Help with nickel strip sizing

[mrdynamite]

I am building a 6s5p molicel p42a pack, my current requirements are 85amps continuous and 150amps peak( <5sec ), please help me out with these 3 questions:
1. if i use 10mm wide pure nickel strips, what thickness should i choose for series connections
2. what sizing of nickel strip for parallel connection( as this one doesn't carry much current, can i use 7*0.1mm, as this size is easily available locally )
3. at the collectors end(+ve and -ve terminal), should i use a 10guage silicon wire running length of the parallel cells or i can use the same 7*0.1mm nickel strip

this is how my pack configuration would look, let me know if there's anything wrong.

 

[amberwolf]

If you need high current, you might want to look into the copper-nickel sandwich technique, there's at least one major thread and various others about it around here (mostly in this subforum).

 

[mrdynamite]

If you need high current, you might want to look into the copper-nickel sandwich technique, there's at least one major thread and various others about it around here (mostly in this subforum).

thanks for the reply, am using this battery pack for agricultural drones for spraying purpose so won't the corrosion on copper will be a problem?

 

[DaLanMan]

That much current with nickel strips is nearly an assurance of failure.

You may want to think through your process. You come to one of the most knowledgeable sites on ebikes and lithium batterie. Ask for help/advice, get it from one of the most prolific builders round these parts. Then tell them you are not interested.

Just sayin

 

[mrdynamite]

That much current with nickel strips is nearly an assurance of failure.

You may want to think through your process. You come to one of the most knowledgeable sites on ebikes and lithium batterie. Ask for help/advice, get it from one of the most prolific builders round these parts. Then tell them you are not interested.

Just sayin

please don't get me wrong, i didn't want to choose copper coz of its corrosive nature and comparatively higher price at pack level.

 

[DaLanMan]

Coppers corrosive nature? ::blinks:: Ok, rare fact, I am ESL... adopted and all that. Occasionally I read a sentence in english and it just kind of sits in my brain staring at me like it is supposed to make sense.

You mean because copper corrodes easily. Absolutely. and if you get water on your battery, corrosion will *not* be your biggest concern. The pop bang event and issuance of much magic smoke will completely frigging obscure any copper issues... except when it melts and follows gravity.

Couiple lil tidbits for you. Nickel is frigging TOXIC Look at all the people who have lifelong lung issues from the fumes. Copper is required by the human body (albeit in tiny amounts)

So... Nickel -- BAD
Copper -- GOOD

Copper -- GOOD conductor
Nickel -- BAD conductor

And to top it all off, ever seen an electric heater? see that stuff in there that gets all red and hot? if it isn't old (if it is old it is probably iron) if it is newer, it is most likely nichrome.. Yes, you guessed it, Iron with NICKEL to make it MORE RESISTIVE., Hence it heats up more in an electric circuit.

And for the record. This is me being nice about it. if you feel picked on, just remember, education that hurts you will remember longer.

 

[amberwolf]

thanks for the reply, am using this battery pack for agricultural drones for spraying purpose so won't the corrosion on copper will be a problem?

If anything can get into the battery to corrode the copper, it's also going to corrode everything else and destroy your battery, regardless of what metals you use.

Same thing for every other non-sealed electrical anything.


Also, you may wish to look at this page

Test of Molicel INR21700-P42A 4200mAh (Gray)

for the actual results you may get with those currents on these cells.

 

[gromike]

I have used this chart from Micah Toll's book for sizing nickel strips. For 10mm strips I calculate the ratios.


By my math,14 amps on a .2mm x 10mm strip is acceptable. You could double that strip up for your series connections.
As for your # 2, I'd say yes, though I would just buy a roll of .2mm x 10mm for all strips.
If you expect to pull 85 amps continuous off the battery your collectors need to be designed for that current. . A 1mm x 7 mm would probably vaporize.

 

[DaLanMan]

You could also wet your fingers and stick them in there as a conducter.

I get that I am not the oldest hat in the woods here, however I have been in the world of electronics and engineering for like 20 years. I am here to assure you, using nickel is stupid. There are other options. I have *GREAT* success with my shitty vevor unit and a nickel/copper alloy that is pretty much industry standard for electronics exposed to high moisture content as in boats and road vehicles. It is a lil sparky when you hit it, but I am ok with little sparks. Just not the ones that turn into raging Battery fires.

If you are looking at that, odds on the spot welder you are gonna be working with will cap out just before that.15mm thickness, it will successfully hit a .13 all day long, but the .15 gets a little spotty, but with practice you can do it. The standard strips that are in use are 10mmx.15mm now it is a matter of how far beween cels. On an 18650 in square set spacing you are looking at about 20 mm center to center. However... that is *NOT* what you are gonna be doing. You are going to be running a line from one end of your set of cels to the other, and ods on you will lay these out like most the people say to.. and hang the wire off the end of the unit. So the distance covered oh say on a 3s7p cel (it is what I have on my desk sue me) would be 13.4cm so you are gonna need a bit of slack off that edge, call it an extra cm, you now have your maximum safe amperage conducted across that distance being a LOT thicker, and this has been argued around here previously There is a chap on-line that made this There is tonnes of resources out there for ya. Feel free to look at all of them and ultimately you are gonna do whatever it is you choose to. I just urge you to think twice and cut once. Or in other words, if you don't follow the math that is being laid out for you. Maybe you should just listen to the smarter people in the room.

Mind you, i am *NOT* saying I am one of them. I just have friends in the engineering world that I listen to, hell, I listen to the people here pretty assiduously. and they at least not that I know of, don't have engineering degrees. They just have 10-20 years experience playing with this stuff. My lame duck bum bought his first ebike in November. So far they have steered me right in playing with everything. The stuff I did not want to air in public was just how little I really knew about storage systems despite having installed and built like 200 of them (large scale corpo IT stuff) in the past 20 years. I am just happy we always had the sparkies do the final hookup, never thought of how close I came a couple times to bein an ex-retired soldier.