Treat replacement as the default first step, not as optional folklore. A Federal Pacific Stab-Lok or a Zinsco-type panel is not a modern, well-supported platform for a new 40-amp or 60-amp EV breaker. The Consumer Product Safety Commission investigated Federal Pacific Electric circuit breakers, and in a 28 February 1983 news release it closed that investigation: it did not determine that the breakers were unsafe, it found that certain breakers failed specified UL calibration and short-circuit tests in some evaluations, and it provided safety information for consumers rather than a recall. That is a narrower official record than internet claims of a “recall” or of a single failure rate, and this site will not invent a percentage.
Zinsco and related Sylvania panels have a separate, also well-known reputation among electricians for overheating and for breakers that may not clear a fault as expected. This page is not a CPSC finding about Zinsco; it is a practical warning that parts, listings, and insurer comfort are all poor reasons to add a large continuous load to an obsolete can.
The honest sequence is: have a licensed electrician identify the panel, talk to your insurer if they have already flagged it, replace the panel (and upgrade the service if the load calculation for the charger requires it), then install the EV circuit under permit. See also the fuse-box page and the insurance page.
This is not a permit calculation, a utility approval, or a substitute for a licensed electrician, HVAC contractor, or the authority having jurisdiction. Panel Headroom is an independent educational site. It is not a utility, a certification body, or a contractor. Electrical and generator work that is done incorrectly can cause fire, shock, or carbon monoxide poisoning. Use the adopted electrical code and manufacturer instructions; pull permits where required.