Want advice on series/parallel battery cables size

[racer4]

Hi all,

I need to order some series/parallel battery cables. I have read a lot on this, used many voltage drop calculators, etc. and still would like some more experienced advice.

Here are the details and questions:

Detail 1. I have ordered a Cedar Creek 36CKTS. It has room for four GC-2 6V batteries. It has a electric only residential refrigerator. Pictures of a similar (2015 CC 32RL) setup can be seen Here. Please ignore the fact that the dealer wired it wrong (no parallel cables etc).

Detail 2. I will be supplying four Trojan T-125 batteries. The total battery bank capacity is 480 AH (20-Hr rate).

Detail 3. When the FW is not plugged into utility 120V AC, the refrigerator runs on a WFCO WF-5100 1000W inverter. It claims >80% efficiency. I figure it's max continuous draw (based on 1000W) will be 100A. Actual use will probably be closer to 40A, but I want to size the cables for the maximum possible draw.

Detail 4. I plan to add a 100A converter (Powermax PMBC-ADJ-100 or a Meanwell RSP-1500-15) with adjustable voltage output (set to ~ 14.8V) to do a daily battery charge when not plugged into utility 120V AC. It will be powered by two Honda EU2000i generators, running in parallel. I plan to plug the converter in to an electric outlet controlled by a mechanical timer (thanks Mex). This 100A converter will only be used for generator charging. The OEM WFCO 65A converter will be turned off during gen. charging and turned on when plugged into utility 120 AC electric. I may upgrade the WFCO converter, but that is another matter.

Detail 5. I will upgrade the factory battery cables if needed, at the time I add the 100A converter. It looks like they are 2 AWG, but I am not sure. The pics I linked to above show the dealer used 2 AWG series cables and they appear to be the same diameter as the factory cables.

Detail 6. I will probably buy the battery cables custom made from Genuinedealz unless I find a better source.

Detail 7. The cable lengths are 2' for the parallel cables and 1' (or less) for the series cables.


Question1. What size series/parallel battery cables should I buy? I am thinking 2 AWG minimum, and maybe bigger at 1 AWG, 1/0, or 2/0.

Question 2. What % voltage drop should I size the cables to? 1.5%, 1.25%, 1.0% ?

Question 3. What cable lug should I get? Genuinedealz (see detail 6 link) offers: Tinned Copper Lug OR Heavy Wall Tinned Copper Lug.

Thanks for your help.

Chris

[Acampingwewillg]

Time will tell but this was my first use of 4/0 welders cable and I was amazed how everything went together so easily. To make the cables, crimp everything, heat shrink and mark with black/red electrical tape(didn't feel like buying red and black heat shrink)..7 short cables in all, took me about an hour. Now, removing the batteries, cleaning them, cleaning the tray took another hour plus...but, I'm very happy with the results. I kept all my old 12 year old cables just in case and for that age, they still looked pretty good...although I did have one fail on me hence my reason to re-do them all.

[wa8yxm]

This may be overkill but this is the method I use.

Be they in series or parallel, what is the LARGEST cable attached.. That is the MINIMUM size you should use as jumpers

If in series, Cable must carry full load

If in parallel. Assume one battery will fail high resistance (Basically vanish) and thus the jumper cable has to carry the FULL LOAD.

So the largest cable connected is the smallest I'd use for jumper.. perhaps larger even.

[2oldman]

westend wrote:
And when the OP connects his 100 amp charger what will be the effect of using that smaller wire advocated?I seriously don't get this mind set of sizing wires to the minimum able to handle the loads envisioned.

Same. I never said anything about minimum size - I like a bit of wiggle room. Is there something wrong with knowing what's going on in your electrical circuits?

Another post mentions using 4/0 interconnects. I can't imagine. I've worked with 4/0, and I hope to never do that again.

[westend]

And when the OP connects his 100 amp charger what will be the effect of using that smaller wire advocated?

I seriously don't get this mind set of sizing wires to the minimum able to handle the loads envisioned. It can't be the cost of the wire as the difference is minimal. Is it a fear of handling larger cables? Are these folks using some type of wire that is hard to work with? The OP will have to configure this once and will be done for the life of the system. Fine strand welding cable is cheap and is easy to work with. A larger cable will provide the most efficiency with charging and may prevent a voltage drop that would interfere with the operation of the inverter.

[2oldman]

If you want to get real technical:

[Acampingwewillg]

I just re-did my cables for the (6) 6 volt batteries in the MH. Yep, I know its over-kill but for the price difference, I did 4/0 cables between the batteries. If you were closer(Calif here), I'd tell ya to bring it over with some Lugs cause I have most of the 20' of cable left. I think total cost for cable, lugs, heat shrink and hydraulic crimmper from Amazon 150.00. (and I'm set for another cable re-do, or more, 10 year's from now). 🙂

[dcg9381]

I'm more in the camp of 2oldman. You size the cables per how much amperage they are going to carry. 2/0 cables are much more difficult to handle than smaller cables if you don't need to handle the amps..

[westend]

Chris,
Definitely do NOT connect your batteries anything like the pictures depicted in the Forest River Forum posts. The owner has that all wrong. Lengths of cable between series batteries should be short. Length of cables between the paralleled pairs should be adequate. I didn't see any circuit protection, either.

I'd suggest to use the largest cable possible for hookups. This is not the place to save a nickel as you will have the most efficiency for the life of the installation. I'd suggest 2/0 cables and that includes the distribution to the inverter and converter. Replace them if necessary.

Heavy lugs are worth the price. The others are not very stout.

BTW, 80 percent inverter efficiency is out of the Stone Age. 90-95 percent is typical.

[racer4]

2oldman wrote:
I don't think the first link is working as intended. I get the site grayed out with a window asking for my email.

That is a small overlay window asking for your email address. Click the "X" in the small window and the intended post is underneath it.

[2oldman]

I don't think the first link is working as intended. I get the site grayed out with a window asking for my email.

I size cables according to what the max amperage will be. Pretty much end of story.