Leaving nimh cells permanently connected will drain them, and going below 0.9v per cell will damage them and quickly shorten their life.
Having everything permanently connected means when it's not running it is still switched on, so with any interference there's nothing to stop it disappearing all by itself, and I wouldn't want to try working on a car that's still turned on.
There's no need to ever remove connectors from the wiring. Decent connectors are as reliable as a soldered joint, and with no more resistance than solid wire.
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