Battery Cable Parallel Sizing

[sailorboy1]

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)

[kmacdonald]

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?

[Cheechako]

[sailorboy1]

Originally Posted by Cheechako

:f ight:

[sailorboy1]

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.

[kmacdonald]

Originally Posted by sailorboy1

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.

[Statistical]

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.

[markcouz]

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]

New = neg, dammit!

[kmacdonald]

Originally Posted by markcouz

New = neg, dammit!

We figured that. Is buzzbar = bussbar?

[markcouz]

Depends if you are a yank or a saffer, is it color or colour?

[kmacdonald]

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.

[Thumbs Up]

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.

[a64pilot]

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.

[Statistical]

Originally Posted by a64pilot

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).