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Lack of confidence in wiring, gives a choice between a light that can't be seen, and may not be working, or a cheap reliable battery light.
Back light uses very little power.
Non familiarity with stand lights.
You can buy rear lamps at Poundland.
Despite all these issues, I have just upgraded to modern dynamo lights, front and back and it is an improvement.
But I don't know what I'll be doing next year!
Many thorn customers fit dynamo with front only; then just a AA battery rear... no idea why....