Wire gauge thickness?

forcefed

10 W
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Oct 27, 2017
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I have a dozen 18v 4ah battery packs i need to connect together in parallel, what size of wire can i safely use to connect them all together with? They'll all be connected into a terminal block and then a 10 or 12 gauge wire from the terminal block to the vesc. But from the battery to the block can i get away with 18 gauge? I currently used 12 gauge but the wire is so thick it just looks horrible and its very hard to stow away neatly, imagine a dozen sets of 12 gauge wires...
The motor is a turnigy outrunner 6374-149KV so i don't except it to draw any crazy amount of amps at 18 or 36 volts.
 
Its a ridgid 4ah battery pack https://www.ridgid.com/ca/en/ac840087-18v-4amp-lithium-ion-pack
I really can't imagine needing 12 gauge, when you take the tool apart the wires are somewhat thin, maybe 16 gauge max. With a dozen batteries in parallel i doubt i'll be pulling 40amps from each battery, maybe 40a total but not from each battery.
 
forcefed said:
Its a ridgid 4ah battery pack https://www.ridgid.com/ca/en/ac840087-18v-4amp-lithium-ion-pack
I really can't imagine needing 12 gauge, when you take the tool apart the wires are somewhat thin, maybe 16 gauge max. With a dozen batteries in parallel i doubt i'll be pulling 40amps from each battery, maybe 40a total but not from each battery.

Those are like most I believe. 2 2000mah 18650 cells paralleled and 5 of these in series. Most are using high current cells in these that can easily put out 20 amps each. Your call my friend. When you calling for high current, the smaller wires will warm a bit and add to pack resistance and voltage drop. No biggie if your not calling for current. IMO it is always best to minimize heat in the pack and connections.
 
speedmd said:
forcefed said:
Its a ridgid 4ah battery pack https://www.ridgid.com/ca/en/ac840087-18v-4amp-lithium-ion-pack
I really can't imagine needing 12 gauge, when you take the tool apart the wires are somewhat thin, maybe 16 gauge max. With a dozen batteries in parallel i doubt i'll be pulling 40amps from each battery, maybe 40a total but not from each battery.

Those are like most I believe. 2 2000mah 18650 cells paralleled and 5 of these in series. Most are using high current cells in these that can easily put out 20 amps each. Your call my friend. When you calling for high current, the smaller wires will warm a bit and add to pack resistance and voltage drop. No biggie if your not calling for current. IMO it is always best to minimize heat in the pack and connections.
But when you have a dozen of these battery packs doesn't the current get compounded? If the motor is pulling 48amps isn't it pulling only 4 amps from each battery?
 
But when you have a dozen of these battery packs doesn't the current get compounded? If the motor is pulling 48amps isn't it pulling only 4 amps from each battery?

Yes. The classic picture of spot-welded packs shows a "ladder shape" of pure nickel sheet that is laser-cut and rolled up to make it easy to ship around the world. Home builders use this because it is what the "big battery companies use" so, it must be the best, right?

Ni-201-1-4H-Pure-Nickel-Strip-4P2S-18650-battery-nickel-strip-2S4P-nickel-belt-0.jpg_640x640.jpg


At low current, pure nickel is not horrible. It works. It can be spot-welded easily on affordable welding equipment by expensive robots. Plus it is so stiff that it actually adds some rigidity to the pack.

On this style of bus, the paralleled connection "bridges" (between each cell) are the same width and thickness as the series connection bridges. If you are only looking at the electrical needs of the pack, the paralleled wires only carry a current of less than 1A, whether charging or discharging, even at very high amps...even 24ga wire would work. However, to ship batteries internationally, the style of pack must pass vibration and drop testing (to avoid shorts and fires on cargo-planes).

Also, when you go to high amps, nickel is bad. No matter how many stacks of nickel ribbon you weld on top of each other...even when you've added enough thickness to reduce max amp heat in the bus-strips...nickel is more of a resistor than a conductor at high amps. Makita uses copper bus-plates that have a thin nickel plating. It helps corrosion-resistance in harsh humid salty weather, and it makes the copper easy to spot-weld. Pure copper is hard to spot-weld...and even if you buy a very expensive plasma welder that easily welds copper buses, what do you do for corrosion resistance? Pure nickel has a price, but a thin nickel coat isn't very expensive when it's done on an industrial scale.

If you use a stout structure to hold the individual cells into the pack shape, then you don't need the buses to handle any of the packs structural rigidity requirements. Especially if its just for yourself, and you are not selling and shipping them.

For the paralleled connections, I wouldn't go smaller than 24ga, and...use whatever is convenient. Of course using large wire won't hurt, but...don't kid yourself about a fat wire helping a 1A balancing current. The series connections from one P-row to the next are where you need a certain minimum to avoid performance limits and heat.

The nickel bus in the pic above has more metal mass connecting the horizontal P-group than necessary, and the four bridges that are the series connections (four vertical pathways) might be adequate for modest amps. If I had a pack like this and I feared the series connections were a bottleneck that was limiting the packs performance and causing a lot of waste-heat? I would overlay the existing series connections with 0.30mm thick copper foil. Its cheap, and any thicker would require shears instead of just scissors, and...as much as I don't like to see builders soldering buses onto cell ends, I don't think its a problem soldering copper foil over spot-welded nickel (as far as the heat damaging the cell electrolyte in the interior)
 
I don't plan to disassemble the battery packs, I'm going to use them just as ridgid sells them, don't want to lose my lifetime warranty :D
I might use my current 12 gauge wiring and see how much current the motor is pulling and then rewire it with thinner wires.
 
18awg will be fine up to 16A per pack in parallel. But if you pull that much you'll need 1awg main cables for the 192A load.
https://www.powerstream.com/Wire_Size.htm
 
wesnewell said:
18awg will be fine up to 16A per pack in parallel. But if you pull that much you'll need 1awg main cables for the 192A load.
https://www.powerstream.com/Wire_Size.htm
I don't expect the little outrunner motor to use 3500 watts anytime soon, the vesc only has 10awg wiring.
 
That motor will run 12s at 70 amps. https://hobbyking.com/en_us/turnigy-aerodrive-sk3-6374-149kv-brushless-outrunner-motor.html
Not sure why you would run them at 5s. 10s or 15s if you can deal with the rpms. Parallel strings personally I would not go below 14g. Series 8 or 6 gauge and all as short as possible. It will not get warm.
 
I'm just waiting for the throttle and it'll be ready to run, just hooked it up to an 18v battery and it was pulling 1.5 amps spinning the tire in the air at 20000 erpm. Shirley it'll pull more under load, these outrunner motors can't be that efficient.
 
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