Hi Vedran,
It is not clear to me where you measured battery current, but thats ok.
Every component, contact and wire will have an "real" effective series resistance (ESR) and "imaginary" or "reactive impedance" inductance (ESL) that will determine the short circuit current. Once you have a diagram of all these impedances, short circuit current can be calculated. Contact Vishay for ESR values vs Temp. then verify with a non-destructive Impedance test.
You can test parts or fused network using Vector Impedance Analyzer method testing or improvise with small signals at high frequency and measure the impedance of signal required to match Network using the CT to back-drive with a signal. At high frequency (eg >=1MHz) impedance of uF Cap should be lower than ESR of Cap. which would determine the S.C. current. You can back-drive the CT using a suitable variable resistance source or use a current source.and compare with RLC meter)
The rise time of a fault is 1ns so high Freq impedance is needed.
Choosing the breaker limit is a matter of temperature rise, cooling, applied voltage and the values of ESR which may rise with aging or oxidation of connections or loose connections, so setting this breaker level must also protect from loose but dangerous thermal failures, unless thermal sensors are also in critical areas of your design.
Each Capacitor will be composed of many parallel elements each with their own ESR and possibly due to built-in fuse of thin section metal film, which affects the ESR. It should be quite low < 1mOhm.
This improves reliability in case of component fault, if "self-healing". It will also have a temperature coefficient determined by your cooling design and ambient temperature.
Once you have this , the short circuit current is function of voltage when breakdown occurs to cause fault current. I am not sure if fault is likely to occur at peak voltage or peak current, but follow-on S.C. current must be stopped well before next zero crossing.
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