg made mid way along the bank.

 

Now I am sure that ALL pos should be at one end of the bank and ALL neg at the opposite corner. Just checking, is there any circumstance when this is not the case?

Many thanks.

[Jen-in-Wellies]

5 minutes ago, OldPeculier said:

Now I am sure that ALL pos should be at one end of the bank and ALL neg at the opposite corner. Just checking, is there any circumstance when this is not the case?

Better to spread some of the low current connections to other batteries than have too many on the end batteries I reckon. Maximum of four connectors per post, if I remember correctly.

Edited May 14, 2022 by Jen-in-Wellies

[Alan de Enfield]

5 minutes ago, Jen-in-Wellies said:

Maximum of four connectors per post, if I remember correctly.

 

 

Correct'

 

 

Section :

10.8 No more than four conductors shall be secured to one terminal stud

 

 

 

 

 

 

[OldPeculier]

Ok, thats interesting.  So fitting a state of charge meter where all negatives need to pass thru the shunt will be difficult.  Should I just run the main cables thru and accept a small level of inaccuracy?  As far as I can make out its all small stuff like water tank guage, bilge pump etc.

 

[Tony Brooks]

5 minutes ago, OldPeculier said:

Ok, thats interesting.  So fitting a state of charge meter where all negatives need to pass thru the shunt will be difficult.  Should I just run the main cables thru and accept a small level of inaccuracy?  As far as I can make out its all small stuff like water tank guage, bilge pump etc.

 

 

No use a suitable bus bar between the shunt and the small negative connections.

 

I think your original statement about all pos on one end and all negs on the other is technically correct, otherwise you may get different rates of discharge on different batteries BUT I am also fairly sure that in real life with the interlink sizes as specified by the BSS it is unlikely to make a noticable difference.

 

 

[Jen-in-Wellies]

Things like a bilge pump, which ought to be used rarely, the positive can go to an intermediate battery positive. Similarly, the positive voltage sense wires for a battery monitor, which carry essentially no current. All negatives have to go on the non-battery side of a battery monitor shunt, including bilge pump, otherwise the battery monitor will tell you even more lies than it will otherwise do. The negative connection to an end battery will just be one, to the shunt. There may be quite a few positives; alternator, solar controller, charger, inverter, boat positive bus bar, bilge pump etc, all suitable fused and the lower power ones, it makes sense to put them on one, or more intermediate batteries and leave the end positive for the high current ones like inverter, alternator, charger etc, assuming some of these aren't connected to a bus bar, down stream of the isolation switch.

[OldPeculier]

Brilliant.  Thats sorted then.  I'll get a small neg bus bar and put all the 'odds' thru that and into the shunt.  I was just a little concerned as I've never seen things connected mid bank.  All my boats have been very basic up 'till now.