Cruisers Forum
 


Join CruisersForum Today

Reply
  This discussion is proudly sponsored by:
Please support our sponsors and let them know you heard about their products on Cruisers Forums. Advertise Here
 
Thread Tools Search this Thread Rate Thread Display Modes
Old 31-07-2020, 11:12   #1
Are you serious?
 
sailorboy1's Avatar

Join Date: Jul 2007
Location: currently in Jacksonville Fl
Boat: Hunter 410
Posts: 16,564
Battery Cable Parallel Sizing

Is it worth it to try to "balance" the cable size of a 4 battery bank in effort to try to get equal amps out of each battery?

If so what is the best way to do it:
- vary the cable size (doesn't really work out)
- add extra cable to each leg (ie. 1 x 1AWG from batt 1 to Batt 2, 2 x 1AWG from batt 2 to batt 3)
__________________

__________________
jobless, houseless, clueless, living on a boat and cruising around somewhere
sailorboy1 is online now   Reply With Quote
Old 31-07-2020, 11:38   #2
Registered User

Join Date: Jun 2010
Location: Easton, MD
Boat: 15' Catboat, Bristol 35.5
Posts: 2,765
Re: Battery Cable Parallel Sizing

There is a correct way of doing it and it does matter. Google it. 4 six volt batteries for 12V system or 4 12V batteries?
__________________

kmacdonald is online now   Reply With Quote
Old 31-07-2020, 11:44   #3
Registered User
 
Cheechako's Avatar

Join Date: Aug 2006
Location: Skagit City, WA
Posts: 22,675
Re: Battery Cable Parallel Sizing

__________________
"I spent most of my money on Booze, Broads and Boats. The rest I wasted" - Elmore Leonard











Cheechako is offline   Reply With Quote
Old 31-07-2020, 11:50   #4
Are you serious?
 
sailorboy1's Avatar

Join Date: Jul 2007
Location: currently in Jacksonville Fl
Boat: Hunter 410
Posts: 16,564
Re: Battery Cable Parallel Sizing

Quote:
Originally Posted by Cheechako View Post
:f ight:
__________________
jobless, houseless, clueless, living on a boat and cruising around somewhere
sailorboy1 is online now   Reply With Quote
Old 31-07-2020, 11:51   #5
Are you serious?
 
sailorboy1's Avatar

Join Date: Jul 2007
Location: currently in Jacksonville Fl
Boat: Hunter 410
Posts: 16,564
Re: Battery Cable Parallel Sizing

the question is the cable SIZE BETWEEN each 12V battery. Not the positive on one end of the bank and the negative on the other.
__________________
jobless, houseless, clueless, living on a boat and cruising around somewhere
sailorboy1 is online now   Reply With Quote
Old 31-07-2020, 12:02   #6
Registered User

Join Date: Jun 2010
Location: Easton, MD
Boat: 15' Catboat, Bristol 35.5
Posts: 2,765
Re: Battery Cable Parallel Sizing

Quote:
Originally Posted by sailorboy1 View Post
the question is the cable SIZE BETWEEN each 12V battery. Not the positive on one end of the bank and the negative on the other.
Lets look at it this way. Battleborn uses 4 10AWG wires to internally connect to its terminals. That's 21mm squared area and that equals 4AWG cable. 4AWG will be fine but I'd use 2 AWG. FYI: Some drop in's use one or two 10AWG wires to connect to internal terminals. Of course this assumes the batteries are close to each other.
kmacdonald is online now   Reply With Quote
Old 31-07-2020, 12:05   #7
Registered User

Join Date: Jul 2020
Location: Virginia, USA
Boat: Tayana 37
Posts: 56
Re: Battery Cable Parallel Sizing

Just make sure they are wired from opposite ends to keep the circuit length the same for each battery. If everything else is done right (no corrosion, proper crimps, consistent torque for each terminal) then variations between resistance through each battery is largely dependent on variations in internal resistance. Beyond that is probably navel gazing. You are never going to get resistance through each circuit identical even if you could the internal resistance of each battery will vary with age.

Statistical is online now   Reply With Quote
Old 31-07-2020, 12:15   #8
Registered User

Join Date: Mar 2019
Location: I'm in Johannesburg, boat in Cape Town :(
Boat: 1986 Bruce Roberts 45 raised saloon
Posts: 88
Re: Battery Cable Parallel Sizing

The best way is to have buzzbars, with each battery connected to the buzzbar using cable of equal spec and length (all new the same, all pos the same, new and pos can differ). There is no better way.
markcouz is offline   Reply With Quote
Old 31-07-2020, 12:16   #9
Registered User

Join Date: Mar 2019
Location: I'm in Johannesburg, boat in Cape Town :(
Boat: 1986 Bruce Roberts 45 raised saloon
Posts: 88
Re: Battery Cable Parallel Sizing

New = neg, dammit!
markcouz is offline   Reply With Quote
Old 31-07-2020, 12:18   #10
Registered User

Join Date: Jun 2010
Location: Easton, MD
Boat: 15' Catboat, Bristol 35.5
Posts: 2,765
Re: Battery Cable Parallel Sizing

Quote:
Originally Posted by markcouz View Post
New = neg, dammit!
We figured that. Is buzzbar = bussbar?
kmacdonald is online now   Reply With Quote
Old 31-07-2020, 12:19   #11
Registered User

Join Date: Mar 2019
Location: I'm in Johannesburg, boat in Cape Town :(
Boat: 1986 Bruce Roberts 45 raised saloon
Posts: 88
Re: Battery Cable Parallel Sizing

Depends if you are a yank or a saffer, is it color or colour?
markcouz is offline   Reply With Quote
Old 31-07-2020, 12:25   #12
Registered User

Join Date: Jun 2010
Location: Easton, MD
Boat: 15' Catboat, Bristol 35.5
Posts: 2,765
Re: Battery Cable Parallel Sizing

The cabling between the batteries is primarily based on ampacity since they are so short. The cables from the battery terminals to the load need to consider voltage drop also. The two cable sizes will be different with the cable to the load being larger cable.
kmacdonald is online now   Reply With Quote
Old 31-07-2020, 12:32   #13
Registered User

Join Date: May 2011
Boat: Hitchhiker, Catamaran, 40'
Posts: 852
Re: Battery Cable Parallel Sizing


Four batteries, there is an easier method, see diagram. Four 6 volts, no because that is equal to 2 12 volt. More than four twelve volt batteries in a bank, probably a good idea.
Thumbs Up is offline   Reply With Quote
Old 31-07-2020, 12:36   #14
Moderator
 
a64pilot's Avatar

Cruisers Forum Supporter

Join Date: Oct 2013
Location: Jacksonville/ out cruising
Boat: Island Packet 38
Posts: 31,052
Re: Battery Cable Parallel Sizing

In my opinion as long as the cables are large enough, which they most certainly are for low amp long term draws like we usually use, that the difference in length is pretty much inconsequential.
If you use the house bank for starting or an inverter, size the cables big, they can’t be too big.
Again in my opinion this is a lot like arguing if the thumb thick stiff coax with no couplers is better than the smaller coax for your VHF, on paper you can “prove” it is, but in a boat you won’t notice any difference.

In a lot of battery installations, the only way to match cable lengths is to make them silly long as they would all have to be the length of the longest cable, not all installations can conform to the laid side by side shown in all diagrams, my battery box for instance is L shaped.

The only difference in lengths is resistance, do we really think there is a significant difference in 6” of OO cables resistance?
I’d bet there is more difference in the resistance of the terminal crippled on the wire.
Why don’t we use gold terminals, they are the best?

Size wise I think it’s logical to use the same gauge wire that the existing ground and pos cables that go to the engine and battery switch are, but no need to go larger than those.
a64pilot is offline   Reply With Quote
Old 31-07-2020, 12:41   #15
Registered User

Join Date: Jul 2020
Location: Virginia, USA
Boat: Tayana 37
Posts: 56
Re: Battery Cable Parallel Sizing

Quote:
Originally Posted by a64pilot View Post
Why don’t we use gold terminals, they are the best?
Common misconception. Gold has higher resistance than copper. It is more corrosion resistant than bare copper but so is tin plated copper at far lower cost. Silver is slightly lower resistance than copper but at more than 100x the cost (~$700/kg vs $6/kg).
__________________

Statistical is online now   Reply With Quote
Reply

Tags
battery

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Parallel jumper cable lengths Eastward ho 24 Construction, Maintenance & Refit 6 07-06-2020 12:36
Cable sizing for battery switch, bus bars etc jonase Electrical: Batteries, Generators & Solar 15 22-01-2019 02:00
Four Solar Panels - Parallel , Series or Series-Parallel west coaster Electrical: Batteries, Generators & Solar 76 07-07-2011 14:35
Battery cable sizing sailorboy1 Electrical: Batteries, Generators & Solar 5 26-06-2011 05:50
Battery Bank Interconnect Cable Sizing? Catamount Electrical: Batteries, Generators & Solar 7 10-04-2010 08:03

Advertise Here


All times are GMT -7. The time now is 19:02.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2020, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2020, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.