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 01-08-2020, 12:59   #61
Registered User

Join Date: Jun 2010
Location: Easton, MD
Boat: 15' Catboat, Bristol 35.5
Posts: 2,788
Re: Battery Cable Parallel Sizing

Quote:
Originally Posted by sailorboy1 View Post
Well YES the batteries are near their end of life. That's the reason for this whole thing!
Well, did you try an equalization charge on them? LMAO
__________________

kmacdonald is offline   Reply With Quote
Old 01-08-2020, 13:06   #62
Moderator
 
a64pilot's Avatar

Cruisers Forum Supporter

Join Date: Oct 2013
Location: Jacksonville/ out cruising
Boat: Island Packet 38
Posts: 31,096
Re: Battery Cable Parallel Sizing

You can’t unfortunately get to balanced by varying cable diameters, except at one load, any higher or lower and there goes the balance.
I believe batteries in parallel will actually self balance as they are all connected together, And after the load is off the higher voltage batteries will “charge” the lower voltage ones until they are all equal, but due to different resistence within each battery they may be under different loads, so one may be working harder than the rest.

That’s not what I said earlier, and I think I was wrong.
__________________

a64pilot is offline   Reply With Quote
Old 01-08-2020, 13:25   #63
Registered User

Join Date: Jan 2014
Location: Panama City FL
Boat: Island Packet 32 Keel/CB
Posts: 607
Re: Battery Cable Parallel Sizing

DC drop 20 ft round trip, load 200 amps

#4/0 copper cable 20 mv. #1 copper cable 50mv.

Typical INTERNAL voltage drop of a decent set of GC2s in series at a load of 200 amps probably 1 volt.

My 300+ amp bow thruster does cause a little flicker in the voltage but not enough to cause a reset in anything electronic, nor does starting my 3GM Yanmar.


You can kill a squirrel with a 30/06 but a 22 will usually suffice.



Frankly
Frankly is offline   Reply With Quote
Old 01-08-2020, 13:33   #64
Registered User
 
Nicholson58's Avatar

Join Date: Jan 2011
Location: Caribbean live aboard
Boat: Camper & Nicholson58 Ketch - ROXY Traverse City, Michigan No.668283
Posts: 4,802
Images: 84
Re: Battery Cable Parallel Sizing

Quote:
Originally Posted by kmacdonald View Post
We figured that. Is buzzbar = bussbar?
I guess bussbar too.

I was going to suggest shortest, largest wire you can manage but bussbar is pretty good.

We have big Lifeline and Firefly banks with tinned heavy robot cables discarded from the machine builder where I retired. Super flexible 2-0. All heavy users are gone or replaced by more efficient stuff so the maximum current draw is 8 amps, normal 5. (24 volts). Charging solar is 12-29 amps. Batteries are happy.
Nicholson58 is offline   Reply With Quote
Old 01-08-2020, 13:54   #65
Are you serious?
 
sailorboy1's Avatar

Join Date: Jul 2007
Location: currently in Jacksonville Fl
Boat: Hunter 410
Posts: 16,602
Re: Battery Cable Parallel Sizing

There is an issue with bus bars as battery interconnects. It is that they are rigid.
__________________
jobless, houseless, clueless, living on a boat and cruising around somewhere
sailorboy1 is offline   Reply With Quote
Old 01-08-2020, 14:09   #66
Are you serious?
 
sailorboy1's Avatar

Join Date: Jul 2007
Location: currently in Jacksonville Fl
Boat: Hunter 410
Posts: 16,602
Re: Battery Cable Parallel Sizing

Quote:
Originally Posted by a64pilot View Post
You can’t unfortunately get to balanced by varying cable diameters, except at one load, any higher or lower and there goes the balance.
I believe batteries in parallel will actually self balance as they are all connected together, And after the load is off the higher voltage batteries will “charge” the lower voltage ones until they are all equal, but due to different resistence within each battery they may be under different loads, so one may be working harder than the rest.

That’s not what I said earlier, and I think I was wrong.
If you do the math

If both total and positive/negative cable lengths are the same, and the pos/neg from each battery to the next to it is the same, and positive is taken off one end of the group and neg the other, the batteries will be balanced.

Now you could nitpick it and thrown out “in theories” due differences in fittings etc., but for any measure of practical engineering it holds.

How i mind dumped and stupidly started this thread was by thinking of only 1 side of the power loop. The mechanical engineer in me tends to treat electrical the same as pumps and fluid flow. And in this case it was thinking like pumping out of a tank via many pumps with one discharge at the end. Which to get equal flow from each pump requires changes in pipe diameters.
__________________
jobless, houseless, clueless, living on a boat and cruising around somewhere
sailorboy1 is offline   Reply With Quote
Old 01-08-2020, 14:23   #67
Registered User

Join Date: Jan 2015
Location: SoCal
Boat: Formosa 30 ketch
Posts: 659
Re: Battery Cable Parallel Sizing

With 4/0 cable being so stiff, isn't there a danger of breaking off the terminals on the batteries?
Bill Seal is offline   Reply With Quote
Old 01-08-2020, 14:23   #68
Marine Service Provider

Join Date: Sep 2008
Location: Victoria B.C.
Boat: CS27
Posts: 2,206
Re: Battery Cable Parallel Sizing

Quote:
Originally Posted by sailorboy1 View Post
There is an issue with bus bars as battery interconnects. It is that they are rigid.
The batteries should be fixed in position so they don't move either. Also the interconnects should not be tight between posts but have a bit extra length.
mitiempo is offline   Reply With Quote
Old 01-08-2020, 14:39   #69
Moderator
 
a64pilot's Avatar

Cruisers Forum Supporter

Join Date: Oct 2013
Location: Jacksonville/ out cruising
Boat: Island Packet 38
Posts: 31,096
Re: Battery Cable Parallel Sizing

Quote:
Originally Posted by sailorboy1 View Post
If you do the math

If both total and positive/negative cable lengths are the same, and the pos/neg from each battery to the next to it is the same, and positive is taken off one end of the group and neg the other, the batteries will be balanced.

Now you could nitpick it and thrown out “in theories” due differences in fittings etc., but for any measure of practical engineering it holds.

How i mind dumped and stupidly started this thread was by thinking of only 1 side of the power loop. The mechanical engineer in me tends to treat electrical the same as pumps and fluid flow. And in this case it was thinking like pumping out of a tank via many pumps with one discharge at the end. Which to get equal flow from each pump requires changes in pipe diameters.
See, I think difference in length are insignificant if the wire is big enough.
If you have an L shaped battery box, the only way for lengths to be the same is if you take the longest wire and make them all that length, thereby having a lot of excess wire that you would have to bend around somehow or other.

What’s the difference in resistance of four foot of 0000 wire as opposed to two foot?

I’ve got so many different wires connecting to the bank with a shorepower charger, the inverter, and solar as well as the bilge pump and the HF radio that I got one large 1”x 2”by 1’ copper bar, cut it in half and drilled and tapped six holes in each bar and bought silicon bronze bolts. This gave me a neg and a pos buss bar. I have 6” of cable to connect them to the battery, that way I’m not stacking terminals on the battery post.
The inverter is wired directly to the bank, and the the boat is wired directly to the bank as well, both connected to the buss bars.
When you get about four terminals stacked on top of a post it’s stupid, plus my current batteries are about 1/4” too tall as it is, so one terminal is shorter.
a64pilot is offline   Reply With Quote
Old 01-08-2020, 14:52   #70
Are you serious?
 
sailorboy1's Avatar

Join Date: Jul 2007
Location: currently in Jacksonville Fl
Boat: Hunter 410
Posts: 16,602
Re: Battery Cable Parallel Sizing

They don't ALL have to be the same. The sections just need to be the same in reverse order.

Example 4 batteries in parallel the cable length connections are (all same awg)

On pos end 8” , 8”, 10”, 20”

On neg 20”, 10”, 8”, 8”
__________________
jobless, houseless, clueless, living on a boat and cruising around somewhere
sailorboy1 is offline   Reply With Quote
Old 01-08-2020, 14:54   #71
Registered User

Join Date: Jun 2010
Location: Easton, MD
Boat: 15' Catboat, Bristol 35.5
Posts: 2,788
Re: Battery Cable Parallel Sizing

Quote:
Originally Posted by Bill Seal View Post
With 4/0 cable being so stiff, isn't there a danger of breaking off the terminals on the batteries?
I was thinking the same but not sure. I would never connect a bussbar directly to the battery terminals because of that.
kmacdonald is offline   Reply With Quote
Old 01-08-2020, 14:56   #72
Registered User

Join Date: Jun 2010
Location: Easton, MD
Boat: 15' Catboat, Bristol 35.5
Posts: 2,788
Re: Battery Cable Parallel Sizing

Quote:
Originally Posted by sailorboy1 View Post
They don't ALL have to be the same. The sections just need to be the same in reverse order.

Example 4 batteries in parallel the cable length connections are (all same awg)

On pos end 8” , 8”, 10”, 20”

On neg 20”, 10”, 8”, 8”
Yes. The total interconnect length for each battery needs to be the same length. I knew you were smart.
kmacdonald is offline   Reply With Quote
Old 01-08-2020, 15:02   #73
Registered User

Join Date: Jun 2010
Location: Easton, MD
Boat: 15' Catboat, Bristol 35.5
Posts: 2,788
Re: Battery Cable Parallel Sizing

Quote:
Originally Posted by Frankly View Post
DC drop 20 ft round trip, load 200 amps

#4/0 copper cable 20 mv. #1 copper cable 50mv.

Typical INTERNAL voltage drop of a decent set of GC2s in series at a load of 200 amps probably 1 volt.

My 300+ amp bow thruster does cause a little flicker in the voltage but not enough to cause a reset in anything electronic, nor does starting my 3GM Yanmar.


You can kill a squirrel with a 30/06 but a 22 will usually suffice.





Frankly
I will look for the article that analyzes connecting batteries in parallel. IIRC minute differences make a HUGE difference. Sort of like milliseconds in electronic terms is light years.
kmacdonald is offline   Reply With Quote
Old 01-08-2020, 17:06   #74
Registered User

Join Date: Jan 2014
Location: Panama City FL
Boat: Island Packet 32 Keel/CB
Posts: 607
Re: Battery Cable Parallel Sizing

"I will look for the article that analyzes connecting batteries in parallel. IIRC minute differences make a HUGE difference. "

I would like to read that article. I have been operating GC2 battery banks (4 on my Hunter and 6 on my IP) in an unbalanced configuration for over 35 boat years. If there is any degradation I sure can't see it, and I keep pretty close tabs on all things electrical.

Until shown differently, I include that in the catagory of "navel gazing" .


Frankly
Frankly is offline   Reply With Quote
Old 01-08-2020, 18:06   #75
Are you serious?
 
sailorboy1's Avatar

Join Date: Jul 2007
Location: currently in Jacksonville Fl
Boat: Hunter 410
Posts: 16,602
Re: Battery Cable Parallel Sizing

Well my last/current set of e set that was T105s definitely had an in-balance. I also didn't think it was a big deal, but they didn't make it 4 years. This in spite of my paying too much of my time treating them nice. And that had what i feel as carrying more load considering the in-balance died first.

So just because “someone” had good luck, or believes they have, doesn't really mean much.
__________________

__________________
jobless, houseless, clueless, living on a boat and cruising around somewhere
sailorboy1 is offline   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 01:49.


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.