never seen solid wire from or to a battery, just sayin
Quote:
Originally Posted by OldBob
Don't use stranded wire. You need solid battery cable. I got mine at Walmart. They have battery cable in 2, 4, and 6 gauge sizes at reasonable prices. 4 gauge is perfect for the job.
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Mark & Annie
2014 COACHMEN PURSUIT 27 KB
Modesto, Central California
Actually there is no difference in the current carrying ability of stranded or solid in the same wire size. The difference is in the space required for the wire. Stranded is much larger in physical size then solid however it is much easier to bend and conform to curves and such.
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Jake my sidekick (yellow Lab) 10/04 - 05/20
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true, electricity flows on the outside of the wire, I have always used motor lead wire, it has a higher amp rating, and it is much easier to work with and makes hooking up motors in the pecker head(motor junction box much easier,,,,
Quote:
Originally Posted by SeaDog
Actually there is no difference in the current carrying ability of stranded or solid in the same wire size. The difference is in the space required for the wire. Stranded is much larger in physical size then solid however it is much easier to bend and conform to curves and such.
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Mark & Annie
2014 COACHMEN PURSUIT 27 KB
Modesto, Central California
true, electricity flows on the outside of the wire, I have always used motor lead wire, it has a higher amp rating, and it is much easier to work with and makes hooking up motors in the pecker head(motor junction box much easier,,,,
As I understand it:
In an AC current, current flows along the outside (skin) of the conductor and the depth of penetration is due to the circulating eddy currents (arising from a changing inductance field from the current alternating direction). These eddy currents cancel the current flow in the center of a conductor and reinforcing it in the skin. The higher the frequency of the alternating current, the more pronounced this effect.
Known as the "Skin Effect" you can get more info here:
DC current goes through the wire in one direction only; basically an electron gets pushed in one end knocking an electron off the other.
A solid conductor will move DC current slightly more efficiently than stranded of similar gauge. However, for a similar current flow demand (wattage) a solid wire would have to be thicker and thus more inflexible (more like a Buss Bar than a wire). That is why battery wires in automobiles are made up of very thick stranded wire.
To reduce resistance in the connection between 2 6 volt deep cycle batteries, use the shortest heaviest battery cable you can find. O or even OO would be best.
The difference in resistance is very minimal 0 gauge = .00032 ohm/meter. 4 gauge = .00081 ohm/meter.
4 gauge would work just fine between your batteries.
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2007 Surveyor SV230 - 200 Watts Solar/MPPT Controller - 220 AH Battery Bank (Two-GC2) - 600 watt PSW Inverter - (2) 2000 watt Inverter Generators - LED Lighting 2009 F150 - 5.4 Litre with Tow Package
In an AC current, current flows along the outside (skin) of the conductor and the depth of penetration is due to the circulating eddy currents (arising from a changing inductance field from the current alternating direction). These eddy currents cancel the current flow in the center of a conductor and reinforcing it in the skin. The higher the frequency of the alternating current, the more pronounced this effect.
Known as the "Skin Effect" you can get more info here:
DC current goes through the wire in one direction only; basically an electron gets pushed in one end knocking an electron off the other.
A solid conductor will move DC current slightly more efficiently than stranded of similar gauge. However, for a similar current flow demand (wattage) a solid wire would have to be thicker and thus more inflexible (more like a Buss Bar than a wire). That is why battery wires in automobiles are made up of very thick stranded wire.
To reduce resistance in the connection between 2 6 volt deep cycle batteries, use the shortest heaviest battery cable you can find. O or even OO would be best.
Thanks for the link, Herk, I'm going to order one of those tonight.
Of course,Boondocking is exactly right. For a 12 inch cable at 200 amps, the difference between #4 and #00 in voltage drop is 34 millivolts or less than .3%...and 200 amps is a heavy load. The rest of the system (cable to loads, power panel, solenoids, etc) will drop a heck of a lot more and totally dominate.
By the way, stranded vs solid will add another millivolt for #4 and .3 millivolts for #00. I wouldn't want to even try to work with solid #00 copper.
Now, since the #00 cables are available, might as well buy them but your system probably has 30 feet of #4 or #6 in it anyway between the batteries and the loads...and back!
Of course,Boondocking is exactly right. For a 12 inch cable at 200 amps, the difference between #4 and #00 in voltage drop is 34 millivolts or less than .3%...and 200 amps is a heavy load. The rest of the system (cable to loads, power panel, solenoids, etc) will drop a heck of a lot more and totally dominate.
By the way, stranded vs solid will add another millivolt for #4 and .3 millivolts for #00. I wouldn't want to even try to work with solid #00 copper.
Now, since the #00 cables are available, might as well buy them but your system probably has 30 feet of #4 or #6 in it anyway between the batteries and the loads...and back!
Yea, good point. And I don't think I'll ever run anything in the camper that would draw more than a few amps.
Remember that we are talking about the inter-battery connection.
While the load wires can be what ever size is appropriate, putting an unnecessarily high resistance between cell 3 and 4 of your 12 volt (6 cell) battery will make balancing the two 6 volt batteries (each with 3 cells) difficult.
The internal connection between cells inside the battery is a solid lead buss bar for a reason.
You can certainly do whatever you want.
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Lou & Freya the wonder dog
2008 GMC Sierra 3000HD Allison Duramax
2019 Flagstaff 8529FL
Remember that we are talking about the inter-battery connection.
While the load wires can be what ever size is appropriate, putting an unnecessarily high resistance between cell 3 and 4 of your 12 volt (6 cell) battery will make balancing the two 6 volt batteries (each with 3 cells) difficult.
The internal connection between cells inside the battery is a solid lead buss bar for a reason.
You can certainly do whatever you want.
Sure, I would think the inter-connect between two 6 volts is more critical since they are in series and you goal is a clean resistance free (as possible) connection to produce 12 volts capable of performing as well as a singe 12 volt battery of equivalent size.
The longer the run the more resistance it has, and the higher the amperage the bigger the wire you need, you are sizing the wire for two things, to limit the resistance and to accomodate the amperage, bigger doesn't hurt, well it might bother the pocket book, but better for the quality of the power you are transmitting, and resistance causes heat, which reaks havoc on a circuit
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Mark & Annie
2014 COACHMEN PURSUIT 27 KB
Modesto, Central California
Sure, I would think the inter-connect between two 6 volts is more critical since they are in series and you goal is a clean resistance free (as possible) connection to produce 12 volts capable of performing as well as a singe 12 volt battery of equivalent size.
The same logic applies when connecting 12 volt batteries in a parallel bank. Short and as big a gauge as you can find/afford.
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Lou & Freya the wonder dog
2008 GMC Sierra 3000HD Allison Duramax
2019 Flagstaff 8529FL
So here is my proposal. I have 2 T 105‘s that are six months old. They have been sitting in my house since October. They have a 6ga cable that connects them together. They have no load. I put them on my charger once a month. I read their voltage every other week or so with my multi meter. 48 hours after charging they read 12.85. If i replace the 6ga cable with a 0\2 or 0\4 would they read differently. How would they be different?
Even with current you won't see a difference in voltage since the voltage delta would be too small for most home voltmeters. Where you will notice a difference is in battery longevity as one of the 6 volt batteries will be more heavily tasked when providing current and will be charged "ahead" of the other during charging. This unequal treatment will effect the depth of discharge between the two batteries and the number of potential charge/discharge cycles.
Thus the "unbalanced" loading I mentioned previously.
Bank batteries (6 or 12 volt systems) work best when matched by manufacturer, age, cycles, depth of discharge, and "inter-battery/cell resistance".
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Lou & Freya the wonder dog
2008 GMC Sierra 3000HD Allison Duramax
2019 Flagstaff 8529FL
Even with current you won't see a difference in voltage since the voltage delta would be too small for most home voltmeters. Where you will notice a difference is in battery longevity as one of the 6 volt batteries will be more heavily tasked when providing current and will be charged "ahead" of the other during charging. This unequal treatment will effect the depth of discharge between the two batteries and the number of potential charge/discharge cycles.
Thus the "unbalanced" loading I mentioned previously.
Bank batteries (6 or 12 volt systems) work best when matched by manufacturer, age, cycles, depth of discharge, and "inter-battery/cell resistance".
Actually, that is not really true. The two 6 volt batteries are in series, you cannot charge or discharge one without the same current flowing from/to the other. When you charge them, the same voltage will be applied (and dropped by each battery.) Herk is correct in that if they are different in any way, one battery(or cells within a battery) will potentially drop a shade more or less voltage than the others, resulting in the other series battery (or cells) seeing a more or less voltage across it in order to recharge and hence a slightly lower final SOC and different specific gravity. In actual fact, they will never be exactly the same anyway, even if they are the same manufacturer and exactly the same age and this is equally true of the cells within each battery as well. That is why vendors recommend occasional "equalization" (only when needed) where you up the voltage way beyond the normal recharge voltage (like above 15 volts and carefully monitor the current) in order to equalize the charge state of all the cells and bring the specific gravity of all of the cells to exactly the same level.
Parallel banks are way different. The current will choose to flow through the path of least resistance. Make sure that each parallel battery has EXACTLY the same cables and cable length to the converter and the RV. If they are different you will eventually find one battery being overused and the other "loafing." After a significant time this will result in one battery ageing faster than another and a loss of total bank capacity.
In series installations...the current has no choice! But when comparing #4 to say #2, or #0, at some reasonable but relatively high charge or discharge current (like 100 amps) we aren't talking volts, we are talking millivolts and only a few at that! Even in a parallel bank installation, a short inter battery cable makes little practical difference, as long as it can handle the current that you want from the bank when it is in use. The total resistance and resulting voltage drop is proportional to the length of the cable, and these are only 6" to 1 foot.
Spend more time worrying about how corroded the lugs are on the batteries...now there is a place to drop some voltage and generate significant heat at the same time...and make sure they all have sufficient water to totally cover the plates at all times.
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