DIY

Alternating current crosses zero a hundred times a second and helps extinguish an arc; direct current does not, so the interrupting mechanism must do all the work.

Being disconnected from the utility does not make a system safe; the inverter is a source, and a fault needs a defined return path and a device that opens.

A big iron transformer gives sustained surge capability and robustness; a high-frequency design gives light weight and efficiency. The difference shows under motor loads.

Surge figures are meaningless without the duration and the conditions they were measured under, and the battery behind the inverter can be the real limit.

Running an engine to serve household loads directly wastes most of its capacity; running it hard to bulk-charge a bank and shutting down is the efficient pattern.

A pulse-width controller connects the array to the battery and discards the voltage difference; a maximum power point controller converts it into extra current.

Usable capacity is set by whichever cell hits its limit first, so a bank with one tired member delivers far less than the sum of its parts suggests.

Cable length, terminal resistance and internal condition decide how much current each string carries, and asymmetric wiring quietly overworks one of them.

Doubling the bank voltage halves the current for the same power, which changes cable size, fuse ratings, losses and which equipment you can even buy.

A system that works in July and fails in December was sized against the wrong month; the design case is the worst production period against real measured load.