Greg Ford

Err, these are the first ones I replace, pre-emptively, with the longest life ones I can find (10,000 h 105°C parts if possible). That's because these protect the MOSFET, and they have to absorb the spikes of energy transferred from the MOSFETs via the inductance of the MOSFET battery-side circuit. Yes, the battery is there effectively across those capacitors, but there are long, inductive battery cables in series, limiting the battery's usefulness in the tens of kilohertz region where the action is happening. And if those capacitors stop doing their job, it doesn't just loop the inverter on power-up, the entire array of MOSFETs and probably more are damaged in spectacular fashion. Also, the battery capacitors are overseeing a multi-kilowatt circuit, not just a multi-tens of watts circuit. So they see very heavy ripple current.