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24-07-2021, 17:23
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#1
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Registered User
Join Date: Jul 2020
Location: SoCal
Posts: 692
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Wiring in parallel - both leads from same battery or from different ones?
So there are two ways to wire leads from batteries in parallel - one is to have the positive and negative leads going to load and ground from the same battery OR having positive going from one and negative from the other.
Does it make any difference?
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24-07-2021, 17:49
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#2
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Registered User
Join Date: Jun 2013
Location: canada
Posts: 4,673
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Re: Wiring in parallel - both leads from same battery or from different ones?
yes the first one is better from different batteries.
first one has bad typo though...
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24-07-2021, 18:30
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#3
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Registered User
Join Date: Mar 2018
Location: New Zealand
Boat: 50’ Bavaria
Posts: 1,809
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Re: Wiring in parallel - both leads from same battery or from different ones?
Yes, always the first way
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24-07-2021, 18:52
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#4
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Registered User
Join Date: Jan 2011
Location: Caribbean live aboard
Boat: Camper & Nicholson58 Ketch - ROXY Traverse City, Michigan No.668283
Posts: 6,375
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Re: Wiring in parallel - both leads from same battery or from different ones?
If the wires are sufficiently large, oversized, the difference is negligible.
The greatest current on Roxy occurs during charging. Pick the cable gauge accordingly. Remember that as batteries approach full charge the current drops so the large wires tend to equalize the treatment of all batteries. If your primary daily charging is solar and wind (lower amps than the generator) then wiring layout is even less of an issue.
There are far worse things we do to our batteries.
I could have made all wires the same length and other considerations but the result would have increased the total length of all wires combined - worse by far and a spaghetti of cables. 24 volts. Max generator and other sources 60 amps. Normal max output 6 amps. Max solar alone 24 amps.
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24-07-2021, 20:24
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#5
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Registered User
Join Date: Dec 2020
Posts: 750
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Re: Wiring in parallel - both leads from same battery or from different ones?
It does make a difference, and it is important.
https://fetchinketch.net/boat_though...y-connections/
The problem is that most people mistreat their batteries in so many other ways, their batteries do not live long enough for this to matter. As a general rule, if the answer to this question is not already known to you, it is very likely the connections aren’t your biggest battery issue.
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24-07-2021, 21:42
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#6
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Registered User
Join Date: Jul 2020
Location: SoCal
Posts: 692
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Re: Wiring in parallel - both leads from same battery or from different ones?
Ok, that helps. Thanks.
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24-07-2021, 23:49
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#7
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Moderator
Join Date: Aug 2009
Location: Solent, England
Boat: Moody 31
Posts: 18,488
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Re: Wiring in parallel - both leads from same battery or from different ones?
Quote:
Originally Posted by BillKny
As a general rule, if the answer to this question is not already known to you, it is very likely the connections aren’t your biggest battery issue.
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What happened to "be nice"? We all have to start somewhere.
Pete
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25-07-2021, 00:21
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#8
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Registered User
Join Date: Mar 2011
Location: Panschwitz, Germany
Boat: Woods Mira 35 Catamaran
Posts: 4,285
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Re: Wiring in parallel - both leads from same battery or from different ones?
Quote:
Originally Posted by Pete7
What happened to "be nice"? We all have to start somewhere.
Pete
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Thanks Pete, very true.
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25-07-2021, 01:06
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#9
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Nearly an old salt
Join Date: Jun 2009
Location: Lefkas Marina ,Greece
Boat: Bavaria 36
Posts: 22,801
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Re: Wiring in parallel - both leads from same battery or from different ones?
Quote:
Originally Posted by Tillsbury
Yes, always the first way
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It doesn’t really matter that much in reality. The life cycle of batteries is complex
__________________
Interested in smart boat technology, networking and all things tech
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25-07-2021, 09:17
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#10
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Registered User
Join Date: Oct 2019
Posts: 756
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Re: Wiring in parallel - both leads from same battery or from different ones?
The difference is very negligible and of no real importance. More important is the gauge of the cable alway go up and never down in size. This is one occasion where bigger is better.
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25-07-2021, 12:34
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#11
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Registered User
Join Date: Jan 2016
Location: Portsmouth, UK
Boat: Westerly Conway 36ft
Posts: 961
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Re: Wiring in parallel - both leads from same battery or from different ones?
This assumes you have only 2 batteries in your battery bank. Get up to 4 & things get different.
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25-07-2021, 12:38
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#12
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Registered User
Join Date: Dec 2008
Location: SC
Boat: None,build the one shown of glass, had many from 6' to 48'.
Posts: 10,208
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Re: Wiring in parallel - both leads from same battery or from different ones?
Electrically they are the same thing. Drawn differently.
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25-07-2021, 12:43
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#13
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Registered User
Join Date: Jan 2016
Location: Portsmouth, UK
Boat: Westerly Conway 36ft
Posts: 961
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Re: Wiring in parallel - both leads from same battery or from different ones?
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25-07-2021, 12:45
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#14
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Nearly an old salt
Join Date: Jun 2009
Location: Lefkas Marina ,Greece
Boat: Bavaria 36
Posts: 22,801
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Re: Wiring in parallel - both leads from same battery or from different ones?
Quote:
Originally Posted by Clivevon
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That analysis is fatally flawed as he takes the steady state soley as a comparison
In reality the SOCs are changing and the batteries that get worked harder discharge so that the lazy batteries shoulder the load
The result is therefore far less dramatic then his calculations suggest.
__________________
Interested in smart boat technology, networking and all things tech
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25-07-2021, 12:55
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#15
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Registered User
Join Date: Dec 2006
Location: Seattle
Boat: Cal 40 (sold). Still have a Hobie 20
Posts: 2,947
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Re: Wiring in parallel - both leads from same battery or from different ones?
Quote:
Originally Posted by Cadence
Electrically they are the same thing. Drawn differently.
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I agree completely, assuming perfect zero ohm wiring.
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