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Author Topic: wire size needed for paralleling batteries  (Read 51521 times)
W8JX
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Posts: 12081




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« Reply #15 on: November 21, 2013, 07:39:49 PM »

What is the recommended wire gauge when paralleling 12 volt batteries for increased current capacity in a solar array? Side by side batteries, three total. Thanks.

Lane
Ku7i

Since batteries are close voltage drop is not a problem. I would suggest 12 ga and no bigger than 10. Reason is you are not drawing extreme current and if there is a bad short, the 12 gauge will burn off quicker and open circuit. Continuous current rating for a single insulated 12 ga wire in free air is about 41 amps. Much higher than in household wiring. 

That is where I got it. Fire and melting metal is just not safe in ANY install. Fuses are safe unless you put in too big a fuse. Then we are back to fire and melting metal.

And as for the generator cables, use the right type of cabling and they are not a problem either. Also turning the generator off before handling the cables also removes the hazard. Which in and of itself is the proper thing to do; wet or dry.

The word amateur in amateur radio does not dismiss liability doing things that are not safe.

I have seen a short circuit on s battery try to burn up heavy wideband it was a mess and caught and burned and cables never burnt through. If it had anfusable wire link there would have been no fire and melt down. Pick your poison.
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Ham since 1969....  Old School 20wpm REAL Extra Class..
W9FIB
Member

Posts: 2103




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« Reply #16 on: November 22, 2013, 02:22:08 AM »

What is the recommended wire gauge when paralleling 12 volt batteries for increased current capacity in a solar array? Side by side batteries, three total. Thanks.

Lane
Ku7i

Since batteries are close voltage drop is not a problem. I would suggest 12 ga and no bigger than 10. Reason is you are not drawing extreme current and if there is a bad short, the 12 gauge will burn off quicker and open circuit. Continuous current rating for a single insulated 12 ga wire in free air is about 41 amps. Much higher than in household wiring. 

That is where I got it. Fire and melting metal is just not safe in ANY install. Fuses are safe unless you put in too big a fuse. Then we are back to fire and melting metal.

And as for the generator cables, use the right type of cabling and they are not a problem either. Also turning the generator off before handling the cables also removes the hazard. Which in and of itself is the proper thing to do; wet or dry.

The word amateur in amateur radio does not dismiss liability doing things that are not safe.

I have seen a short circuit on s battery try to burn up heavy wideband it was a mess and caught and burned and cables never burnt through. If it had anfusable wire link there would have been no fire and melt down. Pick your poison.

Which again proves the point of fuses. Are you really that dense?

Fusable links are never put next to the batteries because of the explosion possibilities. And in KU7I's case, they would have to be next to the batteries.
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Happy being an Amateur Extra!
Nothing says CB on my printed license.
Ares/Races but no lights or crown vic.
W8JX
Member

Posts: 12081




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« Reply #17 on: November 23, 2013, 06:23:35 AM »

What is the recommended wire gauge when paralleling 12 volt batteries for increased current capacity in a solar array? Side by side batteries, three total. Thanks.

Lane
Ku7i

Since batteries are close voltage drop is not a problem. I would suggest 12 ga and no bigger than 10. Reason is you are not drawing extreme current and if there is a bad short, the 12 gauge will burn off quicker and open circuit. Continuous current rating for a single insulated 12 ga wire in free air is about 41 amps. Much higher than in household wiring. 

That is where I got it. Fire and melting metal is just not safe in ANY install. Fuses are safe unless you put in too big a fuse. Then we are back to fire and melting metal.

And as for the generator cables, use the right type of cabling and they are not a problem either. Also turning the generator off before handling the cables also removes the hazard. Which in and of itself is the proper thing to do; wet or dry.

The word amateur in amateur radio does not dismiss liability doing things that are not safe.

I have seen a short circuit on s battery try to burn up heavy wideband it was a mess and caught and burned and cables never burnt through. If it had anfusable wire link there would have been no fire and melt down. Pick your poison.

Which again proves the point of fuses. Are you really that dense?

Fusable links are never put next to the batteries because of the explosion possibilities. And in KU7I's case, they would have to be next to the batteries.

I am not dense here, you are. You place a fuse at load for sure but unless you place a fuse at each battery if one battery shorts internally you will have a mess with smoke and fire unless you have a link that can fail.
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Ham since 1969....  Old School 20wpm REAL Extra Class..
W9FIB
Member

Posts: 2103




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« Reply #18 on: November 23, 2013, 07:48:15 AM »

Batteries hooked in parallel should always be fused between each battery. And the load should also be fused. But at least your starting to get it where protection is needed. Just mine with fuses is much less likely to cause a hydrogen gas explosion then yours. So be it. It is your life to end early not mine.

But looking at other posts your idea of safety is much different then mine. But at least mine will pass any fire inspection. Yours would not. So to argue any further is pointless since you are convinced you are right. I can see that now. Your non safe safety measures are all you want to believe.

As a former fireman, you will never convince me melting wires next to batteries is a good thing. It also violates the NEC code book. I just want to make sure people new to this do things correctly so they don't start a fire and/or kill themselves. You seem to have no such regard. Enough said.
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Happy being an Amateur Extra!
Nothing says CB on my printed license.
Ares/Races but no lights or crown vic.
W8JX
Member

Posts: 12081




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« Reply #19 on: November 25, 2013, 12:26:41 PM »

Batteries hooked in parallel should always be fused between each battery. And the load should also be fused. But at least your starting to get it where protection is needed. Just mine with fuses is much less likely to cause a hydrogen gas explosion then yours. So be it. It is your life to end early not mine.

But looking at other posts your idea of safety is much different then mine. But at least mine will pass any fire inspection. Yours would not. So to argue any further is pointless since you are convinced you are right. I can see that now. Your non safe safety measures are all you want to believe.

As a former fireman, you will never convince me melting wires next to batteries is a good thing. It also violates the NEC code book. I just want to make sure people new to this do things correctly so they don't start a fire and/or kill themselves. You seem to have no such regard. Enough said.

I worked with inspections that make yours a bit of a joke. Work with flight safety and flight test. We always fused wire circuits but never over sized wire bigger than needed for load. Wasted weight. You might not like a 10 or 12 GA wire burning off in a freak battery short but it is a LOT better that a 8 GA or bigger one.
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Ham since 1969....  Old School 20wpm REAL Extra Class..
W9FIB
Member

Posts: 2103




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« Reply #20 on: November 25, 2013, 01:27:42 PM »

Funny, other then giving a link to a chart, I never mentioned wire size. Nor could I since I don't know the gentleman's needs. Which is why I posted the link so he could look it up.

Plus a fuse at the battery as I have said many times will blow long before any wire would melt. If you did that on airplanes and accepted it as safe, I think I will drive from now on. Obviously there are unsafe planes up there! Did you inspect the Boeing 787 that burned up? Sorry, your argument is absurd so I had to put in an absurd question.
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Happy being an Amateur Extra!
Nothing says CB on my printed license.
Ares/Races but no lights or crown vic.
N4NYY
Member

Posts: 4941




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« Reply #21 on: November 26, 2013, 05:54:51 AM »

Quote from: W6EM
Really?  Instead of a battery explosion casting acid everywhere?  Or, one H*ll of a fire from molten copper all over the place?  Can't believe anyone would not use fuses or DC molded-case circuit breakers on each battery source.....and to the load from the paralleled bus formed by the three batteries in parallel.  Short circuit energy can be deadly, if not safely limited.  Telling someone to use a "copper fuse" is irresponsible.


Lee, keep in mind that this is the same guy who insists that running gas powered generators in a garage is a good idea.

Good example that longevity in the hobby does not necessarily equate to smarts.

How quick so are to judge without seeing the conditions involved. My garage faces east and wind rarely comes from east here and I have a back outside entrance door facing south. May garage to house door is so tight that you cannot even smell gas or paint fumes from it. I have a very tight house, maybe you are used to ones with flow through ventilation from garage. I use garage in bad weather. Maybe you like running yours in rain, I do not like running power cables in rain.

Yes the hobby does not mean smarts because some would rather run in rain and risk electrocution than use some common sense.

OMG. You actually defend this? Building an enclosure would be a hell of a lot better, of an idea.
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W8JX
Member

Posts: 12081




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« Reply #22 on: November 26, 2013, 05:58:59 AM »

Funny, other then giving a link to a chart, I never mentioned wire size. Nor could I since I don't know the gentleman's needs. Which is why I posted the link so he could look it up.

Plus a fuse at the battery as I have said many times will blow long before any wire would melt. If you did that on airplanes and accepted it as safe, I think I will drive from now on. Obviously there are unsafe planes up there! Did you inspect the Boeing 787 that burned up? Sorry, your argument is absurd so I had to put in an absurd question.

The absorb part is with you it is white or black, no grey. I have seen a battery pack melt down from a freak short in wire harness before main fuse. It was a mess. If you do not fuse each battery if you not not have a durable link you are playing with fire. Btw the 787 problem was in battery design not external. Boeings solution though was to let it burn in an more fire resistant box.
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Ham since 1969....  Old School 20wpm REAL Extra Class..
W9FIB
Member

Posts: 2103




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« Reply #23 on: November 26, 2013, 06:06:43 AM »


Plus a fuse at the battery

The absorb part is with you it is white or black, no grey. I have seen a battery pack melt down from a freak short in wire harness before main fuse. It was a mess. If you do not fuse each battery if you not not have a durable link you are playing with fire. Btw the 787 problem was in battery design not external. Boeings solution though was to let it burn in an more fire resistant box.

Do you inspect as well as you read?
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Happy being an Amateur Extra!
Nothing says CB on my printed license.
Ares/Races but no lights or crown vic.
W6EM
Member

Posts: 1666




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« Reply #24 on: November 26, 2013, 06:28:24 AM »

Too many avenues going, I'm afraid.  And all away from the main question.  Battery accidents can and do happen.  Although, usually from physical damage first.  There is considerable energy stored in what we call a battery.  LI-O has about the highest energy density.  And, LI-O is gaining some respect as to its formidable capability to cause damage from internal cell issues.  Whether caused by physical damage or from excessive heat dissipated from charging.  (The Boeing problem, as I read it)

As for aircraft wiring. it is a 'horse of a different color.'  In order to keep weight down, high-temperature insulations such as TFE (teflon) are used in order to run conductor temperatures in excess of 100C.  (Better not be close to any PVC when running above 100C, or, HCL gas corrosion will do some nasty things to metals in the vicinity).  Also, AC aircraft systems operate at 400Hz, since less self-inductance is required in transformers and that means less iron than at 60Hz.  Although, with PWM inverters, that argument is going away.  Not in the generators, though.

I, too, prefer to drive or take the train.......
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K1CJS
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Posts: 6252




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« Reply #25 on: December 03, 2013, 05:44:01 PM »

What is the recommended wire gauge when paralleling 12 volt batteries for increased current capacity in a solar array? Side by side batteries, three total. Thanks.

Lane
Ku7i

Getting back to the original question, it depends on what you want to power off the pack.  If you want to power a 100 watt transceiver at full power, 10 gauge is definitely required, there would be a power drop if you used 12 gauge and drew full power through the harness.  Usually also, if there is any distance involved, you should go up to the next heavier gauge wire.  If you just want to power a 50 watt VHF, UHF, or VHF/UHF transceiver, however, you can probably get away with 12 gauge wires.

Now to the knockdown drag-out....  (and to the bunch of "This user is currently ignored" I see here)

Battery accidents happen, but rarely, and physical damage almost always precedes such accidents.  There is no need to fuse every battery.  Dual and multiple battery vehicles (original equipment, not added on after manufacture) don't use any such fuses or fusable links, the batteries are cabled together with standard battery cables.  Yes, there are fuses and fusible links between the batteries and the load--but never between individual batteries, and I'm speaking of diesel pickups/autos--and even trucks and tractors in tractor/trailer combinations.

Being cautious is OK, but some carry it to extremes.
« Last Edit: December 03, 2013, 05:47:19 PM by K1CJS » Logged
W9FIB
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Posts: 2103




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« Reply #26 on: December 03, 2013, 07:11:05 PM »

And some like to do it the right way.
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Happy being an Amateur Extra!
Nothing says CB on my printed license.
Ares/Races but no lights or crown vic.
W6EM
Member

Posts: 1666




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« Reply #27 on: December 03, 2013, 07:54:46 PM »

What is the recommended wire gauge when paralleling 12 volt batteries for increased current capacity in a solar array? Side by side batteries, three total. Thanks.

Lane
Ku7i

Getting back to the original question, it depends on what you want to power off the pack.  If you want to power a 100 watt transceiver at full power, 10 gauge is definitely required, there would be a power drop if you used 12 gauge and drew full power through the harness.  Usually also, if there is any distance involved, you should go up to the next heavier gauge wire.  If you just want to power a 50 watt VHF, UHF, or VHF/UHF transceiver, however, you can probably get away with 12 gauge wires.

The larger the conductor size, the better.  Voltage drop is an issue with 13.5V equipment.

Quote
Now to the knockdown drag-out....  (and to the bunch of "This user is currently ignored" I see here)

Battery accidents happen, but rarely, and physical damage almost always precedes such accidents.  There is no need to fuse every battery.  Dual and multiple battery vehicles (original equipment, not added on after manufacture) don't use any such fuses or fusable links, the batteries are cabled together with standard battery cables.  Yes, there are fuses and fusible links between the batteries and the load--but never between individual batteries, and I'm speaking of diesel pickups/autos--and even trucks and tractors in tractor/trailer combinations.

When you examine your examples, there is one characteristic that stands out.  Automotive environments usually place batteries in compartments away from human proximity.  Fuse blocks are usually also inside the engine compartment and protect all wires running into the driver/passenger compartments.  If an automotive battery were to explode inside the engine compartment, no big deal.  However, on a table with gear and people right next to it would not be a comparable situation.

As for interconnection of automotive batteries, most of your examples are series connections to supply 24V to truck and diesel engine systems.  Again, in engine compartments or places where people aren't......
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K1CJS
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Posts: 6252




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« Reply #28 on: December 04, 2013, 05:57:34 AM »

As for interconnection of automotive batteries, most of your examples are series connections to supply 24V to truck and diesel engine systems.  Again, in engine compartments or places where people aren't......


Nope.  Sorry.  Those batteries parallel connect and supply 12 volts to the vehicles.  Although there are still 24 volt starting circuits in some commercial vehicles, more and more the systems are 12 volt systems.
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W9FIB
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Posts: 2103




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« Reply #29 on: December 04, 2013, 07:06:45 AM »

Actually most long haul trucks now have a deep cycle battery separate from the cranking batteries to run most auxiliary electrical equipment. And it is fused. This started as an option while I was working for Navistar in the early 90s. I believe since then it has become standard.

However CJS is correct that most starting systems are now 12V.

But EM is correct that since a portable set up may be in proximity to people and equipment, the inclusion of fuses at the batteries is an important safety measure. And it is required by NEC code for a solar/wind storage systems.
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Happy being an Amateur Extra!
Nothing says CB on my printed license.
Ares/Races but no lights or crown vic.
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