I want to build a 12s 6p battery pack with Molicel P42A cells. I am super confused about nickel strip/wire/etc sizing for my battery. Here are the specs that won’t change:
Battery: 12S6P, Molicel P42A 21700
Motors: 2x TB 6374, 190kV
How do I spec out the nickel strips to connect the cells? My cells have a maximum continuous output of 45A each. If I have 6 P-groups, do I need the nickel strips to be sized for 270A, 45A, or somewhere in-between? I plan to spot weld the cells together myself.
Any help is appreciated - I have been sitting on this project for far too long, and I want to get started as soon as I feel I know enough.
Are you planning to use the nickel strips as the series connections, or are you going to be using wire or braided copper for the series connections? Whatever you use for the series connections needs to be able to handle the maximum current you will draw from the battery. 270 A would be a lot for those motors, and you definitely wouldn’t be pulling anywhere near that for long without overheating them. In the end, your controller and settings will determine how much current you’re pulling. If it were me, I’d probably try to set things up so that the battery can handle 270 A, so if you want to upgrade things later, you can continue using the battery.
Assuming you’re connecting with nickle strip, then you need to use the width of the strip to go between the cells from different groups and the length of the strip to go across the groups. 0.2 mm thick nickel is good for 20 to 30 A per cm perpendicular to the direction of current, depending on who you ask and your/their safety margin. If you use the full width of 6 21700 batteries, that is 126 mm, which is good for 252 to 378 A. Basically if you’re building a brick pack with nickel series connections, as long as you use the full width of the group and 0.2 mm nickel for the series connection, it should be able to pull 45 A per cell through those connections. You do have to worry about connecting the sides of the pack and the pack to the ESC as well.
If you are in the US, buying 6p nickel would be easiest unless you are planning a pelican case pack. Takes the guess work out of it and makes welding much easier imho.