Batteries...

Almost all the equipment used on a day to day basis is reliant on battery power and some of it uses technology that's now been left way behind.  My Lumedyne location flash is used fairly infrequently (you can usually plug in somewhere) but occasionally is invaluable.  The system is almost agricultural in its simplicity but the biggest problem has always been the NiCad batteries; replacing them is extremely expensive and they need to be charged correctly. I've just had a couple of them rejuvenated by recellyourbattery.com, excellent helpful service and a reasonable cost to prolong the life of the system.