Nickle battery tab ampacity

[emcee]

I'm wondering if anyone can answer this question, since google searches don't yield an answer.

Im building a battery pack and I'm spot welding it together. What size nickle strip would you use for approx 40a draw? .375" x .005" is readily available would this be sufficient?

 

[major]

Im building a battery pack and I'm spot welding it together. What size nickle strip would you use for approx 40a draw? .375" x .005" is readily available would this be sufficient?

That would be over 21,000 Amps/sq.in. current density. Way, way too much. I like to use 2000A/in² for copper being on the conservative side. Nickel is 4 times the resistivity of copper, so I'd keep current density below 500A/in². Those figures are for continuous current. Peak current densities can be proportionally higher. I'd use the continuous current rating of the cell group to figure the allowable density vs the figures I stated.

 

[emcee]

Im building a battery pack and I'm spot welding it together. What size nickle strip would you use for approx 40a draw? .375" x .005" is readily available would this be sufficient?

That would be over 21,000 Amps/sq.in. current density. Way, way too much. I like to use 2000A/in² for copper being on the conservative side. Nickel is 4 times the resistivity of copper, so I's keep current density below 500A/in². Those figures are for continuous current. Peak current densities can be proportionally higher. I'd use the continuous current rating of the cell group to figure the allowable density vs the figures I stated.

When the pack is built it will be 10p of 10a capable cells. Thats 100A max continuous discharge, way above what I will ever draw.
This is the one frustrating hangup on this pack build is trying to find information on ampacity of nickle strips.
Thank you for the input.

 

[999zip999]

I would build a pack without these gasket between the neg. case and the pos. tip. That's if they don't have a specail vent on top.

 

[Punx0r]

They are insulators to stop the welded strip wearing through the can heatshrink and shorting out the cell (the outer rim of the top of the can is part of the negative terminal).

 

[RLT]

I use .01 nickel sheet from Admiral Steel . cut into about 1/2 inch wide strips with a paper cutter, for my battery packs.
It has handled 180 amps intermittent and 80 amps continuous, with no problems..
I have melted some of that thinner and narrower Sunstone strip, though, before I found the .01 stuff.

You are probably OK with 40 amps, but I'd double up, just to be sure.

 

[dnmun]

measure the surface area of each spot weld. you can estimate the radius with a micrometer, then calculate area: pi x R^2 = area

then find the current density of 40A for the 4 spot welds in parallel.

nickel has 4 times the resistance of copper but it takes about 4mm^2 of copper to carry 40A so it takes about 16 mm^2 to carry the same current that copper will.

 

[arkmundi]

In trying to answer the question myself, I want to know the equivalent of nickel strip from Sunstone to copper wire gauge wire. From prior pack building, for a 36V pack driving a 500 watt motor, I know I can safely use 12 gauge copper wire, so as to run 20 amps continuous. So, what is the cross sectional area of that:

.00513 / .005" is 1" wide to be equivalent in area to the wire. For the .375" wide strip, it'd need to be tripled to carry the necessary amperage. Ignoring the relative resistance between the copper and nickel.

 

[Punx0r]

You might need 12 AWG wire to carry 20A over several feet without significant voltage drop, but it's overkill for a <1" cell interconnect. Think how thin a fuse element is compared to the wiring you'd insert it into.

 

[Jon@LiionWholesale]

Sorry to bring a thread back from the dead but is there any consensus on how to find the ampacity of nickel strip? I have Sunstone 0.25" width and 0.375" width by 0.005" thick (0.15mm), and want to make a 4s1p pack that can do 15-17A continuous and 30A short pulses. The cells can handle it but I'm not sure about the nickel. Normally here I'd solder copper wire into the series connections or do more strips but since it's only 1p I don't think I can do that. Any knowledge about whether one strip can handle that? Or what the normal way to do this is if not.

 

[kdog]

All the info you'll ever need is in nobuo's ultimate repository.but very quickly ,Nickel strip amperage = SA(mm)x19/4. It's quite low. Ie 8mm x.15mm nickel = aprox 6amps. Conservative numbers but if you are building a pack you don't want heat build up etc.