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Battery Cables


dewilso

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I’m putting 4x Battle Born batteries in my RV. The batteries will be end to end, parallel wired. I'll use 2/0 cable from the batteries to the inverter. Now.... one end of the bank along with cables will be 50" longer than the other, is this a problem ? What gauge cable should be used between the batteries ?

 

Thanks

Dave W. KE5GOH

Stuck in the 70's ---

In E. Texas

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If you mean say the final cable from the POS to Inverter is 50" longer then the final cable from the NEG, that's no major concern. Of course, the bigger the cable the less line voltage drop, so size your cables to limit voltage drop to whatever you find acceptable. The absolute MINIMUM wire size I suggest is 125% of the maximum continuous current AND THEN UPGRADE AS NECESSARY TO REDUCE VOLTAGE DROP...…...  Sorry, I cant suggest your cable sizes sitting here not knowing the current and wire length...…..

HOWEVER and most don't realize this, to insure EACH battery receives equal charging and EACH battery supplies an equal amount of load current, its best if you do as the Smartgauge  suggests (iffffffff THEIR results, not mine, are accurate???). They have four examples (with detailed test results) of different methods to connect multiple batteries in parallel ranging from better to best BUT this takes more cables and connections mind you. Its NOT for everybody except those sticklers who want each of their batteries to last and function the same and not let a couple do most of the heavy lifting.  Take a look at their test results versus different connection methods ITS QUITE SURPRISING !!

 SURE a simple old straight ladder parallel connection will "work" there are likely hundreds of such out there and all "working". But if better battery load and charging balance is important and in order to protect such a huge investment in Lithium batteries, one might want to consider a connection method to achieve more equal charge and load balance (be it their own method or as Smartgauge suggests) among multiple batteries.

NOTE I support any RV owners to wire as they wish, its their RV their money and their choice NOT ANY OF OURS so wire as you see fit.   

 http://www.smartgauge.co.uk/batt_con.html

Take a look, don't take my word for it (those are NOT my tests or results, no warranty mind you), then make an informed decision that's best for YOU.

 John T

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The smartgauge method #3 Is the same method I used. Using an amprobe on each battery cable shows loads pretty equal. I still have a smartgauge wired in, worked on my lead acids, but not on my lithiums. Still makes a good voltmeter though.

Foretravel 40ft tag 500hp Cummins ISM  1455 watts on the roof, 600 a/h's lithium in the basement.

 

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JC, With my small 29Ft Class C and modest energy requirements I only have three AGM batteries in parallel (520 Amp Hours) so am currently configured with the SmartGauge Method 2, but am considering the improved Method 3 like you used. It just takes more cable and connections. If I was investing several thousand in batteries I would for sure want them connected so each shares the load equally. Our local Interstate Battery shop makes up great looking cables including crimped soldered then heat shrink terminations in all sizes and colors. Of course, any simple ladder method (ton of them out there) still "works".   To each their own.

Nice chatting with you

John T

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On 8/6/2019 at 5:21 PM, dewilso said:

Now.... one end of the bank along with cables will be 50" longer than the other, is this a problem ?

You could attach the battery cables into the center of the bank in order to minimize the distance differential.

Good travelin !...............Kirk

Full-time 11+ years...... Now seasonal travelers.
Kirk & Pam's Great RV Adventure

            images?q=tbn:ANd9GcQqFswi_bvvojaMvanTWAI

 

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I have my 690 ah golf cart batteries connected with 2/0 awg. All the interconnecting cables must be the same. I used method 3. All the positive are the same length. All the negatives are the same length. Negs don't have to be same as pos. I used Blue Sea terminal fuse blocks on the positive battery. These; https://shop.marinehowto.com/products/blue-sea-marine-rated-battery-fuse

 

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method two. All the interconnecting positive cables must should be the same length. All the interconnecting negative cables should be the same length. The positives do not have to be the same length as the negatives. Always use a catastrophic fuse on the positive battery.

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Battery configuration has been addressed. Battery cable terminals are often overlooked,  when left open to the air, they can corrode inside where they are crimped to the cable, this is unseen and unnoticed until a problem arises. There are approved methods to seal the terminal connections to prevent corrosion.

 

2000 Winnebago Ultimate Freedom USQ40JD, ISC 8.3 Cummins 350, Spartan MM Chassis. USA IN 1SG retired;Good Sam Life member,FMCA ." And so, my fellow Americans: ask not what your country can do for you--ask what you can do for your country.  John F. Kennedy 20 Jan 1961

 

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On 8/9/2019 at 2:28 PM, Ray,IN said:

 There are approved methods to seal the terminal connections to prevent corrosion.

It's a non-issue with AGM or Li batteries.  Ok, I know someone will say my terminals corroded using AGMs, so I better say "I" never had any corrosion with my AGMs, and certainly not with Lis.

Edited by hemsteadc
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3 hours ago, hemsteadc said:

Ok, I know someone will say my terminals corroded using AGMs, so I better say "I" never had any corrosion with my AGMs, and certainly not with Lis.

Likewise, "so far" at least (knock on wood) I've seen NO corrosion or accumulation or any deposits (sure maybe a bit of dust) on my terminals since switching to AGM.  FWIW Nothing actually lol

John T

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4 hours ago, hemsteadc said:

It's a non-issue with AGM or Li batteries.  Ok, I know someone will say my terminals corroded using AGMs, so I better say "I" never had any corrosion with my AGMs, and certainly not with Lis.

I can, and will say the same of my SLA batteries cable terminals, at least for the past 6 years after I installed new batteries.. I was pointing out the need for solid, tight crimps, as SEHC detailed in  that link.

Edited by Ray,IN

 

2000 Winnebago Ultimate Freedom USQ40JD, ISC 8.3 Cummins 350, Spartan MM Chassis. USA IN 1SG retired;Good Sam Life member,FMCA ." And so, my fellow Americans: ask not what your country can do for you--ask what you can do for your country.  John F. Kennedy 20 Jan 1961

 

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Wire and cable connections don't only corrode from battery fume. The moisture and pollutants present in the atmosphere can cause bad connections. A note; I have no battery caused corrosion on my lead acid batteries, house or starter. Proper charging and other maintenance is the key to happy campers.

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