You say it breaks the circuit, but parasitic inductance says no.
Parasitics are a bitch, they are giving me headaches in pcb design right now.
When it breaks, it makes a spark, a fairly large spark to say the least, depending on what your pack is made of, that can very well result in a fire anyway.
Proper fuses are designed to minimize and contain this spark.
With my pack (20s7p of 18650PF cells), I used 24AWG tinned copper wire, 10mm long.
Resistance of pack in Ohms equals number of serial cells divided by the number of parallel cells multiplied by the average resistance of the cells in Ohms
Rp=(xS/xV)Rc
with about 190mm ((xS-1)*10mm) of 24AWG per parallel run which is
R=ρL/A =1.86E-8Ω.m * 0.19m / 2.05E-4m^2
=1.7E-5Ω
=.000017Ω
=0.017mΩ
That is the resistance for one leg of 20S7P using 10mm for the length of the fuse wire.
This is how I build all of my battery packs. I haven’t had a problem with any of the 4 packs, 2 of them being over 2 years old now. Don’t understand the stigma against this method, it is quite convenient to not have to buy a spot welder and source pure nickel when I already have a nice 75w soldering iron and get the brass strips locally at the hardware store.
I think you misplaced a decimal somewhere in there, but you’ve got the concept.
Ya my bad. Error Corrected A of 24AWG is 2.05E-7m^2 not 2.05E-5m^2
How does it look now.
Resistance of pack in Ohms equals number of serial cells divided by the number of parallel cells multiplied by the average resistance of the cells in Ohms
Rp=(xS/xV)Rc
with about 190mm ((xS-1)*10mm) of 24AWG per parallel run which is
R=ρL/A
=1.86E-8Ω.m * 0.19m / 2.05E-7m^2
=0.017Ω
=17mΩ
That is the resistance for one leg of 20S7P using 10mm for the length of the fuse wire.
Rp=(xS/xP)Rc
=1/7*0.017Ω
=0.00242Ω
=02.43mΩ
Anyone have a good source for tinned copper wire? Preferably in N. America?
I’ve been using the @akhlut p-group calculator to decide on the gauge for a pack I’m building- been super helpful in wrapping my head around the concept as is the excellent write up (thx homie!).
You should not solder directly on the cells. The heat damages them, and yes , even if you do it real fast
Buying a spot welder on Amazon would be better than soldering. Batteries are dangerous, if a $100 investment in the correct tools is out of the question then so is building a battery.